Identify garden diseases, how to cure problems with plants



Blossom end rot in tomatoes is a physiological disorder or abiotic disease “Symptoms due to abiotic diseases (those caused by non-living factors, such as nutrient deficiencies or herbicide spray drift) usually begin abruptly and show a pattern constant in the garden,” said Inga Meadows, NC State Extension Plant Pathologist.

Plant disease is inevitable, especially in central North Carolina where our summers are very hot and very humid.

But that doesn’t necessarily mean that our factories are ruined.

The News & Observer spoke to Meadows of Ingaa NC State Extension Plant Pathologistto answer basic questions about disease control in our vegetable gardens.

Responses have been edited for length and clarity.

How to identify a plant disease?


“This is the first step in any factory problem diagnosis. This can be tricky, but there are a few clues to help you figure this out.

“Symptoms due to abiotic diseases (those caused by non-living factors, such as nutritional deficiencies or herbicide spray drift) usually start abruptly (overnight) and show a constant pattern in the garden (i.e. each plant will show the same level of severity or an entire row of plants will show the same symptom and to the same extent).

“Plant diseases usually occur in patches in a field/garden, and individual plants can exhibit different levels of severity. Depending on the problem, sometimes plants will “outgrow” the abiotic problem if it is solved, while plants usually do not overcome their diseases – diseases usually progress in severity over time.

“Gardens also usually have more than one culture, so if multiple crops are affected at the same time, it is most likely an abiotic problem. Plant diseases tend to be culture specific or at least occur within a plant family (eg, Solanaceae vs. Cucurbitaceae). Of course there is still exceptions!”

To learn more about abiotic diseases, visit

Are plant diseases curable?


“The short answer is no, there is no cure for illnesses.

“There are pesticides available to commercial growers that say they are ‘curative’, but that just means they are systemic in the plant and can stop disease progression as long as this fungicide lasts in the plant. Once the fungicide is gone (usually one to two weeks), the disease will begin to progress again. Thus, the disease does not go away, the pesticide slows it down for a while.

“Also the environment plays an important role. For example, bacterial spot on tomatoes spreads quite quickly when we have a lot of rain, high humidity and heavy dew. However, if the weather becomes dry and there is no rain for a few weeks, the bacterial spot will literally stop and it may look like the disease has stopped or the plant is cured. Once the rains return, the disease intensifies again.

What is the best way to get information about your specific garden disease?


“The most reliable sources of information are universities. Many land grant universities have extension programs that publish brief websites that describe some of the most common diseases we see on vegetables (and other crops), including what the disease looks like, where/when it can occur, the host range and management. At NC State, we call them disease fact sheets. A gardener can use these fact sheets from any university, but I generally recommend people to look for those of their own state or neighboring states as these will have the most relevant information.

“As we all know, there are a lot misinformation on the Internet. I recommend avoid information (or at least cross-checking information) that you find from sites selling something. Many of these sites are biased and the web is full of supposed cures for plant diseases that just don’t work. You can always check with your local extension agent. In North Carolina, you can use this link to find your local agent.

For NC State Extension disease resources, including fact sheets, visit

To find your local NC State Extension agent by county, visit

Do you have any tips for not being overwhelmed by plant diseases?


“In North Carolina and in the South, in general, our hot and humid environment with frequent rainfall is ideal for pathogenic fungi and bacteriaso realize that’s part of the gardening experience in the East, unfortunately.

Disease pressure peaks later in the summerI therefore recommend that home gardeners plant early (minimizing frost damage, of course) so they can at least get some harvest before the disease completely destroys the plants. If you (as a gardener) still harvest in August and September, consider yourself pretty lucky!

How can you make sure your garden is as healthy as possible so disease is less likely to strike?


“It’s best to make sure your plants are as healthy as possible, which includes adequate fertilizer, water and sun or shade needs. Neither too much nor too little. It is also important to maintain good airflow between plants, spacing them according to recommended practices. If plants are too close together, high humidity among plants can exacerbate fungal and bacterial diseases.

“Keep in mind that even if you do all of the above, you can still see the disease, it just won’t be as bad as if you didn’t do the practices mentioned above. (Not to be too discouraging here.)

“It is also important to rotation between crop families. This means that if you plant tomatoes (nightshade family) in a bed this year, put something from another crop family (e.g. cucurbits or squash) in that space next year. This will help reduce pathogen populations that have built up in the soil.

The first step in diagnosing a plant problem is to identify its disease. It can be tricky, but there are a few clues to help you figure it out, said NC State Extension plant pathologist Inga Meadows. T. ORTEGA GAINES T.Ortega Gaines-ogaines@charlott

Should diseased plants (or parts of plants) be removed?


“Yes, but there is a limit. If you see a root disease where the whole plant is wilting, it’s a good idea to remove and discard to prevent spread. On tomatoes, you can also remove lower leaves that are starting to show the disease, but obviously there is a limit to that. I have seen people take all the leaves off and have no fruit.

“Also, avoid putting diseased plant material in the compost that will be reused because pathogens can survive in the compost. Sending it to the landfill is better!

Do fungicides control disease?


“Fungicides can be very useful to have a good harvest. The fungicides available to homeowners are limited and should be used preventatively (before illness occurs or becomes severe) and reapplied every seven to 14 days for success. You can still see the disease, but it will definitely be less than if nothing was sprayed. Use them according to the label and in the recommended doses.

“Keep in mind that it is really important to do all the cultural practices recommended to limit the disease before opting for a fungicide because they work best when used in conjunction with cultural practices. (Cultural practices are those mentioned above, such as adequate feeding, water, spacing, etc.)

Should I grow organic / use organic products?


“Organic practices are great, but keep in mind that there is many products that are not effective, even though they claim to be effective, so be careful when choosing an organic product. We evaluate a lot of fungicides for effectiveness each year (synthetic and organic), and very few organic products are to be recommended, unfortunately.

Here are Meadows’ recommendations:

neem oil may be effective for general fungal and leaf diseases.

Copper fungicides can be effective against fungal and bacterial leaf diseases.

Sulfur products are good for managing powdery mildew on cucurbits (like cucumber, squash, and pumpkin), but temperatures above 85°F can cause foliage to burn from sulfur, so be careful using them in the summer heat.

Questions about backyard gardening?

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This story was originally published June 10, 2022 11:10 a.m.

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Kimberly Cataudella (her) is a duty reporter for The News & Observer.


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