Submitted to: Proceedings of Northeastern Weed Science Society
Publication Type: Abstract Only
Publication Acceptance Date: January 6, 2003
Publication Date: January 5, 2004
Citation: Eskandari, F., Bruckart, W.L. 2004. Greenhouse evaluation of cercosporella acroptili for biological control of russian knapweed. Proceedings of Northeastern Weed Science Society. 58:162. Technical Abstract: Russian knapweed (Acroptilon repens) is a major perennial weed of rangelands. Two introduced biological control agents and a rust fungus already in North America do not control it. A pathogen from Turkey is under evaluation for biological control of Russian knapweed in the U.S. Objectives of this study were to isolate and identify the fungus, determine pathogenicity, and conduct preliminary evaluations for biological control of Russian knapweed. The fungus is Cercosporella acroptili. Sporulation is best on modified potato carrot agar (broth from 140 g each of potatoes and carrots, 15 g agar, 1 liter water), and conidia harvested from cultures are suspended in water and sprayed on healthy plants. Plants maintained under continuous light in dew chambers set at 12, 15, 20, and 23 C air temperatures were removed after 4, 8, 12,16, 20, 36, and 48 hr, placed in a greenhouse at 25 C and monitored for symptoms. The most infection developed on plants given 48 hr dew at 23 C. Plants inoculated with 106 conidia/ml, given 48 hr dew at 23 C under continuous light had lower root fresh and dry weights 17.7 and 4.64 g, respectively, than controls (22.8 and 6.49 g, respectively; P = 0.008 and 0.002, respectively). More recently, plants kept in continuous dark during a 48 hr dew period had significantly more disease than plants given either an 8-hr photoperiod or continuous light. Cercosporella acroptili is capable of damaging Russian knapweed in greenhouse tests and it is limited in its host range to Russian knapweed in tests of closely related plants in the Tribe Cardueae of the Asteraceae. Future studies will focus on clarifying damage from C. acroptili on Russian knapweed, host specificity of C. acroptili, and if reasonable, propose use of C. acroptili for biological control of Russian knapweed in the U.S.