White Grub Biology and Management
Summary: Larvae (grubs) of the black turfgrass ataenius, Ataenius spretulus, and the masked chafer, Cyclocephala spp. are serious pests of cool season turfgrass throughout the United States. However, little is known about the biology and the timing of appearance of these insects in the Low Desert, nor is there a good, generally accepted method for monitoring of white grubs. This deficit has made management of these pests difficult. To address this gap in information, the PACE Turfgrass Research Institute conducted three different studies on white grubs during 1996 - 97:
Project I: Predicting the Timing of Adult and Larval Populations of the Black Turfgrass Ataenius and the Masked Chafer Using Black Light Traps
Project II: Predicting the Timing of Adult Populations of the Black Turfgrass Ataenius Using Degree Day Models
Project III: Efficacy of Chemical and Biological Controls for Black Turfgrass Ataenius and Masked Chafers Key research findings are listed below and are presented in more detail in the three attached reports.
- Black turfgrass ataenius biology: Black turfgrass ataenius adults were present in all study locations. There were three or more discrete generations of black turfgrass ataenius (BTA) adult beetles, beginning in late May, and ending in October or November, although small numbers of adult beetles were observed on greens throughout the year. In contrast, BTA grubs were infrequently observed in the Low Desert, and only beginning in late August, when they did cause damage to cool season turf. This may indicate that BTA grubs do not survive on greens height turf during the hotter months of July and early August, and that they may not be as widespread a problem as previously believed.
- Predicting the appearance of the black turfgrass ataenius: While several methods were developed that accurately predicted when BTA adult beetles would appear, prediction of grub appearance was more difficult. Based on PTRI data obtained from coastal Southern California golf courses over the past 4 years, it was expected that BTA grub populations would occur two to three weeks after each peak of BTA adult beetle activity. However, although extremely high numbers of BTA adults were detected with black light traps beginning in late May/early June, grubs were not detected until twelve weeks later, in late August. Therefore, while black light traps are a good indicator of when adult BTA beetles will appear, they do not necessarily give an accurate prediction of when BTA grubs will appear on golf course greens. A degree-day model that was developed to predict the appearance of BTA adults was able to use temperature to predict when BTA adults would occur (and was accurate within a range of 2 days before or 14 days after the actual peak), thus making the use of black light traps less necessary. However, like the black light trap, the degree day model only predicts when adult BTAs will occur, and does not predict when BTA grubs will appear.
- Masked chafer biology: Unlike other regions of the country, where masked chafers lay eggs for only a few weeks, Low Desert masked chafer adults were active in June, and then again in August and September, indicating that two different species of chafers may be present in the Desert. Grubs were found on cool season greens beginning in early July, and continuing to the following Spring. The greatest damage from chafer grubs was observed in July and August. Chafer grubs appeared to be a serious pest in more locations than did BTA larvae.
- Predicting the appearance of the masked chafer: Black light trap samples of masked chafer adults accurately predicted the appearance of grubs, with grubs first detected on greens on 7/12/96, or four weeks after the first peak of adults, which occurred between 6/9 and 6/11. A second peak was observed in September/early October. It is likely that the occurrence of two peaks of chafer activity indicates the presence of two different species of masked chafer. Unlike the BTA, masked chafer adults appear to be active during the same time period every year, indicating that changes in temperature from year to year have little effect on chafer activity. For this reason, it is likely that a constant environmental feature, such as day length, has a stronger effect on chafer development than does temperature. Based on these observations, chafer activity can be most accurately and easily predicted using a calendar, with the first peak of adult activity expected during the second week of June, and the first grubs appearing in late June and early July. Black light traps and degree-day models will probably be no more accurate than this calendar approach to predicting masked chafer activity.
- Control of white grubs: The most effective treatments were trichlorfon (Dylox or Proxol), imidacloprid (Merit) and acephate (Orthene and Pinpoint). No phytotoxicity was observed. While Merit provided excellent preventive control of white grubs, its activity declined significantly between 8 and 10 weeks after application. This suggests that two applications of Merit may be necessary to maintain control during the critical months of June, July and August. Applications of Dylox or Orthene provided excellent curative control of grub populations. However, these products have brief residual activity and therefore must be applied several times during the season for optimum control. Dursban, considered by some to be the industry standard for grub management, did not provide acceptable control of white grubs. Other ineffective treatments included two biological insecticides (M-Press and Cruiser), and Tame (a pyrethroid).
Printable version of full report
Project I: Predicting the Timing of Adult and Larval Populations of the Black Turfgrass Ataenius and the Masked Chafer Using Black Light Traps
Principal Investigators: Wendy Gelernter, Ph.D. and Larry J. Stowell, Ph.D., CPAg
Cooperators: Ross O’Fee and Mike Kocour, The Springs Club; Cal Hardin, Morningside Country Club; Douglas Anderson, The Vintage Club; Chris Harvell, Nicklaus Private Course (PGA West)
Sponsors: Hi-Lo Desert Golf Course Superintendents Association; Ross O’Fee and Mike Kocour, The Springs Club; Cal Hardin, Morningside Country Club; Douglas Anderson, The Vintage Club; Chris Harvell, Nicklaus Private Course (PGA West)
Project II: Predicting the Timing of Adult Populations of the Black Turfgrass Ataenius and the Masked Chafer Using Degree Day Models
Principal Investigators: Wendy Gelernter, Ph.D. and Larry J. Stowell, Ph.D., CPAg
Cooperators: Ross O’Fee and Mike Kocour, The Springs Club; Cal Hardin, Morningside Country Club; Douglas Anderson, The Vintage Club; Chris Harvell, Nicklaus Private Course (PGA West)
Sponsors: Hi-Lo Desert Golf Course Superintendents Association; Ross O’Fee and Mike Kocour, The Springs Club; Cal Hardin, Morningside Country Club; Douglas Anderson, The Vintage Club; Chris Harvell, Nicklaus Private Course (PGA West)
Project III: Efficacy of Chemical and Biological Controls for Black Turfgrass Ataenius and Masked Chafers
Principal Investigators: Wendy Gelernter, Ph.D. and Larry J. Stowell, Ph.D., CPAg
Cooperators: Ross O’Fee and Mike Kocour, The Springs Club and Chris Harvell, PGA West
Sponsors: Hi-Lo Desert Golf Course Superintendents Association, Bayer Corporation, Valent Corporation
