Submitted to: Proceedings of the Annual Meeting of the Mexican Society Biological Control
Publication Type: Proceedings
Publication Acceptance Date: 11/1/2004
Publication Date: 11/11/2004
Citation: Pfannenstiel, R.S. 2004. The importance of nocturnal predation in field crops. In: Proceedings of the Annual Meeting of the Mexican Society Biological Control, November, 9-13, 2004, Los Mochis, Sinaloa, Mexico. p. 17-23.
Interpretive Summary: Nocturnal predation on lepidopteran eggs was evaluated in corn and soybean in Kentucky from 1993-4 and in cotton, corn, and soybean in Texas from 2001-4. In both locations, predation on sentinel eggs of Helicoverpa zea Boddie was evaluated, and in Texas predation on the beet armyworm, Spodoptera exigua (Hubner) was also determined. Through the use of visual observation, accurate identification of predators causing mortality was possible and the impact of nocturnal predation confirmed. Predation was typically greater than 30% per 24 h in all crops in all locations and was as high as 98% in a 24 h period. In Kentucky, predation was slightly higher during the day than at night in corn while it was higher at night in soybean. In Texas, observations of predation were similar during the day and at night in corn and soybean; 73.2% of the predation events observed in cotton were at night. This pattern of high nocturnal predation in cotton was consistent through the season. The observations of predation in Kentucky (>400) and in Texas (>1500) were summarized and dominant predators in each crop determined. In Kentucky, the most frequently observed predators were Coleomegilla maculata De Geer in corn and Nabis roseipennis Reuters in soybean. In Texas, the most frequently observed predators were ants in corn, Geocoris spp. in soybean and a guild of wandering spiders in cotton. Predator complexes observed during diurnal and nocturnal observations were typically dissimilar in all crops and locations. The complex of wandering spiders were comprised primarily of Hibana futilis (Banks), Hibana arunda Platnick, and Cheiracanthium inclusum (Hentz) which were responsible for 24.8% of all observations of predation in cotton. If only diurnal observations had been made in cotton, Geocoris spp. would have been the most frequently observed. However, with the nocturnal observations the Geocoris spp. were only the fifth most frequently observed behind spiders, ants, the cotton fleahopper Pseudamatoscelis seriatus (Reuter) and mites. 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. The importance of carefully studying the nocturnal predators was discussed.
Technical Abstract: Predation of pests in field crops is a critical component of pest control. However, despite the effort to quantify the impact of predators, little time has been spent on the activities of nocturnal predators. I studied night time predation on moth eggs in corn and soybean in Kentucky from 1993-4 and in cotton, corn and soybean in Texas from 2001-4. In both locations predation was carefully studied to separate predation occurring during the day and night using visual observation. Through the use of visual observation, accurate identification of predators feeding on eggs was possible and the impact of nighttime predation confirmed. Studies conducted in Kentucky and Texas on predation of lepidopteran eggs found that predation occurring at night was a significant portion of total predation. In south Texas cotton, nocturnal predation was particularly important with about 3/4 of the predation occurring at night. Predator complexes observed during day and night were typically dissimilar in all crops and locations. Night active predators were previously unreported and in Texas cotton were dominated by wandering spiders. If only daytime observations had been made in cotton, big-eyed bugs would have been the most frequently observed. However, with the nocturnal observations the big-eyed bugs were only the fifth most frequently observed behind spiders, ants, the cotton fleahopper and mites. Of the predators observed feeding at night, only the ants have been studied as predators of lepidopteran eggs, little or nothing is known about the predatory characteristics of the other taxa. The importance of carefully studying the night active predators was discussed.