Demystifying Plant Diseases
There are dozens of different types of plant diseases that can affect garden plants from coast to coast. Plant diseases should not be a mystery to most gardeners, and yet…diseases occur almost every season. Solutions are readily available, but understanding the different types of plant diseases is the first step to control & management.
Proper Diagnosis
Plant disease management starts with proper disease diagnosis. Try thinking like a clinical physician. “What symptoms does the plant have?” You may be able to narrow down the possibilities by looking for examples online, however, the best way to get a true and accurate diagnosis is by sending a sample into a university plant disease diagnostic lab for testing. From that expert testing and diagnosis the pathologists will send you back results with recommendations for a treatment plan, if there is one. Short of that, sharing photos with a qualified horticultural professional is best. Avoid asking your neighbor. They almost always have an answer, but is it accurate? Use your own skills.
Control & Management
When plants develop disease symptoms, we ask: What’s this? Where did this come from? And What do I do now?
All are valid questions. The answers depend on what type of disease your plant is infected with. The good news is, this may not be as complex or mysterious as you might think. Every disease type has specific ways they spread. Therefore, there are equally specific ways to control them. Below is a synopsis of the 3 basic disease types with clear and helpful suggestions for basic control measures to follow for each.
Bacterial Diseases
· They are not very common, and their existence can be quite complex.
· Bacterial pathogens are spread mostly by insect feeding or infected tools.
· Control the pests and you can effectively prevent bacterial diseases.
· Clean and sanitize pruning or cutting tools prior to and after use.
· Once infected, plants with bacterial disease is difficult to control, prevention is key.
· With no cure, once diagnosed, the recommendation is to remove & destroy infected plants.
Fungal Diseases
· By far the most prevalent of all types of garden diseases.
· Fungal pathogens are ubiquitous in our environment, making infections common.
· Many pathogens exist with innumerable plant hosts.
· Pathogens are most often spread by wind, rain (splashing water) or they can already exist in soil.
· Typically more problematic during conducive weather patterns throughout the season and from year to year.
· They can, but rarely, spread by pests or mechanical means.
· By far, proper sanitation and prevention are the best control measures.
· Plant resistant varieties. Especially after fungal infections have occurred.
· Follow the 4 rights of fungicides (Apply the right fungicide, in the right amount, at the right time & right rotation)
Viral Diseases:
· Not very prevalent diseases in home gardens.
· Viruses are restricted to a particular host. Meaning they won’t infect everything in a garden, they’re only able to infect plant hosts in the same family.
· Most often spread by insect feeding (aphids, leafhoppers, mites, or nematodes mostly) small % can be spread from infected seed, by mechanical or vegetative means.
· Choose virus resistant varieties, especially vegetables. Read plant labels or ask a horticulturist for assistance.
· Preventing insect vectors feeding is the best control measure.
· Viruses are not curable. Once identified, removing & destroying infected plants is the best option.
Prevention vs Reactiveness
With plant diseases, a gardener has the choice to be proactive or reactive. Most gardeners are reactive, not proactive. Plant diseases are preventable, no matter what type you are talking about. To stay healthy and resist diseases, doctors recommend things like exercise, eating healthy vitamin/mineral rich foods, getting enough sleep and limiting harmful consumptions. Good advice, right? It should not come as surprise then, that horticultural recommendations for plant disease prevention are also this logical and simple.
Here are 6 basic things you can do to significantly reduce potential of plant disease in your garden:
1. Provide plants with proper placement and spacing.
2. Water regularly and consistently keeping their foliage dry, whenever possible.
3. Encourage and produce good air circulation throughout your plantings.
4. Improve soil composition & drainage prior to planting.
5. Provide plants with proper soil pH and nutrition.
6. Limit associations and interference from detrimental weeds and pests.
The cold reality is that for most plants, by the time severe disease symptoms appear, the time for control has passed. The best thing you can do for afflicted plants is to keep them as healthy as possible and trust the plant’s own defenses will hold up through the seasonal infection. Diseases afflict plants in specific ways for specific symbiotic reasons. If you can consistently eliminate those reasons, you will have few to no issues in your garden. Remember, diseases happen, but it doesn’t necessarily mean it’s the end of the world or the plant. Unhealthy or previously stressed plants may very well succumb to the pressures of disease, but most healthy plants are more resilient and can fight through it.
A reactive gardener may be able to limit the spread of a disease once a plant is infected, but in most cases, they will have to live & suffer with whatever disease or diseases appear that year if prevention measures aren’t put in place.
On the other hand, a proactive gardener will choose disease resistant varieties, water and fertilize their plants appropriately, feed and encourage a healthy soil microorganism population, and apply preventative organic fungicides in proper rotation to help suppress fungal outbreaks, especially for plants that have been infected in the past. Understand that previously infected plants will have less immunity to that same type of disease in the future.
Nothing too mysterious about it, being prepared and proactive is the key to plant disease prevention and management. The other 3 things that help the most are sanitation, sanitation, sanitation. I tell people all the time, the happiest gardeners are the cleanest gardeners. Don’t underestimate the power of keeping things clean!
