August 2002. A farmer in Samoa asked for any way to control the problem that has occurred on his watermelon, seeds of which were purchased in Australia. The vines are stunted, the leaves chlorotic and distorted and the fruits small and rot due to early death of the vine.

In response, PestNet members confirmed that the photos show a classic case of virus infection. In Samoa, there are several viruses: CMV, ZYMV and Watermelon mosaic virus 1. It will be impossible to properly identifywhich one is caysing the symptoms unless ELISA or other techniques are used.

From experience, the best options for control are:

Use a floating cover mulch. The theory behind this approach is to delay infection:

1. Prepare the land, apply fertilizer and apply a systemic insecticide to the planting hill;
2. Use a white mulch to control weeds;
3. Use drip irrigation or some other forms of watering the plants;
4. Apply rat bait as rats eats the seeds;
5. Apply snail & slug bait – this is very important, they can do a lot of damage in a short time;
6. Plant seeds in the hills – 3 or 4 per hill;
7. Cover the plants with the floating row mulch (floating row covers) giving enough room so that the plants will push the mulch upwards as they grow;
8. Spray for fungus diseases. This is done by spraying through the mulc;
9. Critical step – uncover the mulch at 2nd to 3rd flowering stage. The mulch is removed to allow for pollination and the plants are not covered again.

Resistant varieties. Check with seed companies. Note, Charlston Grey is very susceptible, but the incidence of virus is improved with the floating row cover.

Mild strain protection. Although it gave good results is it only effective against one virus, ZYMV.

Time of planting. There may be a time when vectors are low. In Tonga, farmers are planting squash around July, when they report the incidence of virus is low.