ABUNDANCE AND MORTALITY OF OVERWINTERING HELIOTHIS SPP.

Abstract

Field surveys, field cage studies, and records of light trap catches were used to follow the abundance and mortality of Heliofhis puncfiger (Wallengren) and H . armiger (Hiibner), through the autumn, winter and spring. over a 9 year period.Both the timing of spring emergence and magnitude of moth flights of H . armiger were consistent with prior observations of autumn and winter populations in the Namoi Valley. Subsequent abundance was greater in 2 seasons when wheat anthesis and spring emergence coincided. but overwintering populations declined considerably during the study period.Although H . puncfiger was not usually abundant in the area during autumn and winter, earlier and larger moth flights of that species than of H . armiger occurred in spring, leading to heavier infestation of crops and pastures. Apparent anomalies in the early spring abundance of H. puncfiger may be explained by migration from other areas, or early emergence of the non-diapausing fraction of the population.Substantial parasitism of overwintering H . armiger by Ichneumonidae and Tachinidae was recorded, while mechanical destruction of pupae during cultivation of crop residues also caused heavy mortality.

Spatial Distribution and Mortality of Helicoverpa spp. Pupae (Lepidoptera: Noctuidae) under Field Crops on the Darling Downs, Queensland

“…promissorius oviposits in pupae (Murray unpubl. data Room (1979) and Wilson (1983) recorded I. promissorius in larval collections in the Namoi Valley but gave no indication of its relative abundance. As expected, I. protnissorius was common in samples of overwintering H. arniigera pupae in the Narnoi Valley (Fitt and Daly 1990 (McDougall 1934;Goodyer 1983;Forrester et al 1984), they are also reported as predators of pest insects in pasture (Robertson et al 1981;Robertson 1987).…”

“…Furthermore, such studies can be used to indicate the contribution of different crops to the carryover of pyrethroid resistance from one season to the next (Daly and Fitt 1990). Because of the relatively low occurrence of overwintering populations of H. punctigera in agricultural regions (Wilson 1983;Learmonth 1986;Fitt and Daly 1990), investigations should examine H . punctigera in more detail in other regions where winter breeding is known to occur (Gregg et al 1989).…”

“…and Helicoverpa spp. (Stadelbacher and Martin 1980;Eger et al 1983;Wilson 1983Wilson , 1987. The similarity in pupal depth between H. punctigera and H. armigera mirrors U.S. studies showing no significant difference in pupal depth between Heliothis virescens (F.) and Helicoverpa zea (Boddie) (Eger et al 1983).…”

“…In irrigated crops the location of pupae on ridges may reduce mortality by drowning during irrigation or flooding (Wilson 1983(Wilson , 1987. By contrast in rain-grown crops where ridging is not well developed mortality from drowning can be significant as shown here for one crop after rain.…”

SURVIVAL OF HELICOVERPA PUNCTIGERA (WALLENGREN) AND H. ARMIGERA (HÜBNER) (LEPIDOPTERA: NOCTUIDAE) PUPAE SUBMERGED IN WATER

“…This is especially so in irrigated crops where most pupae are located in ridges (Wilson 1983). In raingrown crops ridging is less developed and waterlogging may have greater influence.…”