Considering biological pest control

Riviera Country Club in Coral Gables, Fla., has explored the use of biologicals to manage pests. Leading those efforts are (from left): Mike Smith, first assistant superintendent; Mike Heinz, second assistant superintendent; P.J. Salter, CGCS, director of facilities and grounds; Drew Nottenkamper, superintendent; and course dog Jett. Photos courtesy of Steve Kammerer

Pest management on a golf course can be challenging. Managing pests year after year on a perennial “crop” such as turfgrass with the low tolerance for turf loss on a golf course versus an agricultural crop is challenging, to say the least. Most agricultural row crops aren’t typically grown in such environmentally sensitive areas as some of the world’s finest golf courses. Pest outbreaks can have a devastating impact in these environments and require constant monitoring. 

Even though the grasses managed on a golf course have a good capability for natural defense against most pest attacks, at times pest control applications are necessary. These control applications traditionally center on the use of synthesized chemical pesticides, which can be subject to ever-increasing restrictions regarding how, when and where they can be used.

To be proactive, some golf courses have developed working documents to align agronomic standards for golf maintenance. These include options for pest management based on product restrictions, risk assessment and best management practices. Efforts such as GCSAA’s national BMP initiative (see https://bit.ly/43Bbi1W for more information) are a great testament to environmental stewardship and the overall image of golf. Biological controls and biological control products — biopesticides — can be a viable option for pest management.

Table 1. Biologicals may be a preferable solution for pest issues, especially in situations where turfgrass is directly adjacent to water bodies.

The right stuff?

Synthetic pesticides have evolved since their introduction into agriculture, coinciding with World War II. Some of these early pesticides were found to have high levels of toxicity and persistence, creating ecological and environmental concerns, along with off-target effects.

Many of today’s newer chemicals used in the golf course market have very low use rates with greater pest specificity and less off-target effects compared to the older pesticides. As an example, some insecticides will control mole crickets with no activity on grubs, caterpillars or other insects that can also be problematic. There are fungicides that control diseases caused by Pythium but no other diseases, and vice versa. This specificity demands greater attention to monitoring all potential pests as sometimes, when one pest is controlled, others that are unaffected can build in intensity. For this reason, monitoring, mapping, sampling and development of thresholds of concern can be of critical importance in deciding whether to make an application of a pesticide.

There are potential consequences with everything we do, and pesticide applications are no exception. Therefore, it is good to think through some possible considerations before deciding on any chemical or biological pest control application (Table 1).

A close-up of fairy ring mycelium on soil cores in growth chamber 48 hours following removal from a putting green.

The case for biopesticides

Many synthesized pesticides have biological origins. Biocontrol products registered for golf course use may be living organisms — biologicals — and might include products with a direct biological origin, meaning they were not synthesized in a lab. Some biocontrol examples would be botanicals, biological metabolites or pesticides derived from natural materials such as animals, plants, bacteria, fungi or even minerals.

For example, pyrethrum is a naturally occurring bioinsecticide used for centuries, derived from the flower heads of chrysanthemum, whereas Bacillus subtilis strains are living bacteria used for disease control. For simplicity for the rest of this article, biologicals and biocontrol products will be referred to as biopesticides.

Depending on what area of the world you live and work in, biopesticides are being used more and more. Even large multinational chemical companies are now producing or marketing biopesticides as an increasing percentage of their overall business (3). Increasing restrictions on older pesticides and the high costs of development and registration for new chemicals are contributing to this trend. For example, the use of chlorothalonil, a valuable and common fungicide, is being restricted on golf courses and agricultural crops in different areas of the world, with an outright ban on the product in the European Union that went into effect in 2020 (2). This is a good reason to consider the use of these natural pest control products, identifying viable options for the major pests that occur each year on a golf course.

Sometimes a biopesticide is the only option in sensitive environmental areas or where presenting a lessened risk to golfers and wildlife is necessary. Water bodies are an obvious example of a sensitive area where many insecticides could be restricted or have negative effects (4).  In those instances, a specific strain of the bacteria Bacillus thuringiensis (1) — var. isralensis — available in commercially available formulations is registered for applications to water bodies for mosquito control.

Biopesticides often are considerably less expensive than conventional pesticides. A popular Bacillus thuringiensis product labeled for turf use is $15 to $16 a pound with a use rate of 0.5 to 2.0 pounds per acre (0.6 to 2.3 kilograms per hectare). For just one application to 25 acres of fairways for caterpillars, for example, this can save thousands of dollars compared to a standard season-long insecticide. In the case of armyworms, where outbreaks are concentrated around a specific time of the year, a low-cost biopesticide may be attractive.

If a biopesticide can reduce the number of chemical pesticide applications or volume applied, this can be a win for the budget, for the environment, and for the maintenance staff and golfers, and for reducing the duration of exposure from one mode of activity on pest populations, which can reduce the potential for resistance developing. Although less pretty in comparison to butterfly gardens, incorporating biopesticides into pest maintenance can demonstrate additional environmental stewardship.

Some biological products like neem oil may have a shelf life in which they are still effective or require additives in order to be mixed and applied with water.

Best management practices

The first step in deciding whether to use a biopesticide on your course and to maximize the potential for success is setting realistic expectations. Biopesticides tend to be short-lived in the environment and are better at reducing populations than in achieving 90%-to-100% control of a pest. Targeting pests early with a biopesticide or before their populations expand exponentially can result in better results.

Biopesticides have their best chance for success when targeting a pest that has a definitive life cycle, preferably for a short period, or at a sensitive stage in its development. Insects such as mole crickets or grubs in their early life stages would be more susceptible to biopesticides for this reason. For pests with many generations each year (polycyclic) that can be especially aggressive or destructive — think anthracnose or Pythium — biopesticides are less likely to deliver results as consistent as a synthetic pesticide, especially once symptoms occur.

For fungal diseases, a good disease target for a biological would be a disease like spring dead spot or take-all patch on fairways where a definitive life cycle period exists for infection and disease symptom development, and 100% control is not the expectation.

If a chemical pesticide application is desired, pest control and efficacy may be enhanced following a biopesticide application, especially if the biopesticide reduces existing populations. This approach can also decrease the risk of resistant populations developing, as the greater the existing pest populations when a single-site mode of action pesticide is used, the greater the likelihood of resistance developing.

Some biological organisms are capable of establishment after application, especially those delivered to the soil, like beneficial fungi or bacteria to compete with or antagonize less-desirable organisms that impart negative effects on the plant or turfgrass (6). This is an approach to consider with fungi that cause fairy ring that compete with other organisms for available organic matter.

For those using a biopesticide in conjunction with a synthetic pesticide, consider having a designated area, such as a driving range, where the product is used by itself for comparison to being added with the synthetic pesticide and then that pesticide alone. Do a precursory evaluation of the area and take notes on any preexisting pests before application to help with assessing results afterward. Otherwise, it can be a guessing game as to whether the chemical or the biopesticide provided the results. Without previous experience or knowledge, synthetic pesticides may antagonize the biopesticide or vice versa, causing unforeseen effects if applied together.

Avoid “kitchen-sink” mixtures, especially if the biopesticide is a living microorganism like a bacterium or fungus. Start with a product with just one species versus a cocktail of two, four, six or more in a “the-more-the-better” approach. Mixtures of multiple bacterial or fungal species in one product, especially if the label doesn’t specify the exact colonies (CFU = colony forming units) of each, run the risk of having one prevail over the other.

Despite multiple fungicide applications, this fairy ring persisted. Establishing a bacterial biological may help compete with the fairy ring fungus for organic matter.

Attention to detail

When applying a biopesticide, especially if it is a living organism, attention to current environmental conditions is advisable. Under hot conditions and intense sunlight, many bacterial and fungal microorganisms can perish, or the biopesticide can incur enhanced degradation versus wet, overcast conditions.

Biopesticides can be negatively affected by a chemical. You might not want to pair a fungal biological like Trichoderma before or in a tank mix with a fungicide application, as the fungicide may kill the fungal biological. Read the labels, and do your homework. Just like when you make any purchase of a new product, attention to the details can make a big difference in whether something works or doesn’t.

Biopesticides might not be as easy to apply as a synthetic pesticide and might be more sensitive to environmental conditions. Depending on the product and the experience of the manufacturer, formulations and ease of application can vary. The shelf life or stability of the biopesticide over time is likely shorter than it would be with a synthetic pesticide. Some of these may need to be stored in a more controlled environment removed from temperature extremes. These challenges incentivized manufacturers to synthesize and patent chemically synthesized analogs of biopesticides, like the strobilurin-based fungicides. These fungicides were based on naturally occurring strobilurins derived from Strobilurus tenacellus, a mushroom-producing fungus (5).

There can also be shelf-life-survivability issues, especially for bacteria or fungal organisms, more so with mixtures of several species, depending on the formulation characteristics of the product, when it was produced, and in what environmental conditions the product was stored. Microorganisms compete with one another in the environment for a given niche; as such, there can be greater likelihood of an antagonistic versus synergistic relationship when several organisms are mixed, formulated, stored and then applied as mixtures. Biopesticides consisting of biological metabolites or natural products can have greater stability with longer shelf life than living organisms, lending to greater consistency of efficacy.

Case in point

P.J. Salter, CGCS, an 18-year GCSAA member, and his managers and staff at Riviera Country Club in Coral Gables, Fla., do an excellent job maintaining the course but are always looking for different approaches to manage pests, increase efficacy, minimize environmental risks and manage costs. The year-round growing season and the extreme, volatile environment of South Florida present certain challenges in managing pests. I worked with Salter and his team to try to utilize lesser-known biologicals and biological products, hopefully to enhance control of specific pests where synthetic-pesticide options were either limited or failed to provide acceptably consistent control alone.

Nematodes are one such group of pests. Not all nematodes are pests; in fact, there are beneficial nematodes that prey on the harmful species that damage turfgrass roots. By monitoring nematodes every three months and assessing the health of roots, we determined which nematodes were most problematic and impactful on the bermudagrass putting greens. Through the utilization of a biological nematicide consisting of solids and solubles derived from a specific fungal strain of Myrothecium verrucaria applied monthly at low rates when the bermudagrass growth potential is highest (May through September), root-knot and lance nematode populations have been reduced in conjunction with stabilizing sting nematode populations. This resulted in reduced use of synthetic pesticides, with a positive impact on beneficial nematodes. Roots improved, as did surface playing conditions. Additionally, a Bacillus thurin- gensis product was applied several times over the fairways to help supplement a residual insecticide. This has helped reduce damage from insects and the need for continuing curative spot applications of other insecticides.

Through this methodical, detailed positioning of a select few biologicals, pest management at Riviera Country Club has improved, as has the environment and the bottom line. Whether they know it or not, the golfers have also benefited from the improved conditions.

References

1. Bravo, A., S. Likitvivatanavong, S. Gill and M. Soberon. 2011. Bacillus thuringiensis: A story of a successful bioinsecticide. Insect Biochemistry and Molecular Biology 41(7):423-431 (https://doi.org/10.1016/j.ibmb.2011.02.006).
2. Lacey, Lawrence A. 2007. Bacillus thuringiensis serovariety israelensis and Bacillus sphaericus for mosquito control. Journal of the American Mosquito Control Association 23 (sp2):133-163 (https://doi.org/10.2987/8756-971X(2007)23[133:BTSIAB]2.0.CO;2).
3. Mordor Intelligence. Europe biopesticides market — growth, trends, Covid-19 impact, and forecast 2022-2027.
4. Murray, J. 2019. EU chlorothalonil ban comes into full effect in 2020: Here’s all you need to know. NS Agriculture.
5. Schramm, Georg, W. Steglich, T. Anke and F. Oberwinkler. 1978. Antibiotics from Basidiomycetes, III. Strobilurin A and B, Antifungal Metabolites from Strobilurus tenacellus. Chemische Berichte 111(8):2779-2784 (https://doi.org/10.1002/cber.19781110806).
6. Wang, X.Q., D.L. Zhao, L.L. Shen, C.L. Jing and C.S. Zhang. 2018. Application and mechanisms of Bacillus subtilis in biological control of plant disease. Pages 225-250. In: Role of Rhizospheric Microbes in Soil. Springer, Singapore (https://doi.org/10.1007/978-981-10-8402-7_9).

Steven Kammerer, Ph.D., is the former Southeast regional director for the USGA Green Section. He has 35 years of experience working in the golf course industry, with a focus on pest and stress management. An eight-year Educator member of GCSAA, he actively works consulting on golf courses in the southeastern United States, with extensive experience in chemicals, pesticides, golf course management, sustainability and pest monitoring and management.

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