Augmentation of the assassin bug Pristhesancus plagipennis (Walker) (Hemiptera: Reduviidae) as a biological control agent for Helicoverpa spp. in cotton

Third-instar nymphs of the Australian assassin bug, Pristhesancus plagipennis (Walker), were released into cotton plots at two release densities and two crop growth stages to test their biological control potential. Release rates of 2 and 5 nymphs per metre row resulted in field populations of 0.51 and 1.38 nymphs per metre row, respectively, indicating that over 70% of nymphs died or emigrated within two weeks of release. Effective release rates of 1.38 nymphs per metre row reduced the number of Helicoverpa spp. larvae in the plots for a 7-week period. Crop yields were significantly greater in the plots to which P. plagipennis nymphs were released, with the effective release rate of 1.38 nymphs per metre row providing equivalent yields as insecticide treated plots. The data suggest that P. plagipennis has the capacity to reduce Helicoverpa spp. larvae densities in cotton crops when augmented through inundative release.     

Predator Presence Moves <Emphasis Type="Italic">Helicoverpa armigera</Emphasis> Larvae to Distraction

Displacement of herbivorous insects by the presence of predators on whole plants has rarely been studied. By semi-continuous observations of an externally feeding insect herbivore and a predator, we show how the mere presence of the predator, Geocoris lubra Kirkaldy (Hemiptera: Geocoridae), on a plant can have a strong influence on the movement and behaviors of Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) larvae. The presence of predators, as opposed to mortality by predators, influenced the proportion of larvae feeding, resting and implementing avoidance activities. In addition, the proportion of time individual larvae allocated to feeding, resting and dropping off plants was affected when predators were present with and without contact between the two. Predators do more than just reduce numbers of herbivores; they influence feeding, displacement and subsequently the distribution of plant damage.     

棉铃虫多胚跳小蜂生物学特性研究

棉铃虫多胚跳小蜂是棉铃虫的一种寄生性天敌。该蜂一年1代,以幼虫在土内越复越冬（在棉铃虫幼虫体内）,当5月份棉铃虫在麦田产卵时,该峰也同时羽化,并在棉铃虫卵内产卵寄生,当棉铃虫幼虫老熟入土后,该蜂突然行多胚生殖,一个棉铃虫幼虫体内有峰高达800～900头,棉铃虫则很快死亡。本文对该蜂的昼夜活动,田间消长、交配和产卵行为等都作了报道。