IPM of Weeds, Clover, and Endophyte in Tall Fescue Grassland

Tall fescue is the predominant cool-season grass of the transition zone grasslands of the humid eastern USA. Tall fescue grasslands, which are about 45 million acres in extent, support as many as 20 million grazing beef animals, plus other livestock and wildlife. The remarkable adaptability of tall fescue to this transition zone between temperate and sub tropical grasslands is largely because it forms a close association with an internal fungus (endophyte) that synthesizes mycotoxins that limit herbivory and increase plant fitness and survivability. Unfortunately, these mycotoxins cause tall fescue toxicosis, a disease syndrome that impacts animal production and quality and costs American grassland farmers about $1 billion annually. There is no one solution to the problem of tall fescue toxicosis. Many partial solutions are available at the present time and more are being developed. Partial solutions include replacement of endophyte-infected grasslands with endophyte-free varieties or other grass species, replacement with tall fescue varieties inoculated with natural or transformed endophytes that do not synthesize mammalian mycotoxins, dilution of dietary mycotoxins by introducing clover or other species into tall fescue grasslands, feeding livestock dietary supplements or drug remedies to animals, or using animal breeds that are resistant to mycotoxins. An Integrated Pest Management approach to tall fescue toxicosis is the only feasible way to integrate different partial solutions in the most cost-effective combinations. This project aims to determine the use ofIPM in long term solutions of tall fescue toxicosis. We plan to reevaluate the use of new broad-spectrum systemic fungicides to eliminate endophyte and mycotoxins on established hill country tall fescue grasslands with a history of tall fescue toxicosis and where it is unwise to disturb existing grasslands because of a high risk of soil erosion. The costs of fungicide prohibited its use in the past, however, the higher costs and partial success of alternatives warrants re-evaluation in this application. We propose to evaluate the role of clovers in combination with fungicide because elimination of the endophyte should reduce competitiveness of the tall fescue and increase plant diversity. This should lead to higher clover populations in tall fescue grasslands and benefit grassland productivity and dietary also quality, however, weed populations are likely to increase. We also propose to compare new improved cultivars of tall fescue alone and in combination with red clover. The new cultivars to be evaluated include re-releases of Kentucky 31 tall fescue with and without natural endophytes, new tall cultivars with higher herbage dietary quality inoculated with endophytes that confer ecological advantages but do not synthesize mammalian mycotoxins and, therefore, should not cause tall fescue toxicosis. The analysis of field data collected over three years along with economic analyses should enable the formulation of sound IPM-based practices for the cost effective remediation of tall fescue toxicosis.