Controlling the Cucumber Beetle

Rupert Jannasch

Striped cucumber beetle (Acalymma vittatum) is a major pest of cucurbit crops such as squash, melon and cucumbers that is becoming increasingly serious as organic acreages increase. Although natural predators, companion planting and even hand picking can be effective defenses in small-scale polycultures, larger scale organic growers have few controls at their disposal. This article looks at several promising new controls for the cucumber beetle currently in field trials or early commercial use.

The striped cucumber beetle (SCB) has yellow wings and three longitudinal black stripes. The SCB is shorter and broader than the striped blister beetle (Epicauta vittatum) and has no stripes on the head.

Adult striped cucumber beetles (SCB) over-winter in debris along field margins before emerging in mid-spring. At first the beetles feed on wild hosts, but are soon attracted to the plant compound, cucurbitacin, in emerging vine crops. Eggs are laid in the soil close to the plants and these hatch in about one week. Emerging larvae feed on the cucurbit roots and adults feed on foliage, flowers and even fruit later in the season. Transmission of bacterial wilt (Erwinia tracheiphila) to the cucurbit crop by the beetle is serious in some areas. Populations of over-wintering adults can be reduced considerably by early fall cultivation of crop residues.

Cucurbits are most vulnerable to SCB in the first 4-6 weeks of growth, so transplanting is an excellent option to give the crop a head start. Some crops can tolerate high levels of defoliation after the 3 true leaf stage. M.P. Hoffman at Cornell University, has determined that in years of adequate rainfall, pumpkins can tolerate up to 80% leaf damage without economic yield loss. In Minnesota, defoliation levels of 25% are often used as an action threshold before spraying. Floating row covers can be an extremely effective barrier against the SCB provided they are removed before flowering to allow for pollination.

Trap cropping is another control method where cucurbit varieties known to be preferred by the SCB are used as sacrificial bait. One trial in New York State used Seneca zucchini as a trap crop in fields of pumpkin or squash. Ideally, several rows of the trap crop are planted several weeks earlier than the main crop around the field margins, close to the source of the migrating adult beetles. The trap crops are either sacrificed entirely to the beetle or the beetles are destroyed with an insecticide. A broad spectrum botanical insecticide such as Rotenone might be permissable for this purpose.

Another trapping option is to employ insect traps containing cucurbit blossom volatiles to trap beetles. Once the beetles are trapped, a suitable toxin is used to destroy them. Although Hoffman and others proved the effectiveness of the technique in New York State during the late 1990s, further work is needed to design a durable trap that is functional in adverse weather.

Surround WP Crop Protectant â (Englehard Corp.), is a naturally occurring, kaolin clay material that deters insects by forming a white barrier coating on crops. Surround is approved for organic production in the U.S. and is used against the SCB in cucurbit crops. This product is not yet available for commercial use in Canada, but promising trials in conventional and organic apple orchards in Ontario may hasten registration. Surround's effectiveness in cucurbits and other vegetable crops is still not entirely proven, but results so far suggest the material is worthy of further research. Cooperative, on-farm trials with Surround, trap crops and novel insecticides (see below) are essential to develop effective pest management options for organic farmers.

New Insecticide Organic?
Spinosad is a new, non-synthetic class of insecticide produced by Dow Agrosciences which bears watching for possible use in organic crops. Success 480 SC Naturalyte Insect Control Product is derived from the soil-dwelling bacterium, Sacchoropolyspora spinosa, and recently received PMRA (Pest Management Regulatory Agency) registration for a variety of insect pests and crop groups in Canada including European corn borer, Colorado potato beetle and the Oblique banded leafroller in apples (it is not yet approved for cucurbit crops). Success uses a sugar bait to attract the beetles and the pest perish as the active ingredient disrupts their nervous systems. Spinosad formulations against fire ants and fruit flies are approved for organic production by the Organic Materials Review Institute in the U.S. Canadian certification bodies have yet to rule on the admissibility of this new product. Spinosad's main drawback could be the wide variety of pests it destroys as broad spectrum insecticides often harm beneficial insects as well as pests.

Further reading:
Hoffman, M.P. 1998. Developing Sustainable Management Tactics for Cucumber Beetles in Cucurbits. SARE (Sustainable Agriculture Research & Education Program). 1999 Annual Report.

Seaman, A. 2002. Efficacy trials of OMRI approved materials on vegetable crops. New York State Integrated Pest Management Program.


For more information contact the OACC at (902) 893-7256 or by email at oacc@nsac.ca. Thanks to Dexter Sear, IO Vision, for photo of cucumber beetle.


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