Heading into summer, pests that cause damage to turf are going to be increasingly prevalent, and in the era of climate change, some of these threats are evolving and increasing. We caught up with several experts to learn about which pests are likely to cause the most trouble this year, the telltale signs of damage and how to prevent and treat them.
One of the biggest pests that causes damage to turf in Kentucky is the white grub, the larvae of bugs like the green June beetle, Japanese beetle and masked chafer, says Jonathan Larson, assistant professor of extension entomology at the University of Kentucky in Lexington.
Recognizing it: White grubs are C-shaped, creamy white, with reddish brown head capsules. They range in size from under half an inch to about 1.5 inches for green June beetle larvae. “They live in the thatch and root zone interface – that’s usually where they’re feeding,” says Larson.
Telltale signs: It’s not hard to recognize a white grub infestation. “If you pull up on the grass, it lifts up the soil like a rug from a floor because there are no roots anchoring it down,” because the bugs have eaten them, Larson says. The white grubs that are the larvae of bugs like the green June beetle are tunneling pests that move through the soil, whereas white grubs that are the larvae of Japanese beetles and masked chafers feed on the roots of the turf.
Getting rid of them: While the easiest way to get rid of them is to prevent them in the first place, that’s easier said than done. Raising the cutting height of grass helps, since grass with longer, healthier roots is more likely to survive. “Healthier turf is easier to resist. Longer roots are more likely to withstand feeding,” says Larson.
Landscape professionals can also use preventive sprays. Chemical treatments include imidacloprid and chlorantraniliprole.
If the infestation is already there, some curative treatment like trichlorfon may be necessary. “Usually, you don’t get all of them, but you get 75%, and it’s still better than leaving all of them around,” says Larson, who also recommends renovation such as reseeding and resodding.
Even in late winter, Kelly Kopp, a professor and extension specialist in the department of plant soils and climate at Utah State University, was already starting to monitor for the bluegrass billbug, the area’s top turf pest.
They’ve had an unusual winter in Utah, with very little snow and in fact extreme drought, and she’s curious how pests will be affected. If it remains dry, Utah could have a bigger problem with chinch bugs, which historically have not been a huge pest in Utah but have been growing in prevalence over the past 20 years.
Recognizing it: The adult billbug is a small black beetle with a long proboscis or nose. The nose has a joint in it that is often seen as an identifying characteristic. But Kopp says it’s really the larvae that cause the most problematic damage, and they resemble white grubs but smaller and without any legs. “Sometimes people get confused between the two, but the billbug is quite a bit smaller,” she says.
Telltale signs: There a couple ways to recognize billbug pest damage, Kopp says. “If you grab the turf grass at the base of the leaves and give it a little tug and it gives way really easily as if the leaves are not attached to the plant, that can be indicative of the billbug, because larvae get inside the stems and start chewing, allowing the leaves to separate,” she says. “If you dig down into the soil, it looks a bit like sawdust, but that’s actually billbug excrement or frass.”
Treatment: Kopp cautions against rushing to conclusions and says positive identification is the most important thing.
“You really need to determine if what you’re seeing is the result of drought, insect damage or both” before deciding on a treatment option, she says.
She recommends an integrated pest management approach. “With the bluegrass billbug, a lot begins with proper irrigation,” she says. “When we see overirrigation and overfertilization, it can create the right environment for pests to begin, because then when it gets dry, as it does in our summer, they can really explode on the scene.”
There are also chemical options, and beneficial fungi is a choice. Contractors can help the afflicted area recover by overseeding with a persistent species of turf or varieties of turf.
Annual bluegrass weevil
The annual bluegrass weevil is especially prevalent on golf courses in the South and Midwest with annual bluegrass, ryegrass and creeping bent grass, says Larson. He and other extension etymologists are worried about spreading it either through sod movement or people accidentally transporting it. The annual blue weevil can especially wreak havoc where the grass is already stressed from being cut short and being walked on.
Recognizing it: The annual bluegrass weevil is a small beetle, about 1/8 inch, blackish in color, with a short snout in the front of its face. It’s hard to differentiate from other weevils, says Larson. The larval form looks like puffed rice cereal with a red brown head capsule and doesn’t have any legs. If a contractor is having trouble identifying it, they can bring a turf sample into an extension office for help.
Telltale signs: Contractors will be able to recognize yellowing or browning of patches of turf that will grow larger if untreated. Stems of the plants will be hollowed out and have a sawdust-like frass left in them, which is a result of the younger larvae feeding on them. When the adults feed on the grass, you can see notches on blades of the turf.
Treatment: Cultural management practices include adequate watering and removing leaf litter, as this is where they overwinter. However, chemical management of the annual bluegrass weevil is the most effective way to reduce the pest population. Preventive applications of insecticides, especially pyrethroids, can help cut the population before the first generation of eggs are laid for the year.
Adam Dale, assistant professor of turfgrass and ornamental entomology at the University of Florida at Gainesville, focuses his work around sustainably managing insects in urban landscapes and ornamental landscapes. The biggest problem in southern Florida, he says, is the chinch bug.
“It causes the most rapid and severe damage, and it’s one of the most difficult to control,” he says. “One reason for that is that it primarily feeds on St. Augustine grass, which is the number one lawn turf species we have in Florida and throughout a lot of the Southern U.S. Because there’s food all over the place, they cause a lot of damage.”
Recognizing it: The problem with chinch bugs, says Henrique Meyer, urban commercial horticultural agent at the University of Florida in Miami, is that they can be hard to see. “They’re very small, so positive identification is key,” he says. “They’re a half inch or smaller, so difficult to see with your naked eye. You often need to have a magnifying glass. Because of that, many people will say they have chinch bugs, but it’s not the case.”
Meyer recommends using a vacuum cleaner or blower on reverse to collect the bugs. Once you isolate them from the turf, you can see them more easily. The smaller ones are orange, whereas the older ones are black. Meyer said contractors can also put a coffee can over the grass, remove the top and bottom, put it two inches into the soil, and fill it with water – if you have chinch bugs, they’ll float to the top.
Telltale signs: Chinch bugs tend to show up in hot, dry areas. The telltale sign of damage is brown turf. “They’re sap-feeding insects. They have a piercing sucking mouth part, and they stick it into the turf stems and suck out the extra sap and nutrients. The grass turns yellow and pretty quickly turns brown and dies,” says Dale. “In a matter of two weeks or three weeks you can go from a green lawn to a brown dead lawn.”
In addition to looking for yellowing leaves, landscape professionals can get down and dig in the grass a little bit and try to identify chinch bugs crawling around. “If you see damage, they’ll be dense enough populations that you won’t miss them if you’re digging in the grass,” says Dale.
Treatment: In addition to cultural practices like avoiding overwatering and overfertilization, and mowing to appropriate heights, insecticides are a good intervention. “If you find a ton, to help prevent more damage, use a product that does rapid knockdown,” Dale says. “In lawns, the most common solution if you have this problem and need to fix it are pyrethroid insecticides.”
Additional options for prevention include neonicotinoids and chlorantraniliprole. The latter is “a great example of how the industry is shifting toward more environmentally friendly insecticide options that also provide really good, selective pest control,” says Dale.
“It’s very important to convey that chemical control is not the only way to control this pest,” Meyer adds. “Integrated pest management is a combination of practices. Only 1% of insects are bad for turf; the other 99% are good guys. You want to preserve the good guys, and work with the bad guys at a tolerable level.”
When there’s a drought, Kentucky sometimes has a problem with army worms, especially in suburban areas that are near former or current pasture for horses or cattle. “They come through at night and it seems like they eat everything,” says Larson.
Recognizing it: Fall army worms are the larvae of a small brownish-gray moth. They’re striped caterpillars. Some have orange stripes on their sides, while others have yellow and black stripes running down parts of their bodies. One of the more “famous” ones has a yellow Y on the back of its head, says Larson.
Telltale signs: It is not uncommon for army worms to destroy an entire lawn within a matter of days. The grass will be flat and full of brown patches that look like heat, drought or chemical stress.
Treatment: If you catch them while the caterpillars are a half-inch long or smaller, you can spray your grass with a bacterium called Bacillus thuringiensis that kills only caterpillars. For mature caterpillars, spray insecticides work best.
Using multiple approaches with insecticides and grass management practices will give lawns the best chance to stay clear of difficult pests while avoiding building resistance. Keep a sharp eye and use a balanced program to keep clients’ lawns safe this season.
Lee Chilcote is a contributing editor to Irrigation & Green Industry and can be reached at firstname.lastname@example.org.