By Darcy Etcheverry
As gardeners, we have all encountered plants in our gardens that weren’t growing normally. Maybe you’ve seen black spots on the fruit or any number of other oddities. Sometimes the problem appears minor, and other times it looks as though the whole plant or crop is going to die.
Before you call your expert gardening friend for help, try solving the mystery yourself. It will open your eyes to the world of potential plant problems and will give you confidence as you gain gardening experience. Diligent record keeping comes in handy so you can answer the following questions about the history of your plant.
What has been done to the plant? This includes how it was started. Did you purchase it as a transplant, start seeds yourself or direct seed into the bed? How is it grown now? In a container, raised bed, field soil, greenhouse or hydroponically? Also, what is your irrigation regime and your fertilization method and frequency?
Look up the variety. Is it known to be susceptible or resistant to any particular diseases? What is considered “normal” for this variety?
Have there been any abnormal weather conditions lately? Frosts, extremely hot days and heavy rains can all produce interesting symptoms on plants or even promote the establishment of particular pests.
Next, examine the symptoms of the problem. What changes do you observe in your plant? Is it a discoloration, curling or maybe holes in the tissue?
What is the pattern of the problem? Is it on a single plant or widespread throughout the crop? Is it occurring all over the plant or only affecting a single part, such as young leaves or only the fruit?
What is the most likely cause of the damage? A living pest or pathogen, such as an insect, fungus, virus or bacteria — or even a child grazing through the garden — will have distinct symptoms and patterns.
Or the damage could be caused by something in the environment, such as temperature extremes, drought or a nutrient imbalance.
Once you have collected the known information, it is time to consult expert resources, especially books geared toward Alaska gardening and disease diagnosis. The internet is a great resource, but remember to consider the source! Online forums can be useful, but can also send you off on tangents that could lead to an incorrect diagnosis. A trick I learned is to include the word “extension” in searches and to use .edu links to get research-based information.
If you don’t get a satisfying answer through that process, the answers to the above questions will help me, or another diagnostician, figure out what is wrong. Visit www.uaf.edu/ces/ipm to submit a digital photograph of the plant or contact your local Extension office directly.
Diagnosis can be complicated, especially when more than one pest or stressor is present. In some cases, advanced techniques are needed for a definitive answer. Getting tissue analyzed to check for a suspected disease or even a nutrient imbalance can be expensive, but it is worth the cost for a high-value crop. I often recommend this to commercial growers, but not generally for home gardeners unless I suspect the problem is an emerging pest for Alaska that could spread to other gardens and farms.
Keep in mind your goal as a home gardener and learn what you can about common pests and environmental stressors of the plants you grow. Sometimes a definitive diagnosis is not possible, but armed with knowledge and experience, you can make informed decisions to tweak your management and still have a bountiful harvest.
Darcy Etcheverry is a program assistant with the University of Alaska Fairbanks Cooperative Extension Service agriculture and pest management program in Fairbanks. She can be reached at 907-474-5107 or firstname.lastname@example.org.