Integrated Codling Moth Management
MICROBIAL INSECTICIDES
Bacillus thuringiensis (Bt) products, at present, show little promise
for codling moth control. In field trials where Bt products were
applied two times each week, only 80% control was achieved, much less than
would be acceptable in a commercial orchard, and at a very high cost.
However, these products have been moderately to highly effective controlling
leafrollers in northwest USA (Brunner & Smith 1993a,b). In general,
they are not considered detrimental to biological control agents because
they act as stomach poisons. While Bt has been shown to be toxic
to parasitoid adults when given orally (Hamed 1987), it is unlikely that
this form of ingestion would play a major role under field conditions.
Bt products do not immediately kill the host larva, but do stop it from
feeding. Bt products represent a "soft" means of controlling
leafrollers which have been the major pest problem in orchards using pheromones
to control codling moth in apple orchards. Formulations of the endotoxin
produced by different strains of Bt have been tested, but with little success
so far. More effective Bt formulations may become available in the
future with the development of new, genetically engineered strains.
A granulosis virus, originally identified from codling moth, has been
shown to be effective for control of neonate larvae. This virus was
developed for commercial use in Europe and has been used in the United
States under experimental use permits. Development of a virus formulation
is being pursued by Crop Genetics International and the University of California.
Availability of an efficacious granulosis virus formulation for codling
moth would add a highly specific method of remedial control that would
not interfere with natural controls of other pests. Another microbial
that has been tested is Beauveria bassiana, a fungal pathogen.
A nematode, Neoplectana carpocapsae, was identified from codling moth larvae
and is being developed for soil-inhabiting insects. Its use against
codling moth shows little promise.
