I am a new member of our local community garden in Westport and just constructed my raised beds late last summer and managed to get a few cool weather veggies in my plot in the beginning of September.  My fellow gardener and good friend Jennifer and I decided to combine our two adjacent plots to get maximum use of our planting beds and shared pathways.  The community garden opened up additional plot space last year to organic gardeners but because we are in close proximity to a public school and share a common parking lot, the entire community garden has manage pest and disease problems without chemical pesticides and herbicides.

I was told that my seasoned fellow gardeners have had infestations of Mexican Bean Beetles and Cucumber Beetles in their garden plots in the past few years.  Instead of spraying pyrethrins (which is an organic product but also a known neurotoxin), I have compiled the following data using research and recommendations from the Connecticut Agricultural Experiment Station, Cornell University Insect Diagnostic Laboratory and the University of New Hampshire Cooperative Extension.

Recommendations for Control of Mexican Bean Beetles without Pesticides

*Plant beans in a different area than they were planted in last year.  Interplanting beans with other crops may make them more difficult for the beetles to locate.

*Plant early season beans or beans with a shorter maturity date.  Most beetle populations are heaviest in mid to late summer.

*Handpicking is relatively easy in small gardens because the adults, eggmasses and larvae are all together on the underside of the leaves and none of these stages are camouflaged.  If you pick off the adults by hand, make sure you actually crush them or drown them in soapy water, don’t just knock them off the plant because they will crawl back.

*Crush the eggs that are on the underside of the leaves.  Check for yellow eggs in clusters of the bean leaves in mid-to-late spring. 

                *Hand pick and crush larvae which begin to feed in 5-14 days after eggs are laid.

                *Crush beetles when they appear in 3-5 weeks after larval stage.

*Use an insecticidal soap (potassium salts of fatty acids) on the underside of the leaves. 

(Check the Days to Harvest on the label and make sure to wait a sufficient number of days after application, before picking beans for use.)

* A parasitic wasp, Pediobius foveolatus, has been used successfully to control the Mexican bean beetle in both commercial farming and community garden settings. This tiny wasp lays its eggs in Mexican bean beetle larvae. When new adult wasps emerge, they kill the bean beetle. Unfortunately, the adult wasps do not survive the winter in Connecticut, so they have to be reintroduced each year. Because the adult wasps have a short life span, it is important to introduce them when mid-sized bean beetle larvae are already present on the plants. Some commercial growers plant one plot of snap beans earlier than usual to build up a small population of Mexican bean beetle larvae and introduce the wasps before the main population of Mexican bean beetles develops. The adult wasps feed on nectar at flowers, and benefit from composite (sunflower family) or umbellifer (carrot family) flowers near the bean plot. Pediobius foveolatus is available from several mail-order companies that sell biological control agents.

*Pick beans frequently.  Mexican bean beetle populations build up more rapidly on plants where beans have been left to mature than on plants where young beans are picked off frequently.  So, keep picking your snap beans before they get large and mature. (They taste better and are more productive that way, anyway). In a test of 14 bush snap bean varieties, Blue Lake 274 and Idaho Refugee produced the most consistent high yield, whether or not they were treated with insecticides. Destroy bean plants as soon as they are no longer productive to deny the last generation of beetles the plant material and overwintering sites they provide.

*Plant sunflowers near beans.

Recommendations for Control of Cucumber Beetles without Pesticides

*Rotate cucurbit crops to a new place in the garden each year. Deprive adult beetles of homes for over­wintering by removing crop residues and alternative host plants such as asters and goldenrod from around the garden.

*Covering planting beds with floating row covers immediately after planting seed or setting out trans­plants will protect cucurbits from early damage by cucumber beetles. Be sure to remove row covers as plants begin to bloom, to ensure adequate pollination by bees.

Applying a heavy mulch of straw, leaves or grass clippings around established plants may help reduce beetle attack.

*Varieties of squash, cucumbers, and melons vary in their resistance to cucumber beetles. Among squashes, zucchini and caserta types are generally preferred to pumpkins and delicata, acorn, scallop, and yellow straightneck types of squash. Stono cucumber has also been reported to be resistant to both species. Ashley, Chipper, and Gemini cucumbers are notable for having resistance to spotted cucumber beetles both as seedlings and as mature plants. The melons Super Star, Rising Star, Pulsar, Passport, and Galia are less preferred by the striped cucumber beetles than other varieties of muskmelon.

*Cucumber beetles are stimulated to feed by the chemical cucurbitacin, the chemical which can make cucumbers bitter or indigestible to some people. Thus, cucumber varieties advertised as "non-bitter" or "burpless" are not as attractive to the beetles.

*The beetles are attracted by smell to chemicals found in the odor of squash blossoms, and by sight to yellow-green fluorescent sticky traps. With the addition of squash seedlings, the traps catch beetles in May, before the field plantings are up, and the traps can be used in the field throughout the season.

*Damage by beetles can be reduced by starting seedlings in a protected environment and transplanting them to the field and by use of row covers. Row covers must be removed at flowering to permit pollination.