Bhabesh Dutta, an Extension vegetable disease specialist at the University of Georgia, said heavy whitefly pressure is prominent right now as we move from summer into fall.
Whiteflies vector viral diseases, such as cucurbit leaf crumple virus and papaya ringspot virus. These diseases are serious not only for fall watermelon crops, but also for other cucurbits including squash, zucchini and pumpkin. Cucurbit leaf crumple virus is a concern since these commercial crops do not possess resistance to the pathogen. However, Dutta said this issue is seen less in watermelon than on other cucurbits, since most Georgia growers harvest their watermelon crop before the end of summer.
While viruses vectored by whiteflies are not necessarily an issue in watermelon crops, growers still must work to manage fusarium wilt, which continues to have a harsh effect on watermelon growth in Georgia.
Dutta said greenhouse studies and hydroponics testing have been done to view the effects on fusarium wilt in different environments. Hydroponics studies on the effect of micronutrients on fusarium wilt severity have only been conducted for a year, so Dutta plans to continue this research for another year. He said the researchers have observed that micronutrients such as manganese and iron are involved in inducing host resistance in watermelon against the fusarium wilt pathogen.
A portion of Dutta’s research also involves studying the interactive roles fumigants and fungicides play in reducing fusarium wilt severity under field conditions. He said that while the use of fungicides and fumigants did not completely eradicate the fusarium wilt pathogen in the field for watermelon, it did significantly reduce disease severity when evaluated at two different locations in Georgia. Combining these tools and strategies could help growers to manage fusarium wilt in Georgia watermelon crops, Dutta suggests.
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