Did you know that Western North Carolina is classified as a temperate rainforest ecosystem? Most people are surprised to hear this, but not organic gardeners. Our area is bursting with biodiversity, and with that comes other types of living organisms — some which are not as welcome as others.
With our fair share of diseases affecting every plant you can imagine, organic gardeners often feel like we’re in for total losses as we encounter steamy humidity, hot temperatures and seemingly endless rainfall.
Since plant diseases love these climatic conditions, chances are disease control will be your biggest challenge as you develop your organic gardening skills. This article is the first step in giving you the knowledge and tools to help prevent and combat common disease organisms, along with valuable tips and specific treatments that you can find over on the Organic Growers School blog (https://organicgrowersschool.org/gardeners/library/organic-disease-control/).
Looking at the spectrum of potential pathogens, or disease organisms, it’s helpful to divide them into three groups:
Fungi — Grow on or through plants via threadlike mycelium. Fungi require either living plant hosts or decaying organic matter to survive. Fungal pathogens are the greatest challenge in our region.
Bacteria — Single-cell organisms that need a living host to survive. Bacteria reproduce readily when they have warm, moist environments and a host plant to feed on.
Viruses — Sub-microscopic organisms that invade the host plant’s cells and then multiply. Viruses spread via infected pest insects known as vectors.
First, let’s explore some good, preventative measures that you should always try to take. Every season, re-visit this list and try to improve.
1. Strive for healthy soil with lots of organic matter, which will provide good even moisture and good drainage, as well as plenty of nutrients that plants need to stay healthy. Visit our post on feeding the soil for more information on how to achieve dreamy garden soils (https://organicgrowersschool.org/feeding-your-garden-organically/). Note: Soil building will be a goal that lasts throughout your garden career. It takes years, and should be considered an investment.
2. Maintain good airflow between plants by ensuring adequate spacing, minimal weeds and varied architecture (i.e have tall and short plants together). Pathogens love stagnant, hot air. The better the air circulation, the better your chance of avoiding infection.
3. Water enough but not too much. Most pathogens thrive in moist to wet environments, especially as the weather heats up. Make sure you water enough to meet the requirements of your crop plants, but be especially careful about stagnant water in the garden and plants that sit at the bottom of the garden that might collect runoff after heavy rains. Going back to No. 1, the healthier the soil, the better drained it will be, which will aid in your attempts at optimum water balance.
4. Look for disease-resistant varieties of veggies. Note that many hybrid vegetables are bred to resist diseases that are known to affect that particular crop plant. Read this Ask Ruth article to learn why hybridized seeds are not the same as GMO seeds (https://organicgrowersschool.org/ask-ruth-explaining-bt-organic-or-gmo/).
5. Be careful with your hands and tools because many pathogens can spread in water, on tools, on your hands, on clothes, hats, water hoses, etc. The cleaner you keep everything, the better. Also, if you suspect a group of plants have an infection of some sort but you haven’t ruled out nutrient deficiency and don’t want to remove them completely, remember to wash your hands after handling them before handling healthy plants. This will prevent the spread of disease in the garden.
6. Keep garden beds free of decaying debris like weeds you’ve pulled, or leaves you’ve stripped during harvesting. Fungi and bacteria like to grow on decaying organic matter. There will always be some decaying organic matter in an organic garden, but the less you contribute the better. Take weeds to your compost (only if you manage an active, hot pile) or your burn pile. Be especially aware of weeds that are in the same plant family as your crop plants, such as black nightshade (related to potatoes, tomatoes, eggplants, and peppers), as diseases that love a specific family of food plants will often get their start via weeds from the same plant family.
7. Rotate crops. Changing the planting area of crops every season will help prevent disease, especially soil-borne pathogens. Rotating your crops by family will provide extra protection. For example, if all your nightshades are in one area this season, make sure to put them as far away from that area as possible next season.
Now that you’re armed with some effective preventative measures, let’s get down to the nitty gritty, and take a look at some common pathogens in WNC gardens. Head over to read the rest on the Organic Growers School blog for techniques to combat the most common garden diseases (https://organicgrowersschool.org/gardeners/library/organic-disease-control/).