Resistance of Phytophthora porri to metalaxyl

Metalaxyl resistance has been identified in the Phytophthora porri population in the UK. In field experiments the presence of such resistant strains reduced the level of control of leek white tip given by applications of phenylamide-containing fungicides. The level of control achieved by fungicides with alternative modes of action to the phenylamides was not affected. ©1997 SCI     

Systemicity and persistence of cymoxanil in mixture with oxadixyl and mancozeb against Phytophthora infestans and Plasmopara viticola

Uptake and translocation of the fungicide cymoxanil was studied using tomato and potato plants infected with Phytophthora infestans and grape plants infected with Plasmopara viticola. Translocation of cymoxanil was mainly translaminar and acropetal from roots and stems to leaves to an extent similar to that of the phenylamide fungicide oxadixyl. Basipetal translocation from upper to lower leaves, as well as lateral movement, was also observed but to a lesser extent. Plant parts that grew after application were protected against P. infestans and P. viticola because of systemic activity up to 7 days by cymoxanil alone and up to 14 days when cymoxanil was used as part of a three-way mixture with oxadixyl and mancozeb. Drench application of cymoxanil and a simultaneous spray application of mancozeb against P. infestans and P. viticola resulted in a significant synergistic interaction. The spray application of the three-way mixture oxadixyl/mancozeb/cymoxanil was more effective against both sensitive and phenylamide-resistant strains of P. infestans and P. viticola than the individual components alone, representing significant levels of synergistic interactions. Synergy ratios were higher for resistant than for sensitive strains of both pathogens.     

64%噁霜灵锰锌(福乐尔)防治黄瓜霜霉病药效实验

进行了国产恶霜灵锰锌与进口杀毒矾在防治黄瓜霜霉病的药效对照试验。结果表明，两者400倍液的防治效果分析为89.9%和88.6%，两者500倍液、600倍液的防治效果为84%、86.3%、72%、73.2%，结果证实两者对黄瓜霜霉病的防治效果均很好。根据数理统计结果，认为二者在防治效果上无显著差异，但国产恶霜灵锰锌价格低廉，值得推广。     

Control of late blight in potato by full and reduced rates of oxadixyl mixtures

The effect of oxadixyl-based fungicidal mixtures on the development of late blight and the buildup of resistance ofPhytophthora infestans to oxadixyl was studied in potato crops (cv. Alpha) grown in plastic houses. Half-rates of SAN 518F (mancozeb + oxadixyl) applied weekly provided better disease control and reduced resistance buildup more effectively than the full rates of the mixture applied biweekly. Mancozeb applied weekly at full rate was less effective than SAN 518F at half-rate. The data suggest that lowering the dosage together with shortening the interval between sprays is an efficient strategy to combat mixed populations — sensitive and resistant to phenylamides — ofP. infestans when phenylamide-based fungicidal sprays are used.