Controlling Bugs Leads to Unintended Consequences

5/12/2012 10:00 AM
By Chris Torres Staff Writer

Expert Suggests Less Thinning in Orchards

GAP, Pa. — To the naked eye, you would think nothing was out of the ordinary in Elam Beiler’s orchard.

But look closer and you’ll see a tree that has been stripped of any life, withering, with no leaves and seemingly no hope.

It’s the result of a major scale infestation, and while it appears, at least on Beiler’s farm, to be concentrated in one apple tree, it’s an example of the unintended consequence of using broad spectrum sprays to control bugs like the brown marmorated stink bug.

At a meeting Tuesday evening at Beiler’s 10-acre orchard just outside Gap, Greg Krawczyk, senior research associate and entomologist at the Penn State Fruit Research and Extension Center (FREC) in Biglerville, spoke about the impacts of broad-spectrum sprays on beneficial insects, which are usually the first line of defense in controlling insects such as scales.

Beiler’s farm is not the only example of scale infestation Krawczyk has seen. He said he believes the use of sprays such as pyrethroids and neonicotinoids to control stink bugs and other insect pests are also knocking out beneficial wasps and other bugs usually good at controlling scales.

“The reality is, scales are becoming a problem everywhere,” Krawczyk said.

It adds another complication for growers already stressed from having to use more chemicals to control the stink bug, which can feed virtually anywhere and has proved hard to control with less powerful sprays.

Speaking of the brown marmorated stink bug, Krawczyk said growers need to be ready to control them once summer comes around, since they are still emerging from overwintering sites.

The late March cold spell, which came after an unusually warm middle of the month, was actually welcome, he said, since it knocked out some of the population and held some back from emerging at all.

The insects are likely laying eggs right now, and some nymphs are already active. But he expects any major infestation to come in midsummer.

Even then, Krawczyk said, growers should scout their orchards first before making a decision to spray because not all growers will have an issue with stink bugs and less spraying — at least in the sense of saving money and not using broad-spectrum varieties — is a good thing.

As far as scales, he said the tiny critters, which form a protective shield and feed on tree sap when adults, are most effectively controlled when they are young, while they are crawling on trees looking for a place to feed.

Certain horticultural oils and insecticides are most effective against them. But timing is everything, he said, since they are very difficult to control once they grow a protective shield over them.

They move very slowly and usually cluster around a certain area of an orchard. But Krawczyk said scales can spread, if allowed.

May is the time for thinning. But under gloomy skies and a light mist, Jim Schupp, associate professor of horticulture and director of FREC, told the growers that this might be the year to take it easy on trees.

A lot of it has to do with the weather. Schupp said the lack of sunlight, coupled with rainy conditions, leads to less photosynthesis. The effect is a weaker tree, which he said is more susceptible to crop loss.

“I don’t think there will be any problem with chemical uptake this year. This year is a year to take thinning a little lighter. Don’t push things as hard,” he said. “That said, you still need to chemical thin. But this is not the year to throw the whole kitchen sink at it.”

And there are good reasons for growers not to thin too hard. Both apples and peaches could go for good money, since growers in other states are reporting major losses due to late freezes.

Schupp said growers in Michigan, western New York and North Carolina have experienced major losses, with significant losses also being reported in areas such as the Hudson Valley of New York, West Virginia and Northern Virginia.

He estimates between 30 and 40 percent flower mortality in apples in and around Adams County. There was also some losses in peaches, but the timing of the freezes came after the fruit on those trees had already set.

“I think we’re looking at a pretty good peach crop,” he said. “We’re about as well off as any other state in the East at this point.”

Taking it easy on thinning to take advantage of a bigger crop and better prices, though, comes with a caveat. He said large crops of fruit can actually inhibit flowers for next year. He suggested return bloom sprays in June, particularly in varieties of apples that don’t come back as strong next year, even after being thinned.

He said growers planning on thinning their peaches should do it now.

“Big peaches ought to be worth good money this year,” he said.

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