It hurts to see a lovely landscape or expanse of turf turned brown, or an ornamental tree or shrub denuded of leaves or marred in some other way. The pain is greater when it’s a landscape you’ve installed or are maintaining.
Insects and grubs are always going to be with us. We’re never going to completely eradicate them, nor would we want to. Even bugs we’ve labeled ‘bad’ have some role to play in the ecosystem, if only as food sources for other creatures.
What we’re looking for is a guarded truce, sort of like a Berlin Wall or DMZ. We want them to stay on their side of the barrier, and we’ll stay on the other; but we’ll always be out there, patrolling for violators, sprayers at the ready. Our arsenal of weapons includes chemical and organic solutions and preventative cultural practices.
Certain pests are ubiquitous, plaguing just about every landscape in North America—aphids, scale insects, cutworms, stink bugs, etc.
“Mostly, it’s the sucking pests that plague landscape plants,” said Jake Doskocil, product development manager at Bayer Crop Science’s U.S. headquarters in Research Triangle Park, North Carolina. “There’s a long list of scale species alone.”
But to fight them, we don’t always want to automatically reach for the stuff with a skull and crossbones on the label. Instead, many landscape professionals use the principles of Integrated Pest Management (IPM).
As defined by the University of California, Davis, IPM means that “pesticides are used only after monitoring indicates they are needed, according to established guidelines, and treatments are made with the goal of removing only the target organism. Pest control materials are selected and applied in a manner that minimizes risks to human health, beneficial and non-target organisms, and the environment.”
Chris Kujawa, vice president of KEI Enterprises, Inc. in Oak Creek, Wisconsin, believes in and uses the principles of IPM. “If you think about it, IPM practices are nothing more than trying all the different options at hand, other than relying strictly on a chemical solution. It’s a holistic approach to the health and well-being of your landscape, almost like a wellness program.” The basic idea is that the healthier an organism is, the less susceptible it’ll be to pests and diseases.
When you choose species that are more resistant to pests and diseases, you’re using IPM.
Spider mites, tiny arthropods (eightlegged creatures), are another nearuniversal pest, bedeviling many different species of shrubs, bedding plants and ornamental trees. Like aphids and scale bugs, they also feed by sucking juices out of plants, mainly the leaves.
When conditions are right, their populations can build up rapidly and seriously harm plants. Look for the bronze-colored leaves they leave behind. A heavy infestation causes leaves and branches of affected plants to become covered with nearly invisible webbing.
Some pests don’t have good chemical solutions; whitefly, for example. Pruning off infested leaves, washing the bugs off with streams of water, and spraying them with insecticidal soap are the standard treatments.
Closely monitoring susceptible plants, such as hibiscus, and acting as soon as you see the little white moths, can keep their populations from getting too large. Look for a white, cottony honeydew deposit on the undersides of leaves.
Besides the usual suspects, you may also battle bugs that are specific to where you live. “Many pests are regionally important, such as annual bluegrass weevil in the Northeast and chinch bugs in the Southeast,” said Doskocil.
“And then, there are some of these newer invasive insects that have popped up, like the emerald ash borer that’s killed millions of trees in the Midwest. The Asian citrus psyllid is showing up in Florida and California, and is migrating from the crop into the landscape environment to attack ornamental citrus trees.”
In Jackson Hole, Wyoming, “Our main problem is with the mountain pine beetle,” said Rolland Kuhr, owner of Naturescape Designs, Inc., who is also a certified and consulting arborist.
As with all tree borers, once the larvae hatch, they chew their way through the phloem, the main circulatory tissue of the tree, forming tunnels, or ‘galleries,’ and dieback begins. Once these galleries completely encircle its trunk, a tree can no longer draw up nutrients or moisture.
When he finds evidence of a beetle attack, he applies a trunk spray of bifenthrin, carbaryl or permethrin. These active ingredients kill the beetles as they land on the tree.
Our cultural practices can inadvertently help the little buggers in their pursuit of bountiful buffets. “If a plant is either over- or under-watered, it could stress it, and when a plant is stressed, it attracts insects, especially borers and bark beetles and things like that,” said George Biedenstein, coowner of Land Care Management in Littleton, Colorado, and a board-certified master arborist.
Are you doing enough pruning? “Deadwood attracts insects,” said Kujawa. Regular pruning also brings you in close contact with the plants and trees, so chances are better that you’ll spot chewed leaves, egg masses or other signs of infestation before a pest’s population becomes overwhelming.
He’s also wary of soil that’s too compacted. “Plant roots need oxygen; but that often gets overlooked. You need to keep the soil around the bases of plants and trees loose. The more you do that, the better off your plants and turf will be,” and the more resistant to pests and disease.
Feeding your trees and plants too much can inadvertently feed the bugs, too. High levels of nitrogen fertilizer favor aphid reproduction, for instance. “Studies have shown that trees and shrubs that are over-fertilized are more attractive to insect pests,” said Biedenstein. “They become more nutritious for them to feed on.”
Grubs are fat white worms, the larval stages of Japanese beetles, June bugs, European chafers, billbugs, and others, and a major nemesis of turf. As the larvae develop underground, they feed on the tender roots of grass. Brown patches in a lawn can be the first indication that something’s grubbing about just underneath the surface, but is often mistaken for drought stress.
Skunks and raccoons tearing up a lawn is a sign of grub infestation. “They’ll smell the little guys under there, and dig them out and eat them,” said Kujawa. “A lawn will look like someone came in overnight with a hand-trowel, and just dug up patches all over the place.”
If you suspect grubs, digging with a shovel or trowel in the browned area should reveal them. Biedenstein won’t treat a lawn until he eyeballs the grubs in the ground.
“Once we discover the problem, it’s time to come in with a site-specific, targeted application of an insecticide,” said Kujawa. Conventional insecticide remains the most effective method for killing grubs, and timing is everything.
A ‘summer rescue’ isn’t as effective as a spring preventive application, before the larvae hatch and start chewing on grass stems. Use one with thiamethoxam, imidacloprid, carbaryl or deltamethrin as the active ingredient. Waterin after application with at least one-half inch of water. Irrigating a lawn the day before encourages grubs to move toward the surface.
James Compau, commercial services manager at AAA Lawn Care, Inc. in Grand Rapids, Michigan, applies pesticide in June or July to break the grubs’ life cycles and protect a lawn for a year, then repeats it the following year. “You’ve got to repeat the next year, and here’s why; you may have gotten rid of them in that lawn, but they’re still in the area. They’ll come back.”
David Spriggs, co-owner of McKinney, Texas-based Spriggs Brothers Organic Landscape and Lighting, uses absolutely no chemicals. “If you’re on an organic fertilizing program, and you have healthy soil, you usually won’t have a grub problem,” he contends. “It only happens when soil has been bleached out by chemical fertilizers.”
When he does find a grub infestation in a lawn, he treats it by spraying beneficial nematodes, small, unsegmented, spaghetti-like worms that find grubs absolutely delicious.
Once a nematode enters a grub, it kills it by liquefying its insides. The species Heterorhabditis bacteriophora provides good grub and billbug control.
Natural methods can work, but require patience. However, as we all know, many landscape clients want re sults immediately, not six weeks from now. When a pest population gets too large or destructive, even organic contractors can be forced to turn to chemicals. The emerald ash borer is a good example, the only effective treatment so far is chemical injection.
Quite a few of Biedenstein’s clients, concerned about pollinator decline, ask him not to use chemicals on their bugs. “The problem with that is, there aren’t a lot of effective organic insecticides available. Neem oil and bacillus thurigensis, a bacteria that’s effective on lepidoptera (moths and butterflies), insecticidal soaps and oils are some of the few things that actually work.”
“We’re constantly looking at new technologies and developing new things, not necessarily limited to chemical products,” said Doskocil. “The industry itself is moving to a holistic management approach.”
Soil drenches and injections are environmentally-sensitive pesticide delivery systems, as the chemicals go directly into trees or shrubs, and nowhere else; nothing wafts over to kill beneficial insects.
There are soil drenches and injections for trees and ornamental and bedding plants. It takes a bit for a plant to circulate the chemical completely through its vascular system, but once it does, every bit of that plant becomes poisonous to pests.
Insecticides applied via these methods are slower to take effect than sprayed products, but are much more effective over longer periods of time. Protection can last for up to two years, in some cases.
Kuhr only uses soil drenches for aphid control. He stresses the need to apply a soil drench or injection well enough in advance for maximum protection, usually at the beginning of spring.
Like taxes, landscape pests will always be with us. Thankfully, so will the entomologists and biologists who’ll keep working on new ways to combat them.