Jerry Brust, IPM Vegetable Specialist, University of Maryland; jbrust@umd.edu
While out in some watermelon fields recently I happened to turn over some fruit and was surprised to find large numbers of striped cucumber beetles feeding on the undersides of the watermelon on the outer rind. There was almost no feeding on the upper surface of any watermelon and the damage could not be seen until the fruit was rolled over. Normally you would expect to see a few beetles feeding on a few melons, but close to 70% of the watermelons in some fields had feeding damage. The damage was superficial, but few people are going to buy a watermelon with that type of scarring. A pyrethroid spray in a high volume of water (100gal/acre) is needed to control the beetles. Why the population of striped cucumber beetles is so high in some areas of Delmarva I am not sure. It may be due to the perfect weather conditions for them this summer as it has not been extremely hot and we have not had drought conditions.
Many scarred watermelons due to striped cucumber beetle feeding only on the undersides of the fruit