Geminiviruses

Casual Agent – Abbreviation – Distribution

Cucurbit leaf crumple virus – CuLCrV – Mexico, USA (Arizona,California, Florida, Texas)

Loofa yellow mosaic virus – LYMV – Vietnam

Melon chlorotic leaf curl virus – MCLCuV – Guatemala

Pumpkin yellow vein mosaic virus – PYVMV – India

Squash leaf curl virus – SLCV – Central America, Egypt, Mexico, Middle East, USA (Arizona, California, Florida, Texas)

Squash mild leaf curl virus – SMLCV – Central America, Egypt, Mexico, Middle East, USA (Arizona, California, Florida, Texas)

Squash leaf curl China virus – SLCCNV – China, Philippines, Vietnam

Squash leaf curl Yunnan virus – SLCYNV – Southern China

Tomato leaf curl virus – ToLCV – India, Thailand

Watermelon chlorotic stunt virus – WmCSV – Middle East, Sudan

Watermelon curly mottle virus – WCMV – India

Silverleaf whitefly (Bemisia tabaci biotypes A, B, Q)

Geminiviruses infect cucurbits with varying degrees of severity. Cucumber appears to be least affected by geminiviruses. Symptoms of geminivirus infection may include upward curling of leaf margins, foliar stunting, chlorosis, interveinal mottling, vein clearing and thick, distorted veins. Flowers of infected plants are small and fail to develop normally. Early-season infection results in lack of fruit set, whereas fruit set prior to infection may be reduced in size, and exhibit chlorotic blotches and deformation.

Geminiviruses are vectored by the silverleaf whitefly, Bemisia tabaci (biotypes A, B, Q). The adult whitefly acquires the virus from infected plants and can transmit it to healthy plants within a few hours. Symptoms can develop within five days of virus transmission. Symptoms on cucurbits are most severe when whitefly populations are high and the crop is infected early in the season.

Host-free periods have been shown to be an effective measure for controlling the whitefly vector, whereas insecticide spray programs have been largely ineffective. Cultural control methods include weed control, incorporation of infected crop debris immediately after harvest and avoidance of planting new fields near infected cucurbit fields. Plant resistance is limited in commercial cultivars.