Cabbage Integrated Pest Management : An Ecological Guide.

Disease Ecology· Frequent use of fungicides may lead to fungus resistance to that type of fungicide. That means thefungus is no longer susceptible to the fungicide. For example, there are different “strains” of Fusariumwilt in tomato (Fusarium oxysporum). All of these Fusarium strains cause tomato wilt but the geneticcharacteristics of a strain are slightly different. This is comparable with different varieties of tomato:all of them are tomato but they differ in e.g. fruit size, color and maturity. Strains may differ insusceptibility to fungicides.· Many fungicides can actually kill natural enemies of insect pests! For a study example, see box insection 4.9.¦Calendar sprayingThe application of pesticides at regular, fixed intervals during the season is known ascalendar spraying. This practice can be effective in disease control, but may lead to excessivefungicide use or poorly timed applications over the duration of the growing season, resulting in a lossof money for the farmer and environmental pollution. More important, calendar spraying is not basedon what is actually happening in the field, on agro-ecosystem analysis. It does not account forpresence of natural enemies, growth stage, weather conditions etc. Therefore, from an ecologicalpoint of view, calendar spraying should be discouraged.No recommendations for the use of specific fungicides will be given in this guide. The types, brands,doses of fungicides differ per country and local extension agencies or departments of agriculture mayhave national recommendation schedules.7.11.2 Botanical fungicidesNot much “scientific” information is available on the use of botanicals against fungal diseases. However,in practice farmers may use several botanical extracts to control diseases.Garlic is one the more commonly used botanicals, effective both as seed treatment for disease control(see section 3.3.3), and in a spray solution against fungal and bacterial diseases and insects. There aremany methods to prepare garlic sprays. One of them is listed below.Garlic spray: the recipeCrush many garlic cloves with a little water, then strain this and mix with water, 1 teaspoonof baking soda, and 2 or 3 drops of liquid soap. Test its effect as a preventive sprayagainst fungal and bacterial diseases and insects.Milk (not a botanical but of animal origin) can also have a function in preventing fungus and mainly virusdiseases in plants. No “official” trial data are available but milk is used a lot in greenhouses in for exampleNetherlands to dip cutting knifes during pruning of tomato. The milk protein inactivates viruses. Effectsson fungi are unclear. Milk is expensive for use on larger scale.Cabbage Ecological Guide - 2000150