Host Selection, Growth, and Survival of Melonworm, Diaphania hyalinata L. (Lepidoptera: Crambidae), on Four Cucurbit Crops Under Laboratory Conditions

The melonworm, Diaphania hyalinata L. (Lepidoptera: Crambidae), is one of the most serious insect problems affecting cucurbit production.  We evaluated the relative preference and suitability of yellow squash, zucchini, cucumber, and watermelon to melonworm by measuring oviposition, larval preference, survivorship, and developmental responses of melonworm in the laboratory.  Watermelon resulted in the highest pre-pupal weights among the four crops and tended to have the highest survival rates for individual instars (fourth and fifth instars) and for multiple life stages (first instar to pupa, and first instar to adult).  However, results for most of the variables studied indicated that watermelon was an inferior host of melonworm compared to the other crops: egg survival was numerically lowest, preferences by adults (oviposition) and by larvae (defoliation) were lowest, larval development times tended to be longest, and larval head capsule widths and whole-body lengths were smallest.  When differences occurred among these variables, yellow squash, zucchini, and cucumber were each typically surpassed watermelon.  Differences among yellow squash, zucchini, and/or cucumber tended to be less common and less consistent than differences between watermelon and these other crops.  Hence, a more carefully planned and executed management strategy to prevent crop loss by melonworm may be needed for yellow squash, zucchini, and cucumber production than for watermelon.