Cucumber Beetles: Organic and Biorational IPM

Abstract

Cucumber beetles are present throughout the U.S. and are one of the most serious pests on cucurbits in many areas. The overwintering adult insect causes feeding damage on young, emerging plants; larvae maturing in the soil feed on plant roots; and the adults that arise from these larvae feed on plant leaves, blossoms, and fruit. Organic control measures include delayed planting and use of trap crops, parasitic organisms, and botanical pesticides. Pesticide applications should be based on monitoring and conducted during daytime hours on dry days when these insects are most active. This publication includes lists of further resources, websites, and suppliers of crop protection materials.

Table of Contents

• Introduction
• Species of Cucumber Beetles
• Life Cycle of the Cucumber Beetle
• Damage to Plants by Cucumber Beetles
• Organic Control Measures
• Chemical Control Methods
• Further Resources
• References

Introduction

Cucumber beetles are pests of cucurbits in most areas of the U.S. Some species in the western US also feed on the leaves of corn, various vegetables, and other soft fruits. (1) Besides damaging plants by feeding on roots, stems, leaves, and fruits, these insects also transmit bacterial wilt and squash mosaic virus.

Organic control measures include delayed planting, use of floating row covers, trap crops, predatory organisms, and botanical or biorational insecticides. Chemical insecticides that contain feeding stimulants with a small amount of carbaryl (Sevin ™ is a common commercial formulation) can control cucumber beetles while protecting pollinators and other non-pest insect species. This publication will focus on organic and biorational control methods that fit into an IPM (integrated pest management) approach.

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Species of Cucumber Beetles

Correctly identifying the pest infesting your crop is the first step toward choosing and practicing effective control. Several species of cucumber beetles exist in the US, each with a specific range, feeding habit, and ability to transmit diseases.

Western striped cucumber beetle. (47)

Adult striped cucumber beetles are about ¼ inch long and yellow-green, with 3 distinct black stripes that extend from the head to the tip of the abdomen. The larvae are creamy white with a dark head and tail. (2) The eastern striped cucumber beetle (Acalymma vittatum) is found mostly east of the Mississippi River while the western striped cucumber beetle (Acalymma trivittatum) is found mostly west of the Mississippi.

Spotted cucumber beetle. ©Scott Camazine

Spotted cucumber beetles (Diabrotica undecimpuctata howardi), are about ¼ inch long, yellow-green, with 12 black spots on their wings. The larvae (similar in appearance to the striped cucumber beetles) are called southern corn rootworms, though their range is throughout the U.S.

Western spotted cucumber beetle. (48)

The western spotted cucumber beetle (Diabrotica undecimpunctata undecimpunctata) is about 0.36 inches long and is greenish yellow with black spots. It is found only in Arizona, California, Colorado, and Oregon. It is more abundant and destructive in the southern part of its range. (3)

Banded cucumber beetle. (49)

The banded cucumber beetle (Diabrotica balteata) is found primarily in southern California. (4) It is about 0.2 inches in length, greenish yellow, with a red head and black thorax. It also has three greenish blue bands running horizontally across its back and a thin green band running down the center of its back.

Western corn rootworm (adult). (50)

When identifying beetle pests in your field, be aware that western corn rootworms (Diabroctica virgifera) are very abundant in crops of the squash family, especially after corn pollen shed, and the adult stage looks similar to striped cucumber beetles. However, corn rootworms do not cause much damage to cucurbit crops. Instead, this insect is a pest of corn and its larvae can only survive on corn roots. Note that the striped cucumber beetle’s center stripe extends to the tip of the abdomen or underbelly while the corn rootworm’s does not. Also, corn rootworms have yellow abdomens, whereas striped cucumber beetles have black abdomens. (5)

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Life Cycle of the Cucumber Beetle

Understanding the life cycle of an insect pest is critical in using control measures effectively. Organic and biorational IPM pest-control strategies require knowledge of the pest’s life cycle to:

• Adjust planting times so that plants are not in a susceptible growth stage when the pest is most active
  
  
• Distract insects from susceptible crops by using pheromones or trap crops
  
  
• Disrupt the pest’s ability to reproduce or grow

Application of either certified organic or chemical pesticides is most effective and least costly when based on knowledge of:

• The pest’s life cycle
  
  
• The life stage(s) of the pest that will damage the crop plant
  
  
• The life stage(s) of the crop plant when it is most susceptible
  
  
• The life stage of the pest that is easiest to control
  
  
• Local climate and ecological conditions, and how they affect plant growth and insect movement

Temperature and the length of the growing season affect the life cycle of cucumber beetles. In the Midwest and northern states, striped cucumber beetles overwinter as adults in protected areas under dense grass, near buildings, in fence rows, and in woodlots. They become active early in the spring when temperatures begin to go above 50°F. (6) Spotted cucumber beetles do not overwinter in northern areas but migrate in from southern states each year, arriving around June. (5) In the southern states, spotted cucumber beetles emerge two to four weeks after the striped cucumber beetle.

Adults feed on the blossoms of as many as 200 alternate host species, including hawthorns and dandelions, until cucumber, squash, or melon seedlings emerge or transplants are set out in fields. The cucumber beetles then migrate to the cucurbits and feed for a few days on the young seedlings. After mating, the female lays (oviposits) between 200 and 1,200 eggs in the soil near the base of plants. Since the eggs’ survival depends on relatively high soil moisture during the first 24 to 72 hours (7), the females prefer to oviposit in moist soils. (8)

Slender white larvae hatch from the eggs in seven to ten days and feed on the root system of the host plant for three to six weeks. They then pupate in the soil for two weeks. Adult cucumber beetles emerge around midsummer.

Because adult cucumber beetles are strong fliers and can be carried long distances – up to 500 miles in 3 or 4 days – by high-altitude air currents (3), they can disperse rapidly and travel readily from field to field during the summer.

The number of generations an insect pest is able to produce each year greatly affects the damage it is able to cause. In the northern states such as Minnesota (9) and Iowa (10), striped cucumber beetles produce only one generation per year, while spotted cucumber beetles do not survive cold winters and only affect crops after they migrate in from their breeding areas in southern states. In the southern US and in California, cucumber beetles are able to overwinter and complete each life cycle in six to nine weeks. Thus, they can produce two or three generations per year. (3, 11)

Variations in climatic conditions from year to year can affect population densities and the amount of damage caused by cucumber beetles, especially in northern states. For example, in Minnesota, cucumber beetles cause severe bacterial wilt problems about one out of every five years. (9) Population counts conducted in southeastern Indiana showed a high population spike in 1992 and low populations in both 1991 and 1993. (5)

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Damage to Plants by Cucumber Beetles

Cucumber beetles infect plants with bacterial wilt, which causes them to die. Larval feeding on roots and adult feeding on aboveground plant parts affect the growth and marketability of cucurbits and other crops. Cucumber beetles also transmit viral diseases, including the squash mosaic virus and various bean viruses. The type of damage and the plant species affected depend on the species of cucumber beetle (see Table 1).

Feeding damage

Cucumber beetles can inflict feeding damage at three times during their life cycle: (10)

• Overwintering adults feed on emerging plants in spring. These adults can kill or severely stunt young plants by feeding on stems and cotyledons. Adults from the overwintering generation are also responsible for the spread of bacterial wilt.
  
  
• Larvae from eggs laid by overwintering adults feed primarily on plant roots. Larval feeding can stunt plants, but is generally not a serious problem if moisture is sufficient to allow the remaining plant roots to take up water and nutrients while the root system regrows.
  
  
• Adults emerging or migrating into the area at midseason feed on foliage, flowers, stems, and fruit. These adults usually cause minimal damage unless they feed on the rind of developing fruit. This feeding scars the rind, decreasing marketability and storage life. (10) Adult western striped cucumber beetles tend to avoid heat and feed mainly on the underside of young melons. They prefer feeding on runners, plant crowns, and young fruit. (11)

Feeding damage by cucumber beetles differs among cucurbit species. The approximate order of susceptibility to feeding damage, from greatest to least, is:

1. cucumber
2. cantaloupe
3. honeydew
4. casaba melon
5. winter squash
6. pumpkins
7. summer squash
8. watermelon

Also, some varieties of a cucurbit species are more attractive to cucumber beetles than others. For example, muskmelon varieties differ in their susceptibility to cucumber beetle feeding in the following order, from most to least susceptible: (5)

1. Makdimon
2. Rocky Sweet
3. Cordele
4. Legend
5. Caravelle
6. Galia
7. Pulsar
8. Passport
9. Super Star
10. Rising Star

Bacterial wilt

In addition to directly feeding on plants, cucumber beetles are vectors for bacterial wilt (caused by the bacterium Erwinia tracheilphila). While foliage-feeding adult cucumber beetles can injure the crop, especially seedlings, the transmission of bacterial wilt disease is even more serious because bacterial wilt will kill the plant. Striped cucumber beetles and spotted cucumber beetles are the most common carriers of this disease. The western spotted cucumber beetle, the banded cucumber beetle, grasshoppers, and other insects that cause leaf wounds can also transmit this disease. (12)

Bacterial Wilt. (51)

The method by which this bacterium survives the winter remains uncertain. However, recent research indicates that instead of overwintering in the body of the beetle, it overwinters in the sap of various alternate host plants, which curiously do not show symptoms of the disease. (9, 12) Adult cucumber beetles feed on these alternative host crops, become infected with bacterial wilt, then transmit the disease to squash, melons, or cucumbers either by feeding on the crop plants or by depositing their feces on wounded leaves or stems. In Pennsylvania, large numbers of adult cucumber beetles migrate into the state in the spring and up to 10 percent of these beetles have tested positive for carrying the pathogen that causes bacterial wilt (13) although the carrying capacity can go up to 70 percent in some cases. (14) Feeding transmission occurs predominantly on dry days when beetles are actively moving from plant to plant. Feces transmission into wounds – the more common means of disease transmission (14) – occurs when dry conditions, which favor insect movement, are followed by moist conditions, which allow for bacteria found in the feces to swim into plant wounds. (12, 15).

After transmission, disease organisms spread throughout the vascular system of the plant. Growth of the bacterium causes blockage of the plant vessels, impeding the movement of water and nutrients, resulting in wilt symptoms. Wilting may not occur until two or more weeks after transmission, depending on the age of the plant and the growing conditions. The disease develops most rapidly in young, succulent plants when temperatures are warm, the soil is moist, plentiful sunlight is available, and the plant’s nutrient requirements are being met. The spread of the disease decreases as plants mature and cucumber beetle populations decrease in midsummer. (12) Plant vines rapidly die and desiccate when conditions favor disease development.

Weather and nutrient conditions affect the potential for bacterial disease infection. A year with a good winter snow cover followed by a warm March and April – conditions that favor the overwintering, feeding, and reproduction of cucumber beetles – usually sees an increase in numbers of cucumber beetles and therefore an increase in the incidence of bacterial wilt. (16) Temperatures over 86°F retard disease development. (15)

Excessive amounts of soil nutrients make the plant more succulent and thus more susceptible to attack by beetles and bacterial wilt. If nutrient levels are unbalanced, low levels of nitrogen and potassium will increase plant susceptibility. (16)

To determine whether your plants are infected with bacterial wilt, you can use the following diagnostic tests:

• Squeeze sap from a wilted stem that you have cut near the base. If the plant has bacterial wilt, you will see a whitish bacterial ooze on a clean knife that you touch to this stem. (17)
  
  
• Immerse a newly cut segment of a wilted stem in a glass of water. If the plant has bacterial wilt, you will see a whitish bacterial ooze leaking from the stem into the water. (17)
  
  
• Cut the stem with a knife, then push the cut stem ends together. When you slowly pull the stem ends apart, you will see stringy or ropy sap if the bacteria are present. (18)

Bacterial wilt is severe on cantaloupe and cucumber, less damaging on squash and pumpkin, and rarely affects watermelon. (12) Wilt resistance also varies among varieties within a species. For example, County Fair ’83 and Saladin are resistant varieties of cucumber but there are no known resistant varieties of muskmelon. (11) Please see Table 2 for a more complete list of varietal resistance.

Squash Mosaic Virus

The western striped cucumber beetle and the spotted cucumber beetle are alternate vectors for another disease, the squash mosaic virus (the primary vector is aphids). (1) Since this disease is also seed-borne, control is achieved mainly through use of virus-free seed. Squashes and melons are particularly susceptible to this disease because of the greater incidence of infected seeds in these species.

The symptoms of squash mosaic virus vary according to host species and cultivar, but include mosaic patterns, leaf mottling, ring spots, blisters, and fruit deformation. (20) Besides the use of certified virus-free seeds, control measures include practices that minimize cucumber beetle populations and feeding of adult beetles on infected plants. (20, 21) While potentially very important for growers, resistant varieties have yet to be developed. (20)

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Organic Control Measures

Organic control measures for cucumber beetles fall into five categories, each discussed in more detail in the following sections:

• Population monitoring
• Cultural practices
• Trap crops, trap baits, and sticky traps
• Predatory organisms
• Botanical and biorational insecticides and protectants

Population monitoring is used to determine when overwintering cucumber beetle populations emerge and spring flight begins. This information allows for effective timing of control measures to prevent crop damage.

Cornell plant pathologists (19) recommend scouting plants twice a week, especially when plants have less than five leaves. Since cucumber beetles like shade, examine the undersides of cotyledons, young leaves, and stems. Monitoring should involve the inspection of five plants (only one per hill) at each of five sites in a field, paying particular attention to field edges. Use these counts to calculate the average number of beetles per plant.

Thresholds for use of botanical or chemical control measures vary depending on species susceptibility to bacterial wilt. Cucumbers and cantaloupe are susceptible to bacterial wilt and should be treated within 24 hours if plants along the edges are heavily damaged or have 5 or more beetles per plant. Following the first treatment, apply follow-up treatments only if there is at least one beetle per plant.

Watermelon is not susceptible to bacterial wilt and can withstand feeding damage. The likelihood that feeding damage will affect yield decreases as plants mature. For plants with less than five leaves per plant, control measures should be used if at least five beetles are found on each plant.

According to Dr. Rick Storey (22) at Louisiana State University, a general rule of thumb is that established zucchini and summer squash plants can tolerate a 50 percent loss of foliage from feeding without a significant loss in yield (at roughly 50 percent foliage loss, with harvest delayed 1 to 2 weeks compared to undamaged plants). There are two exceptions:

• if the cucumber beetle feeds on newly emerged seedlings, the plants may be killed outright; and
  
  
• if bacterial wilt is being spread by the beetles, then the economic threshold may be less than one beetle per plant.

Since insects are attracted to the color yellow, yellow sticky-traps can also be used as a monitoring tool. Insects caught in the traps are counted and monitored over time to determine when their populations are increasing. One simple monitoring tool uses yellow plastic cups (8-ounce size) inverted over 2-foot wooden stakes and coated with Stickum™ or Tangle-Trap™. (23) A homemade sticky-trap effective for a small garden can be made from a piece of plywood or cardboard painted yellow, then coated with Tanglefoot or some other adhesive. (24) Attaching cotton wicks dipped in oil containing eugenol, a pheromone that attracts female beetles, will lure more beetles to the trap. Allspice oil and clove oil contain between 60 and 90 percent eugenol. (25) Bay oil is another natural source of eugenol. (24) To be most effective, yellow sticky-traps should be positioned near the edge of crop fields. The Further Resources section at the end of this publication provides contact information of companies that sell monitoring tools.

Cultural practices are land- and crop-management practices that affect the reproduction of pests or the time and level of exposure crops have to pests. Cultural practices that can be used to protect against cucumber beetles include:

• delayed planting
• use of row covers
• mulching
• plant trellising
• cultivation and residue removal
• insect vacuuming

Crop rotation, an important management tool for disease control, is ineffective in controlling cucumber beetles, since the beetles migrate from areas surrounding the fields. Also, since these insects can survive on a number of wild hosts, the removal of alternative hosts from the farm would be difficult and again ineffective because of in-migration.

Delayed planting of cucurbits provides some control against cucumber beetles by putting plants in the field after most cucumber beetles have laid their eggs (mid-June in the Midwestern states). However, this control method may be impractical for market growers since it eliminates early-market melon, cucumber, and summer-squash crops. In areas of the country with a relatively short growing season, late planting may not allow some varieties of mid-summer crops such as pumpkins to mature before the first frost. (5, 9)

Floating row covers are an effective control method during the early season of plant growth. They prevent insect attack by forming a barrier between insects and plants. Row covers need to be removed during the late vegetative stage – at the onset of flowering – to allow for bee pollination. Once floating row covers are removed, other control measures – such as treatments with botanical or chemical pesticides – should be employed.

Weed control can be a significant problem under row covers unless they are used in combination with plastic or residue mulches. When row covers are placed over melons growing on bare soil, a favorable environment for the germination and growth of weeds is created. Periodic removal of the covers for hand cultivation, however, would permit the entry of cucumber beetles. Also, row-cover removal and hand cultivation are impractical on a commercial scale. Pre-emergence herbicides, a management tool in conventional production, are not an option in organic production.

Heavy mulching can deter cucumber beetles from laying eggs in the ground near plant stems and may hinder feeding by larvae migrating to fruits. (26) This cultural control method, however, does not protect the leaves against attack from adult insects. (27) Injury to fruit by tunneling of larvae is dependent on very moist soil as fruits ripen. Limiting irrigation at this time can minimize damage. (26)

Research conducted in Virginia (28) showed that aluminum-coated plastic mulch reduced numbers of cucumber beetles, often below the threshold level for pesticide application. The researchers noted that for conventional growers, this reflective mulch could reduce the use of insecticides, while for organic growers, repulsion of cucumber beetles could reduce bacterial wilt transmission. They also noted that the repulsive effect of reflective aluminum-coated plastic may also reduce virus transmission by both cucumber beetles and aphids.

Trellising plants can make leaves less accessible to insect larvae and may decrease egg-laying. Like mulching, trellising does not protect plants against attack by adult insects. (27)

Cultivation and residue removal can help reduce overwintering populations of cucumber beetles. To remove infested root residues, plow the soil deeply to bring these damaged residues to the surface, then remove and destroy them. (19) You can also shred aboveground crop residues and thoroughly cultivate the soil to facilitate the decomposition of above- and belowground residues. (29) However, unless the soil surface is covered by mulch or new plantings, tillage practices may make the soil susceptible to runoff and erosion.

Bug vacuums provide a mechanized method for removing insects from host plants. Vacuuming should be done early in the morning when insects are active and repeated frequently to reduce heavy infestations (29) since this insect can easily migrate into the field from surrounding areas. For more information on bug vacuums, please see the ATTRA publication "Bug Vacuums" for Organic Crop Protection.

Trap crops, trap baits, and sticky traps attract insect pests away from the main crop through the use of smell, color, or pheromones.

Trap crops release chemicals known as kairomones that are highly attractive and beneficial to insects. Kairomones produced by cucurbits include cucurbitacin, a feeding stimulant that imparts the characteristic bitter taste to cucurbits, and several floral volatiles, which are extremely attractive to adult beetles and can lure them from some distance. To be used as a lure, trap crops need to contain a much higher concentration of these chemicals than the main vegetable crop. The high concentration of kairomones in the trap crops encourages insect pests to feed on them.

Pioneering research by R.L. Metcalf (30) in Illinois determined that certain cucurbit species could serve as trap crops in large-scale cucurbit production. Most effective as trap crops are species that are highly preferred by cucumber beetles (see plants with rankings greater than 45 in Table 2).

To deter entry into the field by cucumber beetles and minimize the spread of bacterial wilt:

• Plant trap crops on the perimeter of the field as border strips.
  
  
• Plant trap crops about two weeks earlier than the primary cucurbit acreage since insects migrate to the earliest emerging, or most mature, cucurbit in the field. (9)
  
  
• For organic production, apply botanical insecticides to the trap crop to kill cucumber beetles that have gathered. For conventional or low-spray production, treat the trap crops with systemic insecticides to kill the pests.
  
  
• Apply a yellow mulch around the trap crop to further attract cucumber beetles. (19)
  
  
• Regularly rouge out or remove diseased plants from the main field. (12)

The amount of land devoted to trap crops depends on the amount of land being planted to cucurbits. Generally, devoting 2-5 percent of the land to trap crops is sufficient. (9) However, research conducted in upstate New York showed that planting 15 percent of the test-plot area to dark zucchini, which is highly preferred by cucumber beetles, reduced the numbers of these pests in a pumpkin crop by about 50 percent. (31) In Maine, a 50:50 ratio of the trap crop, squash variety NK-530, with a primary cucumber crop resulted in 90 percent of the cucumber beetles being attracted to the squash crop. However, a mixture of 15 percent squash and 85 percent cucumbers provided only minimal cucumber beetle control. (32)

Trap baits contain insect-attracting pheromones, kairomones, and other chemical attractants. When these attractants are combined with synthetic or botanical pesticides, insects are lured into a feeding frenzy on the pesticides. In their research on cucurbit trap crops, Metcalf and coworkers (30) determined that cucurbitacin can be isolated and used as a trap bait. Eugenol, primarily a pheromone attractant for northern corn rootworm, is being used on an experimental basis as an attractant for the spotted cucumber beetle (southern corn rootworm) and striped cucumber beetle. Researchers in upstate New York used trap baits containing cucurbit blossom volatiles to control cucumber beetles. (33) A new product, Cidetrak® CRW, is a gustatory stimulant for corn rootworm that contains no insecticidal properties but can be mixed with either synthetic or botanical pesticides to control rootworms. (34, 35)

Adios™ and SLAM® are commercial products that contain a combination of cucurbitacin attractants and the insecticide carbaryl. (Please note: These two products are no longer commercially available). Both products use buffalo gourd root powder as their source of cucurbitacin while Adios™ enhances this source with zucchini juice. These products, though not approved for organic production, reduce insecticide use by causing pests to congregate in limited areas where they feed on pesticides. In upstate New York, researchers were able to reduce cucumber beetle populations by 50 percent by placing 40 traps per acre along field boundaries. (36)

Metcalf investigated the use of neem mixed with cucurbiacin baits as an alternative to carbaryl, but no commercial product has been developed based on this combination. Hoffmann (33), working in upstate New York, found that substituting rotenone or pyrethrum for synthetic insecticides in traps only marginally controlled cucumber beetles. He suggested, instead, that organic growers use spores of predatory insect pathogens in the traps and recommended combining trap baits with trap crops. (33)

Please refer to the Products section below for contact information on companies that sell bait traps.

Yellow sticky-traps, besides serving as population monitoring devices, can be used to reduce adult populations in the early stages of infestations. As discussed above, the addition of kairomones to yellow sticky-traps increases their effectiveness. For best results, place the traps along borders or place yellow sticky-tape above a row of affected crops. (29) One problem associated with this method is that insects and debris accumulate on the traps, decreasing their effectiveness. Hoffmann (37) recommends that growers practicing non-organic IPM methods use, instead, insecticide-impregnated oil on a yellow cloth to attack and kill cucumber beetles.

Predatory organisms can be used to control populations of cucumber beetles. Natural predators of this pest include soldier beetles, tachinid flies (Celatoria diabroticae), braconid wasps, certain nematodes (38), and bats. (29) In California, where the tachinid fly is the most important natural enemy, it is rarely sufficient to reduce populations of western spotted cucumber beetles to below economically damaging levels. (11)

Parasitic nematodes infect soil-dwelling larvae of cucumber beetles, thereby reducing larval root feeding and the number of adult cucumber beetles that arise from maturing larvae. In Indiana, researchers showed that trickle irrigation was an effective method for distributing parasitic nematodes for the control of striped cucumber beetles. (39) Pennsylvania studies demonstrated that the parasitic nematode Steinernema riobravis was capable of decreasing the survival of larval striped cucumber beetles by 50 percent in both organic and conventional soil management systems. The decrease in cucumber-beetle larval populations resulted in superior root growth under both soil-management systems. Researchers recommended using Steinernema species in the context of drip irrigation and under plastic mulch production systems since this species is able to survive and reproduce at temperatures up to 95°F. (40)

In her book The Organic Method Primer, Dr. Bargyla Rateaver (41) recommends applying parasitic nematodes 3 weeks after planting at the rate of 90,000 units per linear foot.

The publication Suppliers of Beneficial Organisms in North America provides comprehensive information on sources of nematodes and other parasitic organisms. Please see the Further Resources section below for information on how to obtain a free copy of this publication either by mail or over the "web." The Insect Parasitic Nematode Web site (42), developed and maintained by the Department of Entomology, Ohio State University, contains information on the biology and ecology of nematodes, how to use them as a pest control method, and a comprehensive listing of retail suppliers of parasitic nematodes. This Web site also provides links to nematology specialists who answer questions about the use of parasitic nematodes.

Bats are predators of a wide range of pest insects, including cucumber beetles. In one season, a typical colony of about 150 big brown bats in the Midwest eats 50,000 leafhoppers; 38,000 cucumber beetles; 16,000 June bugs; and 19,000 stink bugs. (43) For more information about creating on-farm bat habitat, please see the ATTRA publication Farmscaping to Enhance Biological Control.

Botanical and biorational insecticides and protectants. Recent research demonstrated that plant-growth-promoting rhizobacteria can decrease feeding by cucumber beetles. The addition of soil drenches containing a mixture of the bacteria Pseudomonas putida, Serratia marcesens, Flavomonas oryzihabitans, and Bacillus pumillis resulted in a reduction in curcubitacin production by treated cucumbers. As concentrations of this feeding stimulant were reduced, feeding by cucumber beetles and transmission of the bacterial wilt virus decreased. (44) Inoculum for this treatment method is not yet available commercially. The botanical pesticides sabadilla and rotenone or pyrethrum are reported to work well against cucumber beetles. You should be aware, however, that sabadilla is toxic not only to bugs, but also to honey bees, care should be taken not to apply this insecticide when bees are present. Pyrethrum is also toxic to all insects, including beneficial species. It is also highly toxic to fish until degraded. (44) Some organic growers use pyrethrum or rotenone in combination with the particle film barrier, Surround WP™ Crop Protectant. (45)

Particle film barriers provide a promising new approach to insect control for organic producers. Surround WP disrupts insects by sight confusion and other non-toxic means. The active ingredient in this product is specially-processed kaolin clay, an edible mineral long used as an anti-caking agent in processed foods, and in such products as toothpaste and Kaopectate. According to the product representative for Surround, John Mosko of Engelhard Corporation, kaolin clay provides good suppression of cucumber beetles. He recommends:

• Using an air blast sprayer to achieve good coverage
  
  
• Applying the product under the leaves where cucumber beetles congregate
  
  
• Applying Surround early in the growing season before cucumber beetle populations explode (while Surround can provide remedial control of cucumber beetles, field trials have shown that early applications that deter beetles from initially entering the field are more effective)
  
  
• Reapplying after a heavy rain
  
  
• Continually agitating the solution while applying it
  
  
• Cleaning harvested fruits with a moist cloth or a post-harvest rinse to remove any film residue of the kaolin clay left on the crop after harvest

See the Products section below for information on how to obtain this product.

Azadarachtin, an extract from the neem tree, has anti-feedant and insecticidal properties. Alone, it is not effective against adult cucumber beetles. However, recent studies (Reggie Destree, e-mail communication) indicate that a mixture of neem with karanja oil (derived from the tree, Pnogania glabra, found throughout India) can reduce cucumber beetle populations by 50 to 70 percent overnight. Alone, neem oil applied as a soil drench acts as an ovicide and is effective against larval damage. (25) Please see the Products section below for sources of commercial neem and karanja products.

Timing of applications. Use of either botanical or chemical insecticides should be based on observed population thresholds or measured risks of population build-up. As discussed above, determining when spring flight begins will enable you to forecast the arrival of cucumber beetles in your area.

If possible, only treat hot spots (areas of high infestations). Insecticide applications made between dusk and dawn, when the striped cucumber beetle is most active, may be more effective.

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Chemical Control Methods

Chemical pesticides are commonly used in conventional vegetable production to control populations of cucumber beetles. If insecticides are used, they should not be applied during pollination to avoid harm to honey bees and other pollinators. Also use insecticides with limited toxicity to pollinators. (10) Pesticides such as Adios® that combine cucurbitacins as a feeding stimulant with a small amount of the pesticide carbaryl (Sevin ™) can be both effective and selective in controlling cucumber beetles. (5, 26, 29)

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Further Resources

Information

The Bio-Integral Resource Center (BIRC)

A leader in the field of integrated pest management, BIRC publishes the IPM Practioner and Common Sense Pest Quarterly. They also publish a directory of IPM products and beneficial insects and offer booklets and reprints on least-toxic controls for selected pests.

For more information and a publications catalogue, contact:
Bio-Integral Resource Center (BIRC)
P.O. Box 7414
Berkeley, CA 94707
510-524-2567
fax: 510-524-1758

Insect Parasitic Nematodes

This website provides information on the biology and ecology of parasitic nematodes, how to use nematodes to control plant diseases, and a comprehensive listing of companies that sell nematodes. Sponsored by SARE and the Lindberg Foundation.

Department of Entomology, Ohio State University

Hunter, C.D. 1997. Suppliers of Beneficial Organisms in North America.

One free copy per request is available from:

California Environmental Protection Agency
Department of Pesticide Regulations
Environmental Monitoring and Pest Management Branch
1020 N Street, Room 161
Sacramento, CA 95814-5624
916-324-4100

Products

Home Harvest® Garden Supply, Inc.
3807 Bank Street
Baltimore, MD 21224
410-327-8403
410-327-8411
ugrow@homeharvest.com
Sabadilla and Safer soap.

Peaceful Valley Farm Supply
P.O. Box 2209
125 Springhill Blvd.
Grass Valley, CA 95945
Orders: 888-784-1722.
Questions: 530-272-4769
contact@groworganic.com
Sabadilla and Safer soap, Eugenol, a pheromone attractant for northern corn rootworm.

Engelhard Corporation
101 Wood Avenue
Iselin, NJ 08830
john.mosko@engelhard.com
Surround WP™, a particle film barrier to control feeding of insects on plants.

Gempler’s Inc.
100 Countryside Drive
P.O. Box 270
Belleville, WI 53508
800-382-8473
608-424-1544
Fax: 608-424-1661
A wide range of integrated pest management products, including yellow sticky traps, identification aids, sampling tools, alternative controls, and pheromone lures.

Trécé, Inc.
031-C Industrial Street
Salinas, CA 93901
831-758-0204
Fax: 831-758-2625
CideTrak® CRW.

Golden Harvest Organics, LLC
404 N. Impala Drive
Fort Collins, CO 80521
970-224-4679
Fax: 413-383-2836
info@ghorganics.com
Organic pest management products, organic fertilizers, heirloom seeds.

Certis USA L.L.C.
9145 Guilford Road
Suite 175
Columbia, MD 21046
800-847-5620
Organic pest management products including neem,parasitic nematodes, and pheromones.

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References

1) Flint, Mary Louise. 1990. Pests of the Garden and Small Farm: A Grower’s Guide to Using Less Pesticide. Statewide Integrated Pest Management Project. Division of Agriculture and Natural Resources. University of California, Oakland.

2) Bellinder, Robin R. et al. 1994. Pest Management Recommendations for Commercial Vegetable and Potato Production. Cornell Cooperative Extension. Cornell University, Ithaca, NY.

3) EPPO. 2003. Diabrotica undecimpunctata. EPPO Data Sheets on Quarantine Pests.
(PDF / 47K).

4) Capinera, J.L. 1999. Banded cucumber beetle. Featured Creatures. University of Florida, Department of Entomology and Nematology.

5) Foster, Rick, Gerald Brust, and Bruce Barrett. 1995. Watermelons, Muskmelons, and Cucumbers. In: Rick Foster and Brian Flood (eds.) Vegetable Insect Management with Emphasis on the Midwest. Meister Publishing Company, Willoughby, OH.

6) Pitblado, R.E. and R.N. Lucy. 1994. Cucumber beetles. In: Ronald J. Howard, J. (eds.) Diseases and Pests of Vegetable Crops in Canada. The Canadian Phytopathological Society and the Entomological Society of Canada, Ottawa, Ontario.

7) Krysan, J. L. 1976. Moisture relationships of Diabrotica undecimpunctata howardi. Entomologia Experimentalis et Applicata. Vol. 20. p. 154–162.

8) Brust, G.E. and G.J. House. 1990. Influence of soil texture, soil moisture, organic cover, and weeds on oviposition preference of southern corn rootworm. Environmental Entomology. Vol. 19. p. 966–971.

9) Burkness, E. and W.D. Hutchison. 1997. Striped Cucumber Beetle. VegEdge Vegetable Pest Factsheets.

10) Lewis, Donald R. 1992. Striped and Spotted Cucumber Beetles. Integrated Pest Management for Commercial Cucurbit Growers. Iowa State University Extension, Ames.

11) Godfrey, L.D. et al. 1999. Cucumber Beetles. In: M.L. Flint (ed.) U.C. IPM Pest Management Guidelines: Cucurbits. University of California Division of Agriculture and Natural Resources, Oakland.

12) Latin, R.X. 1996. Bacterial Wilt. In: Thomas A. Zitter, Donald L. Hopkins, and Claude E. Thomas (eds.) Compendium of Cucurbit Diseases. American Phytopathological Society Press, St. Paul, MN.

13) Otjen, Lew and Shelby Fleischer. 2000. Managing Striped Cucumber Beetle in Vine Crops with Admire and Provado. Penn State College of Agricultural Sciences. Department of Entomology.

14) Penn State Department of Entomology. 1999. Insect control strategies for vine crops. Entomological Notes. Penn State College of Agricultural Sciences, Cooperative Extension, Department of Entomology.

15) Jarvis, W.R. 1994. Bacterial wilt. In: Ronald J. Howard, J. Allan Garland, and W. Lloyd Seaman. (eds.) Diseases and Pests of Vegetable Crops in Canada. The Canadian Phytopathological Society and the Entomological Society of Canada, Ottawa, Ontario.

16) Plant Disease Diagnostic Clinic. 1999. Cornell University Plant Disease Diagnostic Clinic Fact Sheet. Bacterial Wilt of Cucurbits: Erwinia tracheiphila.

17) Gleason, Mark L. 1992. Bacterial Wilt. Integrated Pest Management for Commercial Cucurbit Growers. Iowa State University Extension, Ames.

18) McKinlay, Roderick G. 1992. Vegetable Crop Pests. CRC Press, Boca Raton, FL.

19) Petzoldt, Curtis. 2001. Chapter 18. Cucurbits. New York State IPM Program, Cornell University.

20) Provvidenti, R. and J.S. Haudenshield. 1996. Squash Mosiac. In: Thomas A. Zitter, Donald L. Hopkins, and Claude E. Thomas (eds.) Compendium of Cucurbit Diseases. American Phytopathological Society Press, St. Paul, MN.

24) Peet, Mary. 2001. Insect pests of vegetable crops in the Southern United States. Striped and Spotted Cucumber Beetle. Sustainable Practices for Vegetable Production in the South.

25) Golden Harvest Organics. 2002. Cucumber beetles.

26) Cranshaw, Whitney. 1998. Pests of the West. Revised: Prevention and Control for Today’s Garden and Small Farm. Fulcrum Publishing, Golden, CO.

27) Gardening Guides. No date. Natural Pest Control Striped cucumber beetles.

28) Caldwell, John S. and Paul Clarke. 1998. Aluminum-coated plastic for repulsion of cucumber beetles. Commercial Horticulture Newsletter, January–February 1998. Virginina Cooperative Extension, Virginia Tech.

29) Cantisano, Amigo. 1996. Ask Amigo. Farmer to Farmer. September–October. No. 16. p. 8.

30) Metcalf, R. L. et al. 1979. Bitter cucurbita spp. as attractants for diabroticite beetles. Cucurbit Genetics Cooperative Report. Volume 2. p. 38.

31) Hoffmann, M.P. 2002. Personal communication. Department of Entomology, Cornell University.

32) Grossman, J. 1993. Entomological Society of America’s 1992 Annual Meeting–Part VI: Trap crops. The IPM Practitioner. Vol. 15, No. 8. p. 12–13.

33) Hoffman, Michael P. 1998. Annual Report: Vegetable Systems. Developing Sustainable Management Tactics for Cucumber Beetles in Cucurbits. Northeast Regional SARE.

34) Trece, Inc. 2001. Cidetrak® CRW Gustatory Stimulant.

35) Comis, Don. 2001. New sprays, trap promises to slash insectide use in America’s cornbelt. ARS News and Information.

36) Hoffmann, M. P. et al. 1996. Field tests with kairomone-baited traps for cucumber beetles and corn rootworms in cucurbits. Environmental Entomology. Vol. 25. p. 1173–1181.

37) Hoffman, M. 1999. Cucurbit Crop Small Group Session. In: Kimberly A. Stoner (ed.) Alternatives to Insecticides for Managing Vegetable Insects. Natural Resources, Agriculture, and Engineering Service (NRAES), Ithaca, NY.

38) Lyon, W.F. and A. Smith. No date. Striped Cucumber Beetle. HYG-2139-88. Ohio State University Extension Fact Sheet.

39) Reed, K.K., G.L. Reed, and C.S. Creighton. 1986. Introduction of entomogenous nematodes into trickle irrigation to control striped cucumber beetle (Coleoptera: Chrysomelidae). Journal of Economic Entomology. Vol. 79. p. 1330–1333.

40) Ellers-Kirk, C.D. et al. 2000. Potential ofentomopathogenic nematodes for biological control of Acalymma vittatum (Coleoptera: Chrysomelidae) in cucumbers grown in conventional and organic soil management systems. Journal of Economic En tomology. Vol. 93, No. 3. p. 605–612.

41) Rateaver, B. and G. Rateaver. 1993. Organic Method Primer Update. The Rateavers, San Diego, CA. p. 295–296.

42) Grewal, Parwinder. 2000. Insect Parasitic Nematodes. Department of Entomology, Ohio State University.

43) Long, R.F. 1999. Use of bats to enhance insect pest control. p. 67–70. In: Bring Farm Edges Back to Life! Yolo County Resource Conservation District, Woodland, CA. 105 p.

44) Zehnder, G.W., J.F. Murphy, E.J. Sikora, and J.W. Kloepper. 2001. Application to rhizobacteria for induced resistance. European Journal of Plant Pathology. Vol. 107, No. 1. p. 39-50.

45) Local hazardous waste management program in King County.1997. Pyrethrum.

46) Grubinger, Vern. 2001. Veg Grower News. University of Vermont Cooperative Extension.

47) UC Statewide IPM Project, © 2000 Regents, University of California, photo by Jack Kelly Clark

48) UC Statewide IPM Project, © 2000 Regents, University of California, photo by Jack Kelly Clark

49) © University of Florida, photograph by John L. Capinera

50) © 2001 University of Illinois at Urbana-Champaign

51) © 2000 The American Phytopathological Society, R. X. Latin.

Cucumber Beetles: Organic and Biorational IPM
By Barbara C. Bellows and Steve Diver
NCAT Agriculture Specialists
Sherry Vogel, HTML Production
IP212
Slot 217

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