Field Mortality of the Horn Fly on Unimproved Central Texas Pasture

Abstract

Differential screening techniques and pitfall trap monitoring of dung fauna were used to evaluate some biotic mortality factors of the immature stages of the horn fly, Haematobia irritans (L.), in cattle dung pats on an unimproved east-central Texas pasture. Exposure to dung fauna caused an average of 87.9% mortality to immature horn flies in naturally infested dung pats in tests conducted weekly from April to mid-September. Horn fly mortality in artificially infested dung pats during the same period averaged 93.1%. Indirect correlations were shown between numbers of scarabs and predaceous insects collected in pitfall traps and horn fly mortality in exposed dung pats. Direct correlations were found between pitfall trap collections of predaceous insects and horn fly mortality in dung pats covered with scarab excluder cages. Predation and scarab activity were about equally important as mortality factors of the horn fly at this location. Predation accounted for most of the horn fly mortality from April until mid-June, and scarab activity was the most important mortality factor from July until the tests were discontinued in mid-September.