It’s early summer. Golf play is in full swing (sorry about the pun), the heat is on and turf is getting stressed. Hot air temperatures and warm winds commonly occur simultaneously. This duo of factors can reduce or eliminate soil moisture, reducing root and shoot growth, causing grass blades to wilt and change once-green fairways into long corridors of brown. Grass plants suffering from moisture stress can be especially susceptible to other problems.
At this point, with stress abounding, the last thing you need is damage from summer insects.
However, as with most things that cross your path, it’s best to look on the bright side, to find the silver lining. At least insects can be seen. You can almost always find visible symptoms of chewing, sucking and piercing, if not the actual insects themselves. It’s not like diseases and abiotic causes of turf damage that force you into a guessing game of “well, what could it be?”
With that in mind, a review of the classic summer insect pests will help narrow the range of possibilities.
But before getting into the specifics of each insect, a few words regarding inspection are in order. There are several ways to go about taking a closer look, but all should end up with an indicator in mind … kind of like the Holy Grail or the highest level in a video game. When you find it, knowing what to do and when to do it becomes easier.
Fortunately and unfortunately, summer lasts a long time. On the fortunate side, the kids are out of school, you’re not pushing around snow, and it’s the season for summer cookouts and family gatherings. From an unfortunate standpoint, the need to inspect the turf and look for feeding symptoms never goes away. It’s important to look and look again on a regular basis.
It takes persistence to reach the goal. In this case, the idea is to find the actual insect or insect feeding symptoms before they are no longer discernable as the cause of the damage. Scheduling routine inspections is one of the keys to success.
To inspect properly, a few classic tools are needed:
- a sturdy pocket knife;
- hand lens with 10x magnification;
- sod spade;
- 5-gallon bucket;
- cup cutter, and
- identification guide or app.
A good inspection routine to follow if insects are suspected is to conduct a detection test similar to the “smoke ’em out” routine on the old Westerns on TV. Start by filling a 5-gallon bucket half full of water. Then add a cup of lemon-scented dish soap per gallon, and mix it thoroughly. Mark off a square yard of affected/blighted turf and slowly, gently pour it on, allowing time for absorption rather than runoff. After about 10 minutes, a close inspection on your hands and knees will reveal pests such as chinch bugs and sod webworms, if they’re present.
Since it’s summer, you may wish to hydrate yourself with cool water while you’re waiting on the detecting agent to do its work, but that’s up to you. In any event, such a protocol can be a helpful routine in discerning if surface-feeding insects are present.
Again, since it’s summer, there may be a large number of insects present, or just a few that would otherwise not be all that troublesome if the irrigation system was functioning properly. In addition to scouting and taking a close look for the insects or insect symptoms themselves, inspecting or auditing the water delivery capacity – both volume and uniformity – makes good sense, especially when the turf needs it the most.
Measuring the output of each zone with catch cans is a good first step in determining if the root zone is being wetted adequately to promote good turf root and shoot growth. Inevitably, inefficiencies will be found. Fixing at least the worst quarter of these can go a long way toward addressing insect issues and basic water needs of the turf plants, especially if an insecticide application is required and the irrigation system is the essential tool in getting the control product to the right spot.
When we think of root-damaging pests, our first thought usually goes to white grubs. Many different scarab species are present in the U.S. Among the more important are: masked chafers (Cyclocephala spp.), Japanese beetles (Popillia japonica), European chafers (Rhizotrogus majalis), Oriental beetles, (Exomala orientalis), Asiatic garden beetles (Maladera castanea), green June beetles (Cotinis nitida), May/June beetles (Phyllophaga spp.) and the black turfgrass ataenius (Ataenius spretulus). Each species has a unique biology and life cycle requiring a specific management approach.
White grub species are all similar in appearance, with a C-shaped, creamy white body, reddish brown heads and three pairs of legs. Depending on the species, they range from one-quarter- to one-half-inch in length at maturity. Identification is accomplished by checking the raster pattern on the underside of the beetle’s rear end. These arrangements of hairs and spines form distinct patterns by species and can be distinguished with the aid of a small hand lens.
After hatching from eggs, white grubs feed on the roots and underground stems of turfgrasses. The first sign of injury is localized patches of pale, discolored and dying grass displaying the symptoms of moisture stress.
Damaged areas are small at first but rapidly enlarge as grubs grow and expand their feeding range. White grub-damaged turf has a spongy feel under foot and can be easily lifted from the soil surface or rolled like a carpet, revealing the C-shaped white grubs underneath.
White grub control falls into one of two categories, preventive or rescue. The common preventive insecticides, including chlorantraniliprole (Acelepryn), clothianidin (Arena), imidacloprid (Merit), and thiamethoxam (Meridian), are systemic in nature and will be taken up by the plant and translocated to the root zone where the grubs are feeding. They should be applied in May-July, to areas with a history of grub problems or to high-value areas. Curative insecticides, such as clothianidin (Arena), carbaryl (Sevin) or trichlorfon (Dylox), are applied after egg hatch in August or September. To be successful with either strategy, aerate the affected area before treatment, mix according to label directions, make the application, and apply at least a half-inch of water.
If conditions have been very hot and dry and grubs are deeper in the soil, a pretreatment irrigation of a half-inch applied 48 hours before the insecticide application will encourage grubs to move closer to the soil surface and enhance control.
Several billbug pest species occur in turf: bluegrass billbug, hunting billbug, Denver billbug and Phoenician billbug. Depending on your location, your billbug pests will differ. The immature billbugs resemble white grubs in color and shape, but are smaller and legless. They look like puffs of rice.
As adults they become brown or black shiny weevils with elongated noses. Each species has specific hosts they prefer, but they’re pests of almost all managed turf types including bermudagrass, zoysiagrass, Kentucky bluegrass, perennial ryegrass, tall fescue and fine fescue.
Billbug damage is similar to white grub damage on the surface, with irregular patches of thin turf. After emerging from the egg, newly hatched billbug larvae tunnel in grass stems, hollowing out the stem and leaving fine sawdust-like plant debris and excrement called frass.
The “tug test” is the best method of confirming a billbug problem. Since they hollow out the stem, the turf breaks off when tugged, revealing hollow crowns and stems along with the powdery frass. Subsurface feeding by older larvae can completely destroy the plant’s crown and upper root system, causing the turf to appear drought-stressed. Under heavy billbug pressure, plants eventually will turn brown and die.
Effective cultural practices can significantly reduce billbug damage. Selection of adapted turfgrass cultivars as well as proper fertilization and irrigation programs will minimize the impact of billbug infestations. In addition, several endophyte-enhanced and billbug-resistant cultivars of popular turf species are available.
Insecticide application should be made when the temperature begins to approach 60 degrees Farenheit; this will help reduce the number of overwintered adults depositing their eggs in the spring. Application usually is justified when irritant flushes confirm the presence of one adult per square foot of turf.
If warranted, apply insecticides to newly mowed turf (collect and remove clippings) and irrigate lightly after application to wash the insecticide onto the soil surface, where billbug adults are active. Preventive insecticidal control of billbugs can be achieved using products like Acelepryn, Arena, Meridian or Merit.
Sod webworms are caterpillar pests that mature into small moths. The moth looks like a rolled-up newspaper and, if you look at it under your hand lens, you will notice it has a snout. Caterpillars are cream in color and, depending on the species, have distinct red-brown, brown or blackish spots on each body segment and a dark head.
When mature, they’re about a half- to three-quarter-inch long. Sod webworms feed at night and retreat to silk-lined burrows in the thatch during the day. Adults fly in May, and larval damage usually begins to appear in July or August.
Feeding damage appears as patches of brown, ragged turf that grows gradually in size. Birds, in particular starlings, often are observed feeding on larvae of sod webworms. You can use a dish soap drench to sample for sod webworms. If you find four or more in 4 square feet of sod, you can take action against them.
Control with insecticides can be achieved with bifenthrin, carbaryl, halofenozide and chlorantraniliprole. Insecticide applications should be made in mid-summer before the caterpillars burrow down to overwinter.
Non-chemical control can be achieved by applying nematodes (Steinernema spp.) to the affected turf. Be sure to follow label instructions for application and storage of nematodes, as they can expire before application.
This true bug is a double threat, with nymphs and adults both sucking out plant juices using their needle-like mouths. This feeding results in dwarfing, yellowing and eventually death.
Chinch bugs have more than one generation per year and overwinter as adults. The Southern chinch bug is a small pest, ranging from a 10th to a third of an inch long, and, as an adult, is black with shiny white wings.
Turf infested with chinch bugs will have circular discolored patches. These areas may grow until they combine into large patches of dead grass. Damage is most frequently seen at the height of the summer dry season, especially in water-stressed areas of turf. Use the water flotation method to detect an infestation. The suggested threshold for chinch bug is 15 to 20 insects per square foot.
Preventive chinch bug control is dependent on good thatch management and lower nitrogen inputs. If insecticidal control is needed, products containing carbaryl or any pyrethroid (bifenthrin, cyfluthrin, lambda-cyhalothrin, or permethrin) all are effective at controlling chinch bugs.
Somewhat “cricket-like” in appearance, these bulky, brown insects have modified front legs to dig in the soil. These insects overwinter as adults or large nymphs before completing development and mating in the late winter/early spring. There are three species in the U.S. The Northern mole cricket, Neocurtila hexadactyla, is native to North America and is rarely a significant pest of turfgrasses.
However, the tawny mole cricket (Scapteriscus vicinus) and Southern mole cricket (Scapteriscus borellii) are serious pests of residential and recreational turf throughout the southeastern U.S. By examining the blade-like projections on the forelegs with your hand lens, you can distinguish the mole cricket species.
Mole crickets damage turf when they feed on the roots, stems and leaves. But the most extensive damage is associated with the tunneling they do under the turf. Tunnel size and the extent of damage are correlated with the age/size of the mole crickets. The larger and older they are, the more destructive.
Mole cricket control requires careful monitoring and different strategies depending on the time of year. Spring treatments target adult mole crickets, summer treatments target the nymphs, and fall treatments target both nymphs and adults. The best time to treat for mole crickets is early summer, when nymphs are still small. Most labeled insecticides will provide adequate control at this time.
By late summer and fall, mole crickets are larger, their activity and damage increases, and they are much more difficult to control. Bait formulations, however, may be effective against larger nymphs in late summer. Spring treatments should be done as spot treatments to rescue highly damaged turf. Because mole crickets are active at night, for best results insecticides should be applied as late in the day as possible.
John C. Fech is a horticulturist and certified arborist with University of Nebraska – Lincoln Extension specializing in turf care, arboriculture and water issues. Jonathan L. Larson, Ph.D, is an entomologist with University of Nebraska – Lincoln Extension specializing in turf, tree, ornamental, nuisance and structural pest issues.
COVER PHOTO BY JOHN C. FECH