Cucumber green mottle mosaic virus-a challenging virus disease

Denis Persley and Paul Campbell

Department of Agriculture and Fisheries

• First found in Australia in 2014

• Disease of cucurbits-cucumber, melons, pumpkins, gourds

• Can be carried in seed

• Spreads by contact

• Survives for many months in debris, soil

• Hygiene critical in control

Basic Facts

• Virus first described in 1935 in UK

• Considerable spread in last 10 years

• Most countries now have it.

• First detected in Australia in 2014 in NT in watermelon. Losses of $45M in industry

• CGMMV is a Tobamovirus (Tobacco mosaic virus group)

• Globalisation of seed industry and it seems same strain has moved around world

CGMMV

A B

DC

• Very easily spread by contact e. g. handling plants, brushing plants with equipment, manual operations, harvesting

• Survives in contaminated soil , plant debris for many months and can infect plants via root contact

• Virus can infect through contaminated water, nutrient solutions

• Virus can survive in packaging material, contaminated bins, discarded fruit

Spread

• Virus can infect rootstock plants and grafts

• Survives in seed from infected plants

• Not spread by aphids, thrips, whitefly but bees play a role in spread

Spread

• Most commercial cucurbits are hosts e.g. cucumber, melons, pumpkin, squash, zucchini

• Weedy cucurbits also common hosts

• Other weed hosts include Amaranthus species (Amaranth), Portulaca (pig weed) and Chenopodium (Fat hen).

• Weeds often do not show symptoms

• Likely important in maintaining virus in a district

Host Plants

• Ease of spread, long survival periods in debris, soil, equipment and weed hosts make CGMMV very difficult to control

• Hygiene critical to success

• Spraying insecticides will not do the job!

• Needs same control measures as Tomato mosaic virus in capsicums (now significant issue in Virginia capsicums)

• When not managed yield losses will occur in cucurbit crops

Management

• Farm/ district biosecurity plan

• Healthy seed-All cucurbit seed legally imported into Australia is tested for CGMMV

• Operate greenhouses as separate units and minimise equipment movement

• Have suspect plants tested as several viruses cause similar symptoms

• Isolate affected areas

Specific management measures

• Best disinfectants for viruses, including CGMMV, are bleach and Virkon. Alcohol handwipes and various sanitisers not effective

• Resistant cucumber varieties available-need to use as part of management system; only partially resistant so will harbour virus

Specific management measures