Mar 26, 2012

Spraying oil for pest control

It will be interesting to see just how faithfully arthropod pest development responds to ambient temperatures during this year’s unnaturally early spring warm-up, and whether our traditional correlations with tree phenology will break down in deference to raw heat accumulation and its effects on insect growth processes. For instance, European red mite egg hatch has always been associated with tight cluster bud stage, but will it jump the gun this year, or else maybe lag behind tree growth? We don’t have any good basis for predicting either way, so for the time being, I imagine we’ll just proceed with our recommendations as if the calendar actually said April instead of March.

To that end, we historically take the approach of pointing out the potential value of using horticultural mineral oil as an early season pest management tactic, which used to be a pretty much universal practice years ago, when mites and scales were more problematic and the options for dealing with them were less abundant. Those of us familiar with fruit insect and mite trends still believe it is worthwhile to consider the use of oil applications for early season mite and insect control in both apple and pear plantings, because of its effectiveness, relative affordability, and safety from a biological and pesticide resistance perspective.

Taking advantage of the most favorable spraying conditions to maximize tree and block coverage can be a challenge in our area, but few pest management efforts have such potentially high returns when all factors are taken into account, and this year may offer more opportunities than are normally available. Mite and scale population trends are typically not the same each year, and weather conditions are certainly among the most variable of factors in the pest scenario from one year to the next. Before you decide that it’s too much trouble or cost to invest in a prebloom spray of oil, be sure you’re aware of how much it could cost you (biologically as well scales ends up being necessary later in the season.

Applications are useful against pear psylla all throughout the swollen bud stage. Although it’s capable of killing adults and nymphs that are directly contacted, oil is recommended mainly because the residue repels adult females looking to deposit their eggs, something that is already taking place across the state. The objective of using oil is to delay the timing of any needed insecticide spray until as late as possible start. If your buds are at the dormant stage (most orchards are probably past this point), one spray of three-percent or two at one-percent up to white bud should be adequate for this purpose, especially if applied as soon as the psylla some European red mite control at the same time.

By Art Agnello, Cornell University