Q: I planted a row of lettuce seed in my garden. When the seedlings were about 2 inches high, I noticed there were holes in the leaves. I put slug and snail bait around them, and sprayed them with insecticidal soap. The next morning, the whole row was completely eaten except for the midrib of each leaf. There were other vegetables in the bed that were not touched. I saw no silvery slime trails indicating snails. What could have eaten my lettuce, and how can I prevent this in the future?
Willard Erhardt, Fair Oaks
According to UC master gardener June Bleile, loopers and armyworms are two larvae that can cause severe damage to the lettuce crop.
Loopers have a greenish color and they move by arching their middles up then pushing them forward, kind of like a downward dog yoga position. Armyworms may be green to black. Loopers create holes in leaves, while armyworms skeletonize the leaves.
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Two other possible causes are cutworms or earwigs. Cutworms generally cut the seedling off at or below ground level; however, some varieties chew the leaves, too. Earwigs will also eat holes in lettuce leaves.
All of these pests are night feeders, so by checking your plants with a flashlight after dark, you may be able to spot the culprit.
The preferred method of management is to hand-pick them off your plants on a regular basis. Bacillus thuringiensis can be used on armyworm larvae, but should only be used when numbers are high.
Earwigs can be trapped in rolled-up newspaper (yet another use for your Bee) or shallow tuna cans filled with vegetable oil or bacon fat. Place the newspaper or tuna cans near the lettuce plants and check them each morning. Discard the newspaper (bugs and all) once it’s caught earwigs and replace with another paper trap. The can traps can be reused.
You can find out more about loopers, armyworms and other lettuce pests via the University of California’s integrated pest management website. For a photo guide of these common pests and their damage, click on www.ipm.ucdavis.edu/PMG/C441/m441hppestscv.html.
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