Blueberries with rust and leaf curl
Question from Monty:
Blueberries I’ve had for many years in pots have now developed rust, and one with leaf curl. It appears that a branch on one is dead – all brown. I have three total. Soil remains well drained. Perhaps even dry right now. What can you suggest I might try to control and get ride of the rust?
Answer from Pat:
Blueberries that have done well for many years in pots and then suffer a sudden decline are not an unusual case. People have often told me their plants flourished for years and gave great harvests, then suddenly died. Sometimes they become diseased or pest-ridden first as you relate happened to yours. In most cases this is because the plants have become shaded or they have become stressed once roots filled the pot and water no longer penetrated all parts of the root zone. Blueberry plants need full sun. They also need acid soil that is constantly moist. Gardeners sometimes don’t notice changes that have happened in their gardens as trees grew. A common occurrence is too much shade for sun-lovers after trees or shrubs grew up and shaded a spot that was in full sun some years earlier. All of a sudden a gardener can’t grow a plant that was flourishing before.
Healthy plants can fight off most problems, but rust often afflicts plants that are in too much shade. Cold damp weather could have contributed to the problem. Leaf rollers and other pests attack plants that are already stressed from other causes. So the first question to ask you is are the plants now growing in a garden that is more shaded than it used to be? If so, that is most likely at least one cause of the rust. Move the plants into more sun. Secondly, have hedges grown up or is the garden more crowded than it used to be? A lack of air circulation can also cause rust. Sometimes plants grow so much that they touch whereas they used to be apart with space between them. Try to grow the plants in a place where there is adequate air circulation and enough room so you can spread plants out to keep leaves dry though roots always need to be moist.
Regarding leaf rollers, several types of leaf rollers and leaf tiers attack blueberries. Eggs of these pests are laid by night flying moths onto the leaves or fruit. They hatch into caterpillars that roll up the leaves and feed inside. Leaf tiers tie the leaves by attaching filaments to them and these also destroy the leaf from within. These moths are often attracted to blueberries that are in a group, so crowding could contribute to this problem also. These night flyers finally found your garden and laid their eggs on your plants. Pick off the leaves that are rolled up as soon as you discover the problem and squash the caterpillars inside the rolled leaves, then discard in a closed trash can. Sometimes leaf tiers get inside berry clusters and destroy the berries. Vigilance of hand picking and squashing can get rid of them. Depending on how many leaves are affected, you have you might need to sit down next to the affected plant and just patiently clean it up this way on a regular basis so the moths don’t hatch out and lay eggs on your other plants.
Now lets discuss the climate adaptation and roots: Rabbiteye blueberries are a special type of blueberry that can be grown in Central and Southern California. This is because they are native to the southeastern parts of USA and are adapted to much warmer climates than most blueberries prefer. Unlike other blueberries they do well in our warm dry climate. This year the weather has been unusually changeable and moist and damp. Rabbiteye blueberries prefer warmth in summer to cold, moist, damp air. Spring came late and with cold nights. Rains were excellent keeping roots wet and sometimes causing root rot. Inland, cold temperatures were followed by sudden onset of extremely hot weather. These temperature extremes are not good for blueberries and can lead to stress, root rot, and disease.
Now about the roots: Root damage is the most likely cause of a branch dying. Gardeners, like you, who have succeeded in growing rabbiteyes for many years and with good harvests usually planted them in large containers filled with acid soil mix and they are watered often enough so roots stay evenly moist with good drainage. One gardener I know grows hers on a drip system that turns on every day but the water pours out the bottom of the pot. Roots are always moist, never soggy. After blueberries have been growing in the same container for many years, roots often fill the pot and eat up much of the soil mix. If this happens, you need to prune the roots and lightly prune the top too.
How to prune the roots: First, in fall prune off any dead growth and take off some of the foliage to balance the plant. Then put each pot onto its side and slide the plant out of its container. Using a sharp knife such as a serrated Japanese garden knife, begin by slicing off three or four inches of matted roots on two sides of the plant. Next, slice 2 or 3 inches of the root ball off two opposite sides of the plant. Leave the other two sides as they are now. Clean out the drainage hole and put a fresh piece of broken crockery over the drainage hole. Put three or four inches of fresh acid planting mix in the bottom of the pot to replace what you cut off. Slide the plant back into the pot. Then fill the two sides that you cut off. Use a wood dowel to push the plant mix down. Finish by covering the top with a fresh layer of acid mix. Place the plant in semi-shade for a week to allow it to recover, then put back in full sun and fertilize with acid fertilizer.
I bought a blueberry plant in full bloom growing fruit. It is the middle of May and the plant is suffering. (Leaves wilting and falling off and set growing fruit falling off) It needs to be transplanted but I’m afraid I will kill it if I transplant now. What should I do? I live in the temecula valley.
Leaves wilting means root ball is dry and has been dry for some time. After wilting, leaves will fall off if problem is not caught and plant watered adequately and in time to soak the entire root ball. When soil gets dry it often stays dry and water pours off around the root ball. (Leaves of a wilted plant can sometimes be saved by sinking the pot into a big bucket of water and letting it stay there for half an hour or a whole hour. Put a brick on the roots so they don’t float. Then lift the plant out and put it on the ground in the shade and if you caught it in time, by evening leaves will plump up again. Fruit falling off means roots are dry or damaged. Blueberries grow best in large containers filled with acid soil that is well-drained but holds moisture. Keep roots evenly moist. Don’t let them dry out and fertilize once a month. Never fertilize when roots are dry. The side of the container should be well shaded with foliage especially since roots might have been wound around and around inside the container. It is hot in Temecula. If you allow sun to hit the side of the black nursery container, those roots hitting the side of the container will be fried by the heat and damaged or killed and fruit and leaves will fall off. Same thing can happen from allowing the roots to dry out. This is undoubtedly what happened. You purchased your plant too late and probably failed to water daily as was being done in the nursery. Fall or early spring would have been a better time to buy. Then you should have planted it immediately into a larger container. Do it now, even though it’s late. If it dies buy another next fall and care for it better.
Hi Pat,
We love your books and are using the Month by Month as a book club for one of our OC Master Gardener group. We read your info on Sycamores. I can’t find a UC reference to the bagging up and not composting the leaves. Can you help me out?
I hope you are well and I always loved seeing you at our Seminars.
Jan
Thank you for reading and following my books. I wrote them because I have a deep desire to spread the truth about gardening and help people have success. The edition of my book that came out in 2000 follows UC guidelines in every respect and perhaps that is the one you are using. It gives many organic pest controls but also recommends IPM. The latest edition of my book, which was published in 2010 is totally organic and differs from UC guidelines in many respects. It is never a good idea to compost leaves or refuse that are diseased, but particularly not in the case of anthracnose. UC guidelines say the following: “Rake and dispose of fallen leaves and twigs during the growing season and in fall.” They do not tell you to bag the refuse and send it to the dump. If you have a very hot compost pile, perhaps you could kill this fungus disease, but it tends to be virulent. If you fail to kill it, you will just be spreading the fungus around in your garden. The information in my book is all based on research or my own experience during a long lifetime as a gardener. In this case, since I am blessed with a very good memory, I distinctly remember reading similar words to those I put in my book. I know the source was a bona fide one, but I cannot remember in what publication I found it. Quite likely it came from UC materials years ago. Their guidelines have changed over the years, due to weighing other needs, such as keeping dumps from filling up, for example, or preventing diseased materials from getting into community compost. Though in most cases I revere the UC system of disseminating the most scientific information on farming and gardening and I love the Master Gardeners, am very grateful for their support, and have spoken at their seminars for at least 20 years, please note I disagree with them in several instances. I do not recommend Roundup, for example, and urge gardeners to avoid its use since it gets in ground water and lasts much longer in the environment than the manufacturers admit. Also I consistently say in lectures and my books not to spray with Spinosad anywhere near flowers and never to broadcast it because it kills and sickens bees. Another example of my differing from UC guidelines is that I tell gardeners never to use products on their lawns that contain a grub killer because grub killing “Merit” or amidacloprid and similar products that kill white grubs also kill bees by the same method, which is by confusing them so they forget how to act. This, in my opinion and the opinion of many scientists in Europe, is one of the main causes of Colony Collapse Disorder (CCD). Also I do not believe in feeding roses and other flowers with products that contain systemic pesticides since these kill bees. Additionally, I along with many other people have discovered that earthworm castings kill many pests and do so safely. UC scientists have never tested this out, as far as I know.