Population Dynamics and Dispersion Patterns of Nymphal Threecornered Alfalfa Hoppers (Homoptera: Membracidae)
Abstract
Seasonal abundance and dispersion characteristics of nymphal threecornered alfalfa hopper (TCAH), Spissistilus festinus (Say), were determined for soybean fields located in Alabama and Florida to contribute to a better soybean integrated pest management program. Four fields were sampled in 1985 and two fields were sampled in 1986. Populations were present in each field from vegetative stages of crop growth until senescence. Nymphal populations of two complete generations occurred in each field, with populations broadly overlapping. Population dynamics were similar to that reported from Louisiana, indicating a similar phenology for TCAH throughout the southern U.S. Results also indicate that TCAH is an occasional pest of soybean in the region. Dispersion statistics of variance/mean ratio and Taylor's power law were calculated for nymphal sample estimates. Populations were aggregated most of the time. The Taylor's power law relationships were used to calculate the number of shake-cloth samples needed to estimate nymphal TCAH density at the 10 and 25% precision levels. A large number of samples are needed to estimate density at the 10% precision level, but fewer than 15 samples are needed at the 25% precision level when nymphal densities are > 4 per m of row.Downloads
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