EVALUATION OF TERMITICIDES RESIDUES AND BIOAVAILABILITY FROM FIVE SOIL TYPES AND LOCATIONS IN TEXAS

Abstract:
The results of a four year study with six termiticides including: bifenthrin, chlorpyrifos, cypermethrin, fenvalerate, permethrin, and isofenphos indicate significant differences in effectiveness among products applied to different soil types in Texas. Each of the five field test locations represents very different soil types and environmental conditions. Test locations within Texas included: Lubbock, Dallas, Overton, Corpus Christi and College Station. Termiticides were applied in 1990 with soil samples taken from the replicated treatment plots at 1 and 6 months, and then annually through four years. Soil residues of termiticides were measured with gas chromatography. The amount of pesticide remaining in each sampling period indicates a significant loss of termiticide by the fourth year of the test. The bioavailability of termiticide remaining in the soil was estimated through bioassays utilizing field collected subterranean termites (Reticulitermes flavipes(Kollar)). Both tunneling distance and mortality were used as indicators of termiticide activity and availability. The results of the bioassays confirm the findings of the residue analysis portion of the project. The most stable termiticides, through four years, were permethrin and fenvalerate. Isofenphos was the least stable with significant loss of activity within 24 months post-application. The most challenging conditions, in terms of effective termiticide residuals retained through time, were alkaline soils with high clay content and organic compositions greater than 1%. The most favourable soils were those that are acidic with low clay content and low organic content