besides diseases, it's also important to monitor insects pests as early as possible and control measures be employed appropriately. A common pest is melon fly usual of control by chemical baits before their effects surpass economic injury levels. Another recommendation is planting trap crops (crops loved by these pests) in this case Maize, cassava or pawpaw can planted around the farm or in rows in between the main crop(watermelon) if the farm is big. Remember also to keep your field clean free from weeds.