Tomato Yellow Leaf Curl Virus




Tomato yellow leaf curl is a disease of tomato caused by Tomato yellow leaf curl virus. In March 2007, it was identified for the first time in California and currently has a limited distribution. 

Infected tomato plants initially show stunted and erect or upright plant growth; plants infected at an early stage of growth will show severe stunting. However, the most diagnostic symptoms are those in leaves.

Leaves of infected plants are small and curl upward; and show strong crumpling and interveinal and marginal yellowing. The internodes of infected plants become shortened and, together with the stunted growth, plants often take on a bushy appearance, which is sometimes referred to as 'bonsai' or broccoli'-like growth. Flowers formed on infected plants commonly do not develop and fall off (abscise). Fruit production is dramatically reduced, particularly when plants are infected at an early age, and it is not uncommon for losses of 100% to be experienced in fields with heavily infected plants.

Tomato yellow leaf curl virus is undoubtedly one of the most damaging pathogens of tomato, and it limits production of tomato in many tropical and subtropical areas of the world. It is also a problem in many countries that have a Mediterranean climate such as California. Thus, the spread of the virus throughout California must be considered as a serious potential threat to the tomato industry.

There are a number of factors why it has not yet spread to all the major tomato-producing areas of California, including the Sacramento and San Joaquin valleys. First, its vector, Bemisia whitefly species are not typically found in these tomato-producing areas because it is intolerant of winter temperatures there. Second, the Central Valley's winter season provides a 'natural' tomato-free period, which usually goes from late November through early February. Although the virus can infect other plants, tomato is the host in which it builds-up most quickly. Thus, by having an annual 'tomato-free period', it is likely that the amount of viral inoculum (as well as whitefly populations) will be significantly reduced by the time the tomato planting season starts again in late winter-early spring. This would mean that, even if the virus is able to overwinter, it may take a long time to reach levels that cause economic damage.

Management

  • Plant immediately after any tomato-free period or true winter season.
  • Avoid planting new fields near older fields (especially those with TYLCV-infected plants).
  • Manage WHITEFLIES.
  • Cover plants with floating row covers of fine mesh (Agryl or Agribon) to protect from whitefly infestations.
  • Rogue diseased plants when incidence of virus infection is low.
  • Practice good weed management in and around fields to the extent feasible.


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