Golf Course Management

JUL 2018

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Page 68 of 99

07.18 GOLF COURSE MANAGEMENT 67 with Revolution. e data from the 2008 study were too inconsistent for me to generate a conclu - sion and recommend Arena or Meridian as a management tool for ground pearls. Based on the average of live cysts at nine months after treatement in plots treated with Sevin SL (the highest average in this study), the plots were infested with as many as 912 individuals per 50 cubic inches, or more than 31,500 individ - uals per cubic foot! e study did, however, produce one con - sistent observation. Plots treated with Sevin SL, and to a lesser extent, Malathion, Orth - ene and Talstar (both with or without Revolu- tion) had more live ground pearls than the un- treated check. I think these broad-spectrum insecticides had killed off natural enemies or interrupted their activities. e natural en - emies of ground pearls are unknown, but it is likely that ants and other soil-dwelling arthro - pods might have helped in reducing the num- bers of adult females and crawlers (1). If the natural enemies of ground pearl are removed from the environment, ground pearls have no check on their population growth. Neonicotinoids Among the insecticides evaluated in this study, neonicotinoids (Arena, Meridian and Merit) hold the most promise. Neonicotinoids (except for Arena with Revolution), along with Dylox, slightly reduced the numbers of live ground pearl cysts at nine months after treatment. Studies and observations by Rick Brandenburg, Ph.D., North Carolina State University, and Kai Umeda, University of Ari - zona Cooperative Extension, also support the potential of neonicotinoids (1; Brandenburg and Umeda, personal communication). Overall, however, neonicotinoids did not result in significantly lower numbers of live ground pearl cysts in this study (Figures 4, 5). I believe one application is insufficient to cover the entire activity period of adult fe - males and crawlers. Although an individual adult female lives for less than a month, adult females in a population emerge at different times, so reproduction of the entire popula - tion occurs over a very long period. Even if the application applied in July had killed 85% of the adult females and crawlers present at the time of application, that one application would not have killed adult females that had laid eggs and nymphs that had formed cysts before July or the adult females and crawlers that emerged after July. erefore, the most ef - fective approach may be to initiate treatment with neonicotinoids as soon as adult females have emerged from cysts and to repeat the ap - plication until all crawlers have hatched. Problems with neonicotinoid use Repeated use of neonicotinoids has several drawbacks. e first and most obvious short - coming is that repeated applications can be extremely time-consuming and costly. e second problem is that no experimental data support the efficacy of this approach and re - sources are not available to support a study that could gather such data. It is likely that the same management approach would have to be repeated over several years to result in an improvement in turf health and appearance. A more technical issue with the approach is our general lack of knowledge about ground pearl biology and ecology. Adult emergence time changes from year to year, and there is no method of predicting when emergence will occur each year. Without that predictive abil - ity, turf managers may have to initiate applica- tion from April through August. Again, this would be very time-consuming and expensive. Another consideration is safety to natural enemies and pollinators. Several studies had demonstrated that neonicotinoids, although generally not as detrimental to natural en - emies as organophosphates and pyrethroids, are still harmful to natural enemies and pol - linators. ere is no conclusive information on whether insecticides with better safety pro - files for natural enemies and pollinators, such as the diamides Acelepryn (chlorantranili- prole, Syngenta) and Ference (cyantranili- prole, Syngenta), have any potential in man - aging ground pearls. Other systemic insecticides? Turf managers often ask about using sys - temic insecticides for ground pearl control. e idea is that systemic insecticides will be absorbed into plant tissues and then will be translocated to the roots. e ground pearls will feed on the roots, suck in the insecticide and die. Neonicotinoids and diamides are systemic insecticides. It is important to understand that these systemic insecticides are not fully sys - temic, meaning that most of active ingredients are concentrated in the leaf tissues; very few or any are translocated to the roots where the ground pearls are feeding. Our results on the efficacy of neonicotinoids in this study con - firmed that neonicotinoids are not the stealth bombers we have been looking for. Currently, no fully systemic insecticide is available to the turf industry. Now what? So, no insecticide is labeled for ground pearl control in golf turf, and no insecticide is known to be effective against ground pearls. What else can you do? Improving water penetration As I observed in my study, improving water penetration helped improve the health of an infested lawn. Increased fertilization and irri - gation can result in temporary improvement in turf appearance, but this is only masking the damage. Without an effective method of reducing the ground pearl population, how - ever, it is only a matter of time before the dam- age reappears or is magnified. Replacing susceptible grasses An obvious option is to replace a suscepti - ble grass like centipedegrass with another spe- cies. No warm-season turfgrass species is im- mune to ground pearls. Bahiagrass seems to tolerate infestation better than other species, but I am doubtful that anyone will willingly replace a centipedegrass lawn or rough with bahiagrass. Bermudagrass and zoysiagrass are the obvious alternatives. Cultivars that grow vigorously with supplemental fertilization and irrigation, such as Celebration, may develop symptoms later than other cultivars. Decline of the bermudagrass lawn and rough, how - ever, is inevitable, especially when grown on sandy soil. Damaged turf area can also be replaced with ornamental landscapes. is is the only viable option for severely damaged lawns. With some careful and clever rede - sign, golf course roughs can also be con- verted to plantings of ornamental plants or pollinator habitat. Persistence of infestation One of the most frustrating aspects of ground pearl management is the persistence

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