Incidence, Distribution and Characteristics of Major Tomato Leaf ...

Incidence, distribution and characteristics of major tomato leaf curl and mosaic virus diseases 153
Uganda. It is also the first time to report ChiVMV on tomato in Uganda and East Africa at
large.
We established that weeds act as alternative hosts to some tomato viruses identified, which
lead to a clear understanding of the necessity for timely weeding of tomato fields as an option
for virus disease management. Occimum basilica was reported here to be an alternative host
of ChiVMV and PVMV for the first time.
Combinations of two to five viruses exist in individual tomato plants. These mixtures
contribute to the severity of tomato virus diseases in Uganda.
Tomato yellow leaf curl viruses are amongst major viruses whose incidence and spread are
influenced by presence of the whitefly vector (Bemisia tabaci), and weather conditions within
the agro-ecosystem in Uganda.
We found that whiteflies preferred young tomato plants to old plants. It is recommended that
whiteflies be controlled at nursery stage before transplanting seedlings, and before infection
or when vector and disease levels are still very low. As reported earlier, tomato yellow leaf
curl virus infection at an early tomato plant development stage results into death before
fruiting or only single trush setting, as also was observed by Yassin (1982).
Uprooting diseased plants and applying dimethoate was an effective control for whitefly
vectors. Tomato growers are advised to apply this integrated management package for
TYLCV (sensu lato) and the whitefly vector, especially if done during the dry season and the
first part of the rainy season when whitefly populations are high. Even though there is transprogeny
transmission of TYLCV (sensu lato), which is also persistent in viruliferous
whiteflies (Rubinstein et al., 1999), in this way, farmer expenditure on pesticides would be
minimized and the amount of pesticides filtering through to the environment would be
tremendously reduced.