Powdery mildew field activity

Many of these compounds had good fungicidal activity, which comes as no surprise to us now, but It should be remembered that, when this work was being done, knowledge of the fungltoxlc action of azoles and an appreciation of their mode of action (5) were In their infancy. The compounds were particularly active on powdery mildews and some of them (e.g.IV) were systemic by root uptake. Unfortunately they were less active In the field than they had been under glass and they also adversely affected plant growth. 

Several of these compounds were highly active on powdery mildews and had a broader spectrum of activity than their predecessors. In addition, this activity translated well from the glasshouse to the field. The next part of the review will therefore concentrate on these compounds. 

Folpet s mode of action and field of application are similar to those of captan, though it is less widely used in orchards. The most important difference in application of the two active substances is that folpet also has some effect on powdery mildew, or at least does not increase sensitivity to powdery mildew fungi (Lukens and Horsfall, 1967). Folpet is used mainly against downy mildew of vine (Plasmopara viticola) and foliage diseases of cereals. It is also used as a wide-spectrum soil fungicide. 

Recently, the new development product enestrobin (69 ISO-proposed, SYP-Z071, Shenyang Res. Inst, of Chem. Industry) [156], containing a 4-chlorophenyl unsaturated oximether side-chain, has been presented. Field trial results indicate that 69 is especially a fungicide active against crop diseases on cucumber such as downy mildew, powdery mildew and gray mold, which is useful in plastic sheet-covered cucumber fields. 

Pyridopyrimidinones, quinazolinones and thienopyrimidinones were all evaluated in the field for powdery mildew control on wheat. Field candidates were applied early in the season as protectants (before substantial presence of the disease). Table 6 shows field efficacy of several substituted pyridopyrimidinones. Although highly active in greenhouse tests, these analogs were less effective than standards, e.g. flusilazole, under field conditions with only moderate levels of mildew control observed at 250-125 g/ha. 

Table 6. Field Activity of Substituted Pyridopyrimidinones as Protectants Against Wheat Powdery Mildew...

In 1976 the novel oxazoline 1 was foimd to exhibit interesting fungicidal activity in random screening. Especially noteworthy was its effect against powdery mildew disease on barley and wheat, which could be confirmed under field conditions with application rates as low as 125 g/ha. 

A series of novel 4-phenoxyquinolines has been developed which show potent control of fungicide-sensitive and resistant strains of powdery mildew in grape and cereal crops. Protective, curative, and systemic activity has been observed for these materials, which also control other fungi. Strong activity in field studies has been noted and no crossresistance was encountered when fungicide-resistant strains of mildew were treated with these compounds, thereby suggesting a novel mode of action. The discovery, synthesis and structure-activity relationship of this novel class of fungicides are presented, as well as some data from field and cross-resistance studies. 

As a result of this search for novel fungicides, a series of analogous phenoxyquinolines has been developed which controls sensitive and resistant strains of powdery mildew in cereals, cucurbits and grapes. The discovery and structure-activity relationships as well as the greenhouse and field efficacy of selected compounds are detailed in this report. 

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