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Organic Insect Control for Commercial Vegetable Production

Blake Layton, Ph.D. Extension Entomology Specialist

One of the greatest challenges for organic vegetable production in the South is successfully managing the large number of weed, disease, and insect pests that affect Southern vegetables. The abundant rainfall, long growing season, and mild winters that are favorable for growing vegetables are also favorable for the pests that attack these crops and reduce yield and quality.

One common misconception about organic vegetable production is that it requires growing crops without using pesticides. Although organic production precludes use of synthetic fertilizers, growers who do not use organic fertilizers will not produce successful crops. Likewise, although synthetic pesticides may not be used in organic vegetable production, there are many approved organic pesticides that can be used to reduce pest numbers and improve yield and quality of organic vegetable crops.

This publication focuses on organic methods of managing weed, disease and insect pests and contains sections devoted to each of these major pest groups. Although there are many practices that are useful in managing more than one group of pests, there are also obvious differences in management of weed, disease, and insect pests. For example, organic weed control relies heavily on various types of mechanical control but there are few organic herbicides; organic disease control relies more on practices such as disease resistant variety selection, crop rotation and sanitation, while organic insect control focuses on use of cultural management practices along with judicious use of organic insecticides.

Organic Management of Insect Pests

Organic insect management in commercial vegetables is a challenging task, especially in the South, but it is not impossible. The key to success is to choose your crops and planting times wisely and to use other non-insecticidal management methods and available organic insecticides appropriate for the crop.

A common misconception about organic vegetable production is that it precludes the use of insecticide sprays. However, there are many organic, OMRI-approved, insecticides that can be used by organic producers to produce higher yielding, better quality crops. Although organic insecticides are generally less effective than their non-organic counterparts, many of these products can be effective when used properly and in a timely manner.

Organic insecticides are useful tools, but they should not be viewed as silver bullets. Rely on organic insecticides as your primary means of insect control and you will spend a lot of time, and money, spraying and may still have disappointing results. Rely on organic insecticides to supplement and enhance a well-planned non-chemical pest management program and you will harvest more and better-quality vegetables.

Non-insecticidal Insect Management Tools

Non-insecticidal insect management tools provide the critical foundation of any insect management program. Following are some of the more important non-insecticidal management tools. These tools are available to both conventional and organic vegetable producers, but they are a much more important for organic growers because it is more difficult to ‘spray your way out of trouble’ in organic production.

Choose crops that have relatively few insect pests. Winter brassica crops tend to be easier to grow organically than many summer vegetables. Sweet corn, for fresh market, is a lot easier to grow organically than tomatoes. This does not mean you can not grow tomatoes organically, but it does take more planning, management, effort, and luck. Sweet corn for commercial canning is a different situation altogether. Because of the extremely low tolerance for caterpillar contamination, it is probably not possible to successfully grow organic sweet corn in Mississippi for commercial canning, especially if transgenic varieties are not considered as an organic option.

Grow crops at a time of year when the insect pests they do have are least abundant. Usually, early planted warm-season crops experience less insect pressure than late planted crops, but this is not always the case. There are some situations where it is helpful to delay planting until overwintered pests have left their overwintering sites and moved to other crops. This is true for bean leaf beetles on beans and peas and for cucumber beetles on melons and squash.

But in most cases, early planted crops experience lower insect pressure. Most vegetable insect pests have several generations per year, with populations increasing each generation. By late-summer and fall, populations of pests like stink bugs, whiteflies, and tomato fruitworms can be extremely high. If you have large acreages of agricultural crops growing nearby that generate large numbers of pests, such as stink bugs, loopers, armyworm, or tomato fruitworms, time planting of susceptible vegetable crops so they will be harvested before agricultural crops mature and insects begin leaving the fields in search of other hosts.  

When possible, choose varieties that are resistant to key pests or to important pest-vectored diseases. Sometimes choosing a variety that is resistant to a particular disease can aid in insect management as well. For example, thrips control is less important on tomatoes resistant to tomato spotted wilt virus than on non-resistant varieties. Of course, there are no resistant varieties for many pests, and varieties that are resistant may not have other traits needed to produce a marketable, profitable crop. Consider the big picture when choosing varieties.

Start with pest-free/disease-free transplants. For crops that are grown from transplants it is especially important to begin with transplants that are free of disease and insect pests, especially small insect pests such as thrips and whiteflies that have the potential to vector serious plant diseases, such as tomato spotted wilt virus or tomato yellow leaf curl virus. Be especially aware of transplants grown in greenhouses where other ornamental crops are grown. Transplants that are grown in greenhouses with good pest exclusion and that are isolated from other crops are more likely to be free of serious pests or disease problems. Check transplants carefully after delivery and use appropriate organic insecticide treatments if necessary.

Practice crop rotation. In some cases, repeatedly growing the same crop in the same field can result in increased insect pressure. Cowpea curculio on southern peas is a good example. This pest overwinters as an adult in crop residue and nearby ground litter and rarely flies. Rotating the pea patch to a different location each year can aid greatly in managing this important pest. Rotating the location of the turnip patch can help reduce numbers of vegetable weevils for similar reasons. Crop rotation is even more important in controlling many diseases. Of course, crop rotation will not reduce problems with highly mobile pests, such as stink bugs and fruitworms.

Avoid growing successive plantings of the same crop near each other, especially if the crop is attacked by serious insect pests that have multiple generations per year. For example, if you grow three successive plantings of organic peas in adjacent plots, each planted two or three weeks apart, there will probably be a lot of stink bugs in that last planting!

Think about where you plant a crop in relation to other crops, including crops on neighboring farms. If you are trying to produce organic tomatoes in late summer or early fall, locate them as far as possible from crops such as corn, sorghum, soybeans or peas that generate large numbers of stink bugs and tomato fruitworms. A tomato patch surrounded by timber or pasture will probably have less stink bug and tomato fruitworm pressure than a patch surrounded by annual row crops.

Avoid growing field crops near greenhouses or high tunnels. Greenhouses and high tunnels often develop moderate to heavy infestations of pests such as whiteflies and thrips, especially toward the end of their cropping cycle. These are also the pests most likely to vector serious diseases. When field crops are grown near greenhouses or high tunnels this greatly increases the potential for serious insect pests and the diseases they vector to spread to the field crops. It is difficult to specify a minimum distance to maintain between these two types of crops, but the closer a field crop is to a greenhouse or high tunnel the greater the potential for problems.

Destroy old crop residue as soon as possible after the final harvest. This is an extremely important insect management tool, especially for organic growers!  It destroys large numbers of immature insect pests before they have a chance to become adults and move to nearby crops; destroys adult insects before they have a chance to lay eggs or enter overwintering sites; removes the crop as a breeding site for future generations of pests; and destroys overwintering pests. Prompt crop destruction also helps with disease and weed control.

Know when to quit on a crop. Because pest populations usually increase as a crop ages, vegetables produced earlier in a crop’s growth cycle are more likely to be blemish free and pest free than vegetables produced later. Depending on the situation, it may be worth growing a crop just to get those few early weeks of production and then terminating the crop when insect pressure becomes too great. Destroy old crop residue promptly.

Plant into weed free fields and maintain good weed control. Mechanical tillage is the main method of weed control in organic production. Fortunately, it also helps control insect pests such as cutworms, false chinch bugs, vegetable weevils, spider mites, slugs, and crickets that often begin developing on weeds growing in the field before planting and then move to seedling vegetables. Avoid these early insect problems by planting into a weed free field. For cutworm control, till the field to destroy all weeds and cover crops at least three weeks before planting. Thorough tilling also helps control other pests that overwinter in the field in the soil or under crop debris and it also helps reduce the number of in-field fire ant mounds.

Know which pests are likely to occur on the crops you are growing and know and understand the biology of these pests. Often you can use your knowledge of a pest’s biology to help manage that pest. Know how to identify insect pests and be able to distinguish between insects that are pests and those that are not. See Extension Publication 2347, Insect Pests of the Home Vegetable Garden, for information on identification and biology of common vegetable pests.

Use trap crops when feasible. Trap crops are crops planted to attract pests away from the main crop. For example, around cabbage, a border planting of collards can be used as a trap crop for diamondback moths. Trap crops can also work for stink bugs, leaffooted bugs, and bean leaf beetles. Plant some southern peas near your tomato patch and most of the stink bugs will go to the peas. Similarly, sunflowers can be used as a trap crop for leaffooted bugs.

But there is an important pitfall to using trap crops: you must kill the pests that are attracted to the trap crop before they move to the main crop. Otherwise, you have a nursery crop!  The problem for organic producers is there are no really effective organic insecticides to control stink bugs and leaffooted bugs. One option may be to use conventional insecticides like Baythroid, ProAxis, or Mustang Max to control insect pests in a trap crop that is not going to the organic market. Depending on the organic production goals for a particular farm, this may or may not present a problem. Potentially, one could use a trap crop of southern peas to help keep stink bug numbers down in your organic tomatoes, spray the peas with an effective non-organic stink bug treatment, and sell organic tomatoes and conventionally grown peas. Of course, this will not work if one’s organic certification program does not allow any non-organic products to be used on the farm.

Use metalized reflective plastic mulches to reduce early season infestations of pests such as thrips, aphids, and whiteflies. Research has shown that reflective mulches can greatly reduce the number of thrips and aphids attracted to seedling crops. The increased light reflectance prevents the insects from recognizing and landing on seedling plants. This is especially helpful in reducing incidence of serious insect vectored diseases, such as tomato spotted wilt virus. In fact, some studies have shown reflective mulches to be more effective in reducing TSWV incidence in tomatoes or peppers, than weekly insecticide sprays. Note that reflective mulches do not provide the same degree of early season soil warming as black mulches, but they do help cool the soil on later crops.

Use physical exclusion methods when feasible. Physical exclusion methods are not available for most crops, but there are some specific situations where they may be useful. One is in the production of seedling transplants. Transplants grown in a ‘bug-tight’ greenhouse, in isolation from other plants, are more likely to be free of insects and insect vectored diseases.

Floating, or hoop-supported spun-bond fabric row covers can be used for early frost protection and/or to help protect against early season pests like cucumber beetles and squash bugs on melons or squash. Row covers are costly and labor intensive to install, but they are an effective way to protect many vegetable crops from early pest infestations. Several companies sell row covers in various weights and sizes.

Home gardeners sometimes protect newly set transplants from cutworms with ‘cutworm collars’, made of wax paper or aluminum foil, that extend about an inch below the soil line and two to three inches above. This is usually too labor intensive for commercial production but may still be worthwhile if you have to plant a relatively small number of plants into a cutworm prone situation (weeds destroyed less than three weeks before planting).

Exclude large insect pests from high tunnels. Growers who use high tunnels as a method of season extension often benefit from reduced disease pressure due to the inherent protection from overhead water. Research has also shown that larger insect pests, such as squash bugs, stink bugs, fruitworms, and armyworms can be effectively excluded by the use of 40 to 50 percent shade cloth on the sides of the high tunnels, and smaller mesh sidewall insect screen can be used to exclude smaller pests, such as cucumber beetles. The addition of these types of screening will affect light penetration, humidity, and air movement and growers using this method will need to make appropriate adjustments to maintain adequate crop growth. Such adjustments may include adjusting how high the shade cloth or screen is installed on the sides and managing the stages or times in the crop production cycle when the screening is used. Of course, such screens will also exclude pollinators, requiring the use of bumblebees, other methods of pollination, or parthenocarpic varieties (varieties that set fruit without being pollinated).

Rely on naturally occurring biological control. This is our most important means of controlling insect pests, and it is much more important to organic growers than to conventional growers. Pest insect populations are normally kept in check by naturally occurring populations of the three Ps: predators, parasites, and pathogens. For any given insect pest, there are usually many species of predators that feed on that pest, several species of parasitic wasps and/or flies that attack it, as well as fungi, bacteria, and/or viruses that cause fatal diseases. Collectively, these naturally occurring beneficial organisms are our most important defense against pest insects. Without this free natural control, the pests would have a huge advantage.

Still, it is normal for there to be more pests than predators and parasites—there are usually more rabbits than foxes. When severe pest outbreaks occur, it is usually because the pest population has gotten ahead of the beneficials. The beneficials may eventually catch up and bring the pest population under control, but this does not always happen in time to prevent excessive crop damage, and this is when organic insecticides can help improve both crop quality and yield.

What can you do to take advantage of this free natural insect control?  The main thing is to try to avoid messing it up!  Insecticide applications, even with organic insecticides, kill more than just the target pests; they also kill beneficial insect predators and parasites. This can trigger outbreaks of other pests or allow the population of the target pest to rebound to even higher levels. Don’t spray unless you are sure you really need to spray.

On the other hand, don’t let concern over preserving beneficials prevent you from spraying when you really need to. When you do have to spray, try to choose an insecticide that works well on the target pest but has minimal impact on beneficial insects. Organic growers usually benefit much more from biological control than conventional growers because organic insecticides tend to be less detrimental to beneficial insect populations.

Growing a diversity of plants, especially plants with large numbers of blooms, can also promote beneficial insects. Many adult predators and parasites rely on nectar from blooming plants as food. Some organic producers maintain ‘nursery strips’, planted with a variety of non-crop plants that bloom at various times, to provide habitat and nectar sources for beneficial insects. Just be sure to avoid using plants that are a host to a major pest of one of the crops you are growing.

What about buying and releasing beneficial insects into a crop?  This is usually not effective for field crops. Artificial releases of laboratory reared parasites and predators can work quite well in enclosed greenhouse situations where the environment is carefully controlled, but such releases are usually not successful in annual outdoor crops. The released insects either, fly away, die because they are not adapted to the environment, or fail to find suitable hosts because the timing is wrong.

This does not mean there are no situations where artificial releases of predators and/or parasites will work outdoors. There are special cases where such releases can be helpful. For example, predatory Phytoseiulus persimilis mites can be used to control spider mites in strawberries and other crops. When used properly, applications of these predatory mites can be as or more effective than miticide sprays. Success with artificial releases in outdoor annual crops requires knowing exactly which pest(s) you are trying to control; which specific beneficial insects you need to release; when and how to make the releases, and where to purchase healthy, vigorous beneficial insects.       

Educate your market. Organically produced vegetables usually cost more to produce and have more insect blemishes and infestations than conventionally produced vegetables. Consumers who purchase organic vegetables usually understand this, but it is still wise to be sure the customer understands what they are buying. “This is organic sweet corn. Most ears are probably going to have some caterpillar damage, or even live caterpillars, at the end of the ear.”  “I can supply organic tomatoes, but they are more expensive to produce, and they may have superficial insect damage on some fruit.”  

Grow healthy, vigorous plants. Of course, this is the goal of every farmer and gardener, but it is nice to know it also helps with insect control. Healthy plants are less susceptible to insect attack and better able to tolerate low to moderate insect infestations and still produce. For example, drought stressed plants, and plants suffering from potassium deficiency are more susceptible to spider mites. On the other hand, excessive nitrogen can make plants more susceptible to spider mites and aphids.

Monitor pest populations. Good scouting can help assess effectiveness of non-insecticide management tactics and better time insecticide treatments. Scout crops at least once or twice weekly by making a special trip through the crop specifically to check for insects and diseases. This allows you to know what pests are present and how abundant they are. Use a hand lens to check for small pests like thrips and spider mites. Use pheromone traps and other survey tools as appropriate for the pests you need to monitor. Yellow sticky traps can help monitor pests like thrips and whiteflies in high tunnels. Pheromone traps are available for moths of many caterpillar pests, and a few other types of pests.

Use mating disruption when available and appropriate. The goal of mating disruption is to confuse male moths and reduce their ability to find mates by flooding the field with synthetic pheromone. This results in many of the female moths laying unfertilized eggs. Mating disruption pheromones are species specific and are available for only a few vegetable insect pests. CheckMate TPW and CheckMate DBM-F are commercially available products that work against tomato pinworm and diamondback moth, respectively. Note that while the TPW lure is OMRI approved, the DBM-F, which is applied as a spray, is not.

Use mechanical controls where feasible. Some organic growers use specially designed vacuums or blowers to remove insects from plants. A forceful spray of water can be used to dislodge pests such as aphids. Though too labor intensive for large scale use, hand picking insects and egg masses can help delay pest population build up on small plantings.

Use organic insecticides when necessary. Sometimes you have to use insecticides to avoid excessive crop damage. Scout regularly and begin treating before pests reach damaging levels. Choose approved organic insecticides that are effective against the pest(s) you are trying to control. Use rates that are adequate, but not excessive. Apply sprays in a manner that achieves thorough coverage, especially to undersides of leaves. Target treatments against the most susceptible pest stage, for example, when treating caterpillar pests, target small, newly hatched caterpillars. Retreat at appropriate intervals when necessary to obtain and/or maintain control. Be sure to note and comply with the pre-harvest interval for the specific insecticide and crop.

Be aware of the limitations of organic insecticides. Organic insecticides vary greatly in relative efficacy against various pests. Spinosad and Bts are effective against most caterpillar pests, provided they are applied when caterpillars are small, but they don’t work well on stink bugs and most beetles.  If good spray coverage is achieved, products like azadirachtin, botanical and horticultural oils, and insecticidal soaps can be used effectively against aphids and whiteflies. There are no highly effective organic insecticides for stink bugs and most beetles (though spinosad works well against yellowmargined leaf beetles and Colorado potato beetles), but products like pyrethrins and azadirachtin + pyrethrins and even spinosad can provide some reduction in stink bug populations and fruit injury, especially when applied repeatedly.

Use Integrated Pest Management. Don’t just rely on a single control tactic to control any pest. The more different methods you use the greater your chances for success. Also consider all pests likely to occur in your crop, insects, disease, and weeds, and develop a pest management plan that addresses all of these.

Keep records, keep learning, and use what you learn in the next crop. Every crop, every year, and every farm situation is different. By keeping records, you can learn which pests are problems on your farm and at what time of year they are most abundant. You can also learn which pests are least likely to cause problems and what management tactics work best for you.

Use Organic Insecticides Effectively

Many times, organic vegetable producers are slow to spray—until the insect problem has gotten out of hand, and then it is too late!  Just as with insect control in conventional production, the key to successful insect control in organic crops is to plan ahead and be prepared to spray in a timely and effective manner. Be aware of the pests that are likely to attack the crops you plan to grow and of the organic insecticides available for their control. Have these insecticides on hand, have the equipment necessary to apply products effectively, and be ready to treat in a timely manner. Although organic insecticides tend to be less effective than conventional insecticides, proper and timely use of organic insecticides can provide increased harvest and better-quality vegetables, resulting in increased profits for organic farmers.

Little bugs are easier to kill than big bugs, and controlling insect pests when they are small prevents much of the damage they would otherwise cause. Knowing the crop, the pests that are most likely to attack that crop, and having a realistic plan for how to control those pests is critical. For example, fruitworms and stink bugs are the most important pests of tomatoes. Fruitworms, as well as hornworms, can be effectively controlled using spinosad and/or Bt products. Stink bugs are more challenging, but their numbers and damage can be significantly reduced, but not completely controlled, with timely, repeated sprays of pyrethrin + azadirachtin (Azera is one example) or even pyrethrin alone.

Likewise, caterpillars (a complex of several species) are the most important pests of brassica crops, such as broccoli, bok choy and turnips, and these can be effectively controlled by timely sprays of spinosad and Bt products. Yellow-margined leaf beetle, which is also a problem on some brassica crops, is also controlled by spinosad. Similar relatively simple management programs can be developed for other crops. Organic insecticide management programs rarely give 100% control and are generally much less effective than conventional insecticides (think 50 to 60 percent control vs 90%+ control), but when effectively implemented (with timely sprays, adequate rates, tight spray intervals, and excellent spray coverage), they can greatly reduce insect populations and the damage they cause, resulting in more and higher quality organic produce.

Organic Insecticides for Commercial Vegetable Production

Following is a listing and brief review of many of the insecticides currently approved for organic vegetable production. Note that some of these active ingredients are also sold as formulations that are not approved for organic production. For example, Spintor is a liquid formulation of spinosad that is used in commercial vegetable production, but Spintor contains inert ingredients that are not organic. Entrust also contains spinosad but Entrust SC is specially labeled for organic production.

Also note some of these products are extremely target specific. Spod-X is only active against beet armyworms!  Other products, such as Pyganic, have activity against a wide range of insect pests, but only provide very short-term control and are generally much less effective than conventional inorganic insecticides. Consequently, sprays may need to be applied more frequently than with conventional insecticides. Because most organic insect control products only work by direct contact, obtaining good spray coverage is especially important when using organic insecticides. Neemix and Aza-Direct are effective against whiteflies and vegetable oils, like Vegol, and soaps, like M-pede, will control spider mites, aphids, and other soft-bodied insects but these products only work on pests they contact.

Always read the product label at least twice, once before you buy it and again just before you use it. Be sure the product is suitable for your organic production goals. Follow label directions.

Spinosad:  Spinosad is a biopesticide that is very effective against most caterpillar pests, as well as thrips and leaf miners. It also works well against Colorado potato beetle and yellowmargined leaf beetle, though potato beetles can become resistant if spinosad is overused, and is one of the most effective organic options for grasshopper control. This product is produced through commercial culture of a soil-born microbe that produces the toxic metabolites known as spinosad. These metabolites are harvested and formulated into insecticide, so the final product contains no living microbes. Entrust SC is an organic formulation of spinosad formulated for commercial use. Spinosad is an especially useful tool for organic vegetable production; it is considerably more effective against caterpillar pests than Bt products.

Although not typically thought of as a “bug spray,” spinosad has limited activity against “bug pests” such as stink bugs, squash bugs, and harlequin bugs. Control may only be in the range of 30 to 60%, but this is worth being aware of when treating for other pests and can potentially help increase crop yield and quality.

Bts: ‘Bt’ stands for Bacillus thuringienisis. Bts are naturally occurring soil bacteria that produce toxins that have insecticidal activity. There are many different strains of Bts. Some only control caterpillar pests (Bt kurstaki and Bt aizawai), while others only work on mosquito larvae (Bt israelensis) or beetles (Bt tenebrionis). Bts are generally slow-acting and must be eaten by the caterpillar to work, but they are useful organic insecticides when used properly. Javelin, Dipel, Crymax, and Agree are examples of Bt products used in commercial organic vegetable production. Because of their relatively slow activity, Bts are best used when caterpillars are small and applied as repeated sprays.

Transgenic Bt Crops:  Some varieties of sweet corn have been genetically engineered to produce toxins found in some of the Bacillus thruingienisis bacteria used to control caterpillar pests. These transgenic crops inherently provide significant control of caterpillar pests such as corn earworm and European corn borer, but they do not provide 100% control. Be aware that, although they are organic, transgenic crops are not approved for certified organic production. Use transgenic varieties only if you are sure they are acceptable for your market!   

Azadirachtin:  Azadirachtin is a natural insect growth disruptor derived from the seed of the neem tree. It is especially effective against sucking insect pests, such as whiteflies and aphids, but because it is a growth disruptor, it is slow-acting and must be applied when low populations of immature pests are present. Neemix, AzaGuard, AzaDirect, and Azatin O are examples of azadirachtin products labeled for commercial organic vegetable production. Azadirachtin is one of the better options for organic control of whiteflies.

Neem Oil:  Neem oil, obtained from the seed of the neem tree, controls soft-bodied insects, such as aphids, whiteflies and mites, as well as helping control certain fungal diseases. Products containing “clarified hydrophobic extract of neem” do not contain azadirachtin; they usually contain 70% neem oil.   Trilogy 70% Neem Oil is marketed for commercial organic vegetable production, and Monterey 70% Neem Oil is sold for small scale production.

Beauvaria bassianaBeauvaria bassiana is a fungal disease that infects certain insect pests, especially whiteflies, thrips, aphids, mealybugs, and certain beetles and caterpillars. It is marketed for organic crop production under the brand names Mycotrol, BotaniGard, BioCeres, and Naturalis. These products are slow-acting; begin treating when pest populations are low. Do not tank mix with fungicides. Also be aware of the humidity requirements for successful use of Beauvaria.

Viruses: Virus diseases of insects are very specific as to which species they attack. A few insect viruses are formulated and sold commercially. Spod-X LC is a sprayable formulation containing polyhedra of a viral disease that only attacks beet armyworms. Heligen, Hearken and Gemstar LC are similar products that only control corn earworm/tomato fruitworm and tobacco budworm. Proper pest identification and spray timing are critical when using these products.

Parasitic Nematodes:  Some nematodes only attack insects and some of these entomopathogenic species of nematodes are formulated and marketed for use in organic crop protection. There are several species, but most are in the genus Heterorhabditis or Steinernema. Parasitic nematodes are usually used to control soil-dwelling pests, such as cutworms, squash vine borer, mole crickets, and white grubs. Do your homework before purchasing parasitic nematodes. Be sure that the species you purchase is active on the pest you need to control and be sure you know how to handle and apply the nematodes properly.

Pyrethrin: Pyrethrin, also known as pyrethrum, is a natural extract from the flowers of the pyrethrum daisy. Pyrethrin is a broad-spectrum insecticide that affects most insect pests through contact activity. However, it is short-lived and many pests may be ‘knocked down’ only to recover later. Pyganic and EverGreen Pyrethrum Concentrate are examples. Pyrethrin can be used to control a wide range of insect pests, but repeated treatments may be necessary because it only provides very short-term control.

Inorganic synergists, such as pipronyl butoxide (PBO), are often mixed with pyrethrin to enhance activity. Although the addition of PBO greatly enhances short-term control, it does not greatly increase residual control. Pyrethrin products that contain the inorganic synergist PBO cannot be considered organic.

Pyrethrin + Azadirachtin:  Some companies market premixes of natural pyrethrins and azadirachtin. This is one of the more effective organic options for broad spectrum insect control, and organic stink bug control (though control may only be in the 60% range). Azera and Azera Gardening are two examples. Both contain 1.2% azadirachtin + 1.4% pyrethrins. Of course, growers can achieve the same result using a tank mix of azadirachtin and natural pyrethrins.

Burkholderia spp.:  This is a relatively new bacterial insecticide sold under the trade name Venerate. It works by breaking down the exoskeletons of insects and interfering with moulting. Venerate has activity against aphids, whiteflies, thrips, mites and other pests. Level of control is variable, depending the pest and situation.

Chromobacterium subtsugae:  This is another bacterial insecticide that is applied as a foliar spray. It is sold under the trade name, Grandevo.

Isaria fumosorosea Apopka Strain 97: This is an entomopathogenic fungus that is useful against whiteflies, aphids and a variety of other small leaf-feeding pests, as well as several soil-born insects. Ancora and PRF 97 are two examples. This product requires high humidity (80% or greater) to be most effective, consequently it is more useful in greenhouses or other high humidity environments.

Plant Extract Products:  Several companies market, or are developing, products based on extracts from various plants for insect control   Quite a few companies market ‘garlic spray’ products that have pest repellent properties. Garlic Barrier is one example. Be aware that such products may not be approved for certified organic production. Cinnamite is a commercial miticide based on extracts from cinnamon oil. It is not currently OMRI approved and can be phytotoxic to tomatoes and certain other plants.

Iron Phosphate: Several companies make slug baits that contain iron phosphate and are approved for organic production. Sluggo is an example of an iron phosphate slug bait. This product is only useful to control snails and slugs.

Horticultural oils:  Petroleum based horticultural oils are useful for control of soft-bodied pests, such as aphids, spider mites, and whiteflies. However, most petroleum based horticultural oils are not approved for organic production. Although the oils themselves are classified as organic, many of the secondary ingredients added as emulsifiers are inorganic. Only a few companies formulate petroleum oils using organic emulsifiers. Suffoil-X, TriTek, and Organic JMS Stylet-oil are examples. Stylet oil is most often used to help prevent sucking insect like aphids from transmitting certain virus diseases. Stylet oil does not necessarily kill insects; instead, it forms a fine coat on the leaf and cleans the virus particles off the insects mouthparts as they feed, preventing them from getting into the plant.

Mineral oil, as well as some vegetable oils, either alone or mixed with insecticides such as spinosad or Bts, can be applied to tips of sweet corn ears after silks have turned brown (after pollination), to control earworms. Be sure to review specific details about this method before using.

Vegetable Oils and Fish Oils:  There are a number of organic oils made from various plant seed or fish extracts. These are effective against soft-bodied insects, such as aphids, mites, and whiteflies. Golden Pest Spray Oil is an example of an oil derived from soybeans. Vegol Crop Oil is derived from plant oils and Organocide is a combination of fish oil and sesame oil. Such oils may, or may not be, approved for certified organic production. Some products contain a combination of vegetable oil + pyrethrin. Pyola, a combination of canola oil and pyrethrins, is one example.

Insecticidal Soaps:  Insecticidal soaps are potassium salts of fatty acids. They are useful for control of soft-bodied insects such as aphids, spider mites, and whiteflies, but require direct contact to work. Be sure to read and follow label use directions; insecticidal soaps can cause foliage injury. Be aware that chain length has a big effect on the phytotoxicity of fatty acids. Some short-chain fatty acids are actually used as herbicides. This is one reason it is not a good idea to use commercial soaps as insecticides. Another good reason is that they are not labeled for use as insecticides. If you want to use soaps to control insect pests, stick with labeled insecticidal soaps. M-Pede and Safer Insect Killing Soap Concentrate are two examples.

Sulfur: Elemental sulfur has long been used for control of spider mites and certain plant diseases and is approved for organic production. Organic gardeners primarily use microfine sulfur dust formulated for application as a liquid spray. Sulfur can cause skin and eye irritation and can cause plant injury if improperly used, especially if applied in combination with oils, or if applied within several weeks of an oil treatment. Acoidal, Microthio 80WDG, and Yellow Jacket Wettable Sulfur II are examples.

Kaolin Clay: Finely ground kaolin clay is sometimes applied to crops to help reduce heat stress or prevent sunburn on fruit of crops like tomatoes and peppers. It is applied as a foliar spray at relatively high rates, around 25 lbs per acre, and dries to form a fine coating of clay particles that reflect sunlight. This coating of clay also helps suppress feeding by certain insect pests, such as cucumber beetles, flea beetles, thrips, and grasshoppers. Surround WP is one example of a commercially available product (95% kaolin clay) that is OMRI approved.

Organic Management and Control Options for Common Vegetable Insects and Mites

Pest

Management and Control Options

Aphids

  • Use reflective mulch.
  • Consider resistant varieties if available, or varieties resistant to important aphid vectored viruses.
  • Use strong water spray to wash aphids from plants.
  • Use stylet oil, where appropriate, to help reduce virus transmission.
  • Destroy crop residue promptly after final harvest. Especially helpful with root aphids.
  • Foliar Sprays: Azadirachtin, neem oil, oil sprays, insecticidal soaps,

Whiteflies

  • Grow transplants in isolation from other plants.
  • Use reflective mulch
  • Avoid growing crops susceptible to whitefly borne diseases near greenhouses or nurseries
  • Destroy crop residue promptly after final harvest.
  • Foliar Sprays: azadirachtin, Beauvaria bassiana, neem oil, insecticidal soaps

Thrips

  • Grow tomato varieties resistant to tomato spotted wilt virus.
  • Use reflective mulch.
  • Promptly remove tomato spotted wilt virus infected plants.
  • Avoid mowing or tilling field borders and adjacent fallow fields after transplants are set.
  • Foliar Sprays:  Spinosad, Azera, azadirachtin, neem oil, insecticidal soaps, pyrethrins

Spider mites

  • Plant into a weed free field.
  • Avoid mowing field borders after mid-summer, or during drought.
  • Avoid potassium deficiency, drought stress, or excessive nitrogen.
  • Avoid water stress.
  • Mist leaves with water spray to encourage outbreak of natural fungal disease.
  • Foliar Sprays: neem oil, oil sprays, insecticidal soaps, sulfur.

Cutworms

  • Have field tilled and free of all weeds and cover crops at least three weeks before planting.
  • Use ‘cutworm collars’ when planting small numbers of transplants into cutworm prone situations.
  • Foliar Sprays: Spinosad

Seed corn maggots

Root maggots

  • Work manure or other organic fertilizers into the soil in previous fall, or well before planting.
  • Till field at least four weeks before planting to allow weeds and cover crops time to decompose.

Mole crickets

  • Preventive treatment with parasitic nematodes, Steinernema scapterisci. (These are difficult to find)

Leaf miners

  • Use floating row covers where appropriate.
  • Foliar Sprays: Spinosad, neem oil

Bean leaf beetle

  • Plant crop after beetles have left overwintering sites and moved to other crops, like soybeans.
  • Grow varieties with resistance/tolerance to key beetle vectored virus diseases.
  • Foliar Sprays: Azera, Pyrethrins

Flea beetles

  • Maintain good weed control. Many weeds, especially solanaceous weeds, are hosts to flea beetles.
  • Destroy crop residue promptly following harvest.
  • Grow insect resistant sweetpotato varieties.
  • Insect-parasitic nematodes can help control larvae in soil.
  • Foliar Sprays: Spinosad, Azera, pyrethrins

Colorado Potato Beetles

  • Avoid planting Irish potatoes following another solanaceous crop.
  • Mulching with straw can help reduce populations.
  • Destroy crop residue promptly following harvest.
  • Foliar Sprays: Spinosad (target larvae), spinosad is highly effective against potato beetles

Blister beetles

  • These insects often occur in clusters. Dislodge from plants and crush.
  • Foliar Sprays: Azera, pyrethrins

Cucumber beetles

  • Avoid early planting to avoid the heavy early flush of overwintered beetles.
  • Use floating or hoop-supported row covers to protect young plants. (helps reduce bacterial wilt infection)
  • Foliar Sprays: Azera, Pyrethrins, spinosad

Cowpea Curculio

(southern peas)

  • Rotate planting location-at least several hundred yards from previous pea/bean field.
  • Avoid planting successive crops near earlier crops.
  • Destroy crop residue promptly after final picking.
  • Foliar Sprays: Pyrethrins, Azera

Vegetable Weevil

(turnips & greens)

  • Rotate planting location
  • Avoid locating successive susceptible crops near earlier host crops.
  • Destroy crop residue promptly after final harvest.
  • Foliar Sprays: Azera, Pyrethrins

Sweet potato Weevil

  • Plant only certified weevil-free slips.
  • Do not transport sweet potatoes from weevil infested areas to non-infested areas.
  • Destroy crop residue promptly after harvest.
  • Avoid storing potatoes through the winter, especially in weevil-infested areas of state.

Harlequin Bug

  • Plant mustard as a trap to protect less favored hosts but destroy the trap before bugs move to main crop.
  • Destroy crop debris promptly after harvest.
  • Foliar Sprays: Azera, pyrethrins, insecticidal soap

Wireworms

Whitegrubs

  • Till field deeply in the previous fall.
  • Avoid planting recently tilled pastures or fallow fields.
  • Grow insect resistant sweet potato varieties.

Squash Bug

  • Use floating or hoop-supported row covers to delay infestations.
  • Destroy crop residue promptly after harvest.
  • Foliar Sprays: Azera, pyrethrins

Stink Bugs

Leaffooted Bugs

  • Grow early crops. Stink bug populations are highest from mid-summer through fall.
  • Avoid growing successive crops near earlier crops.
  • Time vegetable crops to be finished before nearby agricultural crops mature.
  • Destroy crop residue promptly after final harvest.
  • Foliar Sprays: Azera, Pyrethrins

Tomato Fruitworm

Corn earworm

  • Grow an early crop. Fruitworm numbers are highest from mid-summer through fall.
  • Foliar Sprays: Spinosad, Bt products, Gem Star (NPV virus) in tomatoes and similar crops.
  • Grow corn varieties with long, tight-fitting shucks
  • Repeated, close-interval sprays of spinosad to silks of developing corn to reduce percent infested ears.

Tobacco hornworm

  • Foliar Sprays: Spinosad, Bt products (hornworms are rarely a problem if fruitworms are well controlled.)

Armyworms

  • Grow early crops. Populations increase as season progresses.
  • Control weeds, especially pig weeds/amaranth
  • Foliar Sprays: Spinosad, Bts, Spod-X (for beet armyworms only)

Loopers

Diamondback Moth

  • Use trap crop of collards to reduce diamondback moth infestation on cabbage and other cole crops.
  • Use mating disruption pheromone (for diamondback moth only)
  • Foliar Sprays: Spinosad, Bts (Spinosad works well on caterpillar pests.)

Squash vine borer

  • Grow resistant varieties when feasible.
  • Destroy crop residue promptly following last picking.
  • Foliar Sprays: Spinosad (must control newly hatched larvae before they bore into plant)

Pickleworm,

Melonworm

  • Grow early crops. Populations are much higher in late season.
  • Foliar Sprays: Spinosad, Bts

Slugs

  • Till weeds and old crop residue before planting.
  • Iron Phosphate slug bait.

Fire Ant

  • Tillage helps reduce number of fire ant mounds in field.
  • Use granular fire ant baits containing Spinosad. (sold in small quantities, large quantities difficult to find.)
  • If compatible with marketing and production objectives, apply non-organic granular fire ant bait around field borders, but not around crop.

 

 

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