Arkansas Turfgrass – Eric Reasor, Ph.D. – Southeast Research Scientist, PBI-Gordon Corporation

Pesticides have undergone significant changes in the past 50 years with an increased focus on environmental and applicator safety. Alabama Turfgrass Association members and the entire turfgrass industry will see pesticide technologies in the future look very different than the past. However, despite many future changes, pesticides will continue being a highly effective tool for turfgrass pest management.

Importance of Pesticides in Pest Management

Pesticides are any substance or mixture of substances used to kill pests or manage the damage they cause and are an important tool for managing turfgrass pests¹. Turfgrasses have been used for functional, recreational, and aesthetic purposes to enhance human lives for hundreds of years,² and many pests can significantly reduce these desired qualities. For example, disease and insect pests can infect or feed on turfgrass plants, leaving infected areas susceptible to wear damage, or environmental stresses such as drought. Furthermore, weed pests such as large crabgrass and white clover can compromise the safety of natural grass athletic fields by increasing the surface hardness ~ 50% compared to hybrid bermudagrass³.

Integrated pest management (IPM) is an approach that combines multiple chemical and non-chemical methods for pest management. Most of these techniques involve maximizing turfgrass growth and plant health by species and variety selection, mowing, cultivation, fertilization, and irrigation. Although these cultural practices are critical for pest management, turfgrass quality expectations and lack of control thresholds drive the need for pest-free turfgrass. As a result, pesticides are still the backbone of turfgrass pest management¹. The widespread use and necessity of turfgrass pesticides will require the industry to evolve as the pesticides change in the future.

History of Pesticides

Understanding the history of pesticides and their use is important to the future of pesticides. There are currently five main time periods of pesticide use that describe the type of pesticides used during those times. Current time periods can be described as 1) early pest management prior to year 1000, 2) 1000 to 1850, 3) 1850 to 1940, 4) 1940 to 1970, and 5) 1970 to present. Additional time periods are likely to occur as pesticides enter a new era in the future.

The first recorded use of pesticides is about 4500 years ago by Sumerians, who applied sulfur compounds to battle insects and mites. This type of pesticide use continued until approximately year 1000 when the use of plant, animal, or mineral derivatives increased. From 1850 to 1940, pesticides were mainly inorganic compounds and industrial by-products. Moreover, pesticide use during these times typically involved high active ingredient application rates and unsafe application methods. Following the 1940s and scientific advancement after WWII, synthetic organic compounds were being developed for pesticides as a result of organic chemistry being applied to pesticide science. These synthetic organic pesticides still had high application rates in the kilograms per hectare for active ingredients, such as thiuram and DDT. However, the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) was established in 1947 to set guidelines for pesticides registered in the United States. FIFRA determines product uses, application rates, and potential hazards. They also developed the pesticide labeling process to instruct end-users on proper and safe applications.

Pesticide science vastly changed in the 1970s. Pesticide research expanded outside of the US and Europe and became a world-wide field. The active ingredients themselves begin to change with lower-risk synthetic organic molecules effective at extremely low dosages. Furthermore, these newer active ingredients are more readily degradable, less persistent in the environment, and are more selective against the target pest⁴. Why the change? In 1972, FIFRA was revised and was moved to the responsibility of the US Environmental Protection Agency (EPA). This revision shifted the emphasis of the regulatory process toward environmental protection and public health⁵.

Another major change with FIFRA was the Food Quality Protection Act (FQPA) of 1996. This legislation tasked the EPA with conducting the most comprehensive and historic review of pesticide and food safety laws. The FQPA amended FIFRA by fundamentally changing the EPA’s pesticide evaluation and regulation processes. Through this change, thousands of pesticides and their uses were either modified or eliminated. Then in 2007, an amendment to FIFRA required the EPA to review registered pesticides at least once every 15 years. This review process has yielded changes with many active ingredients and their uses⁵.

Pesticides of the Future

Pesticides and their applications will continue to evolve in the future just as much as it has changed in the past. Low-risk synthetic organic compounds are still being developed; however, a new focus has shifted to other types of pesticides and pest management strategies. Examples of these include biological and RNAi pesticides (which will be described in more detail). In addition to chemistry changes, pesticide applications and delivery systems will change with formulation technology and site-specific applications^{6, 4}.

Biological pest control and biopesticides are tools with a recent substantial increase in research and development. Biological control is founded on using beneficial organisms to reduce populations of pest organisms, or at least keep them below destructive thresholds. Turfgrass managers already implement some biocontrol by promoting a healthy environment for optimal turfgrass growth. This type of biocontrol can be described as general pest suppression, whereas specific pest suppression uses specific, selected organisms, to manage pests.

Biopesticides are pesticides, but they are derived from natural materials such as animals, bacteria, fungi, plants, and certain minerals. Biopesticides are classified based on their origin and it must provide some level of pest control to be considered a biopesticide⁷. Microbial biopesticides have a living organism or a product of a living organism as the active ingredient, and biochemical biopesticides have naturally occurring compounds, such as plant extracts, as the active ingredient. There are commercially available products of both biopesticide categories. However, pest control may be limited when high pest populations or environmental conditions highly conducive to damage are present. Furthermore, biopesticides may be limited in long-term storage stability and formulation difficulties. In specific turfgrass situations, biopesticides can be one alternative to synthetic pesticides. Examples of beneficial organisms used in turfgrass to manage specific pests are Bacillus spp. and Pseudomonas spp. Research and development into biopesticides will continue to increase in future decades. It has been predicted that the biopesticide market will equal and potentially outpace synthetic pesticides by the 2060s⁸.

Ribonucleic acid (RNA) interference (RNAi) pesticides are another growing area of pesticide research and development. RNAi is a naturally occurring process that uses double-stranded RNA (dsRNA) to interfere with normal RNA processes. Normal RNA processes start with DNA (deoxyribonucleic acid) transcribing into RNA and then RNA translating into amino acids, which are then used to make proteins. RNAi pesticides disrupt a targeted step in these processes. This allows specific genes within plants and pests to be targeted and manipulated to achieve a desired result. Applications of RNAi compounds are being developed to provide an alternative to synthetic organic compounds. The RNAi currently used for pest management involves dsRNA that can silence essential genes in insects, pathogens, and weeds. These applications are highly specific for the target pest, where non-target effects are minimalized, or even avoided. RNAi has already been used to target plant diseases such as cereal rusts and Botrytis grey fruit mold. It has also been used to develop virus-resistant crops such as papaya, plum, squash, and tomato⁹. The use of RNAi pesticides in turfgrass pest management will likely be pest specific and will still rely on proper turfgrass cultural practices.

Pesticide Applications of the Future

Pesticide applications and formulations are evolving similar to pesticide active ingredients with a focus on increased environmental safety and reduced inputs. Precise, site-specific pesticide applications is one method that can reduce overall pesticide inputs, and pesticide formulation technology can increase the environmental safety of the final pesticide product. Applying safer pesticides in more precise locations aligns with the future direction of pesticide regulation. New application strategies will be a significant change from traditional broadcast or blanket applications, but the technology involved will be end-user driven (Photo 1).

The theory of precision turfgrass management (PTM) is to measure detailed, site-specific information to precisely apply resources (e.g., water, fertilizer, pesticides). Precision turfgrass management has the potential to reduce overall pesticide inputs by only targeting areas with a present pest population, areas with repeated history of pest issues, or areas with highly conducive environments. This would rely on sensor technology, GPS, and GIS systems to accurately measure, analyze, and apply the data¹⁰. Sensor equipment could be mounted to a variety of ground or aerial equipment such as mowers, tractors, golf carts, or even drones to make the necessary measurements for management decisions (Photo 2).

Researchers are in the early stages of developing the PTM technology for turfgrass pest management. Initial technology will likely focus on controlling specific pest species or issues and may not be applicable to every situation. Turfgrass managers already practice some sort of PTM by managing various areas differently based on many factors, including soil characteristics, turfgrass species, slope, height-of-cut, traffic patterns, etc. These management differences are based on anecdotal or quantified data, but the evolution of PTM will be based on acquiring real-time, detailed site information to make decision making more precise and efficient.¹⁰ Many hurdles remain for the wide adoption of PTM, nevertheless it is one of the key components of the future of pesticides and their applications.

Pesticide formulation research is important because the pesticide active ingredients comprise only a percentage of the final product. The co-formulants are just as important as the active ingredient for pest control efficacy, product storage/stability, product compatibility, and overall product performance. Different pesticide formulations have advantages and disadvantages, but there has been a shift in trends due to growing concerns on using solvents as co-formulants. Solvent-based emulsifiable concentrate (EC) formulations are being phased out with the focus shifted on solvent-free formulations (granules [G], soluble liquids [SL], suspension concentrates [SC], and water dispersible granules [WDG]). A new, water-based formulation, emulsion-in-water (EW), uses almost no solvents and has emulsifying agents to improve handling, storage, and transport characteristics. Synthetic pesticide formulation research will continue to evolve for increased applicator and environment safety because synthetic pesticides are still the most economical and effective pesticide option.

Nanotechnology is one of the more recent developments in pesticide formulation research¹¹. Nanotechnology research involves manipulation of particles ranging from 1 to 100 nanometers (nm)¹². For reference, one nm is one-billionth (10^-9) of a meter and there are 25,400,000 nm in one inch (Figure 1).

These nanoparticles are being developed to encapsulate nano-sized pesticide active ingredients to potentially provide a “controlled release” of the pesticide to the target pest. Furthermore, encapsulation materials can be biocompatible and biodegradable¹¹.

Pesticides formulated as nanoparticles have the potential to increase the efficacy against target pests, reduce the physical degradation, and further reduce the environmental risk^{13, 14}. For example, nanoparticles have been reported to protect neem oil (Azadirachta indica) from degradation to extend its efficacy against insect pests⁷. However, nanotechnology in pesticide science has been sparsely researched in field conditions and thus not widely commercialized due to several challenges. There are concerns regarding environmental fate, bioavailability and release rates, transport and storage, and cost effectiveness^{7, 15}. Nanotechnology and nanopesticide research will continue, but their application in turfgrass and availability to turf managers is still unknown.

Pesticides and their use have vastly changed within the past 50 years, with an increased focus on environmental and applicator safety. Alabama Turfgrass Association members and turfgrass managers could witness even greater significant pesticides changes in the future. Pesticides will continue to evolve with newer technologies such as biological and RNAi pesticides. It is uncertain when some of these new pesticide technologies will be commercially available for pest control in turfgrass. Moreover, it is possible some will not provide acceptable pest control, be too injurious to desirable species, or too costly for wide adoption. As a result, synthetic pesticides will remain the most effective pesticide tool until these technologies are developed specially for turfgrass.

Literature Cited

1. Koppenhofer, A.M., R. Latin, B.A. McGraw, J.T. Brosnan, and W.C. Crow. 2013. Integrated pest management. In Turfgrass: Biology, Use, and Management. eds. J.C. Stier, B.P. Horgan, and S.A. Bonos. Madison, WI. pp. 933-1006.
   
2. Beard, J.B. and R.L. Green. 1994. The role of turfgrasses in environmental protection and their benefits to humans. J. of Environ. Qual. 23:452-460.
   
3. Brosnan, J.T., K.H., Dickson, J.C. Sorochan, A.W. Thoms, and J.C. Stier. 2014. Large crabgrass, white clover, and hybrid bermudagrass athletic field playing quality in response to simulated traffic. Crop Sci. 54:1838-1843. doi:10.2135/cropsci2013.11.0754
   
4. Umetsu, N. and Y. Shirai. 2020. Development of novel pesticides in the 21st century. J. Pestic. Sci. 45(2):54-74. doi:10.1584/jpestics.D20-201
   
5. Reicher, Z.J., P.H. Dernoeden, and D.S. Richmond. 2013. Insecticides, fungicides, herbicides, and growth regulators used in turfgrass systems. In Turfgrass: Biology, Use, and Management. eds. J.C. Stier, B.P. Horgan, and S.A. Bonos. Madison, WI. pp. 891-932.
   
6. Umetsu, N. and A. Ando. 2004. Development of environmentally friendly agrochemicals. In Frontiers of Environmental Pesticide Science. eds. M. Ueji et al. Soft Science. pp. 224-248
   
7. Damalas, C.A. and S.D. Koutroubas. 2018. Current status and recent developments in biopesticide use. Agriculture. 8(13). doi:10.3390/agriculture8010013
   
8. Olsen, S. 2015. An analysis of the biopesticides market now and where is going. Outlooks Pest Mgt. 26:203-206.
   
9. Mezzetti, B. J. Sweet, and L. Burgos. 2021. Introduction to RNAi in plan production and protection. CAB International. doi:10.1079/9781789248890.0001
   
10. Carrow, R.N., J.M. Krum, I. Flitcroft, and V. Cline. 2010. Precision turfgrass management: Challenges and field applieds for mapping turfgrass soil and stress. Precision Agric. 11:115-134. doi:10.1007/s11119-009-9136-y
    
11. Prasad, R., A. Bhattacharyya, and Q. D. Nguyen. 2017. Nanotechnology in Sustainable Agriculture: Recent Developments, Challenges, and Perspectives. J. Frontier Microbiology. doi: 10.3389/fmicb.2017.01014
    
12. Hobson, D.W., 2011. Industrial biotechnology and commodity product. In Comprehensive Biotechnology (Second Edition). eds. M. Butler and M. Moo-Young. Volume 3: pp. 683-697
    
13. De Oliveira, J.L., E.V.R. Campos, and L.F. Fraceto. 2018. Recent developments and challenges for nanoscale formulation of botanical pesticides for use in sustainable agriculture. J. Agric. Food Chem. 66(34):8898-8913. doi.org/10.1021/acs.jafc.8b03183
    
14. Khot, L.R., S. Sankaran, J.M. Maja, R. Ehsani, and E.W. Schuster. 2012. Applications o nanomaterials in agricultural production and crop protection: A review. Crop Protection. 35:64-70. doi.org/10.1016/ j.cropro.2012.01.007
    
15. Mishra, S., C. Keswani, P.C. Abhilash, L.F. Fraceto, and H.B. Singh. 2017. Integrated approach of agri-nanotechnology: Challenges and future trends. Front. Plant Sci. 8:471. doi.org/10.3389/fpls.2017.00471
    

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