Laboratory studies ofDiadegma cerophagus [Hym.: Ichneumonidae], a parasite introduced to controlPlutella xylostella [Lep.: Hyponomeutidae] in Malaysia

Abstract

Laboratory studies were conducted to determine some of the attributes ofDiadegma cerophagusGravenhorst, a parasite introduced to controlPlutella xylostella (L.). Longevity studies have shown that ♂ and ♀ could live for 40 and 73 days respectively when fed on diluted honey. The parasite is capable of attacking an average of 117±10 caterpillars per ♀. The number of caterpillars attacked per ♀ is dependent on the life span of the ♀. The average area of discovery ofD. cerophagus, based on studies of single searching parasites, was found to be 1.20±0.21. The area of discovery was found to decrease with increase in parasite or host density. However, the k-value would increase with increasing parasite density and decrease with increasing host density. The life-cycle ofD. cerophagus is as follows: egg stage, 1.5 to 2 days; larval stage, 5 to 8 days and pupal stage, 6 to 9 days. There are 4 larval instars and the duration of each instar is dependent on the age of the host attacked. The duration of the larval stage averaged 6.5 days when 1- and 2-day old caterpillars were exposed toD. cerophagus and took 5 days when 3- and 4-day old caterpillars were exposed.