Western grapeleaf skeletonizers
We have found WGSs on our grape vines. Should we try to treat the vines now or wait until spring? We have just finished our harvest. Is the bascillus thuringensis the best control for an organic farmer? Our vineyard is in Santa Fe ,NM.
Thanks so much for using eXtension and "Ask the Expert"!
For Western Grape Skeltonizer, you have a couple of options as an organic vineyard. One option is to apply Bacillus thuringiensis ssp. kurstaki (also sold under the names of; "Biobit", "Condor", "Cutlass", "Dipel","Full-Bac", "Javelin", "M-Peril" and "MVP"). Use the label rates, however it is only effective against young larvae. So, if you are seeing older caterpillars or flying insects, it won't be effective. The other (more expensive) option is to use Entrust, which is a spinosad. This has to be applied when eggs first hatch to target the young larvae, and it is most effective when the larvae ingest the chemical.
For more information: http://ipm.ucdavis.edu/PMG/r302301011.html (be sure to check that all chemicals are allowed in NM, since this is from California) and: http://entnemdept.ufl.edu/creatures/fruit/grapeleaf_skeletonizer.htm.
I hope that helps! Also, there is a great resource in New Mexico for grape related issues - Dr. Bernd Maier. http://aces.nmsu.edu/directory/person.php?person_id=981.