Cucumber Green Mottle Mosaic Virus (CGMMV) is a highly infective, highly stable tobamovirus which infects members of the Cucurbit family, including pumpkins, squash, melons, gherkins and bitter gourds. The damage inflicted on the host plant and fruit can be extensive, resulting in significant yield losses. Weeds such as nightshade, pigweed and purslane can serve as alternative hosts between curcurbit crops, however the virus itself can remain infectious for many months on crop residue, soils, and growing surfaces/tools.
Symptoms of infection will vary between species and strains of the virus, however mosaic mottling of leaves is a common denominator across these variables. At the early stages of infection, the cucumber plants will continue to grow and bare fruit. As the infection becomes more severe, fruit mottling and distortion can be observed. The plant itself will eventually stop growing, or show severe distortion. Unlike some other viruses in this group, CGMMV's ideal growing conditions mimic those for cucumber production, creating a scenario that supports rapid propagation of virus particles within infected plants.
What can be done?
- Adhering to an agreed upon order of entry - the most 'valuable' plants, such as seedlings, or newly transplanted crops are visited earlier in the day, before visiting the least 'valuable plants, such as those that are nearing the end of their harvest window. Once you have been 'contaminated' by the lesser value spaces, you will not re-enter the spaces containing the more susceptible crops
- Wearing clean clothes when working with your crop. These clothes cannot come from the field, or spaces where they may have come into contact with disease-causing agents. The use of greenhouse-designated coveralls or lab coats is a good way to limit transmission of pests and disease from the outside. The same goes for footwear - having designated footwear that is worn in the greenhouse is a good way to limit accidental introductions. Alternatively, the use of footbaths containing virkon, or other sanitizing agents, can limit spread as well.
- Designate production supplies to each greenhouse - instead of having one pair of pruners that float around between all the spaces, try and have a set for each production space. Harvesting buckets, carts, and other lower-cost items should not be shared wherever possible, to limit potential movement of diseases and pests across the farm. For larger tools (sprayers, lifts, ladders), adopt a regular schedule of cleaning before/after use to prevent accidental spread.
- House sanitizing agents (ex. virkon, alcohol, bleach) within each greenhouse for tool sterilization.
- Regular cleaning and sterilization of greenhouse tools to prevent build-up over time. This should be done more frequently than just between cropping cycles. The timing will depend on the item - pruners should be cleaned and sterilized very regularly, whereas larger tools like carts may see this less frequently.
- If you have had previous issues with viruses in your space, that plant material should be destroyed, as opposed to composted, to reduce the risk of re-occuring infection
