Answer: Cucumber beetle is a common name given to members of two genera of beetles, Diabrotica (spotted) and Acalymma (striped), both in the family Chrysomelidae. Cucumber beetles are present throughout the United States and cause serious damage to cucurbit crops. Overwintering adult insects feed on young plants, larvae in the soil feed on plant roots, and second-generation adults feed on plant leaves, blossoms, and fruits. Furthermore, adult cucumber beetles serve as vectors of bacterial wilt and squash mosaic virus.
Although cucumber beetles prefer flowers and leaves, they can also cause cosmetic damage to the surface of the melon that reduces the value of the crop. They are difficult to control through IPM strategies. They do have natural enemies, but introducing these is usually not enough to protect marketable yields of fruit; nor are insecticides particularly effective, as the two major beetle varieties either develop outside of the fields being treated or lay their eggs at the roots, where larvae are difficult to control.
Organic and biointensive IPM measures include delaying planting until beetles have already laid their first generation of eggs and using trap crops, floating row covers, parasitic organisms (such as the Tachinid fly Celatoria), and botanical pesticides. Field scouting or yellow sticky traps can help growers monitor insect populations. Trap crops provide attractive scents and colors for the beetles. These may include zucchini, squash, and pumpkins. Sow 5% or more of the land in strips alongside the crop or in adjacent plots with trap crops; these plants produce cucurbitacin, a feeding stimulant to cucumber beetles. The traps can either be destroyed or sprayed with a highly concentrated (30ml per gallon of water) citrus oil solution to destroy the adult cucumber beetle population.
The ATTRA publication Cucumber Beetles: Organic and Biorational Integrated Pest Management reports that some squash varieties have greater amounts of the cucumber beetle attractant cucurbaticin:
• Black Jack zucchini
• Big Max pumpkin
• Cocozelle summer squash
• Green Eclipse zucchini
• Seneca zucchini
• Senator zucchini
• Baby Boo pumpkin
• Super Select zucchini
• Ambercup buttercup squash
• Dark Green zucchini
• Embassy Dark Green zucchini
• Caserta summer squash
• Classic melon
Large-scale pest vacuums have also proven effective in removing beetles. Insecticides such as pyrethrums, which are derived from the extract of chrysanthemum flowers, can be used to help control beetle infestations. However, it should be noted that these generally not only have long residual activity but also are highly toxic to some beneficial insects. Moreover, their use may destabilize insect populations and result in outbreaks of secondary pests like aphids. Note that while pyrethrums are natural (though potent) insecticides that are generally approved for certified organic crops, pyrethroids are synthetic versions that are not approved for certified organic crops.
According to the Alabama Cooperative Extension Service, Adios (a Sevin bait) has proved moderately successful in controlling cucumber beetles. Although used as a foliar spray, Adios acts as a bait because it contains a cucumber beetle-feeding stimulant along with 13% carbaryl insecticide. When Adios is sprayed on foliage, beetles are stimulated to feed on the compound and are killed by the carbaryl. In field tests, Adios has provided cucumber beetle control ranging from less than to equal to foliar insecticides. It has no harmful effect on beneficial insects, including pollinators, because insects other than cucumber beetles are not stimulated to feed on the compound. However, Adios (Sevin) is not allowed in organic production.
Note that although Adios is a formulation of Sevin, Sevin itself should be avoided because it is toxic to earthworms, pollinators, and wasps (several of which are beneficial insects) and its use can lead to secondary insect pest infestations. Neem has been found to have little effect on beetle survival or mortality, but its anti-feedant trait significantly reduced plant damage caused by beetles. Rotenone and cryolite were both moderately effective. Entomophagous nematodes can control the larval stage in the soil. More information is available in the ATTRA publications Cucumber Beetles: Organic and Biorational Integrated Pest Management and Farmscaping to Enhance Biological Control.
Learn more in the ATTRA publication Specialty Melon Production for Small and Direct-Market Growers. This publication provides an overview of production and marketing of numerous different species and varieties of specialty melons. It addresses production considerations including seed sources, planting needs, soil preparation, and insect pest and disease control. It also discusses marketing outlets for producers to sell their melons and summarizes results of current melon research.
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