As winter transitions into spring, our thoughts should be turning to early-season insect control. Because the arrival of spring varies dramatically from region to region, we are referring to the insects that become active with the onset of warm weather.
Overwintering sod webworms can be a problem in some years.
Regular inspections are important in your overall pest management program. Casual inspections are those made while driving or walking a property to perform other operations, such as spraying broadleaf weeds or applying fertilizer. Any time a patch of turf is observed that looks out of place, off-color or otherwise slightly askew, it’s always wise to take a closer look.
For many early-season insect pests, a simple soapy drench will be effective. Start by combining .25 cup of lemon-scented dishwashing detergent with 2 gallons of warm water. Evenly distribute this mixture over a square yard of suspected turf. Using a watering can will help ensure the solution is evenly spread over the target area. Wait five to 10 minutes after application for the insects to move to the surface, where they can be easily counted. Be sure to inspect the center, around the edges and beyond the suspected infested area.
It’s possible that after closer examination and flushing, no insects will be detected in the damaged area. If this is the case, look for other causal agents such as foliar diseases, root diseases, watering practices, fertilizer application patterns and/or soil fertility issues.
IPM – still chic after all these years
In terms of controlling early-season insects, integrated pest management (IPM) is still a common-sense, realistic and flexible management approach. The components of IPM, cultivar selection, pest monitoring, thatch management, proper fertility, appropriate irrigation adjustments and delivery, and cultivation and use of pest control agents when warranted are still reliable considerations. Just as reliable, in fact, as when IPM was rolled out to deal with the cotton boll weevil in the 1970s. When you find yourself struggling with pest control, think about all the available IPM strategies, and which ones you may be missing.
Though not a huge concern in most years, customers can freak out when they see these large, white larvae in their turf.
There are a number of insect pests that you should include in your early-season scouting program. The first three are actually carryovers from the previous year:
• Overwintering sod webworms
What to look for: Sod webworm larvae (caterpillars) are gray to tan with brown heads and small dark spots on the body. They reach .75 to 1 inch in length when fully grown. Webworms overwinter as partially grown larvae in silk-lined tunnels in the thatch and upper layers of soil. Areas infested with sod webworms take on a grazed or scalped appearance. Small patches of grass will be chewed off at the ground level. Fresh blade clippings and fecal pellets are also usually present.
What to do: With webworms, it’s about numbers. If a dozen or more per square yard are present, apply an insecticide such as bifenthrin (Talstar), carbaryl (Sevin), trichlorfon (Dylox) or spinosad (Conserve) according to label directions.
• Overwintering white grubs
What to look for: The larval stages of all white grub species are similar in appearance. They have C-shaped, creamy white bodies, reddish-brown heads and three pairs of legs. When fully grown, they are .25 to 1.5 inch in length, depending on the species. The best way to tell them apart is to look at the arrangement of hairs and spines on the underside of the last abdominal segment (raster). A distinct pattern can be distinguished for each species 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 underfoot and can be easily lifted from the soil surface or rolled like a carpet, revealing the C-shaped white grubs underneath.
What to do: Unless a large number of white grubs are observed, treatment is usually not recommended in spring for at least two reasons. First, these grubs are likely near the end of their life cycle and feeding has ceased; second, overwintered grubs are large and relatively hard to kill. However, spring rescue treatments may be justified in heavy infestation situations and hot spots on high-value properties or sites.
On the smallish side and pretty well disguised, greenbugs can cause spring damage.
• Overwintering greenbugs (in southern regions)
What to look for: Greenbugs are light green in color and on the smallish size. Down the back of their bodies, a narrow, dark green stripe is visible. Their legs and antennae are tipped in black. Greenbugs have cornicles, sometimes referred to as tailpipes, which extend from the backside of the body, and are also tipped in black.
What to do: If necessary, apply a liquid insecticide such as acephate (Orthene), bifenthrin (Talstar), lambda-cyhalothrin (Scimitar) or permethrin (Astro) to the infested area. Azadirachtin (Neem), horticultural oils and insecticidal soaps may also be effective as spot treatments. Always treat a 2 to 3-foot border around the damaged area, because much of the greenbug activity will be in areas surrounding the yellowed turf. Thorough coverage is important. Do not irrigate for at least 24 hours after treatment.
The next two pests are ones to look out for as it gets later in the spring:
Because they’re quite small and feed inside the plant, bluegrass billbugs are hard to see.
• Bluegrass billbugs
What to look for: Adult billbugs are typical weevils (or snout beetles) with mouthparts located at the end of a curved snout or bill. These insects, about .25 to .5 inch long and dark brown to black, are slow-moving and frequently “play possum” when disturbed. Billbug larvae (grubs) are similar to white grubs, but are legless. They have cream-colored bodies with brown heads, and when fully developed are about .25 to .5 inch long, depending on the species. Their bodies are slightly curved and resemble a grain of puffed rice.
After emerging from the egg, newly hatched larvae tunnel in grass stems, hollowing out the stem and leaving fine sawdust-like plant debris and excrement, called frass. Infested stems discolor and, when pulled, readily break away at or near the crown. 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.
What to do: An insecticide application is usually justified when visual observation or irritant flushes confirm the presence of one adult per square foot of turf. If warranted, apply insecticides to freshly mowed turfgrass (collect and remove clippings) and irrigate lightly after to wash the insecticide off grass blades onto the soil surface. Insecticidal control of billbugs can also be achieved using systemic insecticides such as Acelepryn, Arena, Meridian or Merit applied prior to egg laying. Read and follow all label directions.
• Chinch bugs
What to look for: Chinch bugs can cause significant damage to turf. Unfortunately, they are very small and can be difficult to spot. Except for the color, the immature stages and the adult stages of most chinch bug species are similar in appearance. They start out as tiny, 1/32-inch nymphs, bright red in color with a white band across the abdomen. As they mature through five nymphal stages, their color changes from red to orange to brown to black. Eventually, they develop into adults that reach about 1/10 inch in length. The wing covers of the long-winged forms are conspicuous, with white and black markings. They produce an “X” pattern, a result of the folding of their wings.
Chinch bugs overwinter as adults in and around long grassy areas. Soon after mating, the female lays eggs on grass plants by inserting them behind leaf sheaths in the crown or on roots in the surrounding soil.
Both nymphs and adults feed by sucking plant sap from the leaves and stems of grass plants. Adding insult to injury, during the feeding process a salivary toxin is injected into the plant, disrupting the translocation of water and nutrients, resulting in wilt and discoloration of plant tissue. Damage appears as patchy areas of turf that turn yellow over time. As feeding progresses, the turf dries out, turns brown and appears drought stressed.
What to do: The most effective method of confirming a chinch bug infestation involves removing both ends from a 2-pound coffee can, pressing one end about 1 to 2 inches into the soil where an infestation is suspected, and filling the can with water. If present, chinch bugs will float to the surface in a minute or two. Chinch bugs can also be detected using the same method as described for sod webworms.
If 10 or more are found floating in the cylinder, or 20 per square foot of turf, consider treatment. The best results are achieved by mowing and removing clippings prior to treatment. Immediately following insecticide application, the damaged area (and adjacent areas) should be irrigated with 1/8 to .25 inch of water to wash the insecticide off the grass blades and down into the plant crowns and thatch where the insects are feeding. A follow-up treatment may be necessary, depending on the severity of the infestation and product chosen.
Among the products labeled for control of chinch bugs by commercial turfgrass managers are acephate (Orthene), bifenthrin (Talstar), carbaryl (Sevin), cyfluthrin (Tempo ), lambda-cyhalothrin (Scimitar), permethrin (Astro) and trichlorfon (Dylox).
John C. Fech is a horticulturist, certified arborist and frequent contributor located in Omaha, Neb. Frederick P. Baxendale is a professor and extension entomologist with the University of Nebraska-Lincoln.