“Lots of my tomato plants have curling upward leaves, and in most cases only edge damage. Why?” Questions from James of Greenville, South Carolina
Answer: There is a Tomato Yellow Leaf Curl Virus, but your plant lacks several of the symptoms, including stunting, yellowing, and eventual leaf browning. Tomato plants more commonly experience physiological leaf curl when subjected to various environmental stresses. In this case, I believe yours is caused by environmental stress. Here are four possible sources of stress.
Environmental Tomato Leaf Curl Causes
Too little or too much water — Vines fail to grow as well when water is lacking, and they develop root rot when there is too much water. Either can cause leaf curl. Regular, even watering will yield the best results.
High heat — Temperatures over 85 degrees F will cause most tomato plants stress and sometimes leaf curl. Some tomatoes are more heat-tolerant. Two of the best heat-tolerant varieties include the large, red-fruited ‘Heatmaster‘, which can take the high heat of the South, and disease and heat-resistant ‘Heatwave II‘, which bears deep red tomatoes with good flavor.
Wind stress — High winds cause rapid water loss from the leaves and stresses vines. Leaf curl can result.
Herbicide damage – Glyphosate herbicide damage is most common. It can cause this type of leaf appearance if a small amount reached your tomatoes from a downwind application.
“I have phlox growing in a big container. The bottom leaves are looking mottled/veiny. I have fed them and also added iron, but it doesn’t seem to be improving. Is there something else it needs?” Shawn from Kenosha, Wisconsin
Answer: Tall phlox (Phlox paniculata) varieties are prone to a series of diseases and foliage disorders, but yours sounds like it is physiological leaf blight of Phlox. It is a physical disorder caused by a water imbalance in the plant that can occur in some tall phlox varieties. Water circulation goes haywire–causing water to bypass the older leaves and only supply water to the new shoots. Here are the symptoms and solutions for this disorder:
Physiological Leaf Blight of Phlox Symptoms
Mature clumps are most often affected.
Lower leaves become mottled with prominent green veins before they eventually shrivel and die.
New growth is not impacted.
Physiological Leaf Blight of Phlox Solutions
Cut plants back at the end of the growing season, yearly.
Mulch plants to conserve water.
Water a little bit extra–though this only works in mild cases. Sometimes the circulatory disorder simply disables older leaves from accessing water.
“I have a St.Theresa grapevine that has grown and produced very well. After being devastated by Japanese beetles last year, it developed several distorted leaves. Is it possible the Japanese beetles gave it some virus or disease? I cut it way back. Now, this spring, it has been making a comeback. But I noticed yesterday that some of the leaves at the ends of the new growth look distorted and discolored again. They look like the pictures of Eutypa Dieback. Help! What do I do?” Sharon of Colorado
Answer: Japanese Beetles (Popillia japonica) have been reported to vector some bean viruses, but there is no report or research to support that they spread any diseases of grape (Vitis vinifera). What is more likely is that your vines were weakened by the damage, left more prone to infection, and they obtained a disease. Other grape pests, such as mites, also spread grape diseases and they could have been the vestors. Either way, there are several grape diseases that can cause leaf distortion and discoloration. Here are some possible foliar grape diseases along with identification tips and management suggestions.
Grape Foliar Diseases That Cause Distortion
Grape Anthracnose (Elsinoe ampelina, fungal) causes symptoms on both leaves and fruit. Foliage will appear spotted and have brown lesions that cause leaves to curl. The grapes also develop dark lesions. Apply a Bordeaux mixture spray or Liquid Copper Fungicide to infected vines when they are dormant.
Eutypa dieback (Eutypa lata, fungal disease): Leaves can appear stunted, curled, and cupped. It is easily identified by cutting a stem: infected wood will have a wedge of darker, discolored wood against healthy, lighter wood. It infects older vines that are over five years of age. There is no known cure, so infected vines must be removed.
Getting outside help is my ultimate recommendation. The best way to firmly identify your grape disease is to send a sample to your local extension agent and have it tested in a lab. (Please click here to search for your local extension agent!) Definitive results are necessary because you do not want to destroy your grape if it has a curable disease.
“I have a number of pine trees in my yard. Last year I had a number of trees that dropped new growth, this happened in the fall and winter. This year a larger number of the trees dropped the new growth. It looked like a green carpet. under the trees. The weather was dry warm and the winter was colder than usual. This year was quite warm and the winter was warmer than usual, stayed in the 20deg. Also, we had heavy snow. Also higher wind both years. Is there a problem with the weather or something else? The new candles are falling. All the candles are falling, it looks like a carpet. They are falling in the fall and winter. I’m really not sure what kind of pine they are. The pines did drop some needles in 2019, too.” Question from Raymond of Holt, Michigan
Answer: If the fresh, new candles on your pines are falling to the ground green, then it is likely that insect pests are at work, though some environmental conditions can also cause needle drop. I will cover a few possible answers for you, but without knowing what species of pines you have, and without seeing images of the damage, I cannot provide a definitive answer. I recommend that you follow up with your local extension agent at Michigan State University. Extension agents are paid to help state residents with garden and landscape problems. Yours sounds serious! (Click here to see your local agents.)
“My raised bed gardens were a disaster this year! Mildew, cabbage worms, rodents – even though I thought I had great organic soil mix and high enough barriers. What can I do this fall to get a great start next spring?” Question from Glenda of Sewell, New Jersey
Answer: I am sorry to hear that your vegetable garden was a downer this year. Different pests and diseases need to be dealt with in different ways. Here are some recommendations and resources.
Ways to Ward Off Vegetable Garden Pests and Disease
Clean up. The best way to ward off pests and diseases is to remove all plant material from your vegetable garden in fall and do the same in early spring when winter weeds abound. It removes the overwintering eggs of some pests as well as plant-borne diseases.
Plan for pests: If your cabbages have had cabbage worms in the past, expect the worms to return. Apply pre-emptive applications of safe, OMRI Listed BT spray to stop them in their tracks. By learning the life cycles of different pests that have plagued your garden in the past, you can plan precise strikes with the correct pesticides.
Give your plants a good head start. Choose (or raise) the healthiest plants you can. Large, robust seedlings have a greater chance of resisting pests and diseases and producing high yields. If growing plants from seed, be sure to give your seedlings plenty of light and room to develop stout, dense growth, and ample root systems. (Click here for seed-starting tips.)
I hope these tips help. You may also want to watch the video about overcoming powdery mildew below.
“What is best to use to be on the offensive and keep pests from coming into your garden?” Question from Marilyn of Roseburg, Oregon
Answer: You cannot keep pests from visiting, especially if you are growing their favorite foods. But, cleanliness, monitoring, and planting robust pest-resistant varieties are three excellent tools for keeping pests at bay. Planning ahead for potential pests is another tactic. Let me flesh out these tips a bit more.
Give Good Plants a Good Head Start
Stressed plants emit hormones that attract potential pests, so keeping plants happy and healthy is important. When choosing vegetable starts at your local nursery, select disease and pest-resistant varieties, pick large plants with no leaf damage, and avoid highly root-bound plants. (Bound roots have a dense, interwoven network of roots with little potting mix. Gently lift plants from their pots to see the roots.) Bound root systems must be cut and separated at planting time, which puts undue stress on transplants.
Choose (or raise) the healthiest plants you can. Large, robust seedlings have a greater chance of resisting pests and diseases and producing high yields. If growing plants from seed, be sure to give your seedlings plenty of light and room to develop stout, dense growth, and ample root systems. Planting one seedling per pot will help avoid competition. Fertilize starts lightly, so they are as strong at planting time. (Click here for seed starting tips.)
Keep Plants and Beds Clean
A clean, weed-free garden with open spaces between plants yields better fruit by increasing light exposure and airflow. Under clean, open conditions, pests and diseases are slower to take hold and easier to manage. Walkways covered with straw, leaf mulch, or compost also make is nicer and easier to walk through the garden and care for plants in all weather.
Keep plants clean! Bushy veggies, such as tomatoes, peppers, and eggplant, are especially important to clean and prune to minimize the spread of disease and pests. (Click here to learn how to prune tomatoes.) Remove dying, diseased, or infested leaves and stems or any unwieldy branches that inhibit airflow and light where it needs to reach. When pruning, clean your pruners from one plant to the next by dipping them in a 10% bleach solution to reduce the chances of any cross-contamination of potential diseases. At the end of the season, remove all garden litter and plant material from the garden soil that may harbor overwintering pests and diseases.
Plan For Pests You’ve Experienced Before
If your cabbages have had cabbage loopers or your petunias have had budworms in the past, expect them to return. Apply pre-emptive applications of OMRI Listed BT to stop them in their tracks. By learning the life cycles of different pests that have plagued your garden in the past, you can plan precise strikes with the correct pesticides. (Reach out to the Oregon State Extension Service for more information and to take advantage of their many online resources for Oregon vegetable gardeners.)
“I have many azalea bushes in my yard, and this year, I had three suddenly die off. I couldn’t detect any pests or that type of issue. They were around a tree, and all four lost their leaves very quickly. One has sprouted green. One seems quite dead, and the other two are still bendable and not dead, but have no leaves. Any thoughts on what caused this? Also, do you feel the others that are bendable may come back?” Question from Mary of Longwood, Florida
Answer: There are several fungal diseases that can cause stem dieback and/or sudden death in azaleas. All become more pronounced when there is excess moisture, humidity, and the soil is not sharply drained. Here are the top three possibilities.
Azaleas Diseases that Cause Sudden Death
Phytophthora Root Rot (Phytophthora cinnamomi) is a common, fast-acting, deadly disease of azaleas, and excess soil moisture and warmth encourage its growth and spread. Some infected plants will wilt and die very quickly. Others will grow slowly and may have poor-looking living branches, but infected plants typically succumb to death pretty quickly. To identify this disease, look for discolored, reddish-brown roots that are dead or dying. Badly infected plants will show the same discoloration on the lower stems. Remove all infected shrubs and dispose of them away from your garden. Sadly, this disease remains in the soil, so consider raising the soil in your beds to encourage better drainage, and plant something different in the spots. (Click here for good information about the best Florida landscape plants.)
Phytophthora Dieback (Phytophthora cactorum) is the most common azalea disease that causes dieback. It is also a disease caused by poor soil drainage. The first symptom is wilting with leaves that curve inward. One difference from root rot is that the roots look blackened and pull up easily. The stem will often show brown discoloration at the base near the soil surface. Treat as you would for Phytophthora root rot.
Rhizoctonia Root Rot (Rhizoctonia solani) is a deadly disease that behaves like the others, but the plants exhibit severe brown and black spots on the leaves, so I don’t think that this is the disease that took your azaleas.
When removing any diseased plant material, rake away and remove any dead leaf or stem material that may be contaminated with disease-causing spores. When pruning your surviving azaleas, avoid cross-contamination by cleaning your pruners in a 10% bleach solution when making cuts from one plant to another. Adding additional topsoil and amending beds and new planting areas with fertile organics, like Black Gold Canadian Sphagnum Peat Moss, will help any future azaleas that you plant.
Azaleas properly planted in well-drained soil need regular water. One other less likely option is that your shrubs dried up due to lack of water. If this could be the cause, I suggest laying drip hose around the remaining azaleas, applying mulch, and irrigating the shrubs once or twice weekly in the absence of drenching rain.
“I had a pear tree with pears and then before they were ready, bam, no pears. They all fell to the ground. How can I get them to stay on the tree?” Question from Stephanie of Tylertown, Mississippi
Answer: What a disappointment. There are lots of factors at play when it comes to nurturing a fruit tree to production. Let me simply cover what you can do to keep your pear trees happy, and what factors can potentially lead to fruit drop (information derived from the Pear Production and Handling Manual by Elizabeth J. Mitcham, Rachel B. Elkins (2007)). You can troubleshoot from there.
What Pear Trees Need to Produce Fruit
Fertile, well-drained soil
Mild spring weather and good pollination
Proper fertilization with a balanced fertilizer, such as 10-10-10 (follow the manufacturer’s directions)
Full sun that penetrates into the tree branches
Balanced crop load (thinning small fruits on loaded branches can encourage fruit set and improve quality.)
Causes for Premature Fruit Drop in Pear Trees
Temperatures that are too hot (85 degrees F and up) or too cool (55 degrees F or lower)
High winds and low humidity
Leaf loss due to pests and disease
Excessively wet or dry soils
Heavy crop load
If your trees are missing anything in the “Need” list, or if they experienced any of the negative conditions in the “Premature Fruit Drop” list, the composite caused your trees to lose this year’s fruit. Hopefully, this knowledge will give you what you need to help your trees produce lots of good fruit next year.
“I’m having trouble identifying the disease(s) that is affecting my ‘Black Krim’ tomato plant (and now may have possibly spread to the ‘Rutgers’). In late June I noticed significant leaf curl of some vines of the ‘Black Krim’. June was a dry month, so I thought it might be physiological, but watering did not seem to help. By early July, rains had returned and the leaf curl did not go away. I then started seeing healthy lower leaves turning grey-black in just days, often starting at the outside edge of the leaves. Most recently, however, I’ve starting seeing leaves covered in black spots with possibly light-grey centers (these are leaves 18-24” above ground). Petioles have similar elongated grey/black spots and some fruit stems (that produced no fruit) have turned completely black. Some leaf lesions are larger and could be the small spots merging. The main stem is not solid green and shows some grey-black coloration. There seems to be no correlation between the vines that exhibit wilt and the vines that have spots. I removed the wilted vines. Some had small dark markings on the interior of the stem while some looked healthy. So far, the fruit, which is still green, has not shown any spotting or discoloration.
The leaves do not turn yellow and brown, like you see with alternaria and septoria. Plus, it this just doesn’t look like the normal problems I get on my tomato plants every year. I’m thinking Stemphyllium or possibly TSWV (or both?), but neither seems to fit those symptoms entirely. I’ve looked at the lesions under a macroscope and no fruiting bodies of fungi are apparent. Plus, the lesions don’t have any mold-like fuzziness. The scattered small lesions and the wilting point towards TSWV, but no spotting/discoloration of the fruit is apparent (even on infected stems) and the leaf lesions don’t seem to show circular rings.
I’ve been using B. subtillus spray since transplanting, and liquid copper sulfate spray more recently. Neither seems to be having much effect. This plant was also treated with Trichoderma harzianum strain T-22 to prevent Fusarium wilt (a problem I’ve had in previous years). I realize that plants don’t all exhibit the same symptoms to the same diseases every time. It’s also possible that both diseases are at work here. Any thoughts you have here would be greatly appreciated.” Question from S Saving of Kansas City, Missouri.
Answer: Nothing is worse than experiencing debilitating tomato diseases when all a gardener wants is a successful crop. Unless a gardener plants the most disease-resistant tomato hybrids and has the most aerated raised beds and dry weather, diseases are to be anticipated–especially those of the fungal and bacterial flavor. You’re asking about at least two at once, so I will piece away at your question in an orderly fashion, starting with the photos that you shared of leaves and stems showing signs of black spotting and sootiness.
Black Spots on Tomato Leaves
When black spots like these do not cause leaves to turn yellow and die (or senesce) it usually indicates a surface mold rather than a systemic one. Your spots do not appear to be caused by grey leaf spot of tomato (Stemphylium spp.) or tomato spotted wilt virus (TSWV). Bacterial speck was another pathogen that I considered, but the small, black spots caused by this disease should have a yellow halo. The specks also do not tend to form clusters on leaves like yours.
It looks more like a light infection of sooty mold or related surface fungi. Sooty mold tends to take hold in the presence of sucking insects and the honeydew they produce. Have you observed any aphids, leafhoppers, whiteflies, mites, or the like, on your tomatoes? Even a small population can encourage sooty mold. Moreover, the fruiting bodies can be difficult to see with so little of the disease on leaves, even under a macroscope. Spraying and dry weather conditions will also discourage the development of fruiting bodies and mold spread.
Sooty mold is easily treated. Mix one teaspoon of gentle detergent to 1 gallon of warm water. Dip a clean cloth or sponge into the mixture and wipe down infected leaves and stems. The black mold should come off. Let me know if this is what you observe.
Tomato Leaf Curl
Without seeing a photo, it is difficult to determine what could have caused the significant leaf curl, wilt, and death on your tomatoes. It is certainly not tomato yellow leaf curl virus (TYLCV) because this disease causes leaves to turn yellow and contort over a longer period of time. Herbicide damage and dramatic temperature changes can cause leaf curling and fast necrosis. Herbicide damage is the most common cause. It can appear on old or new growth, depending on what tissues came in contact with an herbicide (click here to see an image of glyphosate drift on tomato.) Broad mites (Polyphagotarsonemus latus) are sucking insects that can cause leaf curl and death of tomato foliage when populations are high. The sucking insects also create honeydew, which can encourage sooty mold.
To determine whether mites are present, do the white paper test. Take a clean piece of white paper, hold it beneath the leaves, then tap the leaves onto the paper. If you have mites, lots of tiny specs will fall, and eventually, they will start crawling around. These are spider mites. Spraying the tops and bottoms of leaves with insecticidal soap and wiping them down will remove spider mites quickly. Multiple applications will be required.
Disease Resistant Tomatoes
Just for future reference, here are some tasty tomatoes with excellent disease resistance. They may not have the allure of unique heirlooms like ‘Black Krim’, but they are tough and tasty.
‘Galahad’ (F3, GLS, LB, N, TSWV): The new, 2020 All-America Selections Winner ‘Galahad’ is a big, red, slicing tomato with excellent flavor that resists five diseases!
‘Granadero’ (F2, PM, TMV, V, N, TSWV): Sauce tomato lovers should try this super disease-resistant paste tomato with uniform, red, well-flavored fruits. It is also an AAS award winner.
‘Mountain Merit‘ (F3, LB, N, TSWV, V): Lots of large, red tomatoes with good, sweet flavor are produced on this compact bush tomato.
‘Toronjina’ (F2, LM, TMV): Highly disease-resistant plants produce lots of sweet and tart, orange cherry tomatoes on shorter indeterminate vines.
‘Sakura‘ (F2, LM, TMV, N): Red cherry tomatoes are produced early and in abundance on this long-vined, highly disease-resistant tomato.
Please follow up! I would like to know if any of these potential assessments are correct. For a more definitive analysis, send some of your diseased leaves to your local extension agent. (Click here to learn more.)
“Most of the leaves on my verbena have become very pale. Not yellow, just faded looking. The plant is still blooming, but the foliage doesn’t look healthy. Any thoughts on what’s going on?” Carlene of Conroe, Texas
Answer: Pale leaves are often a sign of stress, whether it be stress caused by excess heat, excess water, too little water, poor soil, a nutrient imbalance, or some other malady. Yours appear to be chloritic, but the discoloration is white and almost speckly, which is most likely spider mite damage. There also appears to be additional spotting. It is very challenging to provide a definitive diagnosis from a photo, so let me start with what Verbenas need for good growth and follow up with some additional suggestions for the possibility of mites.
Tips for Growing Verbena Successfully
Verbenas grow best in full to partial sun, and even though they are tolerant of hot weather, they should be provided partial sun during the hottest time of the day down in Texas. Plant them in average to fertile soil with excellent drainage. Once they are established, they will tolerate drought, but regular water makes plants happier. If they are in containers, water them daily and make sure the pots drain freely from the bottom. Fertilizer is recommended to keep them blooming all summer long. I recommend feeding them with Proven Winners Premium Continuous Release Plant Food because it is formulated for flowers, and you won’t need to feed weekly. If they become a little overgrown, consider cutting the old stems back to encourage new branches and flowers.
Identifying and Managing Spider Mites
These are tiny plant pests, and once you notice their damage, they are numerous and have already become a large problem. You will notice the damage when the tops of leaves look like they have little white spots across them. These are dead leaf cells that the mites have sucked dry. You might also see little webs on the leaves and tender stems of infected plants.
To see if you have mites, take a clean piece of white paper, hold it beneath the leaves, then tap the leaves onto the paper. If you have mites, lots of tiny specs will fall, and eventually, they will start crawling around. These are spider mites!
To manage them, remove the worst of the damaged leaves if you can. Then spray, wash, and wipe the remaining stems and leaves thoroughly. For potted plants, remove the top inch of potting soil and replace it with fresh. (We recommend using Black Gold All Purpose Potting Mix.) It also helps to wipe the container down, in case any mites have strayed. Finally, spray the plants with insecticidal soap or Neem oil (especially underneath the leaves). Continue to do the tap test and wipe and spray leaves as needed. In time you will overcome your spider mite problem.