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Biological Control of Ground Ivy Using a Rust Fungus 2002

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Project Leader(s):

Dr. Antonio DiTommaso, Assistant Professor, Dept. of Crop & Soil Sciences, Cornell University

Dr. Leslie A. Weston, Associate Professor, Dept. of Horticulture, Cornell University.

Cooperator(s):

Dr. G.W. Hudler, Professor, and Dr. Kathie T. Hodge, Assistant Professor, Dept. of Plant Pathology, Cornell University Cornell Cooperative Extension Educators

Type of grant:

Biological control and pest biology

Project location(s):

Central New York. Counties: Broome, Cayuga, Chemung, Cortland, Madison, Onondaga, Schuyler, Seneca, Tioga, Tompkins, Yates

Abstract:

Ground-ivy or creeping Charlie (Glechoma hederacea) is a creeping perennial in the Mint Family that forms dense prostrate patches in turfgrass, damp shady meadows, and disturbed sites. The control of ground ivy using chemical and mechanical methods has largely been unsuccessful in turfgrass where it is considered a major weed. Thus, there is a pressing need to develop and evaluate alternative approaches for the control of ground ivy in turfgrass that are effective and environmentally sound. Several rust fungi have been reported to infect ground-ivy in its native Eurasian range. In 1998, one of these rusts, Puccinia glechomatis, was found in North America including on ground- ivy plants growing in Syracuse, NY. Research to date has demonstrated that this rust fungus infects only plant species within the genus Glechoma. The goal of this study was to build on the initial data set collected during the 2001 growing season so as to better

(1) determine the distribution of the Puccinia glechomatis rust on turfgrass ground-ivy populations in Tompkins County and surrounding counties,

(2) assess the potential of the rust to effectively suppress ground-ivy in turfgrass,

(3) determine whether the rust infects non-host plant species in turfgrass, and

(4) determine optimal temperature and moisture conditions for disease development under controlled environment conditions.

Field surveys during the 2002 growing season indicate that the rust has infected ground-ivy plants at locations in seven of the 12 Central New York counties surveyed. The slight increase in the number of counties having the rust in 2002 compared with 2001 is likely due to an increase in the number of locations surveyed within each county. In field trials within naturally infected turf, the rust continued to reduce ground-ivy coverage. For instance, by mid-September 2002, 16 months after the start of trials, ground-ivy coverage had declined 80% in test plots. Interestingly, substantial decreases in weed cover were also observed in plots inoculated with the protectant fungicide, mancozeb, as well as in nearby adjacent "control" plots that had little disease in 2001. As in 2001, no disease symptoms were observed on turfgrass species or other non-target plants. Preliminary attempts to infect host plants with the selective rust, Puccinia glechomatis, under controlled environment conditions were not successful and warrant further work. Despite these difficulties, this rust may be a promising biocontrol candidate for suppressing ground-ivy in turfgrass.

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