Control of ground pearls using application sequences of different insecticides

Results

For the six treatment sequences in 2017, the mean number of ground pearls per plot ranged from 1.3 to 82.6 (Table 2). The untreated turf plots averaged 94.6 encysted ground pearls per plot. Areas that showed no visible symptoms had, on average, one or two ground pearls per plot (data not shown).

Table 3

The TS with the highest number of encysted ground pearls included treatment TS 11, which started with Nimitz nematicide (82.6 ground pearls per plot). The next highest was TS 2, which started with Arena (59.6 ground pearls per plot), followed by TS 1, which started with Acelepryn first (22.0 ground pearls per plot).

The TS applications that resulted in the lowest numbers of encysted ground pearls included those in which Ference was applied once in one of the first three applications (TS 4, TS 7 and TS 8) or in which Avid was used earlier in the first three applications (TS 4 and TS 7). The three Ference TS sequences (TS 4, TS 7 and TS 8) had, on average, 1.0, 1.3 and 8.6 ground pearls per plot (Table 2).

Based on the 2017 results, we repeated the best treatment sequences in 2018 on the same turf plots for a second year. We also used the best performing treatment sequence (TS 4, TS 7 and TS 8) programs from 2017 as new initial treatments starting in 2018 to new plots having ground pearl counts ranging from 79 to 234 per plot (Table 3). Thus, there would be a total of six treatment sequences for 2018, now all based on rotations of Zylam, Avid and Ference products.

The three repeated treatment sequences from 2017 are TS 4+4, TS 7+7 and TS 8+8, and three that were new starts in the 2018 season are TS 4, TS 7 and TS 8. We followed the same sampling procedures for the plots (two greens cup-cutter plugs) in early October 2018 and completed ground pearl counts within seven days. Plot maintenance was identical to that described for 2017.

The results for 2018 show that when we applied the first rotational application of Zylam, Avid or Ference, nearly all cysts were eliminated from infested plots. It is essential to note the first application was during the exposed female stage. The two-year repeat treatment series, e.g., TS 4+4, TS 7+7 and TS 8+8, averaged 1.6, 0.5 and 1.0 pearls per plot, respectively, when applied over two years. In October 2018, the nontreated control plots averaged 167 pearls per plot (Table 3).

For the plots that received the treatment sequence of TS 4, TS 7 or TS 8 on previously untreated plots for the first time in 2018, the number of encysted pearls ranged from 6.0 to 39.1, among the three designated treatment sequences involving Zylam and Avid and Ference. As in 2017, TS 7 ranked third for the lowest number of encysted pearls, then TS 4 and TS 8 (Table 3). The number of ground pearls in the nontreated control plots was quite large in October 2018, averaging 167 encysted ground pearls per plot (Table 3).

Conclusions

In our case, we harvested soil samples from mid-May to mid-June to determine the ratio of pink exposed females to encysted pearls. We found that a population of 90 percent females was correlated to 1790 AZMET (cumulative) heat units when using the 55/85 degree F sigmoidal model. For locations not covered by the AMET network, it is critically important to make multiple soil samples across multiple dates to determine the ratio of females to encysted pearls. Start doing so before mid-May and continue repeating the process every five days to determine when the females predominate the population.

This data shows that, at least under extreme desert heat conditions, ground pearls can be dramatically reduced in numbers on bermudagrass by performing closely timed applications of three systemic insecticide products, each applied once at the full label rate on nonencysted, egg-laying females. We used a single high label rate of Zylam, Ference and Avid in a narrow time window when exposed females predominated the population. These chemicals worked best when applied over two seasons. Thus, applying select insecticides in rotations while maintaining full label compliance for all products used appears to be an effective chemical treatment for turf with ground pearl infestations under desert conditions.

Research takeaways

• Ground pearls have become extremely problematic to control on golf courses because of the removal of many older turfgrass insecticides with environmental issues.
• Ground pearl adults (when they are exposed as nonencysted egg-laying females) were severely reduced in numbers by rotational and closely spaced single applications of Zylam, Avid and Ference under desert conditions.
• This research presents a protocol of product use sequences to achieve significantly enhanced ground pearl control.

Acknowledgments

Thanks to Mac Blevins, golf course superintendent, Desert Hills Municipal Golf Course, City of Yuma-Parks and Recreation, for allowing his course to become a ground pearl research site.

References

1. Camerino, A. 2002 (revised 2015). Featured creatures: Ground pearls. University of Florida Pest Guide Extension Bulletin (http://entnemdept.ufl.edu/creatures/orn/turf/ground_pearls.htm#top)

2. Hoffman, E. 1981. The biology and control of the pearl scale, Margarodes meridionalis Morrison (Homoptera: Coccoidea). Master’s thesis. University of Arizona, Tucson, Ariz.

3. Hoffman, E., and R. L. Smith. 1991. Emergence and dispersal of Margarodes meridionalis (Homoptera: Coccoidea)in hybrid bermudagrass. Journal of Economic Entomology 84(6):1668-1671 (https://doi.org/10.1093/jee/84.6.1668).

4. Jensen, J., and K. Umeda. 2019. Arizona Golf Industry Best Management Practices Resources Guide. Cactus and Pine Golf Course Superintendents Association, Scottsdale, Ariz. (https://cactusandpine.com/resources)

5. Kouskolekas, C.A., and R.L. Self. 1974. Biology and control of the ground pearl in relation to turfgrass infestation. Pages 421-423. In: Eliot C. Roberts, ed. Proceedings of the Second International Turfgrass Research Conference, June 1973, Blacksburg, Va. American Society of Agronomy and Crop Science Society of America, Madison, Wis.

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