Plant viruses can be difficult to deal with. Together with AECI Plant Health, Food For Mzansi readers get insight into why their plants are sick. If you have any plant health questions, please email your questions and pictures to firstname.lastname@example.org.
Sandiswa Dlamini, from Hammanskraal in the Gauteng, writes: The leaves on my squash plants have strange, discoloured spots on them, and even in some cases, what looks like odd bumps or blisters. I have no idea what they are. Can you please help?
Simon Louw, technical advisor at AECI Plant Health, writes:
Sorry to hear about your plants, Sandiswa. From your description, it seems that your squashes are afflicted with the squash mosaic virus. The virus is seed-borne, and affects squashes and melons in the Cucurbitaceae family. The virus is spread primarily by beetles, including the leaf beetle and spotted cucumber beetle, and is transmitted by the saliva of the beetles when they feed. The beetles in turn are infected when they feed on infected plants. Unlike other viruses affecting squashes, the mosaic virus is not transmitted by aphids.
In many cases, the disease does not kill the plant but reduces the size and number of leaves, which decreases fruit production. Symptoms include mottled leaves, raised dark green blisters on fruit, and rapidly dried-out stems. The fruit produced from infected plants often has unusual colour patterns and ring spots, and may also be malformed.
To limit this virus, plant virus-free seed that is certified by a reputable seed producer and implement a thorough insect management control programme, including Prev-Am, Grab 500 EC, and a natural pyrethrin i.e. Xterminator.
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