The light-colored tissue we see here is the result of squash beetle behavior known as “trenching.” Trenching cuts off (at least temporarily) the translocation of cucurbitacin defense compounds to preserve the palatability and quality of the squash foliage feeding site. The beetles in this particular field were sprayed and killed after trenching this section of the leaf, so the yellow tissue remains and was not eaten. Similar behavior occurs with other insects, such as dogbane leaf beetles. For more information, see HGIC 2207, Cucumber, Squash, Melon, and Other Cucurbit Insect Pests.
What Is It? Wednesday – Squash Beetle Trenching
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