Author
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Fielding, Dennis |
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Submitted to: International Journal of Pest Management
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 5/17/2011 Publication Date: 6/30/2011 Citation: Fielding, D.J. 2011. Assessment of grasshopper abundance in cereal crops using pan traps. International Journal of Pest Management. 57(3):239-247. Interpretive Summary: Grasshoppers and locusts frequently invade cereal crops from adjacent source habitats. To protect the crops from grasshopper damage, areas bordering crop fields may be treated with insecticides. Study of grasshopper dispersal into crops and evaluation of various management alternatives is hindered by a lack of simple, reliable sampling methods in small-grain crops. Water-filled pan traps were tested as a means of assessing grasshopper abundance in barley. Sample size recommendations were developed based on field data collected over two seasons. Knowing the optimal number of pans to use allows researchers to obtain reliable grasshopper population assessments with the most efficient use of resources. Overall, pan traps show promise as a means of studying grasshopper dispersal into field crops. Technical Abstract: Grasshoppers and locusts frequently invade cereal crops from adjacent source habitats. To protect the crops from grasshopper damage, areas bordering crop fields may be treated with insecticides. Study of grasshopper dispersal into crops and evaluation of various management alternatives is hindered by a lack of simple, reliable sampling methods in small-grain crops. Water-filled pan traps were tested as a means of assessing grasshopper abundance in barley. Sample size recommendations were developed using Taylor’s power law to describe the relationship between sample mean and variances. The slope of the regression of log10(variance) on log10(mean), 1.63, indicated a highly clustered distribution of grasshoppers per trap. Based on these data, given a mean of 10 grasshoppers per pan, 13 pans would ensure, with 95% confidence, a SE within 15% of the mean. With a mean of 20 grasshoppers per pan, 10 pans would provide a SE within 15% of the mean. In comparisons of species proportions in sweep net and pan trap samples on fallow fields, there was a good correlation between the two methods, but some differences were noted. In particular, proportions of Chorthippus curtipennis tended to be greater in sweep samples than in pan traps. Overall, pan traps show promise as a means of studying grasshopper dispersal into field crops. |
