Fungicides curative action

When the EBI fungicides are applied later than 72-96 hours after the beginning of the scab infection period but before symptoms are visible, chlorotic spots or flecks with few or no conidia are produced in place of typical sporulating lesions (Figure 2). This is referred to as presymptom control by Szkolnik (23) and it is a form of post-infection or curative action. Dodine and benomyl are examples of fungicides with presymptom activity. Presymptom activity becomes more obvious as the time of application increases beyond the 72-96 hour after-infection period. In greenhouse trials, sprays of bltertanol, etaconazole, fenarimol and triforine reduced conidial production 85 to 99% when applied five days after inoculation (20). 

The various fungicides have either specific or broad spectrum efficacy. These can be deployed for either prophylactic or curative action. Beyond the farm crops and horticulture, maintenance of turf and lawns free of insects and weeds, and the preservation of natural and agricultural forestry are significant markets for insecticides and herbicides. 

Minimize Fungicide Selection Pressure. Treatment of harvested fruit with a selective fungicide should be limited to situations which require unique action by the treatment (e.g., curative action, spoliation control, etc.). Non-selective treatments such as heat, active chlorine, sodium carbonate, and low temperature should be emphasized whenever possible to discourage the buildup of fungicide-resistant biotypes of Penici Hi urn. 

Tolkmith (1966) developed the active substance 0,0-diethyl phthalimidophos-phonothioate (ditalimfos 36), which is a very effective fungicide against powdery mildew in apple and cherry orchards, cucumbers and roses, and is also effective against apple scab ( Venturia inaequalis) and diseases caused by Monilia fructicola, etc. (Huisman, 1972 Huisman and Peskett, 1973). In addition to its protective effect ditalimfos also has a curative action, and is virtually nontoxic to warm-blooded organisms. 

In the plant pathology literature, only systemic fungicides with kick-back action are considered curative, but here, we include any pesticides that limit further spread of pests and diseases in the plant population. Provided no petroleum-based synergists or carriers are used. 

Schwabe, W.F.S., Jones, A.L., and Jonker, J.P. 1984. Greenhouse evaluation of the curative and protective action of sterol-inhibiting fungicides against apple scab. Phytopathology 74 249-252. 

Detached leaf assays provide us with the opportunity to evaluate new fungicides directly on the leaf surface in a dose-response format (Table 1). This assay allowed us to benchmark potential lead compounds such as CAY-1 and sampangine with a commercial standard (azoxystrobin) of known mode of action (Qo I inhibitor). The number of diseased lesions was used to determine effective concentrations needed for disease control. Lesion size is used to determine the relative effectiveness of the systemic activity that produced curative activity 24 hrs after inoculation. The detached leaf assay was also used to establish experimental field rates for future studies. Study of protectant activity indicated that 1250 ppm. CAY-1 or sampangine appeared to be an effective concentration for disease control of anthracnose on the leaf surface, or between 100-1000 times the concentration required for in vitro activity (Post, Table 1). 

A few fungicides have also been developed in the group of quaternary ammonium compounds. Deciquam (3), didecyl-dimethyl ammonium bromide, has a protective and curative effect against apple scab, while allyl-didecyl-methyl ammonium bromide (4) is a fungicide with a wide range of action on several cereals, and is also used in the field of hygiene. 

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