Cucumber Beetles: What Are The Options?

By Debi Kelly on 02 Jun 2015 | read
Organic management of hard-to-control insects such as cucumber beetles in cucurbit crops will entail a combination of sequential tactics. Below are four management options that can be integrated. Use of resistant varieties and cultural practices such as crop rotation and sanitation are very important but they are not discussed below.

TRANSPLANTS: If possible, use three-week-old transplants, set out in the field at the same time as a direct-seeded crop instead of direct seeding. This provides various advantages: (1) good germination (germination of untreated seeds in cool soils can be spotty), (2) transplants provide a jump on the weeds, (3) plants are bigger when cucumber beetles arrive so that they are less vulnerable to both feeding damage and to wilt, (4) planting dates are more flexible (plants can be held inside to avoid late frost or growers can wait until fields are dry (or wet) enough to plant. This approach can produce not only earlier but also higher yields (summer and winter squash).

DELAYED-REMOVAL ROW COVERS: If the planted area is not too large, research conducted by Iowa State University researchers in muskmelon indicates that spunbond polypropylene row covers can significantly suppress bacterial wilt throughout the growing season and enhance yield if removal of covers is delayed for 10 days. Two treatments were proven effective at preventing cucumber beetles from attacking the transplants resulting in suppression of bacterial wilt when compared with plots having, either no row covers or row covers removed at the time of bloom (standard practice): (1) row cover ends were opened at anthesis to enable pollinator access, then covers were removed 10 days later and (2) after a bumble bee hive was inserted under one end of the row cover at anthesis, the row cover was re-sealed and then removed 10 days later.
APPLICATION OF KAOLIN CLAY: At the moment of transplanting, treat seedlings with Surround WP (kaolin clay). Kaolin clay acts as a repellent, mechanical barrier and irritant. It also disrupts the insect’s host-finding abilities. Research at Lincoln University of Missouri has been shown that weekly applications of Surround can significantly reduce (up to 82% reduction) numbers of spotted and striped cucumber beetles present on Surround-treated cucumber plants compared to untreated plants. Cucumber beetles deterred from treated plants have to go somewhere; thus, this approach would work best when used in combination with TRAP CROPS (see below).

Concerning the picture in today's blog: "Surround can significantly reduce (up to 82% reduction) numbers of spotted and striped cucumber beetles present on Surround-treated cucumber plants compared to untreated plants"). Surround is an OMRI-approved material that acts as a repellent, mechanical barrier and irritant. Because treated plants get covered with a white dust, insects are also less likely to find them. Research that Dr. Pinero did last year at LU's Carver Farm has shown that Surround can significantly reduce the number of cucumber beetles present in treated cucumber plants. It also reduces the number of flea beetles present in eggplant compared to untreated plants."

TRAP CROPS: Use of trap crops has proven effective in other systems but almost no research has been conducted in organic systems. A trap crop can be planted early around the perimeter of the cash crop. It is important for trap crop plants to be larger than the main crop plants. For 2-6 acre fields, planting of 2 rows of a highly attractive cultivar such as Blue Hubbard squash (which is not susceptible to bacterial wilt) along the perimeter can lure cucumber beetles to those plants. Monitor for cucumber beetle activity in the trap crops as well as in the cash crop. Apply insecticides to the trap crop only based on the results of scouting. At low beetle populations, sprays may not be needed. The OMRI-listed insecticides PyGanic EC 5.0 (Pyrethrins) and Entrust (spinosad) only show moderate efficacy. After spraying, scout again to determine if repeat sprays are needed in the border. Several sprays may be needed as beetles continue to colonize.