Tomato leaves turning brown

Leaf Browning In Vegetable Plants: What Is Causing Brown Leaves On Vegetables?

If you’re noticing brown spotted leaves on veggies in the garden or complete leaf browning in your vegetable plants, don’t panic. There are a number of reasons why you may see leaf browning in vegetable plants: inadequate water, too much water, overzealous fertilization, soil contamination, disease, or insect infestation. Let’s learn more about leaves turning brown on vegetable plants.

What is Causing Brown Leaves on Vegetables?

The symptom is obvious; now we need to diagnose what’s causing those brown leaves on your vegetables. If the entire garden has turned brown and died back, it’s highly unlikely the issue is disease since pathogens generally attack specific plants or families and not an entire garden.

Irrigation Causing Leaf Browning in Vegetable Plants

Too much or too little irrigation may very well be at the root of the issue and is the simplest place to start with the easiest fix. All plants need water to grow, but too much of a good thing prevents oxygen from reaching the roots, resulting in vegetables with brown leaves and ending in death.

Improve the drainage of the soil by amending with organic matter and reduce your watering if the soil seems waterlogged. Also, water early in the day at the base of the plant, not the foliage, to deter any fungal diseases, which will surely turn to brown spotted leaves on veggies.

Similarly, inefficient watering or lack thereof, equals the same result: rapid wilting followed by the leaves turning brown on the vegetable plants due to their inability to photosynthesize.

Fertilizer

The appearance of vegetables with brown leaves may also be due to over-fertilizing. which will affect the roots and stems. A buildup of salt in the soil prevents the plants from absorbing either water or nutrients and will eventually kill the plant.

Contaminated Soil

Another culprit may be soil that is contaminated, often by petroleum-based products like gas or fuel runoff, salt runoff from the road, or other chemicals. Herbicide use may cause scorched leaves, turning brown around the leaf border and at the tip. You may need to have the soil tested to determine if this is a potential cause of vegetables with brown leaves.

Insects

There are some cases where the entire garden is afflicted with insect infestation, although more like only certain plants are attacked. Spider mites are common pests which are found on the underside of the leaves. The resulting damage is brown, scorched leaves that are dry and brittle to the touch.

Root maggots, as the name suggests, feast on root systems of a variety of veggies such as:

  • Broccoli
  • Cabbage
  • Onions
  • Radishes
  • Rutabagas
  • Turnips

The adult root maggot is a fly that lays its eggs at the base of the plant where the larvae subsequently hatch and munch away on the roots. If you suspect insects may be at the root of your problem, the local agricultural office, master gardener’s association, or nursery may be able to assist with identification and a means of eradication.

Disease

Finally, leaf browning in vegetable plants may be caused by a disease, usually fungal in nature such as Alternari solani or early blight. Early blight develops when temps range between 75-85 F. (14-29 C.) and appears as concentric bull’s eye blotching on foliage, which then turns yellow.

Leaf spot diseases also cause brown spots on leaves and eventually necrotize the entire plant. Fungicide application is the best remedy for leaf spot diseases.

Are your tomato leaves turning yellow?

Whether you have cared for your tomato plant from seed or you’ve hand-picked the right transplant from the garden center, a bit of panic may set in when you spot the leaves of your tomato plants turning from green to yellow.

Especially as beginners, it’s hard to know what is normal and what isn’t. And if we find more and more leaves turning yellow, we rightly become alarmed. Still, sometimes it’s difficult to identify the problem and even harder to know what to do about it.

While yellow leaves on tomato plants can be caused by a dozen or more culprits, I’ve found these five among the most common. In this episode of the Beginner’s Garden Podcast, I discuss these five possible causes of yellow tomato leaves, along with identifying markers, prevention measures, and what to do about each of them. to the episode or read the post below for the highlights.

Transplant Shock Can Cause Leaves to Turn Yellow

When you first transplant your tomatoes into the ground, especially in the early spring when nights aren’t warm yet, tomatoes will go through a transplant adjustment period. In this week or two following transplant, you’ll notice your once-vibrant green leaves lightening in color. But, if you look at the newer leaves at the top, they are young, healthy, and growing.

What to do about it: Yellow lower leaves should be snipped off anyway (see below), so as long as you see healthy, vibrant leaves at the top of the plant, cut off the yellow leaves at the stem. They won’t benefit the plant and will likely only serve as a gateway for disease.

Transplant Shock Prevention: Some varieties of tomatoes are more susceptible than others, but waiting to plant the tomato plants until the optimum time will help to prevent transplant shock. Wait until the nighttime temperatures stay in the 50s.

Related: When to Plant What: Guide to Getting Your Crops in the Ground at the Right Time:

Early Blight: Most Common Cause of Yellow Tomato Leaves

Early blight is the culprit every year in my garden, and it’s easy to spot when you know what you’re looking for. Caused by a soil-borne fungus, early blight travels from the soil to the lower leaves. At the earliest stage of infection, these lower, older leaves will begin showing irregularly shaped yellow splotches that progress into brown spots with a yellow “halo” around them. The splotches appear almost like a target with a brown center.

As the disease progresses unchecked, these entire stem and leaves turn yellow and then brown, and finally, they shrivel up completely.

What to do about it: At the earliest sign, cut off the affected leaves. The longer the leaves remain on the plant, the more likely the fungus will spread up the plant to the healthy leaves.

Early Blight Prevention:

Keep plants spaced out well (3 feet minimum) to allow airflow between the plants. Wet, humid conditions exacerbate early blight.

Mulch heavily in the entire tomato area, creating a barrier between the soil and the tomato leaves.

As the young plants grow, cut off lower leaves completely, especially if they are touching the ground (even if they’re healthy). Leave a 12-18″ gap between the ground and the lowest sets of leaves.

When irrigating, chose a drip or soaker hose method to dispense water to the root zones of the plants (view my choices here). Aim not to let the leaves get wet, which will allow the disease to spread more easily. If you must use overhead watering, do so at the beginning of the day so the water can evaporate quickly. At the end of the season, remove all plants and destroy them; do not compost. Rotate crops next season.

(Note: proper irrigation will not only help prevent the spread of disease, but it will also prevent blossom end rot. Read more in this post: Troubleshooting Tomato Plant Problems.)

Read more about early blight on this post: Yellow Leaves at the Bottom of Your Tomato Plants?

Septoria Leaf Spot

Another fungal disease, septoria leaf spot mimics early blight in many ways. Like early blight, spots on the lower, older leaves begin yellow but then darken into brown and then to tan or gray. These spots are smaller and more numerous than those in early blight, and they take more of a circular appearance. As the disease progresses and the spots grow, they will coalesce to larger brown area. Water-soaked lesions may also appear, sometimes on the underside of the leaf. Tiny black, pimple-like spots in the center can form a secondary infection, infecting the rest of the plant. Left unchecked, the leaves turn yellow, brown, and then die.

What to do about it: Use same measures as you would for early blight.

Septoria Leaf Spot Prevention: Use the same prevention measures as you would for early blight.

Verticillium Wilt

With verticillium wilt, leaves will exhibit yellow and brown areas from the middle vein of a leaf to the edge, often in a V-shape. Plants wilt in the hot part of the day. Verticillium wilt is slow to progress and more uniform throughout the plant, but unfortunately, there is no cure and it will eventually overtake the plant. If you suspect verticillium wilt, scrape the stem at ground level, and if you see brown in the normally white vascular tissue, the infection has taken hold. Remove and destroy the plant, rotate tomatoes into a different area next year, and use seed labeled with a resistance to verticillium wilt, since the fungus can remain in the soil for many seasons.

Fusarium Wilt

Fusarium wilt normally doesn’t begin appearing until the fruit begins to mature on the plant. Lower leaves turn yellow, and sometimes this is limited to one stem or shoot, which is bright yellow and wilting. Initially the wilting will show recovery at night. The plant’s growth becomes stunted, but it’s possible if the progression is limited to one stem, some of the crop may reach maturity before the plant succumbs. If you suspect fusarium wilt, scraping the stem will reveal brown vascular tissue, and like with verticillium wilt, there is no cure. You’ll need to follow the same measures and destroy the plant, practice crop rotation, and grow resistant varieties in the future.

As I always recommend when encountering a problem with any plant, utilize your local cooperative extension service if you are in the US. The agents are always willing to help you identify problems in your garden. You can locate your closest extension service here.

Have you had any experience with any of these tomato plant conditions?

Further resources:

Verticillium Wilt — Ontario Crop IPM
Septoria Leaf Spot — University of Minnesota Extension
Septoria Leaf Spot — Dr. Sharon M. Douglas, The Connecticut Agricultural Experiment Station
Early Blight and Septoria Leaf Spot — University of Illinois Extension
Tomato Disorders: Early Blight and Septoria Leaf Spot, Karen Delahaut and Walt Stevenson, University of Wisconsin Extension
Early Blight and Septoria Leaf Spot — Cornell University Extension
Fusarium Wilt — University of Maryland Extension
Fusarium Wilt — Missouri Botanical Garden
Bacterial Wilt — Clemson Regulatory Services

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Information On Common Tomato Plant Problems

Tomatoes are often considered to be among the easiest and most popular vegetables to grow in the home garden. But, while tomatoes are easy to grow, this doesn’t mean that you won’t have tomato plant problems. Both novice and experienced gardeners may find themselves asking, “Why is my tomato plant dying?” Knowing the most common tomato growing problems will help you keep your tomato plants happy and healthy.

Tomato Plant Diseases

Perhaps the most common reason for tomato plant failure is disease. Tomato plants are susceptible to a wide variety of diseases. These include:

  • Alternaria Canker – brown depressed spots on the leaves, fruit and stems
  • Bacterial Canker – leaves wilt, turn yellow, then brown and die from the bottom up
  • Bacterial Speck – small brown dots with yellow rings on fruit and leaves
  • Bacterial Spot – wet, black spots on the leaves that eventually decompose and leave a hole
  • Cucumber Mosaic Virus – the tomato plant will be stunted and will have thin leaves
  • Early Blight – large black irregular shaped spots with yellow rings around them on the leaves
  • Fusarium Crown Rot – whole plant turns brown, starting with mature leaves – brown lines can be found on the stems
  • Fusarium Wilt – plants wilt despite proper watering
  • Gray Leaf Spot – small brown spots on leaves that rot out and leave small holes in the leaves
  • Late Blight – leaves turn pale brown and papery and the fruit develop indented spots
  • Leaf Mold – light green or yellow spots on the undersides of the leaves that eventually cause whole leaves to turn yellow
  • Powdery Mildew – leaves will be covered with a white powdery coating
  • Septoria Leaf Spot – brown and grey spots on the leaves, mostly on older leaves
  • Southern Blight – plant wilts and brown spots can be found on the stem near or at the soil line
  • Spotted Wilt – Bulls-eye type spots on the leaves and the plant will be stunted
  • Timber Rot – The tomato plants will have hollow stems and moldy spots on leaves and stems
  • Tomato Tobacco Mosaic – The plant is stunted with patchy yellow and bright green leaves
  • Verticillium Wilt – Plants wilt despite proper watering

Environmental Tomato Issues

While disease is a common reason for tomato plants dying, disease isn’t the only thing that can kill tomato plants. Environmental issues, such as a lack of water, too much water, poor soil and too little light can also cause tomato plants to fail and die.

  • Watering issues – When a tomato plant is under watered or over watered, it reacts the same way. It will develop yellow leaves and will look wilted. The best way to determine if you are under watering or over watering is to examine the soil. If it is dry, dusty and cracked, then it’s likely your tomato plants aren’t getting enough water. If, on the other hand, your tomato plants are in standing water or if the soil seems swampy, the plants may be over watered.
  • Nutrient issues – Poor soil often leads to tomato plants with stunted growth and fewer low quality fruit. Plants in poor soil are lacking in nutrients and are unable to properly grow without these.
  • Light issues – A lack of sun also can affect a tomato plant. Tomato plants need at least five hours of sun to survive. Less than this, and the plants will be stunted and eventually die.

Tomato Plant Pests

There are many garden pests that can damage or kill tomato plants. Typically, tomato pests will either attack the fruit or the leaves.

Tomato pests that attack the leaves include:

  • Aphids
  • Blister beetles
  • Cabbage loopers
  • Colorado potato bug
  • Flea beetles
  • Leafminers
  • Stink bugs
  • Thrips
  • Tomato hornworms
  • Whiteflies

Tomato pests that can damage fruit are:

  • Rodents
  • Slugs
  • Tobacco budworm
  • Tomato fruitworm
  • Tomato pinworm
  • Vegetable leafminer

Discovering what’s causing your tomato plant problems will help you to work to correct them. Remember, tomato growing problems are actually rather common. Even gardeners with years of experience can find that their tomato plants have been killed by disease or pests.

What is causing my tomato leaves to turn brown and die?

Tomatoes are susceptible to a number of leaf diseases that usually appear when fruit begins to form and become severe in late summer when conditions are favorable.
The following management practices will reduce, but probably not eliminate, the damage they do.
1. Plant disease resistant varieties. Look for letters such as VNFT on the seed packet that indicate a variety’s disease resistance.
2. Allow plenty of space between the plants to provide good air circulation so they dry off quickly after wetness.
3. Avoid overhead watering.
4. Spread mulch around the plants to keep soil from splashing onto the leaves during heavy rain.
5. Remove and dispose of dead and dying leaves.
6. Remove diseased tomato plants after the growing season. Do not compost them.
7. Do not grow tomatoes and related plants such as potatoes and peppers in the same place year after year. Practice “crop rotation.” If tomatoes are grown in containers, use fresh soil each year.
8. Apply fungicides if the above measures aren’t sufficient. Begin using them before any evidence of disease is present.
Some years conditions are more favorable for tomato diseases than others. The amount will vary whether or not you follow the recommended management practices.
After a heavy crop, the plants’ energy is mostly spent by late summer. Shorter days and cooler nights slow their growth and metabolism accelerating the decline.

Leaves are turning brown from the bottom up

by Danielle
(NH)

Q. I have two tomato plants in my garden. They grew up and out very quickly and appeared to be thriving during the beginning of the summer. The past couple weeks they have been looking worse and worse. There are lots of fruits on the plants but they take forever to ripen. I have noticed that the leaves are brittle and brown starting on the bottom, near the soil and has been working its way up. I thought maybe I was over-watering but I have since slowed my watering and they are still not looking the way I would like. I also have zucchini, pepper, onions, and cucumbers. My zucchini and cucumbers have been doing wonderfully all season but the past few days the zucchini is starting to look a little dead on the bottom as well. My peppers still are not growing. They were looking real bad for a bit but I cut back the watering and opened up the area for more sun and the leaves look better but no peppers. What is wrong with my garden? Could it be my water? I have also noticed this morning that that my hanging basket that was beautiful is looking a little yellow and crusty in the leaves as well.

A. It’s been a tough summer for gardeners and you are not alone.
Tomatoes. It’s natural as the season progresses for lower leaves to yellow and brown and even fall off. This is particularly true if you’ve had temperatures higher than normal, which creates stress in plants. Furthermore, as summer progresses, plants are working to both survive and produce enough fruit to ensure their species survival in perpetuity (that is, seeds!). If your weather is particularly hot, then ripening in tomatoes will slow.
Having said that, several diseases can impact tomatoes which produce yellowed and brown leaves. Most common are the Big Blight Three (Early Blighthref>,Late Blighthref>, and Septoria Leaf Spothref>.) Check out how how to tell them aparthref>. Tomato wilts also present themselves with yellowed or brown leaves, particularly fusarium wilthref> and verticillium wilthref>.
Blight and wilts can impact other crops in the garden, too. Organisms overwinter in the garden and present themselves particularly when conditions create stress for plants.
Peppers. These plants thrive in dry conditions. They also take much longer to produce fruit than other crops in the garden (like tomatoes.) Plus, excess heat may be inhibiting pollination. Shake the plants to encourage blossoms to pollinate … and be patient.
Good luck and happy gardening!
Your friends at Tomato Dirt

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