PINK-BOLLWORM ADULT AND LARVAL SUSCEPTIBILITY TO STEINERNEMATID NEMATODES AND NEMATODE PERSISTENCE IN THE SOIL IN LABORATORY AND FIELD-TESTS IN ARIZONA

Percentages of infected pink bollworm, Pectinophora gossypiella (Saund ers), (PEW) adults emerging from pupae placed on soil treated with Ste inernema carpocapsae (Weiser) or S. riobravis Cabanillas, Poinar and R aulston were 16.7-34.0% and 20.7-26.7%, respectively. Some (0-13%) pup ae that did not produce adults were also infected. Under laboratory co nditions in moist soil, PEW larval mortalities were 91.9% on the day o f treatment and 5.1% on day 35 following treatment for larvae released on soil surfaces treated with S. riobravis and 50.0 and 7.0%, respect ively, for larvae buried 1.7 cm in the soil. Mortalities for larvae re leased on soil surfaces treated with S. carpocapsae were 90.5% on the day of treatment and 38.5% on day 35 following treatment. Mortality of larvae buried 1.7 cm in the soil was 31.0% on the day of treatment an d 3.0% on day 35 following treatment. When soil treated with S. riobra vis was allowed to dry between PEW larval releases on soil surfaces or burial in soil, but wetted on the day of larval exposure, percentage mortalities ranged from 37.3-97.8% for larvae exposed on the soil surf ace and 62-84% for buried larvae over a 35-day test period. Also, unde r laboratory conditions S. riobravis parasitized higher percentages of PEW larvae buried in the soil than S. carpocapsae but S. carpocapsae parasitized higher numbers of larvae released on the soil surface than did S. riobravis. Under field conditions, with irrigations about ever y 14-21 days, PEW larval mortalities after exposure to soil samples fr om plots treated with S. riobravis at the rate of 5 nematodes per cm(2 ) of soil surface were 50% on the day of treatment and 2.5% on day 90 following treatment. Larval mortality percentages after exposure to so il samples from plots treated with S. carpocapsae at the rate of 5 per cm(2) of soil surface were 32.5, 15.3, 5.3 and 2.5, respectively, for the day of treatment and day 1, 7, and 15 following treatment. No fur ther mortality occurred in bioassays conducted up to 90 days following treatment. With plots treated with 25 nematodes per cm(2) of soil sur face, PEW larval mortalities ranged from 100% on the day of treatment to 7.5% on day 63 following treatment with S. riobravis and 92.5% on t he day of treatment to 5% on day 7 following treatment with S. carpoca psae. Percentages of larval mortality after exposure to soil samples f rom plots treated with S. riobravis increased after each irrigation, b ut did not increase after exposure to soil samples from plots treated with S. carpocapsae.