Bad insects are wreaking havoc on gardens and yards, and decimating ash trees in Boulder County. Here are ways to keep these invaders in check.
By Carol O’Meara
Boulder County has long been a mecca for lovers of nature, beauty and the outdoor lifestyle. But lately it’s become the destination location for newcomers of a different ilk, those who look at our area as a veritable buffet of opportunity. A buffet starring the flowers, trees and fruits of our landscape.
Four invasive insects are new to our area, thugs whose reputations preceded them: Japanese beetles, spotted wing drosophila, multicolored Asian lady beetles, and the worst of the worst, the emerald ash borer. Be on the lookout to protect your plants against these destructive invaders.
Pretty but Potent
The Japanese beetle (Popillia japonica) is a scarab beetle with a shiny, metallic-green body and bronze-colored wings. Six tufts of white hair line each side of their half-inch-long body. Look for the beetle munching on plants in early to midsummer. The larvae are white grubs that live in soil, making them easily spread by gardeners who give plants to friends.
The beautiful beetles gorge on more than 300 types of plants, including grapes, raspberries, beans, apples and roses. Mobbing the plants, they cause serious injury. “It’s a bummer of a pest, because this one just doesn’t care (what it eats),” says Susanne Thorne, owner of Innovative Outdoor Designs and Services. “It’s voracious and can do a lot of damage, plus there are few options for control.”
Western Colorado successfully fought off the bug by not watering. But when it appeared in south Denver, the challenge grew tough; dried landscapes were unfeasible here. Boulder County dodged any damage for a few years, but in 2013 the Japanese beetle arrived. Now Louisville, Lafayette and Boulder residents have reported the beetles; it’s unclear how widely they’ll spread through our county.
Gardeners can gear up to battle them by readying containers of soapy water to knock the pests into. If you can, target the grubs using parasitic nematodes in the genus Heterorhabditis. Dilute the nematodes in water and drench the soil in late summer during cool, overcast hours.
Thorne is focusing on designing with more Western and native plants to try to outwit the bug. These might prove less appetizing to the beetle. “In the past few years, more eastern plants are making their way in,” she says of plants that struggle to survive here. “Insects attack stressed plants, and if you have a plant being attacked yearly, it could be it’s the wrong plant in the wrong place.” Keeping plants healthy through proper placement, fertilization and watering is her recipe for reducing insect problems.
Catch Flies with Vinegar
Gardeners with strawberries, raspberries and other fruit should be on the lookout for spotted wing drosophila (Drosophila suzukii), a tiny bug that’s a big pest. A member of the fruit-fly clan, this little bug lays hundreds of eggs on soft, ripe fruit. Once they hatch, the larvae burrow inside, where they eat and grow into plump maggots. With nary an outward sign, your luscious fruit turns into a mouthful that’s hard to swallow.
Expanding its range rapidly throughout northeastern Colorado, populations of the drosophila take time to build during summer, so fruits that ripen later in the season—like fall-bearing raspberries or everbearing strawberries—are most at risk. Grapes and other fruit are attacked as well, although less often. Out-think the insect by planting early-bearing crops and make a commitment to pick ripe fruit often. Eat the fruit immediately or store it in the refrigerator to prevent the bugs from developing. Destroy any fruit that has the maggots inside.
In the garden, scout for spotted wing drosophila with traps filled with cider vinegar. Pour a bit into a cup and place it outside. Drosophilas are lured to the trap, where they drown in the vinegar. If you place enough traps outside, you can reduce the number of adults laying eggs once the bug arrives.
Stronger insecticide solutions are available, such as Spinosad, a product approved for use on organically raised crops. Look for formulations that state it can be used in certified-organic production, and apply the product just as the fruit begins to color up.
Nuisance Beetle Bug
Multicolored Asian lady beetles (Harmonia axyridis) can turn your house into a hotel. A good bug with bad habits, the lady beetle is beneficial in the summer, snacking on aphids and scale that pester trees and shrubs. Due to this, the Asian lady beetle was brought to the United States as a biocontrol from its native range in Russia, Japan and Korea.
In their native range, the lady beetles congregate en masse on cliffs to overwinter, pressing into rock crevices. In the U.S., they make do with the next best thing—our houses, which have plenty of hiding places. Siding, shingles, attics, soffits, inside walls, or door and window frames are perfect places for the little orange insect. They stay tucked away until the outside temperature drops to the point where your home’s warmer interior attracts them. There they become nuisances that get into food, drink and furniture.
They have a penchant for exploring their world by nibbling or nipping at things, which alarms people. But relax—they aren’t after your blood, and the nip shouldn’t break the skin.
The lady beetles’ “multicolored” designation is due to the variations in spots on different individuals. Some can have many spots; others have none. But all have the familiar rounded shape of the common beneficial ladybugs found in our landscapes. Lady beetles defend themselves by exuding a yellow-orange fluid with a foul odor; it stains surfaces so don’t swat, crush or otherwise annoy these bugs. Spritz them with soapy water or a household cleanser.
The best defense is making sure they don’t enter in the first place. Weather strip windows and doors, caulk foundation cracks, and seal openings around pipes and soffit vents.
Everything Emerald Isn’t Oz
The emerald ash borer (Agrilus planipennis) is a pest so destructive, it’s federally regulated. Native to Asia, it found its way to North America in the late 1990s, likely in a cargo hold. First identified in Michigan in 2002, the borer has already killed millions of ash trees in 21 states, decimating our native ash forests. It was detected in the city of Boulder in September 2013, making Colorado the 22nd state in which the pest has been found.
To halt its spread, the Colorado Department of Agriculture (CDA) quarantined Boulder County. “Ash trees do more than provide beauty to our neighborhoods; they’re also an important sector of our nursery economy,” says Mitch Yergert, plant inspection division director with the CDA. “It’s vital that all Coloradans maintain the emerald ash borer quarantine in order to prevent further spread of this destructive pest.” (Visit www.eabcolorado.com for quarantine details.)
The small borer is a brilliant emerald-green color, with a deep-purple body under its wings. Although it’s only a half-inch long, the bug kills by laying eggs on ash tree trunks. Once they’ve hatched, the white larvae bore into the wood under the bark, where they feed and grow larger. Their meandering, serpentine tunnels cut off the flow of water and nutrients to the tree, killing it in three to four years. The borers attack the same tree over and over, increasing their population until the tree is unable to fend off the assault.
All Fraxinus species of ash, including white, purple, green and their cultivars, are hosts, and stressed trees are particularly at risk. (Mountain ash is not affected, as it’s in the Sorbus genus.) “I encourage residents to not take this quarantine lightly,” Yergert says. “Boulder alone has nearly 100,000 ash trees and it would be sad to see this pest destroy our urban forests.”
[accordion title=”A Tree Expert’s Advice by Fred Berkelhammer” close=”1″]After 27 years of avoiding the frequently environmentally questionable, often unethical and largely cosmetic “pest-control” side of the arborist trade, my company, Berkelhammer Tree Experts Inc., will treat ash trees for emerald ash borer by injecting “TreeAzin” (with an active ingredient of azadirachtin, or neem seed extract). This treatment is manufactured by BioForest Technologies in Canada. Unlike other effective treatment options for emerald ash borer, TreeAzin is registered with the Environmental Protection Agency as a bioinsecticide.
There are highly toxic alternatives to TreeAzin. Two of these chemicals—imidacloprid, sold as “Merit,” “Xytect” and other brands, and dinotefuran, sold as “Safari,” “Transtect,” etc.—are in the neonicotinoid class. This class of systemic pesticide has been strongly linked by entomologists to honeybee colony collapses worldwide. Peer-reviewed science has shown that these chemicals kill entire hives in extremely small (parts per billion and smaller) doses. These chemicals are usually either sprayed on the bark or dumped into trenches around the tree, increasing the likelihood of bee exposure. They are less expensive per application, but both must be applied annually, and at regular doses don’t kill borers after they’ve already mounted an attack.
TreeAzin has been shown to be effective pre- and post-attack, even when applied biannually. A fourth treatment, ememectin benzoate, sold as “Tree-age,” is “highly toxic to fish, mammals and aquatic invertebrates,” according to its label.
The first decision tree owners should make, however, is whether to remove a given tree (perhaps to be replaced with a non-susceptible species).
In many cases, this will be the sound decision, especially when the tree in question is still small and easily replaced, or perhaps is poorly sited, unhealthy or unwanted. In most cases, this will be the more economical choice, too, compared with treatment for the life of the tree. And it’s important to note that there is a small chance that treatment, if chosen, will not work.
—Fred Berkelhammer is president of Berkelhammer Tree Experts Inc.[/accordion]
Carol O’Meara is a local gardening enthusiast and entomologist. Read her posts at gardeningafterfive.wordpress.com.