INFLUENCE OF PLANT-SPECIES ON HOST ACCEPTANCE BEHAVIOR OF THE BIOCONTROL AGENT ZYGOGRAMMA-BICOLORATA (COL., CHRYSOMELIDAE)

The parthenium leaf beetle, Zygogramma bicolorata Pallister (Chrysomel idae), is a biological control agent for parthenium weed, Parthenium h ysterophorus L., in India and Australia. It generally feeds on plants within the subtribe Ambrosiinae (Asteraceae), but starvation-induced a dult feeding on sunflower, Helianthus annuus L. (Asteraceae: Helianthi nae), has occurred in India. Adult feeding and locomotor behavior on d ifferent host plants was investigated. Behavior on the field host part henium weed differed significantly from that on the nonhost sunflower. Beetles on parthenium weed expressed shorter latencies to the first s ample bite and to feeding, ingested continuous meals compared to only a series of bites on sunflower, and spent a higher proportion of time feeding and resting following feeding. Beetles on sunflower showed the highest locomotor activity level and shortest plant residence times. Behavior expressed on a less preferred held host Noogoora burr, Xanthi um occidentale Bertol. (Ambrosiinae), was intermediate between that on parthenium weed and sunflower. On the basis of these results, Z. bico lorata can be confirmed as specific to plants within the Ambrosiinae. Behavioral observations are suggested as a useful additional tool for host specificity testing of weed biocontrol agents, (C) 1998 Academic Press.