Tomato

Pests of Field Crops in Southern Africa

TOMATO

(Lycopersicon esculentis, Solanaceae)

Text Box: See general section. Bollworms can cause considerable damage to tomatoes by boring into the fruits. Damage to small fruits may result in their abortion, while damage to older fruits leaves a hole that may allow penetration of rotting fungi or bacteria. Since tomato fruit is mostly eaten raw, care must be taken to observe harvest intervals in the application of pesticides. TOP

Text Box: Amongst the other leaf feeders which may be found on tomatoes are lesser armyworm, Spodoptera exigua (see pea section), tuber moth, Phthorimaea operculella (see potato section), hawk moth caterpillars (Acherontia atropos) and occasionally leafworm, Spodoptera littoralis (see cotton section). Tomatoes are also host to the aphid species that attack potatoes and small green leafhoppers (Empoasca spp.) may cause some yellow stippling on the leaves by their sap-sucking. The seedling stage is susceptible to damage by cutworm. TOP

African Bollworm

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Red Spider Mite

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Liriomyza Leafminer

African Bollworm

Text Box: See general section. Liriomyza has become a major pest of tomatoes in the last few years, and crops may be seriously affected in the early part of the season before the rains become established. Damage by the leafminers may result in little functional foliage being left, and the developing tomatoes often become sun-scalded by their resulting exposure. The seriousness of this pest in tomatoes may often be due to the application of pesticides for other pests, or ineffective sprays applied against this pest, which results in the death of natural enemies. On occasion, lush tomato plants grown in plastic tunnels are able to cope with a certain amount of foliage damage without serious leaf loss, but feeding by the flies and mining by the caterpillars makes the crop very susceptible to early and late blight disease, to which tomatoes are very susceptible. The application of yellow sticky strips in greenhouses to attract and trap the flies is recommended. TOP

Liriomyza Leafminer

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Tomato Semi Looper

Text Box: See general section. Tetranychus spp. can be a serious pest of tomatoes in hot, dry seasons, or simply dry spells within the season. The first symptom is fine yellow stippling of the leaves caused by the mites feeding on the undersurfaces. If left uncontrolled, however, they may soon cover the plants with fine webbing, and the stippling will even appear on developing fruit. Outbreaks are usually in “hot spots” in the field, and these should be spot-sprayed early on to avoid the infestation getting out of control. Several acaricides are registered for mite control in tomatoes, amongst which are abamectin, amitraz, clofentezine, dicofol, propargite and sulphur, but there is also the possibility of using predatory mites (such as Phytoseiulus spp.) in protected greenhouses. The latter system has been perfected in the Northern Hemisphere, but has not been seriously tested in Southern Africa. TOP

Red Spider Mite

Text Box: See soyabean section. The chief semi-looper culprit in tomatoes is Chrysodeixis acuta, whose larva consumes the leaves and may damage fruit superficially. The caterpillars are cryptically coloured and difficult to observe on the plants. There are a variety of parasitic wasps and flies which attack this species, but sprays may be necessary in sporadic heavy outbreaks. TOP

Tomato Semi Looper

Text Box: See general section. Tomato crops are often infested with clouds of whiteflies, particularly during dry seasons. Although they usually do not kill the plants, their feeding may shorten the productive period of the crop. They are also vectors of Tobacco Leaf Curl Virus, which affects tomatoes, producing stunted crops with curled leaves. TOP

Root Knot Nematode

Root Knot Nematode

Text Box: Eelworms, particularly Meloidogyne javanica, are a serious pest of tomatoes, causing heavily galled and stunted root systems, and poorly-growing crops. This is one of the main reasons for using crop rotations in tomatoes, and avoiding the planting of tomatoes in potato- or tobacco-growing areas. Several tomato varieties that exhibit resistance or tolerance to this pest are now available. TOP

Red Spider mite on the underneath of the leaf.

Liriomyza leaf miner in Tomato.

Typical stippling and webbing associated with heavy infestation with red spider mite in tomato.

Semi-looper caterpillar.

Bollworm entering a tomato at the calyx. Droppings on the outside.

Whitefly adults and nymphs on underside of leaf.