Time-specific life tables for the pea aphid,Acyrthosiphon pisum (Harris ), on alfalfa |
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Authors: | William D Hutchison and David B Hogg |
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Institution: | (1) Department of Entomology, University of Wisconsin, 53706 Madison, Wisconsin, USA;(2) Present address: Western Cotton Research Laboratory, Agricultural Research Service, USDA, 4135 E. Broadway, 85040 Phoenix, AZ, USA |
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Abstract: | Summary Time-specific life tables were constructed for three pea aphid,Acyrthosiphon pisum (Harris) (Homoptera: Aphididae), populations using a modification ofHughes' analytical procedure. All populations were studied on second-growth alfalfa (mid-June to mid-July) in south central Wisconsin;
data for two populations were collected during 1980, and data for the third population were collected during 1982. The intrinsic
rate of increase (r
m) estimated on a physiological time (day-degree) scale under field conditions but in the absence of natural enemies, provided
a reliable estimate of potential population growth rate and was used in preference toHughes' approach of estimating potential population growth rates directly from stage structure data. Emigration by adult alatae and
fungal disease were the major sources ofA. pisum mortality in each of the three populations studied. These factors were most important because of their impact on reducing
birth rates within the local population. Parasitism was never greater than 9 percent. Mortality attributable to predation
ranged from 0.0 to about 30.0%; however, even at the highest predator densitiesA. pisum populations increased exponentially. |
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