Plant Disease

healthy tomato plant

A healthy tomato plant from our garden

Many plants appear to be succumbing to disease of late and many are in areas that never had much problem with disease in the past. The past several years, early blight, late blight and other diseases have been wiping out entire farms worth of tomatoes, even in New England, where the problems were minimal in the past. What can we do to help?


While mulching is consistently recommended to help, we have not found that mulching helps fight the diseases in and of itself. However, mulching has other advantages, so it certainly can’t hurt and other preventive measures in tandem with mulching do help.

The premise that mulch helps is based on the idea that mud will not spatter on the plants when they are watered or when it rains, and because soil can carry the disease, this will prevent the soil from reaching the vulnerable plant. However, many diseases are air born as well and attack and spread in numerous ways. In many cases it is uncertain how they spread among plants.


Another possible suggestion we have seen is to irrigate your tomatoes from below rather than watering them from above. This is again an attempt to keep the water from splattering mud or dirt on your plants. We have actually found this recommendation to be harmful. Tomatoes love to be misted and the stems and leaves thrive on exposure to water. If you only water the roots, you will often find that the leaves and stems wither.

Further, in actuality, if you have a small garden, watering from above should wash away pathogens not spread them. We have found some interesting results for driving some pests away using our hose and we believe after following the general guidelines provided on most websites, this recommendation is hooey. Rain falls from above. God doesn’t follow the advice. Why should we?

However, watering from above only when you have time to do it right may be prudent. Just spraying the plants from a distance with a hose won’t cut it. And even if not attempting to prevent disease, deep watering is also helpful to the roots of your plants. So, in those cases, irrigation using soaker hoses can work quite well. Just don’t overdo it.

We have discovered, however, that flushing plants from above with clear fresh water helps strengthen the plants. It also helps flush disease spores and other infestations from our plants. We will actually film this later this year. One case in point from last year’s crop was in infestation of cabbage worms attacking our Brussels sprouts in large numbers. We searched for solutions and none suggested what we found to be the best solution. Water!!! We sprayed the plants heavily with water and it washed the eggs and unwanted guests to the ground. Two or three treatments and we never saw the worms again. Our plants thrived in response.

Clean Water

Clean water is a gardener’s best friend in our experience. However, you should try to make sure you do actually clean the plant. In this instance, mulching does work. When you flush a plant with clean clear water, if you splash up mud, you defeat the purpose. It is like washing your car in a mud pit. Useless. Mulching is a good thing, but not to prevent disease as much as to allow you to use water to your advantage, including fresh rains. It shields the plant from splatter and retains moisture making watering less necessary.

Diseases like early blight result in the plant leaves and branches turning yellow, typically with black spots or yellow blotches with black spots. The leaves wither and eventually die. Fruit production is severely curtailed. If blight and other infections proceed without some kind of intervention, they will kill the entire plant.

Clean water sprayed vigorously on your plants (when strong enough to withstand the pressure) combined with proper mulching is the best approach to keeping the problem from taking hold in the first place.


Some mild organic fungicides you can make right at home also work well. We will show you how to make a home fungicide brew from baking soda shortly in a new video.  Applying fungicides to the soil when first transplanting your plants into the garden, and also applying it to the newly transplanted tomatoes helps keep fungal diseases from ever getting started.  Once disease starts, even strong chemicals have trouble ridding  you of the problem.  Make sure to use a sprayer and to get the BOTTOMS of the leaves as well as the tops.


Diseases can spread plant to plant by contact, so proper separation is key to preventing that.  Air flow is also important.  Ensuring your plants have enough separation keeps them dry and many of these fungal based diseases thrive in overly moist environments.


One nearly certain way to get plant disease is to plant your garden vegetables in an area that is shaded much of the day.  The plants will not be as strong and will be much more susceptible to disease.  This is especially true for tomatoes, which need to be in the sunniest location possible.  The sun not only feeds the plant, it keeps the foliage dry, helping protect  it from fungal and bacterial attack.  If you cannot plant your tomatoes where they will get at least 8 hours of direct sunlight, don’t plant them at all.


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