With all the headaches that sports turf managers have to deal with throughout the year – unreasonable coach requests, complaints from players and parents, lack of adequate rotation possibilities, budget restrictions and unseasonable weather – another one isn’t welcome. Certainly, not one that’s complicated and challenging. Yet, the management and control of insect pests is just that: a multifaceted and complex issue that must be dealt with. As with other pests, such as nematodes, weeds and diseases, prevention is the most important element, or at least the most effective one.
Scouting and monitoring
Effective prevention begins with scouting and monitoring. Though it may seem obvious, a couple of definitions are helpful in this step.
Scouting is a thorough examination of a particular area, inspecting for any unwanted deviation from the desirable, healthy turf that’s needed to support play. Scouting tends to be a one-off activity, where a cursory awareness or peripheral observation has been made that something isn’t as it should be. In most cases, a detailed inspection is sufficient to determine if any pest activity is responsible for the apparent demise of the turf.
Monitoring is a series of scouting events, usually used when long-term scrutiny is called for, such as during times of historic insect infestation. Both are valuable and worthwhile of the time and energy required.
Scouting and monitoring are essential for controlling insects early in their life cycle, when they’re most vulnerable, instead of waiting for total destruction of turf. As such, it’s necessary in all seasons: spring, summer, and fall in the north, with the addition of winter in the south.
When scouting, workers need to know what to look for. The old adage of “if it was a snake, it would have bit me” is appropriate here, in that the telltale signs and symptoms of damage from a certain insect pest might be right in front of the scout, but without the knowledge of what’s typical, the inspection isn’t helpful.
Three categories of insect activity are important considerations in scouting and monitoring. First, broadscale, general appearances of abnormal-appearing turf – usually, brown and stunted stems and leaves. Second, the symptoms of insect activity, which include hollow stems, chewed roots, crowns, stems and leaves, pinprick holes in leaves and small black, dark green or brown pellets of fecal material. Third, the signs of the insects themselves – eggs, larvae, pupae and adult insects. Recognizing these symptoms and being able to relate those to particular pests will be crucial to success in scouting.
Unfortunately, insects aren’t the only pest or abiotic issue that must be dealt with while managing a sports field. It’s common to spot look-alike symptoms while scouting. The most common ones are fungal diseases, such as leaf spot, dollar spot and summer patch, as well as nonliving causal agents, including compaction, irrigation nonuniformity and fertilizer burn. That’s why pairing symptoms with the sign, or actual pest, is needed.
As the process moves from general to specific, it’s helpful to use tools to identify signs and symptoms, as well as eliminate abiotic causes. Fortunately, these are low-cost, everyday items, such as pocket knives, sod spades and 5-gallon buckets. Pulling, lifting and looking closely are the common human tools and actions required. When making a fine-scale inspection of the plant parts, a disclosing solution will often help determine if insects are present in damaging numbers. A mixture of soap products, such as lemon-scented dish detergent (i.e., Dawn, Joy, Ivory) at a rate of one half cup per gallon of water spread on a square yard of turf will irritate and encourage caterpillar feeders to come to the surface where they can be collected and counted. If no insects appear, the logical next step is to move on to the root system by cutting a wedge of turf and carefully lifting and breaking apart the soil to look for insects. Pulling on turf stems is useful as well; if they break off easily, stem-active insects, such as billbugs, may be present.
Stem and leaf-feeding insects
Chinch bugs: Nymph and adult chinch bugs use piercing mouthparts to suck plant juices from the leaves and stems of turf plants. Their feeding disrupts the movement of water and nutrients and results in wilt and discoloration of plant tissues. Damage appears as gradually yellowing patches of turf that eventually dry out and turn brown. In addition to close looking, utilizing a method where both ends of a 2-pound coffee can are removed, pressed into the soil on the edge of the suspected area of infestation and filled with water. If present, chinch bugs will float to the surface in a few minutes. Treatment is usually justified when numbers exceed 15 to 20 chinch bugs per square foot. Before treating for chinch bugs, mow and remove clippings to allow better insecticide penetration into the target zone. Bifenthrin, lambda-cyhalothrin, and carabryl are all labeled for use against chinch bugs.
Greenbugs/aphids: Greenbugs feed in a similar way as chinch bugs, inserting mouthparts and extracting cell sap from leaves and stems. Initial injury appears dotted or stippled, progressing to a graying or silvering of infested areas. At high levels of infestation, extreme thinning can occur. In sunny areas, greenbug injury is often mistaken for drought stress and vice versa. Greenbugs typically build up in shady areas near trees or buildings. If sampling reveals more than 20 aphids per leaf blade, a liquid application of a pyrethroid or neonicotinoid insecticide would be warranted.
Billbugs: Billbug adults and larvae are most noticeable when scouting with the adults appearing as black weevils with extended mouthparts, about 0.125 to 0.25 inches in size. Larvae are creamy white with tan heads and are legless, slightly larger than the adults, ranging from 0.25 to 0.50 inches. The greatest damage occurs in early summer, when newly hatched larvae tunnel in grass stems, hollowing them out and leaving fine sawdust-like excrement. Infested stems turn off color and break off easily when pulled. Flushing techniques described above can help determine if billbugs are present in the turf. Before using insecticides, mow turfgrass and collect and remove clippings. Following application, lightly irrigate the treated area to wash the insecticide onto the soil surface where billbug adults are found. Several insecticides, including clothianidin, imidacloprid, chlorantraniliprole and halofenozide are labeled for use against billbugs.
Sod webworms: Sod webworms injure turf in the larval or caterpillar stage of development. Larvae feed on grass leaves and stems during the daytime in burrows in the thatch and upper soil layers. An early first sign of infestation is the presence of small ragged brown spots, which upon closer inspection have a scalped or grazed appearance. To confirm the presence of these pests, a flushing agent of pyrethrin or lemon-scented household detergent can be applied over a square yard of turf. If 10 to 20 caterpillars are uncovered, chlorantraniliprole or a pyrethroid applied to the turf will help control.
Cutworms and armyworms: Cutworms and armyworms are the larvae of several species of night-flying moths that – you guessed it – cut off stems and feed in great numbers. Larvae are black to brown to grey in color with prominent legs and stripes on their bodies. Sampling and control methods are the same as for sod webworm.
Annual bluegrass weevil: Often referred to as ABW, this insect pest feeds both inside and outside the plant. Monitoring can be done by checking grass clippings for adult weevils or by using the aforementioned lemon soap flushing method. Chlorantraniliprole can be applied to help control adults and larvae early in the season and in the summer. Pyrethroids, spinosad and indoxacarb can also help to control ABW. Base your timing on local phenological data for forsythia shrubs.
White grubs: The most notable insect pest in the soil are white grubs. In most situations and regions of the country, they’re an every-year pest, one whose damage must be prevented because of the potential severity of the damage. Several species of grubs cause damage in sports turf, including the northern masked chafer, May/June beetle, black turfgrass aetenius and Japanese beetle. When unchecked, white grub feeding can easily eliminate the entire root system of a turf stand. After hatching from eggs laid in early summer, white grub larvae begin feeding on the roots and underground stems, producing symptoms of patches of pale, withering grass displaying symptoms of moisture stress. In late summer, turf in infested areas usually has a spongy feel when walked on and can be easily lifted and rolled up like a piece of carpet. At this point, the larvae become attractive as a food source for blackbirds, skunks and raccoons, which often cause additional damage. Preventative control is typically done in May or June using neonicotinoids or chlorantraniliprole. Sampling turf later in August can help to reveal if there are significant grub populations, more than 5 to 10 per square foot could create significant damage. Clothianidin or Dylox can be used as curative control in August or September.