IPM Identification and Mangement Of Turfgrass Diseases
A number of other strategies may play a role in a turfgrass disease management program, especially when used in combination with other, more traditional methods.
Biological control
Research efforts have looked at two ways to achieve effective biological control practices in a turfgrass disease management program. One approach is to introduce microbial inoculants that have a demonstrated negative effect on target plant pathogenic fungi. The second is to stimulate resident populations of competitive or antagonistic microorganisms through the application of organic amendments and other microbial food sources.
Research trials with various microbial inoculants, including fungi and bacteria, have been ongoing and well supported by the United States Golf Association, Golf Course Superintendents Association of America, industry, state turfgrass organizations and the federal government for more than 25 years. Although many of the microbes have given promising results in greenhouse or small-scale field trials, few have been successfully developed as commercial products. Of the 33 microbe–disease combinations studied as biological control agents in a turfgrass system (summarized by Eric Nelson,Cornell University, in a 2003 review), only six have been registered as microbial pesticides by the EPA. The six organisms include two fungi(Trichoderma harzianum strain 1295-22 and Gliocladium catenulatum strain J1446), three bacteria (Bacillus licheniformis strain SB3086, Bacillus subtilis strain GB03 and Pseudomonas aureofaciens strain TX-1) and one actinomycete(Streptomyces lydicus strain WYEC 108). Since the first product was registered in 1996, there have been numerous changes in trade names and manufacturers, and the availability of these six products is limited in the United States. Visit http://epa.gov/pesticides/biopesticides for the most up-to-date registration information. One of the major limiting factors to successful use of microbial inoculants in a turfgrass system is the difficulty of delivering and sustaining adequate populations of the microbial inoculant in the turfgrass environment.
The second method of biological control— promoting resident microorganisms — gives promise for a more sustainable approach. This approach ranges in scope from composting with different organic amendments to applying food sources such as molasses, with the ultimate goal of “feeding” or promoting a diversity of naturally occurring soil microorganisms that suppress disease. Again, the level of success with these methods has varied considerably and is hampered on a commercial scale by difficulties in achieving high-quality, consistent product from one batch to the other.
Biopesticides
Biopesticides include the microbial pesticides mentioned above as well as biochemical pesticides and plant-incorporated protectants. Biochemical pesticides are naturally occurring substances in contrast to conventional products that are generally synthetic. One such product registered for use on turfgrass by Arvesta Coorporation and licensed to Cleary Chemical is Endorse. Endorse is polyoxin D zinc salt, a naturally occurring product produced by a soil borne bacterium. The bacterium is grown commercially and the polyoxin D zinc salt is extracted and formulated as the fungicide Endorse. Another example is hydrogen dioxide (registered as Zerotol by Biosafe Systems). Essential oils and other plant extracts are included as biochemical pesticides. A more complete listing of registered biopesticides by active ingredient can be found on the EPA Website cited above. Unfortunately the list is not searchable by crop, so finding all the products labeled for use on turfgrass is difficult.
Plant-incorporated protectants (PIP) are pesticides produced within a plant as the result of the addition of foreign DNA. There are currently no PIP products registered for use on turfgrass.
Plant defense activators
Plant defense activators are naturally occurring or synthetic products that have been shown to induce systemic acquired resistance in various plants. Rather than impact the plant pathogen directly, these products enhance or stimulate a plant’s own natural defense mechanisms. The efficacy of several such products against brown patch and dollar spot has been evaluated in recent years. Although some disease suppression has been shown, the level of disease control with these products alone has not been acceptable. However, some plant defense activators show promise when used in combination with fungicides or cultural practices, such as the application of foliar nitrogen.
The information herein is supplied with the understanding that no discrimination is intended and that listing of commercial products, necessary to this guide, implies no endorsement by the authors or the Extension Services of Nebraska, Colorado, Wyoming or Montana. Criticism of products or equipment not listed is neither implied nor intended. Due to constantly changing labels, laws and regulations, the Extension Services can assume no liability for the suggested use of chemicals contained herein. Pesticides must be applied legally complying with all label directions and precautions on the pesticide container and any supplemental labeling and rules of state and federal pesticide regulatory agencies. State rules and regulations and special pesticide use allowances may vary from state to state: contact your State Department of Agriculture for the rules, regulations and allowances applicable in your state and locality.
