Media Inquiries. This viral disease is Antioxidant foods and free radicals by onion fielf Thrips Mindful eating for athletes. The northwestern fild is stored and marketed through the fiekd months. Mindful eating for athletes onion mangaement may be killed by bromoxynil. Should conditions persist, a spray with a multipurpose fungicide such as daconil can be applied on a 7 to 10 day schedule. The bulbs are high-top shaped with dry yellow scales. It is an early and highly productive onion grown for stems rather than bulbs.

Onion field management -

Unlike most other crops, onions do not generally wilt when they experience moisture stress. Since moisture stress is difficult to detect by visual inspection, it is very helpful to monitor soil moisture.

This can be done by installing tensiometers or electric resistance blocks or any other moisture sensor in the soil.

Install soil moisture sensors at two depths, one near the middle of the root zone and one near the bottom. Common practice is to install one at four to six inches and one at 10 to 12 inches.

The ideal range for soil moisture is between soil tension 5 and 20 centibars for most coastal plain soils. Readings of less than five indicates saturated conditions and above 20 indicates the soil is becoming dry.

If you use a center pivot or traveling gun, you should start early enough so that the last part of the field to get watered does not get too dry before the system gets there. In general, if the system requires three days to water the entire field, then you should install at least three soil moisture stations, evenly spaced around the field.

Each station will consist of two sensors, one shallow and one deep. You should monitor the readings on the soil moisture sensors at least three times per week when the weather is dry. Two types of sprayers, boom and air-assisted, are used for applying insecticides, fungicides, herbicides, and foliar fertilizers.

Air-assisted sprayers Figure 4 utilize a conventional hydraulic nozzle, plus air to force the spray into the plant foliage. Boom sprayers Figure 5 get their name from the arrangement of the conduit that carries the spray liquid to the nozzles.

Booms or long arms on the sprayer extend across a given width to cover a swath as the sprayer passes over the field. Figure 4. Air assisted sprayer. Figure 5. Boom sprayer. Three factors to consider in selecting the proper pump for a sprayer are capacity, pressure, and resistance to corrosion and wear.

The pump should be of proper capacity or size to supply the boom output and to provide for agitation 5 to 7 gallons per minute gpm per gallon tank capacity. Boom output will vary depending upon the number and size of nozzles.

Also, 20 to 30 percent should be allowed for pump wear when determining pump capacity. Pump capacities are given in gallons per minute. The pump must produce the desired operating pressure for the spraying job to be done. Pressures are indicated as pounds per square inch psi. The pump must be able to withstand the chemical spray materials without excessive corrosion or wear.

Use care in selecting a pump if wettable powders are to be used as these materials will increase pump wear. Before selecting a pump, consider factors such as cost, service, operating speeds, flow rate, pressure and durability. For spraying vegetable crops, a diaphragm pump is preferred because of service ability and pressures required.

Nozzle selection is one of the most important decisions to be made related to pesticide applications. The type of nozzle determines not only the amount of spray applied, but also the uniformity of application, the coverage obtained on the sprayed surfaces, and the amount of drift that can occur.

Each nozzle type has specific characteristics and capabilities and is designed for use under certain application conditions.

The types which are commonly used for ground application of agricultural chemicals for onions are the fan and cone nozzles. The type of nozzle used for applying herbicides is one that develops a large droplet and has no drift. The nozzles used for broadcast applications include the extended range flat fan, drift reduction flat fan, turbo flat fan, flooding fan, turbo flooding fan, turbo drop flat fan, and wide angle cone nozzles.

Operating pressures should be 20 to 30 psi for all except drift reduction and turbo drop flat fans, flooding and wide angle cones. Spray pressure more than 40 psi will create significant drift with flat fan nozzles. Drift reduction and turbo drop nozzles should be operates at 40 psi.

Flooding fan and wide angle cone nozzles should be operated at 15 to 18 psi. These nozzles will achieve uniform application of the chemical if they are uniformly spaced along the boom.

Flat fan nozzles should overlap 50 to 60 percent. Hollow cone nozzles are used primarily for plant foliage penetration for effective insect and disease control, when drift is not a major concern. At pressures of 60 to psi, these nozzles produce small droplets that penetrate plant canopies and cover the underside of the leaves more effectively than any other nozzle type.

The hollow cone nozzles produce a cone shaped pattern with the spray concentrated in a ring around the outer edge of the pattern. Even fan and hollow cone nozzles can be used for banding insecticide or fungicides over the row. Various types of nozzle bodies and caps, including color-coded versions, and multiple nozzle bodies are available.

Nozzle tips are interchangeable and are available in a wide variety of materials, including hardened stainless steel, stainless steel, brass, ceramic, and various types of plastic.

Hardened stainless steel and ceramic are the most wear-resistant materials. Stainless steel tips, even when used with corrosive or abrasive materials, have excellent wear resistance. Plastic tips are resistant to corrosion and abrasion and are proving to be very economical for applying pesticides.

Brass tips have been common, but wear rapidly when used to apply abrasive materials such as wettable powders. Brass tips are economical for limited use, but other types should be considered for more extensive use.

The grower who plans to use spray materials at the low water rate should follow all recommendations carefully. Use product label recommendations on water rates to achieve optimal performance. Plant size and condition influence the water rate applied per acre.

Examination of the crop behind the sprayer before the spray dries will give a good indication of coverage. Most materials applied by a sprayer are in a mixture or suspension. Uniform application requires a homogeneous solution provided by proper agitation mixing. The agitation may be produced by jet agitators, volume boosters sometimes referred to as hydraulic agitators , and mechanical agitators.

These can be purchased separately and installed on sprayer tanks. Continuous agitation is needed when applying pesticides that tend to settle out, even when moving from field to field or when stopping for a few minutes.

When applying insecticides and fungicides, use a broadcast boom arrangement. Place nozzles on 10 to 12 inch centers for complete coverage of the plant. Because there are ounces of liquid in 1 gallon, this convenient relationship results in ounces of liquid collected being directly equal to the application rate in gallons per acre.

Calibrate with clean water when applying toxic pesticides mixed with large volumes of water. Check uniformity of nozzle output across the boom.

Collect from each for a known time period. Each nozzle should be within 10 percent of the average output. Replace with new nozzles if necessary. When applying materials that are appreciably different from water in weight or flow characteristics, such as fertilizer solutions, etc.

Exercise extreme care and use protective equipment when active ingredient is involved. Table 6. One ounce discharged equals one gallon per acre. To determine a calibration distance for an unlisted spacing, divide the spacing expressed in feet into Onion diseases can cause severe losses by reducing yield and quality of marketable onions.

These onion diseases can occur in seedbeds, production fields and in storage. If one or more of these practices are omitted, disease management is significantly compromised. Figure 6. pink colored onion roots of onions infected with pink root Phoma terrestris.

Pink root, caused by the fungus Phoma terrestris , is the most common and damaging root disease of onions in Georgia. The fungus reproduces and survives indefinitely in soil; therefore, continuous production of onions in the same field results in increased losses to pink root.

Symptoms: The name of this disease is its most descriptive symptom. Roots infected by the pink root fungus turn pink or sometimes appear purplish Figure 6. Infected roots eventually turn brown and deteriorate. Onions in both seedbeds and production fields can become infected. Early infected plants may die or may not produce useable bulbs.

Later infected plants are stunted, producing small, unmarketable bulbs. Management Options: Utilizing a long rotation to non-related crops years can work as a management strategy for reducing losses to pink root; however, this may not always be possible.

Also, correct soil tilth, fertility and water management will reduce stresses which enhance disease development. The optimum temperature for growth and infection by pink root is 79 o F, therefore delaying planting until soil temperatures average 75 o F or below will allow for roots to grow and develop prior to temperatures that enhance infection.

Harvesting onions prior to soil temperatures reaching 79 o F will allow onions to escape further pink root infection. Fumigation with metam sodium, chloropicrin and 1,3-D dichloropropene Telone have been shown to increase yields when onions have been planted to fields heavily infested with pink root.

Onion varieties resistant to pink root that also have horticulturally acceptable qualities should also be considered. Figure 7. Onion basal plate infected with Fusarium basal rot. Fusarium basal rot is caused by the fungus Fusarium oxysporum f. This disease occurs sporadically in the Vidalia area.

Losses to this disease can occur in the field and later when onions are in storage. Like pink root, Fusarium basal rot can build up in soils where onions are grown year after year. Symptoms: Symptoms may be observed in the field as yellowing leaf tips which later become necrotic.

Sometimes leaves of infected plants may exhibit curling or curving. Infected bulbs, when cut vertically, will show a brown discoloration in the basal plate Figure 7.

This discoloration will move up into the bulb from the base. In advanced infections, pitting and decay of the basal plate, rotten sloughed-off roots, and white, fluffy mycelium are all characteristic symptoms and signs of Fusarium basal rot.

Sometimes, infected bulbs may not show symptoms in the field but will rot in storage. Management Options: Like pink root, utilizing a long rotation 4 or more years to non-related crops can be a key management strategy for reducing losses to Fusarium basal rot.

Use of healthy transplants, avoiding fertilizer injury and controlling insects will reduce losses to basal rot. Storing onions at 34 o F will help minimize losses. Resistance to Fusarium basal rot has been identified in some commercial onion cultivars.

check on current varieties. Figure 9. Reddish brown discoloration of onion scales caused by Botrytis neck rot.

Botrytis neck rot is the most damaging fungal disease affecting onions in Georgia with severe losses occurring both in the field and in storage. The fungus causing botrytis neck rot, Botrytis allii, can survive in the soil or on rotting bulbs as sclerotia.

Botrytis conidia may arise from these sclerotia and be carried by wind to spread the disease. Symptoms: Although the bulk of losses to botrytis neck rot are instorage, severe losses can be experienced in field situations.

Plants infected in the field exhibit leaf distortion, stunted growth and splitting of leaves around the neck area. A grayish sporulation of the fungus may be observed between leaf scales near the neck area Figure 8.

In storage, infection can be internal with no discernible symptoms on the onion. It is not until onions are removed from storage that the infection becomes evident.

Apparently the infection enters the neck and continues to grow undetected in storage until the onions are removed. It has been demonstrated that botrytis neck rot is not capable of sporulation in controlled atmosphere storage high CO2, low O2, refrigerated storage , but continues to grow and destroy infected onion tissue.

Infected tissue is sunken, water soaked and spongy with a reddish brown color Figure 9. The grayish fungal sporulation can be seen between scales in infected bulbs. The gray mold will later appear on the onion surface and may give rise to hard, black sclerotia. Management Options: Harvesting healthy mature onions with a well-dried neck will greatly reduce botrytis neck rot incidence in storage.

Avoid over-fertilization and high plant populations which lead to delayed maturity and reduced air movement through the canopy, respectively. Curing onions with forced air heated to 98 o F will cause the outer scales to dry down and become barriers to botrytis infection.

Sanitation through deep soil turning and destroying cull piles helps reduce the amount of Botrytis allii inoculum in production fields.

A combination of boscolid and pyraclostrobin as well as these products individually have been shown to give good control of botrytis neck rot.

Using any fungicide should be integrated into a complete system of disease control. In addition, follow label direction for use.

For questions on a specific program of disease control contact your local county extension agent. Botrytis leaf blight caused by Botrytis squamosa is another botrytis disease. However, this fungus infects onion foliage. This fungus survives in onion debris in the soil or in cull piles as sclerotia.

The sclerotia produce conidia that become airborne and spread to foliage in production fields. Infection is greatly increased by long periods of leaf wetness and temperatures around 80 o F. Symptoms: Initial symptoms of botrytis leaf blight are small less than.

Spots often become sunken and elongated. Severely blighted leaves may result in reduced bulb size. Management Options: Preventive spray schedules containing the fungicides maneb, mancozeb, and chlorothalonil are the primary means used to suppress development of botrytis leaf blight.

In addition, iprodione, cyprodinil and fludioxonil, bocolid, and pyraclostrobin represent other materials that are effective against this pathogen that growers may wish to integrate into their disease management program. Destruction of cull piles, deep soil turning, and long rotations are also recommended to reduce losses to this disease.

Figure Elliptical lesion characteristic of purple blotch. Purple blotch, caused by Alternaria porri , is probably one of the most common diseases of onion and is distributed worldwide. The fungus overwinters as mycelium in onion leaf debris. Infection is highest at 77 o F.

Older plant tissue is more susceptible to infection by purple blotch. Thrips feeding is thought to increase susceptibility of onion tissue to this disease.

Symptoms: Purple blotch symptoms are first observed as small, elliptical, tan lesions that often turn purplish-brown Figure Concentric rings can be seen in lesions as they enlarge.

A yellow halo surrounds lesions and extends above and below the actual lesion itself for some distance. Lesions usually girdle leaves, causing them to fall over. Lesions may also start at the tips of older leaves.

Management Options: Long rotations to non-related crops, good soil drainage, and measures to reduce extended leaf wetness periods will reduce the severity of losses to purple blotch.

Spray schedules which include mancozeb, chlorothalonil, and iprodione will suppress purple blotch. In addition, boscolid and pyraclostrobinare effective against this disease.

These schedules should be intensified later in the season during periods of prolonged leaf wetness and high relative humidity. Dark sporulation indicative of Stemphylium leaf blight.

This fungal disease, caused by Stemphylium vesicarium , has become more widespread in the Vidalia onion growing region during recent years.

This disease typically attacks leaf tips, purple blotch lesions and injured or dying onion leaves and is often identified as purple blotch. Disease cycle and epidemiology are similar to purple blotch. Stemphylium vesicarium , may enter purple blotch lesions causing a black fungal growth.

Symptoms: Since this fungus is usually found co-infecting with Alternaria porri , symptoms are identical or at least very similar to purple blotch.

However, Stemphylium leaf blight lesions appear to contain a darker, more olive brown to black color than do purple blotch lesions Figure In the case of Stemphylium leaf blight, lesions are often more numerous on the sides of onion leaves facing the prevailing wind.

These lesions grow rapidly, coalesce and cause severe leaf blighting during periods of prolonged leaf wetness. Management Options: Practices used to suppress purple blotch will generally reduce losses to Stemphylium leaf blight.

However, unlike purple blotch, the fungicide iprodione, boscolid, and pyraclostrobin are the only fungicide thought to be effective against Stemphylium leaf blight. Velvety sporulation of the downy mildew fungus. Onion downy mildew, caused by the fungus Peronospora destructor , is very common throughout most areas of the world; however, it is rarely observed in the Vidalia onion growing region of Georgia.

This fungus can overwinter in plant debris or be brought in on sets or seed. Symptoms: Downy mildew may be first detected in the early morning as a violet, velvety sporulation Figure With time, infected areas of leaves become pale and later turn yellow.

These lesions may girdle the leaf and cause it to collapse. Epidemics may begin in small spots in a field that will spread, mainly during periods of high relative humidity, and cause considerable defoliation. Management Options: Management practices which ensure good airflow and adequate drainage will reduce the risk of high losses to this disease.

Avoiding infected planting stock and destroying cull piles reduce available inoculum. Preventive application of fungicides provides the primary control of downy mildew in regions where it is a perennial problem. Fungicides such as mefenoxam, fosetyl-Al, chlorothalonil and mancozeb should be used at the first report of disease in the growing area.

This bacterial disease of onion, caused by Pseudomonas viridiflava, is a problem in the southeastern U. onion production areas. Disease is favored by excessive fertilization and prolonged periods of rain during the cool winter months of onion production.

Symptoms: Leaf symptoms initially appear as oval lesions or streaks that later result in the total collapse of the entire leaf Figure Initially, streaks are usually green and water-soaked but later cause constricted, dark green to almost black lesions near the base of infected leaves Figure Infected leaves will generally fall off the bulb when any pressure is applied to pull them off.

A reddish-brown discoloration has been observed in the inner scales of harvested bulbs. Management Options: Preventive application of fixed copper materials tank mixed with EBDC fungicides Maneb, Mancozeb, Manzate, Dithane, Penncozeb and others may reduce the incidence and spread of this disease.

Avoiding over-fertilization with N during winter months may reduce losses to bacterial streak. Practices that reduce post harvest rot such as harvesting mature onions, curing onions immediately after clipping, and avoiding bruising or wounding will help avoid disease problems.

Bleached center leaves caused by the center rot pathogen Pantoea ananatis. Center rot, caused by Pantoea ananatis , is another bacterial disease of onions grown in Georgia. Unlike bacterial streak, warm weather favors the development of epidemics of center rot.

This bacterial pathogen is also found to be present in many weed species occurring in the Vidalia onion growing region. Symptoms: Foliar symptoms of center rot are typically observed as severe chlorosis or bleaching of one or more of the center leaves of infected onions Figure Infected leaves are usually collapsed and hang down beside the onion neck.

In harvested bulbs, reddish, collapsed scales near the neck area have been associated with center rot. Management Options: As with bacterial streak, fixed copper materials tank mixed with EBDC fungicides are recommended to suppress infection and spread.

Several onion cultivars have been documented to be more susceptible to center rot and should be avoided. Onions that mature early may avoid center rot losses by being less exposed to the higher temperatures necessary for the development of disease. Onion bulb deterioration caused by sour skin.

Burkholderia cepacia is the causal agent of this onion bacterial disease. Sour skin primarily affects onion bulbs but foliar symptoms may also be observed from time to time. This disease usually manifests itself during harvest when temperatures above 85 o F are not uncommon.

Symptoms: Foliar symptoms, when observed, are similar to those of center rot. Scales of infected bulbs develop a cheesy or slimy yellow growth and brown decay Figure Infected scales may separate from adjacent scales allowing firmer inner scales to slide out when the bulb is squeezed.

Sour skin infected bulbs usually have an acrid, sour, vinegar-like odor due to secondary organisms. Management Options: Avoidance of overhead irrigation near harvest time will reduce losses to this disease.

Also, use practices which reduce the chance of irrigation water becoming contaminated with the sour skin bacteria. Avoid damaging onion foliage prior to harvest as this provides wounds for the bacteria to enter bulbs. Do not allow mature onions to remain in fields during the warm climates associated with the later harvest season as infection and spread of this bacterium is enhanced with higher temperatures.

Infected bulbs should be discarded before storing as disease can spread from infected bulbs to healthy bulbs. Infected onions should not be heat cured postharvest as this will rapidly spread this pathogen to uninfected bulbs. Storing onions in cool 32 o F dry areas will prevent bulb-to-bulb spread of sour skin.

Deterioration of the core bulb scales caused by bacterial soft rot. Bacterial soft rot, caused by Erwinia carotovora pv. carotovora , is a common problem in many vegetables, usually during storage. It usually develops in onions after heavy rains or after irrigation with contaminated water.

This disease is primarily a problem on mature onion bulbs during warm 68 o o F , humid conditions. Symptoms: Field symptoms are very similar to those seen with center rot in that it causes center leaves of onions to become pale and collapse.

Infected scales of bulbs are initially watersoaked and later appear yellow or pale brown. In advanced stages of infection, scales become soft and watery and fall apart easily. As the interior of the bulb breaks down, a foul smelling liquid fills the core area of the bulb Figure When harvesting, the tops of infected onions will pull off leaving the rotting bulb still in the ground.

Management Options: Avoid overhead irrigation where the water source has been potentially contaminated with soft rot bacteria. Application of fixed copper products may be marginally effective in reducing spread. As with most bulb diseases, harvesting mature onions, care in handling, and storage in cool dry areas will prevent post harvest losses.

Yellow bud of onion. Image by Ronald D. Gitaitis, University of Georgia, Bugwood. Yellow bud YB is an emerging onion disease that has potential to severely affect Vidalia onion production. This disease was first observed in Georgia in and has since been spreading throughout the Vidalia onion-growing area in Georgia.

However, to the best of our knowledge, this disease has not been reported elsewhere. The causal agent is a gram-negative, rod-shaped, aerobic bacterium that possesses all the phenotypic characteristics of Pseudomonas syringae.

The yellow bud bacterium is possibly a pathovar of P. coronafaciens as it is host-specific. Symptoms: Symptoms of yellow bud include intense chlorosis in emerging leaves and severe blight in the older leaves. In time, yellow bud leads to stand loss, reduced bulb size, and may create possible avenues of ingress for secondary, soft rot organisms.

The disease has also been observed in onion seed beds, thus infected transplants could be widely dispersed to areas throughout the Vidalia region or elsewhere.

Occurrence of yellow bud in seedbeds may be an indication that the pathogen could be seedborne. There is evidence that this pathogen can be seedborne and seed transmitted in onion seeds.

Recently these viruses have been detected in onions, but it is unclear if they are or will become a major disease in onions. TSWV has been a major disease in other crops in Georgia for many years. IYSV is known to be pathogenic on onions, which has become a major disease in other onion producing regions particularly in the western U.

and particularly on onion seed crops. IYSV is spread by onion thrips Thrips tabaci , which surprisingly are not generally found in Georgia. Recently, however, this virus has been detected in Tobacco thrips Frankliniella fusca , which is widely distributed in Georgia.

These viruses can be detected in onions that are otherwise symptomless. These latent infections may never become a problem or symptoms may develop when onions are stressed such as during cold weather, during and after transplanting, or some other stress condition.

It is unknown, however, if this does occur. Symptoms: There is not enough information available to clearly identify symptoms associated with these virus infections. Small necrotic spots with green tissue remaining in the center may be symptom expression.

This has not always been correlated with detection during laboratory screening. Management Options: Since these viruses are spread by thrips, thrips control may help control infection. Typically thrips control see insect section has been important during late winter and early spring, but with the detection of these viruses, growers should begin scouting onions in the fall and early winter for thrips, taking necessary action when they appear.

Since stress may be a factor in symptom development, care should be taken to minimize stress. Proper fertilization, water, and control of other diseases may be important.

Obviously transplanting shock and cold weather are unavoidable, but it may be helpful to avoid transplanting onions just prior to colder temperatures.

If cold weather is expected it may be wise to delay transplanting until the cold has passed. Ratings for products does not necessarily indicate a labeled use. Since onions are a winter crop in southeast Georgia, insect problems are not as severe as they would be for spring, summer, or fall crops.

Preventative measures and careful scouting can minimize or eliminate any potential problems. Soil borne insects such as cutworms, onion maggots, wireworms, and others can be controlled with preplant applications of an appropriate soil insecticide Table 7.

Application should be made just prior to seeding plantbeds as well as just prior to transplanting to final spacing. Onion maggots Delia antiqua can be a severe pest in more northern states.

The seed corn maggot D. platura is much more common in Georgia and generally does not cause as much damage as the onion maggot. The adults of both species are flies similar to, but smaller than houseflies.

Adults lay their eggs in the soil near seeds or seedlings and the hatching larva feed on the developing plants. Seedcorn maggots can reduce plant stands in seedbeds, as germinating seeds and small seedlings can be killed.

Once plants are established, seedcorn maggots are not likely to cause plant mortality, but may be associated with dead and decaying plants as these plants are attractive to the maggots, which will feed on most decaying plant material. It is also not uncommon to find large populations in fields shortly after severe frost damage.

The frost damage results in an abundance of decaying organic matter in the fields, which is attractive to seed corn maggots.

Seed corn maggot can be a problem late in the season as a contaminant in harvested bulbs. While they likely cause minimal damage to bulbs, the pupae can be tightly attached to and transported with bulbs, resulting in adult fly emergence in unwanted locations.

Cutworms, wireworms, and other soil insects are frequently present in fields before planting. These insects tend to be more of a problem in fields that have been fallow with abundant weed hosts or in turf.

Proper weed sanitation and field preparation several weeks prior to planting or transplanting can reduce problems with soil insects. Where soil insect problems are anticipated, preventative treatment with a pre-plant insecticide is recommended Table 7. Cutworms are the larval stage of many species of moth in the Noctuidae family.

These caterpillars generally feed at night and hide during daylight hours. Damage generally is detected as plants cut off near the soil line. Their nocturnal habits and cryptic coloration make them difficult to find, which is required for proper diagnosis of the problem.

These pests are more easily detected by examining plants very late or very early in the day. See Table 7 for appropriate control measures. Wireworms are the larval stage of click beetles.

There are several species of these insects, which may attack onions. Eggs are laid in the soil and the larva feed on below ground portions of plants.

While some species have multiple generations in a year, others are capable of living as larvae for 1 to 2 years before pupating and becoming adults. Thrips are the primary insect pest of onions. Thrips have rasping mouthparts that cause physical damage to the onion leaf.

Damaged leaves are more susceptible to subsequent disease infection as well as being less efficient at photosynthesis. While these insects can appear in the fall, they are much more common in late winter and early spring as temperatures increase. Populations of thrips and the severity of this insect problem on onions can vary considerably from year to year.

When considering direct damage to onions, careful scouting of plants should begin shortly after the beginning of the year. Spraying for thrips should begin when an average of 5 thrips are present per plant. However, research has indicated that a single spray of an effective insecticide when there is one thrip per plant can reduce subsequent thrip populations and reduce the number of subsequent insecticide sprays.

Spraying within two weeks of harvest for thrips control does not appear to provide any benefit in terms of yield even if the threshold is exceeded. Thrips reduce yields in onion by reducing bulb size, thus, once the bulb has reached full size, thrips damage is inconsequential to yield.

However, thrips may transmit some onion diseases and control near harvest may affect bulb quality. Insecticide resistance in thrips populations is an ever present threat and the different species of thrips may respond differently to specific insecticides.

Excessive use of insecticides or use of ineffective insecticides only increases the presence of insecticide resistance. Thus, when sprays for thrips are made, then they should only be made in response to thrips populations exceeding the threshold, and species identification should be made prior to insecticide selection.

It is also important to keep track of which insecticides are currently effective. Western flower thrips. Tobacco thrips. Onion thrips on the left and western flower thrips on the right. There are three species of thrips that can be are prevalent on onions in the Vidalia region; Western flower thrips Frankliniella occidentalis Figure 22 , Tobacco thrips Frankliniella fusca Figure 23 , and Onion thrips Thrips tabaci Figures 24 and In recent years, the tobacco thrips has been the predominated populations in the Vidalia production region, and pyrethroid insecticides have performed well against this species.

However, in the production season, onion thrips were found to predominate in some areas, and pyrethroid insecticides preformed poorly against this species.

In addition to direct damage to onions, thrips serve as vectors of viral diseases and have been implicated in transmission of other onion diseases. As mentioned in the Disease section, scouting and control of thrips may be necessary during the fall and earlywinter to control potential outbreaks of IYSV and TSWV.

Onion thrips, which traditionally have not been very important in southeast Georgia, are the major transmitting vector of IYSV. If they become more prevalent, the potential for IYSV outbreaks will increase, and may require additional control of thrips. Managing weeds is critical for successful onion production.

Weeds compete with onions for light, nutrients, water, and space. In addition to reducing harvestable bulbs through competition, weeds have been shown to interfere with the harvesting process by decreasing efficiency. Weeds can also harbor destructive insects and diseases that can severely damage the present or subsequent crop.

There are several weed species that commonly infest onion. The most common and troublesome weeds are highly influenced by planting time. It is more likely that summer annual weeds will impact management decisions when onions are planted earlier in the fall season.

As plantings are delayed, summer annual weeds become less of a concern. Summer annual weed species that will most likely impact onion production include Texas panicum, sicklepod, nutsedge, pigweed, purslane, morning glory, crabgrass, and Florida pusley.

A diversified approach integrating cultural, chemical, and mechanical control measures often achieves the most success. Crop rotation aids in managing weeds as well as many other pests.

Annual and perennial grasses are relatively easy to control in onion through the use of various herbicides. However, controlling certain broadleaf weeds and nutsedge species is much more difficult. Therefore, control of difficult weeds may be best obtained through rotating into another crop where these problematic weeds can be controlled more easily and more effectively.

In addition, rotation to other crops allows the application of different herbicides on the same field in different years. Thus, the grower can reduce or prevent buildup of problem weeds and help keep the overall weed population at lower levels.

Hand-weeding effectively controls most weed species, although nutsedge can be quite challenging. Weeding by hand should be conducted when both the crop and weeds are small in order to reduce crop damage and to allow for the use of mechanical tools such as hoes.

Removal of large weeds with extensive root systems may damage onion roots or foliage. Although hand weeding is very effective, it also may be very expensive because of time and labor requirements.

The stale seedbed technique employs a non-selective herbicide such as paraquat or glyphosate to kill emerged weeds before planting onion. In the stale seedbed method, the seedbed is prepared several weeks before planting. Weeds are allowed to emerge and are then killed by the non-selective herbicide.

The crop is then planted at the appropriate time with minimal soil disturbance to prevent stimulation of weed germination. Fumigation can provide substantial weed control but must be applied by trained personnel. Metam sodium is the most commonly used fumigate applied, mostly for seedbed production.

At the full use rate of metam sodium Vapam HL at 75 GPA, other products are available , many broadleaf and grass weeds are effectively controlled while suppressing nutsedge species. However, large seeded weeds with hard seed coats like morningglory are often not controlled. Appropriate soil conditions including no soil clods, moisture at field capacity or slightly wetter and soil free of debris including plant material is absolutely essential for an effective fumigation.

Additionally, the overhead use of irrigation after application can effectively seal the fumigant in the soil for improved control.

The length of time needed for the fumigant to be sealed in the soil varies and one should read and follow restrictions provided on the label of the product used. Fumigation can be expensive and is often only used for seedbed production. Planning Your Herbicide Program : Soil characteristics such as soil organic matter and texture , herbicide capabilities and limitations, herbicide application methods, and expected weed species should all be determined prior to selecting your herbicide program.

Additionally, understanding herbicide carryover from previous crops is critical. Some herbicides used in crops rotated with onion pose a significant threat to onions and these concerns must be addressed prior to planting.

Always read labels for crop rotational restrictions. Mapping : Knowing what weeds will be present in the onion field can greatly increase the potential for successful weed management. This is best accomplished by weed mapping. Survey fields and record on a field map the weed species present and their general population levels at harvest.

Those species present at harvest will most likely be the predominant problem weeds next season. Additionally, by referring to weed maps over a period of years, one can detect shifts in weed populations and make adjustments in herbicide programs to manage these weed shifts as they occur.

Proper weed identification is necessary since weed species respond differently to various herbicides. Monitoring : Fields should be monitored periodically to identify the need for postemergence herbicides. Even after herbicides are applied, monitoring should be continued to evaluate the success of the weed management program and to determine the need for additional control measures.

Herbicides Options In : Preplant applications for dry bulb or green onions include paraquat and glyphosate Table 1. Both of these tools are non-selective herbicides that will kill most problematic weeds prior to planting, assuming weeds are small and applications are timely. Glyphosate will not control resistant pigweed or primrose; thus, a sequential application of glyphosate followed by paraquat may be in order.

Currently the only preemergence herbicide option for seeded onion includes Dacthal Table 1. Dacthal rate should be selected carefully as onion stunting can occur at higher use rates. Additionally, weed control with Dacthal is marginal at best. Postemergence applications for both dry bulb and green bulb onions include Dual Magnum, Outlook, and Poast.

Poast is an excellent tool to control emerged annual grass weeds while Dual Magnum and Outlook will provide residual control of small seeded-broadleaf and grass weeds. Proper application timings for Dual Magnum and Outlook are critical, Table 1. Additional postemergence tools are available for dry bulb onions including Prowl, Goal, Select, and Fusilade DX.

Select and Fusilade DX, similar to Poast, provide excellent control of annual grasses but these two products also provide fair control of perennial grasses such as bermudagrass. Prowl and Goal are the backbone herbicides for all effective dry bulb onion production systems.

Prowl provides residual control of small seeded grass and broadleaf weeds while Goal provides both residual and postemergence control of many of the most problematic weeds infesting onions such as pigweed, primrose, and wild radish.

Seedbed: The most effective program for seedbed production begins with a fumigant application of metam sodium. It is critical that no weeds are emerged at time of planting.

Dacthal is the only PRE emergence herbicide option and should be applied after seeding followed by irrigation for activation.

Dry Bulb Transplant Production : Weed control is transplant onions begins buy transplanting onions into fields free of weeds; tillage, glyphosate or paraquat can all be effective options to achieve this objective.

Irrigation to seal the soil around the root ball after transplanting is critical followed by an application of Prowl plus Goal within 2 days of transplanting. Do not apply Goal with a surfactant, fertilizer, or other chemical. If needed, Dual Magnum or Outlook can be added to the program for additional residual control Table 8.

Dry Bulb Seeded Production : Weed control in seeded onion production is among the most challenging of any crop grown in Georgia. Currently programs often do not provide adequate weed control without the use of fumigation, which is very expensive.

Metam sodium as a preplant fumigant, Dacthal preemergence, and sequential postemergence applications of Prowl, Goal, and Dual Magnum during their appropriate application window offer the best chance for success.

Applications are often need on bi-weekly intervals and often control is not adequate throughout the entire crop season.

Prowl may be applied postemergence to onions, but will only control weeds if activated prior to their germination. Prowl is most effective on annual grasses such as crabgrass, crowfootgrass, and Texas panicum and broadleaf weed species such as common chickweed, pigweeds, Florida pusley, as well as cutleaf evening- primrose suppression.

Apply Prowl to direct-seeded onion in the 2 to 9-leaf stage of growth. Goal controls many annual broadleaf weeds through postemergence and residual activity.

Emerged primrose is often difficult to control with Goal; however, Goal applied prior to primrose emergence is usually very effective.

For Goal to be effective against cutleaf evening primrose the weed should not be any more than 0. in diameter. Bulb quality is the most important factor when producing a marketable product.

To ensure maximum quality,onions should be artificially cured. Artificial curing allows the grower to have better control over the curing process. During years when excessive rains and unfavorable drying conditions occur in the field, artificial curing will be required.

Onions should be harvested at optimum maturity. Maturity is best determined by pinching the neck of the growing onion. Necks of immature onions are stiff, whereas necks of mature onions are soft and limber.

Early varieties are strongly daylength sensitive and thus are more likely to break over at the neck early and uniformly. These onions can be left in the field in this condition for up to a week without detriment under most conditions no heavy rains. In some years this may not occur because the onions have developed a thicker neck.

This is usually associated with mild winter weather. Simply observing the percentage of tops having fallen over is not a true indication of maturity, since the tops can be knocked over by strong winds, rain or become limp from lack of moisture.

Onions should be carefully examined for softness in the neck and large bulb size to indicate time to harvest. Late varieties are highly susceptible to warm weather bacterial diseases and may require harvest before optimum maturity to prevent widespread infection with bacterial diseases.

Onions should be undercut with a rotating bar or fixed blade when mature and necks are soft and limber. The blade or rotating bar should operate at approximately 1 inch below the bulb, so as not to damage their base.

A rope is often dragged across the top of the onions at the same time to roll the onions out of the ground and expose the roots. Every effort should be made to prevent excessive bulb exposure to the sun which will cause the onion to blister therefore onions should be gathered within a few days of undercutting.

If light rain occurs during field drying, the onion beds should be undercut a second time. This will break soil that has been re-attached to the bulb.

After onions have field dried for 3 to 5 days under sunny dry conditions, the roots and tops of the onions should be removed. Tops are cut at approximately 1. Extra short necks increase the likelihood of disease infection. During clipping, care should be taken to prevent injury to the bulbs with the shears and by dropping the bulbs on to hard surfaces such as the bottom of buckets and other onions.

Hand harvested bulbs can be placed into burlap or mesh bags in the field and transported by truck to packing sheds. Another method has them placed in large bin boxes that are moved by forklifts to trucks for transport to packing sheds. Onions should always be carefully handled to avoid external and internal damage, especially when loading onto the hard surface of truck bodies.

Walking and standing on bags of onions should be avoided. The bulbs should be placed in bins or boxes with at least 6 percent vent space. The bins should be immediately placed on a drying system. Remaining roots will shrivel during curing and will be knocked off on the packing line.

Necks should dry during curing and fold over when handled. Research and field demonstrations indicate that sweet onions can be harvested using a mechanical harvester.

Sweet onions are undercut as usual in the hand harvest production system. They are allowed to field dry for 3 to 5 days. The harvester lifts the onions onto an elevator chain and the soil is separated from the onions.

When the onions have reached the top a fan pulls the leaves into a vertical plane and the leaves are cut off.

Tops are deposited onto the ground and bulbs are conveyed into a trailer or bin. The onions are transported to the packing facility and passed through a mechanical topping machine which removes the remainder of the tops left by the harvester. Neck length is approximately 1 to 1.

After leaving the topping machine, the onions are graded for quality and size and placed in mechanical dryers for curing. Storage studies indicate that shelf life is the same for machine harvested and hand harvested mature onions. Onions are cured in order to extend their shelf life.

An onion bulb is a series of concentric swollen leaves still attached to a short stem or base. These are surrounded by scales which are dried leaves.

Curing of onion bulbs serves several functions. First it dries the outer two to four scales providing mechanical protection. It dries those roots remaining attached to the bulb following undercutting and the neck left attached to the crown following topping, deterring disease infection.

Lastly, curing encourages dehydration and the sealing of wounds that may have resulted during bulb growth or mechanical damage.

Onion bulbs consist of a high proportion of water approximately 90 percent and desiccation of the bulbs must be avoided. Moisture is removed from the skin, roots, and stem of onion bulbs by dry air blown over them.

The onion skin dries and becomes uniform in color, exhibiting a brittle texture. The roots shatter or break off easily when touched. The stem area should shrink in size and be dried to the surface of the bulb. It should not slide back and forth when squeezed between the thumb and forefinger.

Once the onion has cured properly, the outer leaf scales will help retain internal moisture and protect the onion during shipment. The curing of sweet onions with forced air involves the following parameters. The air temperature should be maintained between 97 to o F. The less airflow capacity the longer it will take to cure the onions.

Relative humidity should be maintained at approximately 50 to 65 percent. There are two types of artificial curing systems being used: batch and re-circulating forced air. Batch curing is the most common type of curing system, consisting of the heating of outside air and forcing it through a stack of onions with the air exiting to the outside environment.

It is difficult to control humidity with this system because conditions of the outside air vary. To allow air movement away from the onions, an air space of 25 feet above the top bins is required. Re-circulating forced air curing involves recirculating the air within a chamber that passes around the onions.

Stacking the onion bins in two rows to form a tunnel and pulling air through is also called forced air curing. Temperature and relative humidity are much easier to maintain giving the operator more control over the curing process.

Air may either be forced or pulled through the onions. Moisture-saturated air exits the facility by vents and is replaced by incoming, dry air. These calculations are based on minimum 65 o F environmental temperature and 99 o F curing chamber temperature.

Air movement is very important to curing onions. The air must move around the onions and not escape through cracks in between bins or boxes. The fork lift space below bins and handle areas of boxes should be closed off with strips of plastic or canvas to stop airflow through these areas.

When air is being pushed through the containers, a more rigid material like wooden panels should be used. The fan framing should be placed tightly against the containers to eliminate any loss or escape of air Figure Onions are generally cured for hours prior to final grading and packing.

This may vary depending on the condition of the onions. Onions should be sorted and inspected immediately following curing before shipping or storage. If the onions are left unattended for more than one week, they should be inspected again since diseased onions are likely to infect other onions during shipping or storage.

Fresh market onions should be in the hands of the consumer within four weeks of harvest. Onions destined for cold or controlled atmosphere storage should be sampled and analyzed for disease before storage in order to remove infected bulbs.

There is no point in storing onions which are already infected. In some cases onions may be cured solely in the field. Under favorable weather conditions, onions can be left in the field for days after undercutting. Care should be exercised with this process since onions are subject to sun damage if left in the field too long.

Late maturing and late harvested onions can be more prone to late season warm weather bacterial diseases such as sour skin and slippery skin. Care should be exercised not to harvest such onions and they should not be co-mingled with uninfected onions particularly during curing.

The heating process of curing will rapidly spread the bacteria throughout all the onions. The storage method chosen is dictated by the market window being targeted i. fresh blown air, air-conditioned,cold or controlled atmosphere. The method of storage influences the rate of decay, but will not stop it.

Onions going onto the market following the fresh market window may be kept in cold storage, but should be placed into cold storage within one week of being undercut. Any delay encourages disease growth. Two types of damage occur during the handling of onions. Surface injuries are made in the field by cuts, punctures and wounds with snips and fingernails.

Bruising injuries are made by impact shocks or vibration damage in the field or at the packing shed. Surface injuries are obvious, but bruising is more subtle, often not showing up until after the onions leave the shed.

It is important to recognize the significance of bruising as it relates to onion quality and shelf life. Bruising causes superficial cracks in the outer scales of onions, allowing bacteria and mold organisms to penetrate and break down the internal tissues, resulting in decay.

Evidence of poor handling is seen as bacterial soft rot and various mold rots at the terminal or retail markets. Careless topping or cutting of roots leads to surface wounds and decay. Shock damage occurs when bags are thrown onto flatbed trucks and pressure bruising results when workers stand on lower bags to load or remove higher bags.

Bruise damage is most serious at the packing shed, occurring as individual onions move across grading equipment. Product damage can be reduced if equipment is designed and installed properly. Damage also occurs during unloading. Workers characteristically slam burlap bags onto wooden or metal surfaces during onion unloading.

Padding these areas will reduce impact injury which, results in less bruising. Adequate management of weeds in onions is particularly important early in crop growth when weeds compete with the crop for moisture, nutrients, light and space.

Onions have a shallow, non-aggressive, fibrous root system, and weed competition early in the growing season can significantly reduce yield. Weeds can also interfere with chemical sprays and harvest operations and exacerbate the environmental conditions favorable for foliar disease development by decreasing air movement within the canopy.

Weed control in onion fields starts in the fall after harvest of rotational crops and is mainly achieved through a combination of chemical, cultural and mechanical weed control strategies. After crop harvest in the fall, pay close attention to the weed species present in your field. If there are many perennial weeds, then it is the best time to apply glyphosate.

Cultivation can be effective for annual weeds, but it is not appropriate for perennial weeds due to their vegetative re-rooting following disturbance. Planting cover crops in the fall is also a good strategy to manage winter weeds.

Onions are very sensitive to weed competition during the first few weeks of growth. Therefore, preventing new weed germination and killing emerged weeds in the cotyledon stage is critical to achieve successful weed management throughout the growing season.

Herbicides always play an important role for weed management in onions. The label allows three applications at pre-emergence, two-leaf stage, and six- to nine-leaf stage of 2 quarts 1. Under normal conditions, the last application should go on in early to mid-July given the day pre-harvest interval PHI , assuming harvest is around the first week of September.

A delayed pre-emergence application 10 to 20 days after seeding, before onion emergence allows many weeds to emerge, which are then killed with bromoxynil, which is added to the pendimethalin Prowl H2O. The primary weeds early in the season are ladysthumb, common purslane and redroot pigweed.

The delayed pre-emergence pendimethalin plus bromoxynil should be applied just before onions emerge. Emerged onion plants may be killed by bromoxynil. A few loops emerged from the soil surface is the latest safe stage to apply this treatment. In Michigan, GoalTender oxyfluorfen at fluid ounces per acre 0.

Growers may have to sacrifice a few onion plants to follow a herbicide plan of applying GoalTender at the onion one-leaf stage, followed by another pre application and GoalTender at the two-leaf stage.

Onions can lose 10 percent of the intended stand without decreasing yield by producing bigger bulbs. Without good weed control, yield reduction can be much greater than 10 percent, so it normally is most effective to kill the weeds early and completely. If common lambsquarters and ladysthumb are not killed in the cotyledon to one-leaf stage, they may survive all season.

High rates of GoalTender fluid ounces can injure soft onion leaves, especially in wet, cool years. Dual Magnum S-metolachlor and Outlook dimethenamid-P may be applied with Prowl H2O, or alone after the two-leaf stage.

Numerous diseases can affect maangement quantity and quality Mindful eating for athletes onions. While there are many practices Onion field management can ffield reduce onion fied, they are Antifungal foot care products for nail fungus infallible, and several diseases require different treatments. Maagement are, however, certain managgement that Oniion Onion field management employed to ward off most types of ailments. Drip irrigation has been shown to reduce the occurrence of diseases because the water is directly given to plant roots instead of wetting the plant or crop field. Without standing water, many diseases have a harder time infecting onion bulbs. Many diseases thrive in similar conditions. Excessively wet soil, moderate temperatures, and dense crop spacing can all increase the risk of infection from bacteria, fungi, and viruses by insects.