Timing Early Season Cucumber Beetle Control to Manage Bacterial Wilt in Muskmelon

Muskmelon (Cucumis melo var. reticulatus), is one of the most important vegetable crops in the United States. It is grown throughout the US, and Indiana ranked 3rd in production after California and Arizona with 2,088 Mg in 2013. Bacterial wilt of cucurbits, which is caused by (Erwinia tracheiphila) and vectored by striped cucumber beetle (Acalymma vittata), is one of the most serious diseases of muskmelon that influences muskmelon quality and yield. The primary method for managing bacterial wilt is controlling the striped cucumber beetle before it can infect the plant. However, it is not known whether there is a critical stage during early plant growth when muskmelon plants are more susceptible to infection and therefore control of striped cucumber beetle is especially important. We conducted three field experiments at two locations (Lafayette and Vincennes, IN) in 2013 and 2014 to investigate whether there is a critical period for striped cucumber beetle control sometime during the first three weeks after muskmelons are transplanted to the field. We found that using row covers that exclude beetles, or seed treatment or soil drenches with insecticide thiamethoxam significantly reduces wilt and increases the number of marketable fruits and total yield compared to not controlling striped cucumber beetle, because these methods protect the plants from cucumber beetle feeding and increase plant vigor. However, the length of time row covers were left on the plants (for 7, 14, or 21 days after transplanting, DAT), or the time beetles were permitted to feed on plants (7, 14, or 21 DAT), or the time when beetles began to feed on plants (0, 7, 14, or 21 DAT) did not significantly influence disease or yield in a consistent manner, suggesting that there is no clear ‘critical period’ during early muskmelon growth when controlling striped cucumber beetles is especially important.  The data also show that maximum incidence of bacterial wilt occurred in June and July, which corresponds to the two generations of cucumber beetles.