Submitted to: HortTechnology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 9/1/2002
Publication Date: 4/1/2003
Citation: HortTechnology 13(2):365-367 Interpretive Summary: Powdery mildew severely infects young shoots and leaves of gooseberries in the Pacific Northwest. Environmentally sound control measures are being sought as alternatives to chemical fungicides. This study examined the effect of a mineral oil spray, a biological control, a standard fungicide and the combination of oil and biological control on infection in mildew-susceptible gooseberries. Treatments were applied at 2 wk intervals from February through April in 2002. Disease severity of mildew infection of shoots and leaves were rated in mid April. Both the oil and fungicide applications significantly reduced mildew on stems and leaves of treated plants as compared to the unsprayed control and biological control alone did not reduce the mildew.
Technical Abstract: Powdery mildew [Sphaerotheca mors-uvae (Scw.) Berk] severely infects young shoots and leaves of gooseberry (Ribes uva-crispa L.) in the Pacific Northwest. Less environmentally damaging control measures are being sought as alternatives to sulfur or de-methylation inhibiting fungicides. This study examined the effect of a mineral oil spray JMS Stylet Oil®, the biological control agent (Trichoderma harzianum Rifai strain T-22) PlantShield®, a combination of the mineral oil and the biological agent, and the chemical fungicide Cleary 3336® on powdery mildew severity in R. uva-crispa cv. Industry, a susceptible gooseberry. JMS Stylet Oil® at 8 ml/l, PlantShield ® at 4 g/L and Cleary 3336® at 1.5 g/L and a mineral oil-PlantShield® mix was applied to plants until run-off at 2-wk intervals from February through April, 2002, on the potted 'Industry' plants growing in a greenhouse in Corvallis, Ore. Shoot and leaf surface areas covered by powdery mildew were visually rated in mid-April. The oil and the fungicide applications significantly reduced powdery mildew severity on stems and leaves as compared with that of the unsprayed control. A combination of oil and biological control agent also significantly reduced mildew on stems and leaves.