Accuracy of Lygus hesperus Knight (Hemiptera: Miridae) Egg Counts Improves with Egg Development

Abstract

The western tarnished plant bug, Lygus hesperus Knight, is a key cotton (Gossypium spp.) pest, managed primarily by application of insecticides according to nominal thresholds. Efforts to reduce reliance on insecticide-based tactics will require a more astute understanding of the physiological ecology of L. hesperus than is currently available. A key biological parameter that may be manipulated through cultural or genetic means is reproduction. Estimates of L. hesperus oviposition are commonly obtained by visual inspection, but the accuracy of those estimates has been questioned. Because the eggs swell during development, we hypothesized that delaying counts of eggs to permit some development might improve sampling accuracy. Estimates of L. hesperus egg numbers were obtained immediately after oviposition and again at three days after oviposition, and counts at both times were regressed with total eggs determined by the sum of either hatched eggs or the number of nymphs, and unhatched eggs. Sampler experience was a major factor influencing fidelity of egg counts with total eggs, but a single repetition of the experiment accompanied by knowledge of the results was sufficient to optimize sampler effectiveness. Regressions relating total eggs to counts, whether the counts were taken immediately after oviposition or after three days, were significant. However, compared with counts of newly-laid eggs, the regression relating egg counts at three days with total eggs was more stable and showed better agreement. These results can be used to maximize statistical power and minimize sampling errors in future examinations of L. hesperus oviposition.