Sometimes it seems like war in the garden, with a never-ending brigade of pests, diseases and wildlife that wants to eat your crops. Most parents are too busy to analyze every little thing that attacks their vegetables, much less do anything about it. When it comes to pumpkins (Cucurbita spp.), there's no shortage of diseases that can infect and even kill the plants. To figure out what might be going on with your pumpkin plant, it's helpful to first understand the broad classifications of pathogens that affect the species. Then look at the characteristics of each one to see which matches the symptoms you're observing.
Fungal diseases are the most common type of pathogen affecting pumpkins. Pumpkins tolerate many fungal infections without completely succumbing to the diseases, but a few are particularly lethal. If pumpkin leaves suddenly wilt, even though you've been watering regularly, fusarium wilt is likely the cause. The entire plant usually dies within a few days of the first signs of wilting. Gummy stem rot begins with dry spots on the leaves that become holes, leaving a ragged appearance. Later, portions of the main stem near the soil crack open and ooze a sticky brown sap.
If your pumpkin leaves are wilting and there also are signs of insect damage, bacterial wilt may be the cause. Bacterial wilt is transmitted by aphids and certain beetles that chew holes in pumpkin leaves. The aphids can be observed living in clusters on the foliage, especially the tender growing tips. Cucurbit yellow vine disease is another common pumpkin infection that often ends up killing the plant. The signs of this bacteria don't usually show up until a few weeks before harvest time. The outer margins of the leaves begin to appear scorched and then the whole leaf usually turns yellow. The roots begin to rot next, and the entire plant then declines quickly.
Splotchy patterns of light and dark green or yellow on the leaves or the baby pumpkins is a sure indicator of viral disease. There are numerous viral diseases, and often several are working together against the poor pumpkin plant. Many include the word "mosaic" in the name as a reference to the splotchy pattern -- such as cucumber mosaic virus, watermelon mosaic virus and squash mosaic virus. Others use the term "ringspot" because the lesions begin as deformed rings or round bumps on the surface of leaves and fruits. Papaya ringspot virus and tobacco ringspot commonly affect pumpkins, often leading to the death of the plant.
The best treatment for the lethal pumpkin diseases is prevention. Many diseases are completely resistant to chemical means of control. The primary form of prevention used by seasoned gardeners is to practice crop rotation. In a nutshell, this means not planting the same crop in the same place year after year. If you observe signs of pumpkin diseases, it is better to dispose of the plant and try again in a different bed or, ideally, somewhere on the other side of the yard. This way, you won't have to figure out exactly which disease is infecting your pumpkins and how to treat it, and you can spend more time enjoying the parts of gardening that you love.