A STUDY OF TYROPHAGUS-PUTRESCENTIAE (ACARI, ACARIDAE) AS A FACULTATIVE PREDATOR OF SOUTHERN CORN-ROOTWORM EGGS

An acarid mite, Tyrophagus putrescentiae (Schrank), was found to feed on southern corn rootworm (SCR) eggs in peanut and corn agroecosystems. In laboratory studies, T. putrescentiae eggs were generally oviposited directly on SCR eggs, and immatures fed only on previously damaged SCR eggs, depending upon adults to penetrate the chorion of SCR eggs. Individual adult T. putrescentiae significantly reduced (P < 0.05) the number of larvae to eclose from 40 SCR eggs. Initial population levels of 1, 2, 5, 10, and 20 adult mites reduced the SCR egg population by 19, 43, 69, 92, and 98% respectively. Mites were attracted to SCR eggs from a distance of 8 cm, with significantly (P < 0.001, .chi.2 test) more mites found in containers which included SCR eggs as compared with containers without SCR eggs. In greenhouse experiments, significantly (P < 0.05) fewer SCR adults emerged from soil-filled containers which included 25 T. putrescentiae and 100 SCR eggs, as compared with containers which had only SCR eggs. We suggest that T. putrescentiae may be an important biological control agent of the SCR in certain agroecosystems.