Growing cucumbers (Cucumis sativas) yields attractive green vines and a delicious, edible harvest. When caterpillars, such as loopers (Trichoplusia ni), show up on the scene, your anticipation for potential salads and pickles may turn to anxiety. Become familiar with common cucumber caterpillar pests and use a control program the moment they appear.
1. Preventive Control
A key part of preventing caterpillar infestations and their damage to cucumber plants is providing consistent care to ensure strong, healthy growth. Grow cucumbers in areas that provide full sun for a minimum of four to six hours daily. Maintain moist, well-draining soil. Water cucumbers to a depth of 1 foot each week. Water near the bases of the cucumber plants to keep the leaves dry.
2. Removal by Hand
Handpick caterpillars off of cucumbers when possible. You may need to scout caterpillars at night. Keep your garden free of weeds to remove caterpillar hiding spaces and host plants. Remove and destroy heavily infested or affected parts of the cucumber plant. Wear gardening gloves when handling sharp tools, and when picking off caterpillars, which can cause skin reactions.
3. Barrier Control
Consider protecting your plants from caterpillars and their damage by gently covering them with floating row covers. Floating row covers are made of fabric and you place them gently over your plants to create a barrier to prevent butterflies and moths from laying eggs. Or, you can use a support system to use the covers to hang above and over plants without resting against them.
4. Microbial Control
For severe caterpillar problems, apply Bacillus thuringiensis, a microbial insecticide that will help control caterpillars without harming cucumber plants. Follow the instructions on the Bt label, which will probably direct you to mix 2 to 4 teaspoons of concentrate per 1 gallon of water in a sprayer. Apply once a week until the problem subsides, saturating the plant. If you're pregnant or nursing, ask a friend to apply any garden chemicals for you. Always keep children out of the way when you're working with pesticides, even if they're organic.
- University of Illinois Extension: Cucumber
- University of California Statewide Integrated Pest Management Program: Cucumbers
- University of California Statewide Integrated Pest Management Program: Site Selection
- University of California Statewide Integrated Pest Management Program: Watering Cucurbits
- University of California Statewide Integrated Pest Management Program: Loopers
- University of California Statewide Integrated Pest Management Program: Cutworms
- University of Minnesota Extension: Caterpillar Pests of Cole Crops in Home Gardens
- University of Wisconsin Department of Entomology: Controlling Caterpillars on Cabbage and Broccoli
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