Moving Targets

The preventive programs for lawns outlined here are presented with the view that one pest (i.e., chinch bug, billbug, etc.) or group of pests (i.e., grubs, cutworms, mole crickets, etc.) is often the primary, but not necessarily the only, concern or focus of treatments directed by the lawn care operator. We call this the primary target. The impact of the programs and treatments on other pests that also occur at the time of application (i.e., secondary targets) is also considered. Remember, turf insects rarely, if ever, occur one at a time at only one time.

The target may be grubs, but billbug larvae and/or chinch bugs (pictured) that may be present at the same time can also be controlled or surpressed with a well-timed application. Photo: Destructive Turf Insects.

NORTHERN LAWNS. In our view, an insecticide or other form of insect control should be applied only when its use is justified. The major justification for following a preventive approach program should be a past history of infestation and/or damage and confidence that damage from insect pests will reoccur. Such history is based on previous years’ experience(s), observations, monitoring and knowledge of the seasonal spectrum of pests occurring at any specific location.

Consideration of the impact of a treatment on not only the primary target, but the spectrum of potential secondary pests as well, can reduce the number of applications needed to achieve the objective. Primary Target – Grubs. If grubs (Japanese beetle, masked chafer, European chafer, Asiatic garden beetle or Oriental beetle) are the primary target, and a preventive approach is selected, late April through May is the optimal time to apply imidacloprid (sold by Bayer as Merit).

Label directions regarding application rates should be followed carefully. In addition to providing seasonal control of grubs, the systemic activity of the material should also provide season-long control of billbug larvae, greenbug aphid, and as least suppression of chinch bug below damaging levels. Little or no control of overwintered sod webworm larvae is expected and influence of succeeding sod webworm generations is unknown. Mid- to late-June application of imidacloprid provides season-long control of grubs, but probably will not provide adequate control of billbug larvae.

The impact of this treatment on the first generation of chinch bug and sod webworm is notknown at this time. Application from July to mid-August will prevent annual grubs (including green June beetle), but is probably too late to impact other secondary pests in the spectrum (though this is unknown). Our experience has shown that May application of thiamethoxam (a new product from Syngenta called Meridian, still awaiting EPA approval) provides season-long control of Japanese beetle and masked chafer in Ohio.

Studies in other states have shown similar control of European chafer and Oriental beetle. Infestations of billbug and sod webworm larvae also can be controlled by May applications, but no research has been performed to determine the effect of a May application on future generations of sod webworms. June application of halofenozide (sold by Dow AgroSciences as MACH-2) provides season-long control of Japanese beetle and masked chafer. Control of European chafer and Oriental beetle has been maximized when halofenozide is applied at egg laying. Infestations of billbug and sod webworm larvae existing at application time may also be controlled with treatment.

Application from July to early August prevents infestation of Japanese beetle and masked chafers and controls existing sod webworm larvae. Treatments applied from mid-August through mid-September also control these grubs. Primary Target – Billbug. Billbugs are the most common cause of damage to lawns. Damage is often misdiagnosed as drought or sod webworm injury. Labeled pyrethroids (i.e. bifenthrin, beta-cyfluthrin, cyfluthrin, deltamethrin and lambda-cyhalothrin) applied between mid-April and mid-May kills overwintered billbug and chinch bug adults and sod webworm larvae (fluvalinate is another pyrethroid that is for billbugs and chinch bugs only).

Treatment at this time prevents development of a first generation of these pests. Application after mid-May could result in some billbug damage if significant egg laying occurred before the application. Primary Target – Chinch Bug. At locations where chinch bugs have one generation each year, a labeled pyrethroid applied between mid-April and early May should provide season-long control. In areas with two generations of chinch bug, the need for a second treatment depends upon the abundance of rainfall or irrigation during development of the second generation.

Further, if adjacent lawns were not treated for chinch bugs, there is a higher risk of this pest migrating into the treated lawn. When moisture for good turf growth is adequate during late August and September, a fungus disease, Beauveria, infects and kills many chinch bugs. In many, if not most cases, the population can be reduced to the point where a second insecticide application is unnecessary. The fact that most northern lawn care programs include a fertilizer application at this time also helps the turf withstand feeding from the second generation.

Application of fungicides significantly reduces Beauveria effectiveness. If August or September are dry (a condition under which chinch bugs thrive), reinfestation limited to the border can be caused by chinch bugs moving from adjacent untreated turf. Some border damage from first- and second-generation migrants is possible under such circumstances. If the adjacent turf has been treated or has a low level of infestation, reinfestation is very unlikely since the source of reinfestation is not there. In this case, the spring treatment could take care of the chinch bug problem for the year.

SOUTHERN LAWNS. Regions with Bermudagrass, zoysiagrass, centipedegrass, bahiagrass and St. Augustinegrass have general pests (e.g., mole crickets, grubs, armyworms, chinch bugs and fire ants) and turfgrass-specific pests (e.g., Bermudagrass mite, spittlebugs and ground pearls.). Primary Target – Mole Crickets. When previous experience indicates mole crickets to be a perennial pest problem in a lawn, a preventive control program is warranted. At this time, fipronil (sold by Aventis as Chipco TopChoice) is not registered for mole cricket control on home lawns. At present, imidacloprid can be used on lawns as a preventive treatment.

For most mole cricket zones, imidacloprid should be applied within the first three weeks of mole cricket first egg hatch. The calendar time of this period varies considerably from south to north in areas where mole crickets occur. For example, tawny mole cricket egg laying may begin as early as late March in south Florida, mid-April in northern Florida and mid-May in South Carolina. Egg hatch occurs about 20 days later.

Generally, each major biological event in the life history of mole crickets is delayed by one week as one moves 100 miles from south to north. Mole cricket populations in coastal or island areas are often ahead in development when compared with inland populations. A single surface application of imidacloprid (at the highest label rate), made within three weeks of first egg hatch (as determined by occurrence of the first nymphs), should effectively prevent damage from tawny and southern mole crickets.

Imidacloprid applied during this period should also control secondary pests, such as masked chafer or annual species of May/June beetle grubs that can appear 60 to 90 days after the application. Spring applications also appear to control hunting billbug and suppress southern chinch bug populations. Though neither labeled nor thoroughly tested, thiamethoxam should also control mole cricket nymphs as well as a broad spectrum of secondary pests when applied at the same time as outlined for imidacloprid.

The key to successful use of imidacloprid (and possibly thiamethoxam) is to determine when mole crickets in an area are ready to lay eggs. Lawn care providers who have used a preventive program for mole crickets should still warn clients that such applications will neither stop migration of nymphs from surrounding lawns nor stop incoming flights of new adults in late fall and early spring. If fall or spring migration of adults produces unacceptable tunneling, curative materials or baits may need to be applied. Primary Target – Grubs. If grubs (southern and southwestern masked chafer or annual May/June beetles) are the primary target, and a preventive approach is selected, May to early June is the optimal time to apply imidacloprid.

In addition to providing seasonal control of grubs, the systemic activity of the material should also provide control of secondary targets, such as hunting and Phoenician billbug larvae, and some suppression of early generation southern chinch bugs and fire ants. Control of first generation armyworm and tropical sod webworm larvae should also be achieved for 20 to 30 days after application, but will not prevent late season outbreaks. Late June to early July application of imidacloprid provides season-long control of grubs and will provide some control of billbug larvae.

This late application will likely have little effect on the secondary targets, southern chinch bug and mole crickets, but development of armyworm and tropical sod webworm populations should be suppressed for 20 to 30 days. May, June or July application of thiamethoxam will control grubs in southern turf and secondary targets, similar to the activity spectrum of imidacloprid. A June preventive application of halofenozide provides season-long control of masked chafers and Phyllaphaga crinita.

Control of Phyllophaga latifrons (the species common to south Florida) is limited. Infestation of the secondary targets, billbug, armyworm and tropical sod webworm larvae existing at the time of application may also be controlled with treatment at this time, but do not expect extended residual control. Application of imidacloprid, thiame-thoxam, or halofenozide from July to early August will also control southern grubs as well as the green June beetle, but this is too late for control of early generations of billbug, armyworm and sod webworms.

The impact of treatment at this time on sod webworms that will overwinter is unknown. Primary Target – Fire Ants. Control of fire ants generally requires both curative and preventive approaches in lawns. While the two-step or ant-elimination method can be used, most clients prefer the ant-elimination strategy since it reduces the chance of havng contact with fire ants in the landscape. Two-step approach: This method includes a bait-formulated insecticide application over the entire lawn once (spring) or twice a year (spring and early fall), and it’s more effective if entire neighborhoods cooperate with residents making similar applications. In step one, baits are broadcast over the entire lawn.

Unfortunately, baits act slowly on the fire ants within their nests. Some baits take three to five weeks to achieve maximum effect, while others produce maximum control four to nine months after application. After one to three weeks, many of the smaller fire ant mounds will have disappeared or become inactive. Where fire ant mounds are located in high use areas (nuisance mounds) or if larger mounds continue to persist, step two is to treat nuisance and persistent mounds directly.

These mounds should be treated directly with drenches, dusts, granules, or an aerosol injection. A range of insecticides is registered for this purpose. Once fire ants in an area have been brought under control, the two-step program can be used every year to prevent extensive build up of fire ant colonies. This is best done by applying the baits in the fall (September or October) and treating remaining mounds in the spring. In founding becomes extensive, reapply baits. Ant-elimination approach: A bait-formulated insecticide is broadcast over the entire turf area or the bait is spread around individual mounds.

After two to three days (to allow foraging fire ants to pick up the bait), a contact insecticide is applied to the entire lawn. Depending on the number of foraging fire ants, the contact insecticide may need to be applied every four to eight weeks. The goal is to reduce mounds (baits) but minimize encounters with fire ant workers (contact sprays). When acephate or a pyrethroid is used as the contact insecticide, the secondary targets, cutworms, armyworms and sod webworms will also be controlled.

If these applications are made when mole cricket eggs are hatching, many young mole cricket nymphs can be killed. The authors are professor emeritus, department of entomology, The Ohio Agricultural & Development Center, The Ohio State University, Wooster, and associate professor, department of entomology, The Ohio State University, Columbus.

EDITOR’S NOTE: Mention or omission of specific product names is neither an endorsement nor criticism of such products by Lawn & Landscape magazine or this article’s authors.