Steinernematid Nematode Infections of Pink Bollworm Larvae in Field Tests

Abstract

Under field conditions, pink bollworm (PBW), Pectinophora gossvpiella (Saunders), larvae were exposed to soil samples from plots treated with Steinernema riobravis at the rate of 5 nematodes per cm² of soil surface. Larval mortalities were 50% on the day of treatment and 2.5% on day 90 following treatment with irrigations about every 14 to 21 days,. Larval mortality percentages after exposure to soil samples from plots treated with S. carpocapsae at the rate of 5 per cm2 of soil surface were 32.5, 15.3, 5.3 and 2.5 for the day of treatment and day 1, 7, and 15 following treatment, respectively. No further mortality occurred in bioassays conducted up to 90 days following treatment. With plots treated with 25 nematodes per cm² of soil surface, PBW 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 the day of treatment to 5% on day 7 following treatment with S. carpocapsae. Percentages of larval mortality after exposure to soil samples from plots treated with S. riobravis increased after each irrigation, but did not increase after exposure to soil samples from plots treated with S. carpocapsae.