Gardeners, do not focus on diseases themselves, be keen on disease prevention. While it’s always important to know what’s happening to your vegetable garden, even with a trained eye, it can be difficult to distinguish one disease over another.

By Matt Even

[This article was first published in The Gateway Gardener July/August 2017 issue.]

Gardeners, do not focus on diseases themselves, be keen on disease prevention. While it’s always important to know what’s happening to your vegetable garden, even with a trained eye, it can be difficult to distinguish one disease over another. Take time to learn about diseases during your “gardening career”, but first learn the basics of disease prevention. Trust me, it will go a long way.

Tomato diseases in Missouri are common, and fungi love our long, humid summers. Some of the main culprits that you find in the garden throughout the season include Fusarium Wilt, Fusarium oxysporum sp. (soil-borne fungus), and Early Blight, Alternaria sp.

Early blight is a fungus that typically spreads by old plant debris being left in the garden. Identifying factors include circular dark spots that eventually enlarge to concentric rings surrounded by a yellow area on leaves. Unlike early blight, yellowing on one side of the plant or leaves often identifies fusarium wilt. Both diseases creep from the bottom, older growth of the tomato plant to the top. This creates stunted growth, sunscald on fruit, defoliation, and stress the plant. Instead of attempting to diagnose diseases, prevent them from happening in the first place with some gardening best practices.

PREVENTION IS KEY

Resistant Tomato Varieties

Select adapted varieties that are disease resistant to ailments that we combat in the St. Louis region. University of Missouri Extension has a list of tomato varieties that are resistant to a host of diseases, and recommend growing techniques for disease prevention in our area.

MULCH!

As summer sets in, mulch, mulch, and…mulch. My favorite is leaf mulch, or leaf mold (half decomposed leaves), which retains moisture, prevent weeds, and keeps soil from splashing on the bottom leaves of plants. Typically, 2’’-3’’ inches of good mulch spread on your garden bed is what you want to aim for.

Many diseases are caused by soil borne fungus and bacteria being splashed up onto our plants. Mulching our garden beds reduces the chance of diseases spreading from the soil to our tomatoes.

Watering Techniques

Low and slow. If possible, water at the base of tomato plants and attempt to reach deep into the root system. This takes time; let water soak into the soil without washing away your topsoil. Moisture that penetrates deep into layers of soil encourages dense and strong root systems, making tomatoes more drought-tolerant and resilient.

Pruning and Sanitation

Many indeterminate tomato varieties will require pruning for healthy and vigorous fruiting. Make a habit of sanitizing your shears when pruning a single plant, or moving from one tomato to another. The same goes for cutting away visibly unhealthy parts of the plant. Without sanitizing your tools properly, it is possible to spread harmful diseases from one plant to another.

Use a 1:10 ratio of household bleach to water, or, 70% isopropyl alcohol in a spray bottle to disinfect your tools.

Matt Even has worked on organic farms from Northern Minnesota to Austin, Texas, and has been growing food since he decided to put his Sociology degree to good use. When he wrote this article in 2017, Matt was working as Outreach Manager and Educator for Gateway Greening, helping to start urban agriculture projects across the country.