Organic Solutions to Control Brassica Insect Pests
Horticulture & Turfgrass
Haley Sater
Agriculture Extension Educator; Agriculture and Food Systems
University of Maryland Extension
Salisbury
Abstract
Organic vegetable growers face persistent challenges managing insect pests in brassica crops due to limited insecticide options and variable product performance under field conditions. To improve management recommendations for Mid-Atlantic growers, field trials were conducted to evaluate several commonly used insecticides in brassica production systems. A spring 2024 study evaluated insecticide treatments in collards, primarily targeting caterpillar pests such as diamondback moth (Plutella xylostella) and imported cabbage worm (Pieris rapaae). Treatments included neem oil, Bacillus thuringiensis (Bt), and the conventional insecticide Coragen for caterpillar control. Both the Bt and neem oil reduced the caterpillar populations. However, there was variability in control based on date and pest species. A subsequent fall trial in 2025 examined management of harlequin bugs (Murgantia histrionica) in kale. Treatments included commonly used organic insecticides such as neem oil, spinosad, and pyganic, along with untreated control plots. Trials were conducted as an RCBD field plot at the University of Maryland, Lower Eastern Shore Research and Extension Center, and insect populations were monitored through repeated visual counts following insecticide applications. In the fall kale trial, neem consistently resulted in significantly fewer harlequin bug adults and nymphs compared to the control, while pyganic and spinosad provided inconsistent suppression across sampling dates. However, plants treated with neem exhibited leaf discoloration likely associated with neem oil's effects on the leaf cuticle. Results from these trials provide practical information on the relative performance of insecticide options for managing brassica pests organically.
Authors: Haley Sater, Emily Zobel
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Haley Sater Agriculture Extension Educator; Agriculture and Food Systems, University of Maryland Extension, Maryland, 21801
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Emily Zobel Agriculture Extension Educator; Agriculture and Food Systems, University of Maryland Extension, Maryland, 21613