Extraction precision of sieving and brine flotation for removal of wheat midge, Sitodiplosis mosellana (Diptera: Cecidomyiidae), cocoons and larvae from soil

Accuracy of extracting wheat midge, Sitodiplosis mosellana (Gehin), cocoons and larvae from soil samples averaged 99 and 94% for a sieving method and a brine flotation method, respectively. The time required to process bulk soil samples containing wheat midge cocoons was almost twice as long by sieving as by flotation. The time required to process field-collected soil samples containing wheat midge cocoons was also significantly longer by sieving and longer for a silty clay loam than for a very fine sandy loam. Extraction costs varied from $1.65 to $3.99 per sample unit depending upon method and soil type. Sieve extraction is the best method for studies on population dynamics and flotation extraction is the best method for distributional surveys and density estimates.