Possible alternative host plants for some major pod sucking bug pests of pulse crops in the South Burnett region of Queensland

Abstract

The alydids Riptortus serripes (Fabricius) and Mirperus scutellaris Dallas (Hemiptera: Alydidae), and the pentatomids Piezodorus hybneri (Gmelin), Dictyotus caenosus and Plautia affiinis Dallas (Hemiptera: Pentatomidae), feed on the pods of pulse crops in Australia. Farmers currently control these bugs with insecticides. Alternative plant hosts could potentially be used as pest monitoring tools or in an integrated pest management approach as trap crops. Consequently, a survey of the possible alternative host plants of these bugs was carried out in southeast Queensland between 1992 and 1995. Additional information was obtained by searching host plant records compiled by the Queensland Department of Primary Industries, and from records in the literature. In the South Burnett, R. serripes was found only on legumes, especially Sesbania cannabina, and only in autumn which suggests it is an immigrant species. M. scutellaris, P. hybneri, and P. affinis were taken on many common weeds found by roadsides and in farmers’ fields. In most cases these bugs were found only on plants that were fruiting. The data were insufficient to make conclusions about D. caenosus. The survey was conducted during a period of prolonged drought so the abundance of possible host plants in non-cultivated areas, which is largely determined by rainfall, was reduced. Also the numbers of bugs taken were low on both cultivated and non-cultivated plants. Many possible alternative host plants were found but few appeared to be powerful attractants. Low numbers of bugs in the ‘wild’ host plants correlated with low numbers in cultivated crops. The opportunity to compare large populations in ‘wild’ host plants with populations in cultivated crops never arose, because of the drought. The main possible alternative hosts of Riptortus serripes were ‘Senna’ trees and Sesbania cannabina and these have a very restricted distribution in the South Burnett. S. cannabina was frequently observed to host two other pests of cultivated grain legume and pulse crops viz. Maruca vitrata (Fabricius) (Lepidoptera: Pyralidae) and Zygrita diva (Coleoptera: Cerambycidae). Removal of ‘Senna’ trees and S. cannabina should result in big reductions of populations of those three insect species. Macroptilium atropurpureum (siratro), M. lathyroides (phasey bean) and Medicago saliva (lucerne) appeared to be attractive to R. serripes, M. scutellaris and P. hybneri and could be evaluated as potential trap crops or as pest population monitoring tools.