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Data were analysed from 24 experiments, done between 1984 and 1988 in the Namoi Valley of NSW, Australia, in which cotton crops were subjected to various amounts of damage. There were three sets of experiments: pest management on a research station, pest management on commercial farms, and manual dis budding. The okra-leafed variety Siokra was infested with fewer pests than the normal leaf 'DP90' and suffered less damage from a given density of pests. Both varieties compensated for early-season damage at low yield levels but not at high levels. The reduction in yield caused by damage at high yield levels was less in 'Siokra' than in 'DP90', Three physiological explanations for these effects are offered: (1) where low yield is caused by heavy phYSiolOgical shedding of fruit resulting from adverse weather or agronomic practices, the shedding caused by pests can substitute for physiological shedding and thus insulate low-yielding crops from pest damage; (2) if the yield of the low-yielding crops is limited by the incomplete interception of radiation, then delaying the termination of the expansion of the canopy will increase yield; early damage can delay the onset of the metabolic stress that terminates expansion of the crop canopy by reducing the rate at which the fruit load increases; (3) loss of early fruit under some conditions conducive to high yield can cause rank growth, whose increased respiratory requirements may reduce the assimilate supply available to set and grow the extra bolls that could compensate for those lost. The implications of the results for pest management are discussed. Thresholds should not be raised above the lower end of their current range in Australia except in 'Siokra' crops, which are expected to yield <7.5 bales/hectare.
Document Type: Research Article
Publication date: August 1, 1992
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Journal of Economic Entomology is published bimonthly in February, April, June, August, October, and December. The journal publishes articles on the economic significance of insects and is divided into the following sections: apiculture & social insects; arthropods in relation to plant disease; forum; insecticide resistance and resistance management; ecotoxicology; biological and microbial control; ecology and behavior; sampling and biostatistics; household and structural insects; medical entomology; molecular entomology; veterinary entomology; forest entomology; horticultural entomology; field and forage crops, and small grains; stored-product; commodity treatment and quarantine entomology; and plant resistance. In addition to research papers, Journal of Economic Entomology publishes Letters to the Editor, interpretive articles in a Forum section, Short Communications, Rapid Communications, and Book Reviews.