|Elliott, Norman - Norm|
Submitted to: Biological Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/26/1999
Publication Date: 3/1/2000
Interpretive Summary: Factors determining the effectiveness of lady beetles in cereal aphid biological control in wheat are not well understood. Further knowledge would help in predicting when lady beetles will control cereal aphid infestations, and in finding ways to improve their performance as biocontrol agents. The purpose of this study was to determine biological and environmental factors involved in foraging for prey by lady beetles. Field observations of lady beetle behavior were made over a 2-year period. The proportion of time lady beetles spent searching for aphids was correlated with air temperature, aphid density, and time of day. The relationship between searching and these variables differed among lady beetle species. The frequency of short flights by lady beetles increased with temperature and decreased with increasing aphid density. The frequency of long flights was influenced by temperature and calendar date. The frequency with which aphids were encountered and eaten was related to aphi density and temperature. Results of the research will contribute toward developing tools for predicting when lady beetles will control cereal aphid infestations in wheat fields, thereby precluding the need for insecticides to control the aphids.
Technical Abstract: Improved understanding of coccinellid activity and predation on aphids in the field could clarify their potential in aphid biological control. Our objective was to determine the influence of abiotic and biotic factors on activity and predation by adults of three coccinellid species (Hippodamia convergens Guerin-Meneville, H. tredecimpunctata tibialis (Say), and Coleomegilla maculata DeGeer) in spring cereal fields. The proportion of time coccinellids spent searching was correlated with air temperature, aphid density, and time of day. The relationship between searching and these variables differed among species. Average walking speed ranged from 66.4 cm/min for C. maculata to 83.2 cm/min for H. tredecimpunctata, and increased with temperature for all species. The frequency of short flights (< 2 m) by beetles increased with temperature and decreased with increasing aphid density for all species, but differed among species. The frequency of flong flights (> 2 m) was similar for all species and was influenced by temperature and calendar date. The frequency with which aphids were encountered and eaten was correlated with aphid density and temperature for H. convergens and H. tredecimpunctata. In spite of over 250 h spent observing adult coccinellid behavior in the field, predation data were insufficient to develop a useful predation model.