At early stages of the disease, light yellow-green spots and vein clearing can be observed on young leaves. Severe infections result in a yellowish mottling, crumpling and deformation of leaves as well as plant stunting and necrosis at later stages of growth. Mature leaves can become bleached or yellow-whitish and drop prematurely. Symptoms on fruits range from completely symptomless (at least externally) to severe spotting or streaking, deformation or dropping. The latter symptoms are particularly visible at elevated temperatures. In some cases, fruit showing no external symptoms may be internally discolored or necrotic. Premature dropping is also common.
The symptoms are caused by the cucumber green mottle mosaic virus (CGMMV), which infects cucurbits, including cucumber, watermelon and cantaloupe. The virus can stay active for very long periods of time in dead plant material in the soil. The transmission is via infected seeds, mechanical wounds made with cutting tools, farming equipment, and through chewing insects such as beetles. It can also be passed to other plants through grafting or other tasks that could injure the crop. Sucking insects (e.g. aphids, mites, whiteflies) do not transmit this virus. Once it infects a plant, there is no known cure against this virus. In greenhouses especially, the number of infections from this virus is on the rise.
If you treat seeds at 70°C dry heat for up to three days, they will be free from active virus particles, but still able to germinate. Apply CGMMV test kits, if available. Apply organic insecticides targeting chewing insects.
Always consider an integrated approach with preventive measures together with biological treatments if available. The application of chemical insecticides targeting chewing insects can prevent spreading of the virus. The direct treatment of viral diseases like the cucumber green mottle virus is not possible.