BIOLOGICAL CONTROL OF POWDERY MILDEW BY AMPELOMYCES QUISQUALIS IN PROTECTED CROPS
Department of Plant Pathology and Microbiology, The Hebrew University of Jerusalem, Faculty of Agriculture, Rehovot 76100, Israel
Background and objectives
The hyperparasite Ampelomyces quisqualis (AQ), isolate 10, is the biocontrol (BC) agent included in the biofungicide developed by Ecogen Israel Partnership. This isolate was found to be efficient as a biocontrol agent of powdery mildews (PM) in various crops . Ampelomyces is a biotroph hyperparasite on the PM pathogen, having a direct effect in colonizing hyphae, conidiophores, haustoria and cleistothecia [1, 2]. Indirectly, the hyperparasitism causes shrivelling of PM pathogen conidia, non-maturing conidia thus avoiding additional spread of conidia and significant reduction on sporulation. In glasshouse trials AQ supressed Erysiphe graminis f.sp. tritici sporulation by 70%. PM cleistothecia are parasitized by AQ thus avoiding ascospore production, primary inoculum and allowing overwintering and survival of AQ in the infected cleistothecia. Glasshouse trials (temperature: day 28-32°C, night 15-18°C) have been performed on pepper, tomato and cucumber to study the effectiveness of biological control of powdery mildew disease with AQ.
Results and conclusions
Similar patterns of parasitism were observed in the host-parasite relationship, examined under electron microscopy, in pepper and tomato PM caused by Leveillula taurica and cucumber PM caused by Sphaerotheca fusca. In a glasshouse experiment conducted on pepper PM, var. Manor, the efficiency of AQ was tested compared to quinomethionate. The AQ non-formulated treatment reduced PM severity of leaves by 76%, AQ formulated reduced by 92% and quinomethionate by 98.5% compared to the untreated control. The above treatments increased similar pepper yield by 25% over the untreated control. In a glasshouse trial on tomato PM testing the above treatments, an increase of yield was seen of 30% in the quinomethlonate, 20% in AQ non-formulated and 38% AQ formulated over the untreated control. In PM cucumber trials disease control was assessed by measuring PM severity and yield. High AQ hyperparasitism on PM of glasshouse-grown cucumbers (cv. Hazera 205) was achieved. Thus, PM severity was reduced, leading to the following yields: untreated cucumbers, 0.76 kg/plant; treatment with pyrazophos 0.05 and 0.1%, 1.61 and 1.43 kg/plant, respectively; AQ, 1.14 kg/plant; and two AQ treatments alternated with pyrazophos 0.05%, 1.46 kg/plant. AQ, and AQ alternated with pyrazophos, treatments increased yield by 50% over the untreated control.
These results confirm that AQ is effective as a bicontrol agent for PM and can serve as a significant component of an integrated pest management alternated with reduced application of fungicides. More knowledge is needed in order to achieve a more consistent control of PM in the diversity of systems of protected crops.
1. Sztejnberg A, Galper S, Mazar S, Lisker N, 1989. Journal of Phytopathology 124, 285-295.
2. Abo-Foul S, 1994. PhD thesis, The Hebrew University of Jerusalem.