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Disease Control and Pest Management

Efficacy of Darluca filum for Biological Control of Cronartium fusiforme and C. strobilinum. E. G. Kuhlman, Plant Pathologist, U.S. Department of Agriculture, Forest Service, Southeastern Forest Experiment Station, Forestry Sciences Laboratory, Research Triangle Park, NC 27709; F. R. Matthews(2), and H. P. Tillerson(3). (2)Plant Pathologist, U.S. Department of Agriculture, Forest Service, Southeastern Forest Experiment Station, Forestry Sciences Laboratory, Research Triangle Park, NC 27709; (3)Technician, U.S. Department of Agriculture, Forest Service, Southeastern Forest Experiment Station, Forestry Sciences Laboratory, Research Triangle Park, Athens, GA 30602. Phytopathology 68:507-511. Accepted for publication 24 August 1977. Copyright © 1978 The American Phytopathological Society, 3340 Pilot Knob Road, St. Paul, MN 55121. All rights reserved.. DOI: 10.1094/Phyto-68-507.

In Florida, in a pure stand of Quercus minima, Darluca filum naturally infected 93% of the Cronartium strobilinum sori; only 0.8% of the sori contained telia. In an adjacent mixed stand more sparsely populated with Q. minima, only 32% of rust sori were infected and 26% had telia. Spread of D. filum effectively controlled the rust within the pure oak area, but not in the more sparsely populated area. In greenhouse studies, simultaneous inoculations with C. fusiforme and D. filum on water oak and northern red oak produced only rust sori. When rust inoculations preceded D. filum inoculations by 4-21 days, sori of C. fusiforme were infected by the mycoparasite, but this infection did not reduce the number of telia formed in sori. After inoculation of sori of C. fusiforme with D. filum, moist incubation for only 4 hr resulted in some infection. However, maximum infection occurred after 16-24 hr of moist incubation. Pycnidia of D. filum began forming in rust sori 4 days after inoculation. Half-leaf inoculations of 8-or 14-day-old rust infections with D. filum reduced basidiospore casts 7-21 days later in comparison with casts from control half-leaves. Because of the short irregular cycle of C. fusiforme on oak, biological control of C. fusiforme by D. filum does not appear to be practical.