Application of fungicides to foliage through overhead sprinkler irrigation- a review

Articles on chemigation with fungicides targeting foliage have been reviewe d. They included 23 fungicides tested on 10 crops. Many studies compared ch emigation to a check treatment, while others also included conventional met hods. Chlorothalonil, followed by mancozeb, fentin hydroxide and captafol w ere the most studied fungicides, while peanut (Arachis hypogaea), potato (S olanum tuberosum), tomato (Lycopersicon esculentum), and dry beans (Phaseol us vulgaris) were the most studied crops. Gentes pivot, followed by solid s et, were the irrigation systems most frequently used. The minimum volume of water applied by some center pivots (25 000 litre ha(-1)) is 25 times the maximum volume of water used by conventional ground sprayers. The reduction of fungicide residue on foliage caused by the very large volume of water u sed by chemigation might be offset by the following factors: (1) fungicide application at the time of maximum leaf wetness when fungi are most active, (2) complete coverage of plants, (3) reducing greatly the inoculum on plan t and soil surface, (4) better control of some soil pathogens, and (5) more uniform distribution of fungicides by center pivot. Furthermore, chemigati on avoids mechanical damage and soil compaction. Additionally, some systemi c fungicides seem to be absorbed rapidly by the leaves, by root uptake from the soil, or by both. In general, all fungicides applied through irrigatio n water can lessen disease severity. However, when compared to conventional methods, chemigation with fungicides can be less, equally or more effectiv e depending on crop, pathogen, disease severity, fungicide and volume of wa ter. For Cercosporidium personatum control on peanuts, application of prote ctant fungicides through irrigation water is less effective than convention al methods, but the results with some systemic fungicides mixed with non-em ulsified oil and applied through a relatively low volume of water (2.5 mm) are encouraging. Important diseases of potato and tomato can be controlled nearly as well by chemigation as by conventional methods without impairing yield. The main advantage of chemigation for these crops is avoiding a larg e number of tractor trips through the field and reduced costs of fungicide application. Chemigation has also been shown to be a good option for contro l of white mold [Sclerotinia sclerotiorum] on dry beans. (C) 1999 Society o f Chemical Industry.