When dealing with turf insects, you can generally divide them into two categories — those that feed on shoots (surface feeders) and those that feed on roots (subsurface feeders). Your mileage may vary on which group causes more damage, but both cause unacceptable injury to turfgrass.
Insects that feed on shoots cause problematic damage by hindering photosynthesis, respiration and oxygen exchange. When damage includes deterioration of the crown as well as the leaves, the potential for turf plants to produce new leaves, tillers, rhizomes and stolons is compromised.
Crown injury usually results in reduced capacity for lateral expansion into voids left by other damaging influences such as excessive thatch, uneven irrigation and fungal diseases. If you hope to avoid these types of issues then performing regular scouting or dedicated monitoring of the following pests will be an invaluable tool in protecting your turf.
Famous for being the subject of a conversation between Carl Spackler and Ty Webb in “Caddyshack,” chinch bugs are tiny as immature nymphs, only 1/32 of an inch in size, and depending on the species range from red to grey with a white band across their abdomen. They start as eggs and then progress through four to five nymphal stages.
With each advancement, their color changes to orange, to brown and finally to black. Adults are larger than the immature nymphs, usually in the 1/10-inch range, and are commonly observed with black and white bodies. You will find that some adult chinch bugs have wings that cover the length of their abdomen while others are a short-winged form. The wing covers of the long-winged adults are conspicuous, with white and black markings. They produce an X pattern, a result of the folding of their wings.
In early spring, adults emerge from overwintering sites and mate. Once fertilized, females insert their eggs behind the leaf sheaths in the crowns and on the upper roots of turf plants. Eggs hatch in three to four weeks and will mature to adulthood by mid-summer. Chinch bugs have two to four generations in a year, depending on the species.
All chinch bugs feed by sucking sap from the leaves and stems with their needle-like mouthpart. During the feeding process, a salivary toxin is injected into the plant, which disrupts the translocation of water and nutrients, resulting in wilt and discoloration of plant tissues. Damage from chinch bug feeding will appear as patchy areas of turf that thin and turn yellow over time. If feeding continues, turf stands will steadily dry out and turn brown.
Commonly, injury is heaviest in sunny locations and often mistaken for drought stress. Control efforts must be directed where the highest feeding activity is occurring. When chinch bugs are active mainly on leaves, liquid insecticide treatments should be applied to the foliage. If feeding is on the crowns, a granular insecticide should be applied and followed by 1/8 inch of water to move the product off the leaves to contact the insects.
In either case, mowing and removal of clippings is recommended before treatment to allow better penetration into the canopy. You can monitor for chinch bugs by using the drench method. Take a container, like a metal coffee can, and insert it 2 to 3 inches into the turf. Fill it with water and wait at least five minutes for the bugs to surface and the count them. Treatments are usually justified when numbers exceed 15 to 20 chinch bugs per square foot.
Also called aphids, greenbugs are aptly named. Light green in color with narrow dark green to black stripes down their backs, most greenbugs are also noted for “tailpipes” or cornicles that extend from their abdomens. Greenbugs are prolific family makers. A single female can produce several offspring each day for two to three weeks per life cycle. The potential of damage is high, considering that young aphids reach maturity in six to 10 days and can begin reproducing without mating.
Just like the chinch bug, greenbugs feed by removing sap from leaves and stems via needle-like mouthparts. Heavily infested plants turn yellow and die from the loss of cell sap.
In the field, roughly circular patches of yellow to light orange turf should be inspected for signs of greenbugs. If infested, close examination should reveal between 10 and 25 aphids per leaf blade.
When large numbers are found on highvalue turf, a liquid insecticide application may be warranted unless natural enemies (lady bird beetles, lacewings, parasitic wasps) are present. Thorough coverage with a liquid carbamate or pyrethroid insecticide will increase the potential for control.
Sod webworms are caterpillar pests that mature into small moths. The moth looks like a rolledup newspaper. If you look at it under a 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 caterpillars are at their largest, they are about 1/2 to 3/4 of an 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.
Though the larvae hide during the day in the thatch or upper-soil surface, the majority of their feeding is on crowns, lower stems and leaves. One of the first signs of webworm infestation is small, ragged patches of turf. Upon closer inspection, these areas take on a grazed or scalped appearance.
If not noticed in the first week or two of feeding, the patches enlarge and coalesce into larger areas of affected turf. To confirm the presence of these pests, a flushing agent of pyrethrins or lemon-scented household dish soap can be applied over a square yard of turf. These materials irritate the webworms, forcing them to the surface where they can be identified and counted.
Simple scratching with a pocketknife may also reveal their presence. When 10 to 20 larvae are present in stressed turf, insecticide applications are usually warranted. Even though the adult moths do not feed on turf, noting their presence can also serve as a monitoring tool. Adult moths fly in a zigzag pattern about a foot high above turf at dusk.
Control with insecticides can be achieved with bifenthrin, carbaryl, halofenozide and chlorantraniliprole, or Bt. Insecticide applications should be made in mid-summer before the caterpillars burrow down to overwinter. Nonchemical control can be achieved by applying nematodes to the affected turf. Be sure to follow label instructions for application and storage of nematodes, as they can expire before application.
Billbugs are a pest that could be categorized as both a surface and a subsurface feeder. As young larvae, the baby beetles feed inside of turf stems while the older larvae will move and focus on the roots. Billbug larvae (grubs) appear similar to white grubs but are legless. They have creamed-colored bodies with brown heads, and when fully developed are about 1/4- to 1/2-inch long, depending on the species.
Their bodies are slightly curved and resemble a grain of puffed rice. Adult billbugs are typical weevils (or snout beetles) with mouthparts located at the end of a curved snout or bill. These insects, which are dark brown to black in color, are slow moving and frequently play possum when disturbed.
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. Infested stems become discolored and, when pulled, readily break away at or near the crown. This easy breakaway action is called the “tug test” and is a great way to confirm if you have billbugs or not. Subsurface feeding by older larvae can completely destroy the plant’s root system, causing the turf to appear drought-stressed. Under heavy billbug pressure, plants will eventually 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 Fahrenheit. This will help reduce the number of overwintered adults depositing their eggs in the spring. Application is usually 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 on to the soil surface where billbug adults are active. Preventive insecticidal control of billbugs can be achieved using products like Acelepryn, Arena, Meridian or Merit.
Though not a feeder in the traditional sense, mole crickets can cause significant disruption in play on a golf course.
The tawny mole cricket is generally considered the most destructive because it feeds exclusively on the root and shoots of turf. The Southern mole cricket, which resides primarily in the South and Southwest, feeds a little on the roots, but mostly eats other insects.
Like the tawny mole cricket, short-winged mole crickets are vegetarians and feed only on plant material. However, tawny, Southern and shortwinged mole crickets tunnel extensively in search of food resources, creating significant interference with golf activity. Northern mole crickets occur from Nebraska south to Texas and along the East Coast from southern Canada to Florida. This native insect rarely injures turf.
Early detection through monitoring is important when controlling mole crickets. Sampling is performed with 1.5 ounces of liquid dishwashing soap in 2 gallons of water with a sprinkling can to 4 square feet of turf. If you capture two to four mole crickets during the first three minutes of sampling, then you may want to consider a control program. Depending on the location and season, it may be necessary to include spring, summer and fall insecticide applications in an overall control protocol.
Pre-irrigation helps the insecticide penetrate into the soil, or in the case of baits formulations, encourages mole crickets to come to the surface to feed on the bait. On the other hand, overirrigation could create a situation where runoff is likely or where the control products are diluted.
The goal is simply to enhance movement of the insecticide through the thatch to the zone of mole cricket activity. Post-irrigation will move the active ingredient down into the root zone where the mole crickets are feeding.
Armyworms and cutworms
Cutworms and armyworms are the larvae of several species of night flying moths. Caterpillars in this group are characterized by having three pairs of legs behind the head, fleshy prolegs and a distinct head. Adults are drab-colored and hairy with wingspans from 1 to 1.5 inches across. The larvae of black cutworms, variegated cutworms and bronzed cutworms typically reach 1 to 2 inches and have dark brown, lightly striped bodies with a gray head.
Cutworms feed at night, cutting (grass blades off near the soil surface. Damage initially appears as small, circular dead spots, which increase in size as the worms mature. Armyworms also feed at night, with smaller worms causing grass blades to appear skeletonized; as the caterpillars mature, all above-ground parts of the turf plant can become consumed. When feeding is extensive, control armyworms and cutworms as outlined for sod webworms.
Ants can occasionally become a problem when they invade turf areas. While they don’t eat plant material, they create construction zones with mounds of sand that interfere with play on greens and tees. The mounds can be flattened out to smother and kill half dollar-sized patches of turf.
A typical ant colony consists of an egglaying queen, males, immatures (eggs, larvae and pupae) and hundreds to thousands of sterile female workers. Ants consume a variety of foods including seeds, small insects, plant sap, flower nectar and fungal growth.
In the spring and fall, colonies produce winged ants that leave the colony for new nesting sites. Ants normally establish colonies in sunny, well-drained spots.
In turf, a nest consists of a series of underground tunnels and galleries that may extend 3 or more feet beneath the surface. Ants are best detected by inspecting turf areas for mounds and worker ant activity.
Effective ant control normally requires destruction of the queen which, in many cases, necessitates one or more applications of a liquid or granular insecticide. In situations where only a few colonies are present, apply insecticides directly to colony openings and the areas immediately surrounding the mounds.
If colonies are numerous, broadcast treatments over the entire infested area may be the most practical solution. Pyrethroids and combination products can both work against ant problems.