Biological control of chrysanthemum white rust using hyperparasites
2000
Villanueva, L.M. | Boteng, M.D.C. (Benguet State Univ., La Trinidad, Benguet (Philippines))
The effect of hyperparasites, Verticillium sp. and Paecilomyces sp. as a potential component of a disease management system against white rust of Chrysanthemum (Chrysanthemum morifolium) was studied. Findings showed that both hyperparasites were found to be compatible with pesticides, Avermectin and Acephate. All fungicides tested, namely: Triforine, elemental sulfur and Mancozeb were toxic to both hyperparasites using recommended rates. Sub-lethal doses of fungicides, Propamocarb hydrochloride, Triamidefon and Difenoconazal exhibited no adverse effect on the hyperparasites. Effect of Triforine and elemental sulfur was slight. Copper hydroxide and copper oxychloride were found toxic. Application of Verticillium sp. two days ahead of the pathogen significantly delayed disease development from 7.6 to 14.4 days, and reduced the number of rust pustules from 40 to 7. This hyperparasite gave 82% disease control. In terms of cutflower yield, plants sprayed with Mancozeb gave more number of long, medium stems, while those sprayed with the hyperparasites had comparable yield. Although stems were longer in Mancozeb-treated plants, the quality was relatively lower compared to those sprayed with hyperparasites. This was attributed to the yellow residue left by chemical spraying on the leaves. Sequential spraying of Triforine, Mancozeb and elemental sulfur (60%) was most effective for disease control closely followed by Paecilomyces sp + Verticillium sp. + Triforine with 48.8%; Verticillium + Triforine with 45.45%,; and Paecilomyces sp. with 43.18%. Using tolerant cultivar, Fiji, highest ROI [return on investment] of 97.8% was obtained from plants sprayed with Verticillium sp. + Triforine, followed by Paecilomyces sp. + Triforine (89.4%). Use of high susceptible cultivar, Veron, gave negative ROI
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