YOUR PRODUCTION
Virus diseases of capsicums in Wes tern Aus tralia
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BY DR CRAIG WEBSTER DEVELOPMENT OFFICER, DPIRD
everal viruses can affect capsicum production in all regions of Western Australia. It can be difficult to tell the difference between the three viruses by the symptoms alone. Most importantly, the best way to control of each viruses differs so accurate identification is important.
3 TSWV is spread by thrips and they need to be born and feed for a long time on an infected plant to spread the virus.
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WA Grower SPRING 2020
The three main viruses detected in capsicum include Tomato spotted wilt virus (TSWV) (see Figure 1), Cucumber mosaic virus (CMV) (see Figure 2) and Pepper mild mottle virus (PMMoV) (see Figure 3). A fourth disease that is occasionally seen is a phytoplasma (see Figure 4), which is a type of bacteria. When infected by each virus, the symptoms in capsicum are very similar, and can often not be distinguished by eye alone. The symptoms of a plant being infected differ with the variety of capsicum but they usually cause the leaves to become pale in colour (chlorotic) and can be reduced in size or distorted in shape. These will first appear on the newest leaves and often cause the plant to stop growing or grow only very slowly. The size of the fruit can be affected and ripen unevenly. Necrosis in spots or rings may also be observed on the fruit.
Once a plant is infected, all the remaining fruit will continue to show the same symptoms, and nothing can be done once the plant has become infected.
Each virus is spread in a different way so knowing which virus is causing the disease will help focus on the best approach to control the disease. 1. TSWV is spread by thrips and they need to be born and feed for a long time on an infected plant to spread the virus. This means the disease moves relatively slowly. It is not spread by seed but it is spread by thrips moving from volunteers, weeds and adjacent infected crops with thrips can cause virus to be continually spread into the crop.
Each virus can also be found in weeds, volunteers or adjacent crops.
