Tomato is one of the crops where pesticides are frequently applied. The reasons for spraying tomatoes with synthetic chemicals are mainly disease infections and insect pest damage.
Diseases that attack tomato include late blight which comes early during vegetative stages of the tomato, and early blight which comes at the stage when tomatoes are aging.
Late blight is more destructive and is favoured by misty dull weather with high humidity. The causal fungus can be transmitted by wind as spores, and also in water as zoospores (look like tadpoles) which can swim. In order to manage these diseases, fungicides are sprayed. The most common fungicide used in Uganda is Mancozeb (Dithane M45). However, copper fungicides are also used. Fungicides are not very toxic and their minimum allowed Minimum Residual Limit is usually higher than that for insecticides.
Tomato has very many insect pests that cause damage to it. The most notorious insects are aphids, whiteflies, thrips, African bollworm, and in highlands green mites. The first three transmit viruses in tomato, while the last two simply cause economic damage to leaves and fruits. Aphids and whiteflies are most prevalent during the early vegetative growth stages of the tomato. Thrips, African bollworm and mites have high population during the dry season and at mature/fruiting stage of the tomato.
With more consumers cautios of the health threats associated with more consumption of fruits that have excess synthetic chemicals, more farmers are adopting organic agriculture. Organic agriculture has its core value of non use of synthentic chemicals intertwined together with best environment conservation practices and respect of nature.
This being the understanding of organic agriculture, tomatoes can be grown without use of synthetic chemicals and with best conservation practices. According to Dr. Charles Sekyewa Member of Board, the International Societyfor Organic Research (ISOFAR), the best time to grow tomato organically is the wet season. During that time, late blight is the major constraint. However, the late blight can be dealt with using a number of organic fungal control measures which include.
One can apply yeast mixed in lukewarm water. Spray the solution on leaves of your tomatoes once every two weeks.
Make ash of dry pawpaw leaves, mix with water (1kg per 20ls of water) and spray the suspension onto your tomato crop.
Prune off diseased leaves and stems as soon as they are seen. Note that such tomatoes will have a thin skin. To avoid this problem which is true for variety Heinz, grow hard skin varieties such as Money maker.