Curative fungicides

Encapsulation of haustoria could also be seen after curative fungicide treatment. Primary haustoria usually were not encased but all haustoria produced during and after the treatment were distinctly encapsulated, causing a complete inhibition of fungal growth and blocking spore formation. 

Most organic sprays and dusts available to control plant diseases are fungicides. These may act either to cure or to protect a plant from disease. Most fungicides used on growing plants are protectants, not curatives. Fungicides also may be used as disinfectants to kill fungal hyphae or spores on plant tubers, seeds, bulbs, or other parts used in prcpcaauoni. 

All garden enthusiasts know about the nice autumn crocus (Colchicum autumnale), which flowers in late autumn. It is not difficult to understand that this very conspicuous plant profits by containing a strong poison that protects it from pathogens and herbivores. It contains colchicine, which is very toxic and has a complicated structure. The substance is well known to plant breeders because it is used to double the number of chromosomes artificially in plants. A synthetic benzimidazole derivative, l-methyl-3-dode-cylbenzimidazolium chloride, was developed in 1960 as a curative fungicide against apple scab. Thiabendazole, another synthetic benzimidazole derivative, has been used as an anthelmintic since 1962. 

Cymoxanil is a protective and curative fungicide for foliar application it is especially active against Peronospora spp., Phytophthora spp. and Plasmopara spp. in... 

This systemic fungicide has both protective and curative properties for preventing fungal growth and penetration from infection cushions, causes collapse of hyphae and infection cushions. 

Use pattern Tebuconazole is a broad-spectrum triazole fungicide which provides protective and, in some cases, curative activity on a wide variety of crops including cereal grains, peanuts, grapes, bananas, pome fruit, stone fruit, nuts, and vegetables... 

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. 

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). 

Ellis, M.A., Madden, L.V., and Wilson, L.L. 1984. Evaluation of an electronic apple scab predictor for scheduling fungicides with curative activity. Plant Dis. 68 1055-1057. 

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. 

Experimental compounds were evaluated in a dose-response format. Azoxystrobin or other fungicides that have both protective and curative activity were used as a standard, and a solvent control was used in every study. The number of disease lesions per leaf was used to determine the ability of the test compounds to prevent infections. The size of the lesions was used to determine the curative activity of compounds. Each fungicide concentration is replicated four times and the experiment is repeated at least once. This bioassay does not differentiate between direct effects on the fungus and indirect effects through induction of plant defenses. However, if a compound is much more active in this in vivo assay than than the in vitro microtiter assay, induction activity is indicated. 

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). 

Fluoxastrobin (Fandango , Bariton ) [211-213], a new strobilurin fungicide with curative and leaf-systemic activity, was developed by Bayer CropScience, for use as both a seed treatment and a foliar spray to treat a variety of diseases in cereals. Fluoxastrobin initially was submitted for registration as an (E)/(Z) isomer mixture and later changed to the (E)-isomer. 

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. 

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