We have a heavy infestation of cucumber beetles and flea beetles in both veggie and flower garden this year, worse than past years. Tried beneficial nematodes (three separate applications this year) to no avail. We have always gardened without using any pesticides and would be very reluctant to use any thing that would endanger bees or other beneficials. We also have dozens of black swallowtail caterpillars currently inhabiting our garden and do not want to put them at risk. It seems that every "safer" method of dealing with these pests presents some level of danger to beneficials. What would you recommend as a safe but effective course of treatment? Are there predatory insects that can be obtained and introduced? Can you please "rank" potential treatments according to two factors: most effective/least harmful?
Oakland County Michigan
We can use some more guidance in how to use the Neem oil. Our bottle of Garden Safe Neem Oil extract concentrate (meant to be diluted 2-4 tablespoons in a gallon of water, and applied with a sprayer) says to spray on foliage, underside as well. "Kills on contact": does this imply that the Neem oil has to be sprayed directly on the beetle? or that the beetle will pick it up from the foliage? The container also states that it is harmful to bees if there is direct contact, so not to spray when bees are active (so, I assume, spray later in the evening). Additionally: what is the shelf life of Neem oil? The bottle we have was bought prior to last year: is it too old?
Related question: we made 3 applications, in a heavy concentration, of predatory nematodes, purchased from one of the supplier companies. We made these applications 2-3 weeks apart, starting after last frost, wetting the ground both before and after application, concentrating on the vegetable and flower garden areas, along with adjacent lawn areas. We haven't noticed a benefit from this application, so of course we're wondering if this was correctly used, or if others have found this to be an effective remedy for the beetle problem. Some feedback on the use of predatory nematodes, please?
And the last caution: the damaging-causing adult beetles are very mobile. So just because you are diligent in managing them in your own garden-it doesn't mean they won't just fly in from neighboring yards!