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INFLUENCES OF TEMPERATURE, HUMIDITY, AND CORN CANOPY MICROENVIRONMENT ON POPULATION DYNAMICS OF THE BANKS OF GRASS MITE, OLIGONYCHUS PRATENSIS (BANKS)
Abstract
Age specific developmental rates were determined for all stages of Banks grass mite (BGM) Oligonychus pratensis (Banks) (Acariformes:Tetranychidae) at constant temperatures from 23 to 39 C. Developmental rates were shown to be highly temperature dependent and maximum development was predicted to be near 37 C. A wet-dry, forced air humidity system was designed to provide high, medium, and low vapor pressure deficits (VPD) at 25, 33, 36, and 39 C. Humidity was shown to have little effect on development. However, at 39 C and low VPD, egg hatch was severely reduced. Temperature had a greater influence on longevity than did humidity. BGM lived longer at cooler temperatures. At high temperatures, longevity tended to be reduced at lower VPD. The intrinsic rate of natural increase (r(,m)) was dependent on temperature and humidity. At 25 C, r(,m) was similar for the 3 VPDs. However, at 33, 36, and 39 C, low VPD conditions caused a reduction in survival rates and fecundity, resulting in lower r(,m). The highest r(,m) occurred at 36 C and high VPD. Field studies indicated that BGM numbers increased most rapidly over a narrow range of plant stress. Severe stress resulted in low numbers, probably due to reduced nutritional quality of the host. Non-stressed plants also had low BGM numbers. On moderately stressed plants, mite populations tended to be directly related to the amount of stress. Corn canopy and leaf temperatures were higher on stressed plants and canopy temperatures were significantly correlated with BGM numbers. These data suggest that high canopy temperatures and low humidities may promote fast developmental rates, high survival rates and increased fecundity of BGM, resulting in a high r(,m). Therefore, BGM densities appear to be closely linked to microenvironmental conditions.
Subject Area
Entomology
Recommended Citation
PERRING, THOMAS MCADAM, "INFLUENCES OF TEMPERATURE, HUMIDITY, AND CORN CANOPY MICROENVIRONMENT ON POPULATION DYNAMICS OF THE BANKS OF GRASS MITE, OLIGONYCHUS PRATENSIS (BANKS)" (1983). ETD collection for University of Nebraska-Lincoln. AAI8318673.
https://digitalcommons.unl.edu/dissertations/AAI8318673