1a.Objectives (from AD-416)
Objective 1: Determine the effect of temperature and reproductive state on susceptibility of tarnished plant bugs to Beauveria (B.) bassiana (ARSEF 8889).
Objective 2: Determine the effect of exposure to insect growth regulators (IGRs) and B. bassiana (ARSEF 8889) on immature tarnished plant bug survival.
Objective 3: Determine the effect of host plant and application timing (season) on susceptibility of tarnished plant bugs treated with ARSEF 8889 and IGRs (in situ).
1b.Approach (from AD-416)
The effect of temperature and reproductive state on the susceptibility of tarnished plant bugs to Beauveria (B.) bassiana (ARSEF 8889) will be determined in replicated laboratory tests. The two reproductive states tested will be normal reproductive adults and nymphs and diapausing adults and nymphs that produce diapausing adults. Temperatures tested will range from 10°C to 30°C. Insect growth regulators (IGRs) will be tested with nymphs in replicated laboratory tests to determine which IGRs are effective and the rate at which to use them. The most effective IGR(s) will be tested in laboratory tests in combination with ARSEF 8889 to determine the most effective combination treatment. Results from the laboratory tests will be tested in the field in replicated tests in cotton (for in-season plant bug control) and in the fall and winter on wild host plants (for control of the diapausing overwintering generation). The effect of IGRs and ARSEF 8889 treatment on beneficial arthropod populations will be evaluated in the field tests and with additional laboratory tests.
The effectiveness of ARSEF 8889 (NI8) against reproductive and diapausing Tarnished Plant Bug (TPB) was evaluated in several laboratory tests at temperatures from 10° to 30° C. The fungus was found to be equally effective against reproductive and diapausing TPB with higher infection rates at the warmer temperatures. A replicated small plot test in cotton was conducted during July 2010. Treatments tested were NI8, NI8 + novaluron, novaluron, and an untreated check. Results were inconclusive because of adult movement between the plots. A large replicated test in cotton is currently being conducted in which plot size is one acre. This should allow us to have a valid evaluation of the results. A preliminary test was conducted in October and November 2010 in which NI8 was used alone and in combination with novaluron to kill overwintering TPB adults and nymphs on pigweed and tall goldenrod. Beneficial arthropods found on the wild hosts were also identified and their populations estimated before and after treatment. The novaluron and novaluron plus NI8 treatments were very effective in reducing numbers of nymphs on both wild hosts with infection rates as high as 41.5%. Infection rates among adults with NI8 were as high as 77.7%. This test will be conducted in October 2011 using replicated plots. The most abundant beneficial arthropods on both wild hosts were spiders in the families Thomisidae (crab spiders) and Salticidae (jumping spiders). Crab spiders made up 48.5% of the total number of beneficial arthropods while jumping spiders were 22.2%. Crab spiders and jumping spiders were evaluated in laboratory tests for susceptibility to NI8 infection. Crab spiders were mostly immune while a low percentage of jumping spiders were infected. Green lacewing, ladybird beetle and big-eyed adults were also tested in the laboratory for susceptibility to NI8. Infection rates were low for these predators.