Bagworms are on the list of the top five worst pest insects in Delaware.

Native Delaware: Bad bugs

UD expert releases list of top five bad bugs of summer

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9:51 a.m., May 7, 2013--Summer is right around the corner and along with the good (long days, holiday weekends and lush, green landscapes) comes the bad (humidity, beach traffic and bugs). 

Admittedly, there are plenty of beneficial insects that pollinate flowers or gobble pests, and plenty of insects that just hang around, doing neither bad nor good.

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In fact, beneficial insects far outnumber pests, according to Brian Kunkel, an entomologist with University of Delaware Cooperative Extension. “More than 97 percent of arthropods typically seen in the home landscape are either beneficial or innocuous,” he says.

But it’s the other three percent that can drive us crazy, wreaking havoc with our prized rose bushes, tomato plants or elm trees. Or, in the case of biting insects, leaving itchy welts all over us.

Kunkel has pulled together a list of the worst pests – what he’s dubbed the “top five bad bugs of summer.”

“Another entomologist might come up with a very different ranking – pest conditions change from year to year and from location to location. I’ve had people call me about a stink bug outbreak in one neighborhood and the next neighborhood only had mild issues,” notes Kunkel. “But these ‘top five bad bugs’ are the ones that Extension gets the most calls about; the ones that inflict the most damage in area gardens, nurseries, and neighborhoods.”

Here’s Kunkel’s list of the top five bad bugs of summer 2013:

1. Scale pests

2. Wasps

3. Bagworms

4. Japanese beetles

5. Stink bugs

You might be wondering why cicadas didn’t top this list – after all, it’s been all over the news about the millions of cicadas ready to emerge in the Mid-Atlantic after a 17-year slumber. 

While plenty of cicadas will be flying around southeastern Pennsylvania, southern New Jersey and Maryland this summer, Delaware will see only the occasional cicada crossing the state line. That’s because Delaware’s brood – called Brood X – is still burrowed under ground and isn’t due to emerge until 2021.

Far more worrisome than big, fat cicadas are teeny tiny scale pests, notes Kunkel. In fact, scale pest are the single biggest threat to Delaware home landscapes virtually every growing season, he says. 

These insidious pests are easy to overlook because of their diminutive size and inconspicuous color. Oystershell scales are about one-eighth of an inch long and dark brown, blending right into the tree branches that they latch onto. It usually isn’t until the branch is dying that the homeowner realizes that these bumps are actually insects sucking sap from the tree.

While oystershell scales prefer certain trees – willows, lilacs, dogwoods and poplars here, as well as aspens and cotoneasters out West – they aren’t picky. They’ve been found on 130 different species of plants. And oystershell is just one of 8,000-plus different scale insects; almost every plant is vulnerable to some type of scale insect.

Kunkel rates wasps as the number two bad guy, not because of damage they do to the landscape but because of the damage they can do to people. 

Only the female wasp stings but when she does, you’re going to know it. Even a normal, non-allergic reaction usually results in pain, swelling and redness around the sting site. A localized reaction can bring swelling to an entire limb. Allergic reactions, of course, require immediate medical attention. 

Next up on the bad bug list are bagworms. Kunkel says there is variability from year to year in the size of Delaware’s bagworm population. “Some years are a lot worse than others,” he says.

Like scale pests, bagworms start out very small and aren’t likely to be noticed by the homeowner. They are generalists in their eating habits – they are known to eat about 100 different species of plants, including cherries, pines, junipers, arborvitae and birch.

Japanese beetles makes Kunkel’s list primarily because of Sussex County outbreaks in recent years “The population of Japanese beetles in Sussex is much higher than in Kent and New Castle counties,” says Kunkel. “Georgetown has some decent-sized populations but throughout Sussex they can be an issue.” 

The last pest to make it onto the bad guy list – the stink bug – is the one everyone loves to hate. The brown marmorated stink bug made serious inroads into Delaware in 2011, particularly in New Castle County. Last summer, the population was considerably lower.

Farmers and homeowners in other states have seen considerable damage to their plants. Fruit orchards have been particularly hard hit.

“Thus far, brown marmorated stink bug has been more of a nuisance than a pest in the home landscape in Delaware,” says Kunkel. “However, some of our farmers have experienced issues. We have a number of UD research projects underway so we can work to control this pest.” 

Help for what’s bugging you

Got a pest problem in your yard or garden? Call Cooperative Extension’s free garden help line. In New Castle, call 831-8862; in Kent call 730-4000; in Sussex call 856-2585, ext. 535. 

Article by Margo McDonough

Photo by Brian Kunkel

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