Growth Response of Corn Earworm (Lepidoptera: Noctuidae) Larvae on Meridic Diets Containing Fresh and Lyophilized Corn Silk1

Abstract

Fresh and lyophilized silks of a susceptible corn, Zea mays (L.), ‘Stowell’s Evergreen’ (SEG), and a resistant line, ‘Zapalote Chico 2451# (PC3)’ (ZC), were incorporated as base-plant materials into standard and substandard corn/soy/milk solids(CSM) and pinto bean (PB) diets and used to measure corn earworm (CEW), Heliothis zea (Boddie), larval growth and development. Eighty grams of fresh ZC silks had to be mixed into 300 ml of the standard CSM diet to reduce CEW larval weights as much as on those reared on fresh ZC silks. When added to the CSM diet, ZC silks held in the laboratory or left on the ear in the field for 5 days did not have the resistance that was shown by silks blended immediately or refrigerated or frozen for 5 days. Significant weight differences were detected between larvae fed on lyophilized SEG and those fed on ZC silk powder mixed in 300 ml of diet. All concentration levels (2, 4, 8, and 16 g per diet) of ZC silk powder added to PB diets produced significantly smaller larvae than did the SEG silk powder added to those diets. Results from the CSM diets were more variable, but ZC resistance was shown at higher concentration levels. Weights of larvae fed for 10 days and longer indicated that the resistance factor was more effective in the PB diets than in the CSM diets.