Neem, a botanical pesticide approved for use by organic farmers, has been shown to reduce pest numbers or damage in more than 100 trials on a wide range of insects, says Brian Caldwell, NOFA-NY Farm Education coordinator. Writing in the mid-fall newsletter Organic Farms, Folks & Foods, he lists many of the situations in which neem has proven effective:
In the greenhouse, neem sprays controlled aphids, flies, mealybugs and mites. In field vegetable crops, it worked well against aphids and beet armyworms. Promising results also were obtained against squash bug, diamondback moth, Colorado potato beetle, flea beetles and Southern armyworm. On fruit crops, neem controlled leafhoppers, leafminers, tarnished plant bug and aphids. It was sometimes effective against the apple caterpillar complex.
Neem products approved by the Organic Materials Review Institute that were effective in the trials mentioned above included AZA-Direct, Neemix .25 and 4.5, Trilogy and Triact.
Caldwell noted that neem does not have immediate knockdown effect in most cases because it doesn’t kill most pests directly. Instead, it reduces feeding, repels egg-laying and disrupts molting from stage to stage. It should be applied on immature stages of insect pests and applied frequently because it is not persistent. Good coverage is also important because neem must be ingested to work.
(Brian Caldwell, Hemlock Grove Farm, 180 Walding Lane, Spencer, NY 14883; education@nofany.org.)