The use of aerial color infrared photography as a survey technique for Psorphora Columbiae (Dyar and Knab) (diptera: culicidae) oviposition habitats in Texas riceland agroecosystems

Abstract

Soil samples were collected from permanent pastures, rice and soybean fields in Chambers County, TX over a 2 1/2 year period to study the oviposition behavior of Psorophora columbiae (Dyar and Knab) and gather ground verification data in support of the study of the use of aerial color infrared photographic techniques to detect oviposition sites in southern riceland agroecosystems. Fields planted to soybeans appeared to be important oviposition sites during the summers when heavy rainfall was experienced in the study area. During dry summer conditions, oviposition within soybean fields was concentrated in low areas. Oviposition on nearby rice field levees was low during the wet summers and relatively high during the dry summer. Within the permanent pastures, oviposition activity was relatively low and restricted to lower areas of the pastures. Soil sample data from soybean fields provided insight into Ps. columbiae oviposition behavior within this component of the riceland agroecosystem. Data suggest there is no difference in frequencies of positive samples between those collected from the base of plants and samples collected from the area between the rows. However, a significant difference in abundance of eggs was observed, with more eggs present in samples collected from the rows. During wet years, positive samples appeared to be scattered randomly throughout the field. During dry years, a greater abundance of eggs was found in samples collected from low areas.Eight photographic missions were flown over the study fields during a variety of seasons and at various altitudes. Features attractive for oviposition by Ps. columbiae females (i.e. rice field levees, tire tracks, ditches, and low areas) can be readily detected on aerial color infrared photographs. Features associated with Ps. columbiae oviposition sites were easily visible on photographs at scales as small as 1/42,000. Two photographic missions per year are recommended to provide information on land-use and oviposition habitats. A winter mission, following a rain, will provide a view of low areas within fields which may be obscured by summer vegetation. A summer mission will provide current land-use and crop-distribution information and may show plant stress conditions due to excessive soil moisture.