Evaluation of organically acceptable insecticides as stand-alone treatments and in rotation for managing yellowmargined leaf beetle, Microtheca ochroloma (Coleoptera: Chrysomelidae), in organic crucifer production.

BACKGROUND

Yellowmargined leaf beetle, Microtheca ochroloma, is the most damaging pest of organic crucifer crops in the southern United States. Experiments were conducted over four growing seasons (2007-2010) in Alabama to evaluate some botanical and microbial insecticides approved by the Organic Materials Review Institute (OMRI) against M. ochroloma in organically grown crucifer crops. Insecticides evaluated included PyGanic(®) (pyrethrum), Aza-Direct(®) (azadiractin), Entrust(®) (spinosad), Mycotrol O(®) (Beauveria bassiana strain GHA) and NOFLY(®) [Isaria ( = Paecilomyces) fumosoroseus strain FE 9901]. Two experimental organic formulations, Tick-Ex (Metarhizium anisopliae strain F52) and MBI-203 (Chromobacterium subtsugae), and one non-OMRI-listed formulation, Novodor(®) (Bacillus thuringiensis subspecies tenebrionis), were also evaluated. The insecticides were applied as stand-alone treatments at recommended field rates on a weekly schedule. In 2010, some of the treatments were also evaluated in rotation/alternation with Entrust(®) . Insecticide efficacy was determined by comparing densities of M. ochroloma larvae and adults and crop damage ratings in treated versus untreated turnip plots.

RESULTS

Entrust(®) consistently performed well in suppressing M. ochroloma adults, larvae and crop damage. PyGanic(®) was the second best treatment. PyGanic(®) or NOFLY(™) can be applied in rotation with Entrust(®) for effective management of M. ochroloma.

CONCLUSIONS

Entrust(®) applied weekly or in alternation with PyGanic(®) or NOFLY(™) provided acceptable control of M. ochroloma in organic crucifer production.