Superintendents need to understand that fall armyworm infestation in the South is as “sure as hot weather in the summer – wait for it and it will come,” says Dr. Juang-Horng Chong, associate professor and extension specialist in turf and ornamentals entomology at Clemson University.
While nearly every year there are reports of severe fall armyworm infestations, there is no consistent pattern in the severity of infestation, Chong says. For example, one course might suffer severely, while another course a mile away experiences no issues. The damage – or infestation level – of this pest depends on the weather and environmental conditions in Florida and Georgia, he says.
“The fall armyworm does not overwinter in South Carolina,” Chong says. “The entire population dies soon after the first frost in November. A permanent population occurs in Florida, which begins to build up in the spring, and spreads north into Georgia. The population grows and continues to spread north, and eventually reaches South Carolina in June.”
Superintendents should keep an eye on infestation in the summer, especially along tree lines. Chong adds timing depends on where their courses are located. A staple of southern turf, the fall armyworm is starting to be reported in South Carolina (in June), but the worst is yet to come, with the most severe damage to take place in late August and September, Chong says. The worst infestation Dr. Chong ever witnessed was on a golf course in Charleston, S.C., in 2010, where the fall armyworms were so numerous that “the entire rough seemed to be moving.”
“Fall armyworm adults prefer to lay eggs on anything that is erected – tree trunks, flags, markers, posts, signs, walls, etc.,” he says. “Population and damage often radiate from these erected structures.”
While soap flush is a good way to sample for population, Chong advises superintendents to pay attention to paper wasps, which are predators of fall armyworms. Areas where the wasps are actively flying around, close to the turf surface, are likely areas with fall armyworm or other caterpillar infestations, he says.
Fortunately, fall armyworms are not difficult to control curatively. “Most insecticides registered for management – organophosphates, pyrethroids, diamides – are effective at the label rate,” he says. “The residual of organophosphates and pyrethoids are relatively short, so supers may have to come back and make reapplications on a biweekly basis.” He adds that it may be weekly if infestation is particularly intense.
Preventatively, superintendents can apply a long residual diamide insecticides (chloratraniliprole or cyantraniliprole) on roughs bordering tree lines or areas where there has been consistent infestation over the years, Chong says. In some cases, one application of diamide may provide protection for two months.
Traditional reactionary practices of spraying an outbreak with a pyrethroid insecticide delivered less than stellar results and were labor intensive, says Dr. Lane Tredway, Syngenta senior technical representative. However, new chemistries for managing fall armyworms outbreaks can preventatively control this insect in an effective and efficient way, he says. “One application of Acelepryn insecticide can prevent fall armyworms for 90 days or longer,” he says.
Like fall armyworms, mole crickets destroy large areas of turf in a very short period of time if their populations are allowed to build through the summer, Tredway say.
With any infestation, smaller insects, in the early stages of their life cycle, are more sensitive to insecticide chemistries, while larger insects, later in their life cycle, can be controlled by fewer chemistries and high label rates for effective performance. Mole cricket management can happen at either phase, Tredway says, while prevention is preferred.
“Several options are available to control small (mole cricket) nymphs in the spring or early summer, but large nymphs and adults in the late summer and fall are much more difficult,” he says. “Advion Insect Granule, a bait formulation of indoxacarb, is one of the few options, but provides very effective control of larger mole crickets in the late summer and fall.” Areas where mole crickets were active in the spring will also be areas where mole crickets will become active in late summer and fall, Chong says. These are the areas superintendents should keep an eye on every year. Most turf managers have a pretty good handle of mole cricket suppression, but damage can still sneak up on them, he says.
The best approach is to reduce the mole cricket population – and thus their tunneling activity – in the spring and early summer. Fipronil (TopChoice) is the best product available for mole cricket control, Chong says. Because of its cost, some courses mainly use this product on the most critical areas such as greens and tees, he adds.
Japanese beetle grub
Kentucky and surrounding states have seen “very heavy flights” of adult Japanese beetles during summer 2017, says Dr. Daniel Potter, University of Kentucky professor of entomology. Heavy rainfall and moist soil conditions favor the survival of Japanese beetle eggs, so this is expected to mean high grub populations in August and September.
“Much of the damage may be masked if turf remains vigorous from above average rainfall,” he says. “But if it turns dry and turf is stressed in late summer, there will be plenty of grubs in the soil. So, watch for grub damage such as turf that is wilting, dying and easy to pull back like a loose carpet due to lack of roots, and digging by skunks, raccoons, armadillos, birds and other critters that feed on these `land shrimp.’”
The best window for preventive grub applications with Acelepryn or neonicotinoids (Merit, Arena, Meridian or combo products) is in May or June, Potter says. However, if superintendents missed areas and experience grub damage, trichlorfon (e.g., Dylox), clothianidin (e.g., Arena), Aloft (which contains clothianidin), or carbaryl (Sevin) can be used as spot-treatment for curative control, he says.
Hunting billbugs are also problematic on zoysiagrass and Bermudagrass golf courses. And to complicate matters, they’re often confused with grub damage or drought stress, Chong says. Identifying the problem correctly goes a long way toward developing the proper control strategy.
Bermudagrass and zoysiagrass are most frequently impacted by billbugs, and areas stressed by drought or low irrigation amount/frequency (bunker faces or slopes) are often areas where problems first appear. Adults can often be found walking on turf surfaces in the morning, but the presence of adults does not automatically indicate severe infestation and warrant immediate pesticide application.
Instead, superintendents should conduct soil core sampling in areas that show thinned or weak turf, particularly areas that do not retain moisture. “Our experience indicates that billbug grubs can be quite spread out in an area, so multiple samples should be taken to check for their presence and density,” Chong says. “Another good way to sample for billbug damage is to tuck at the impacted turf.” If the desiccated or chlorotic grass break off easily at the crown, and fine saw dust (these are actually a mixture of waste and grass by young billbug grubs) come out of the stems or fall out when the superintendents split the stem, billbugs may be present, he says.
Chong’s research suggests there may be two generations of billbugs in the Carolinas – adults are active in March to July and August to November. “The activity of adults can be monitored with a simple pit fall trap,” he says. “Applications of pyrethoids can be applied in April and September to target adults, or a combination of pyrethoids and neonictinoids can be applied at about the same time. Cyantraniliprole also has been shown to be very effective against billbug grubs.”