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Nocturnal Predation of Lepidopteran Eggs in South Texas Cotton – 2002

R.S. Pfannenstiel


Predation on eggs of the cotton bollworm, Helicoverpa zea Boddie, and the beet armyworm, Spodoptera exigua (Hübner), in south Texas cotton was measured using direct observation of sentinel eggs to quantify mortality, identify key predators and partition nocturnal and diurnal sources of mortality. Mortality (24 h) ranged from 56.8 to 89.1% of H. zea eggs and 57.7 to 84.2% of S. exigua eggs. There were 395 predation events observed in 2002. Predation was more commonly observed at night with 73.2% of predation events occurring at night. No differences in predation rates on eggs of either prey species were observed. The dominant predators were a complex of wandering spiders comprised primarily of Hibana futilis (Banks), Hibana arunda Platnick, and Cheiracanthium inclusum (Hentz) which were responsible for 28.4% of all nocturnal observations of predation (and 20.8% of all observations). Ants, dominated by Solenopsis invicta Buren, was the second most commonly observed predator (16.2% of all observations) and was the 4th most frequently observed nocturnal predator (14.5% of nocturnal observations). The 3rd and 4th most observed predators were the cotton fleahopper Pseudatomoscelis seriatus (Reuter) [13.4% of total and 17.0% of nocturnal observations (3rd)] and predatory mites [13.2% of total and 18% of nocturnal observations(2nd)]. Taxa that were primarily nocturnal represented the four arthropod groups most frequently observed feeding on lepidopteran eggs. Only the Geocoris spp. (Geocoris lividipennis Stål and Geocoris punctipes Say), which are exclusively day active, were among the five most frequently observed predators. Of the predators observed feeding nocturnally, only Solenopsis invicta has been studied as a predator of lepidopteran eggs, little or nothing is known about the predatory characteristics of the other taxa.

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Document last modified 04/27/04