Every month, botanist Josef Gall helps readers find answers to questions about what is bothering their plants.
Hello, Canadian blueberries are presented on the Internet or in garden centers as plants that do not suffer from any pests or diseases. Last year, I found out that the blueberry, which in the previous years bore abundantly with tasty and large fruits, started to wither and turn yellow. The fruits were drying up, so I thought it was a lack of water and that’s why I increased the watering. I noticed hollows on some of the fruit and thought it was attacked by some kind of pest. I looked for an answer, but I couldn’t find anything. Blueberries had a rough year this year. After a warm pre-spring, frosts set in and the blueberries froze. To my delight, the plants regenerated without any problems and set fruit profusely, but this time the hailstorm caused minimal fruit and leaves to remain on the plants. After fertilizing, the blueberries regenerated again, but not to the same extent as the first time. Indentations appeared again on the fruits. Not after the hail – this time I found the reason – the depressions could be caused by a fungal disease that gets into the plants in the spring. Since I have not found a photo of this disease anywhere, I am contacting you to see if my assumption is correct. Thank you and have a nice day. Jaroslava Horázná, Zbiroh
In this case, the blueberry fruits are probably damaged by wasps, which were very abundant this year, or by other insects.
Clever wasp
Hello, as a subscriber I read your magazine very thoroughly and in detail. I would like to ask you a question: during a walk, we discovered an oak at the edge of the forest, whose acorns have been modified into a different shape. There are many fallen under the tree, so we picked one up. Is it cancer or some disease? Thank you for your stimulating read. Irena Hudcová, Chvalčov
Galls on oaks are not caused by a disease, but by a wasp chalice groove Andricus oakum. Its larvae live in the cup (calyx) of the acorn, where they have an abundance of food. It is they who stimulate the formation of galls, and this is to make them safer – the galls, bitter due to a lot of tannins, deter other animals from eating the acorn.
Sick vine in the greenhouse
Hello, I am writing because of the problems with the vines I have in the greenhouse. There is always a gray coating on it, the fruits are small, moldy and do not ripen. I would like to ask your opinion, where is the problem? Could it be the high temperature in the greenhouse because there are also tomatoes, peppers and cucumbers? Or something else entirely? Thank you in advance for your reply and have a nice day. Zdenka Hermanová
The gray coating causes fallen vines (Erysiphe slayer, syn. Uncinula slayer). In the spring, soon after emergence, primary infections occur. First, shoots growing from infected buds (eyes) are attacked. For treatment, it is advisable to use a sulphurous preparation at temperatures above 16 °C – Kumulus WG, Sulfurus, Thiovit Jet, which is also allowed in the ecological regime of agriculture and others. At the same time, these products are also effective against whiteflies, which are often harmful in the greenhouse. In sunny weather, treat in the evening, when the temperature drops below 25°C, to avoid burning the plants.
Why does rhododendron wither?
Hello, our rhododendron started to wither last year after twenty years. First we noticed the nibbles (apparently a leafhopper) so we applied nematodes in the spring, the nibbles are 90 percent better, but the browning, curling and dropping of the leaves is getting worse and worse. Thanks for the advice. Helena from Prague.
Beetles Libečko’s lobokonosce (Otiorhynchus ligustici L.) they nibble the edges of the leaves of rhododendrons and strawberries and many other plants. But their larvae do the most damage by nibbling on the roots and root neck of attacked plants. Larvae develop over two or three years, so applied nematodes did not have to eliminate all larvae. By scraping the soil away from the root neck of the rhododendron, you will find out how much the roots and root neck have been damaged, or if you still find any larvae – if so, dispose of them. A rhododendron with damaged roots does not have time to supply all the leaves on a mature bush with water and nutrients. Therefore, cut the bush and water it sufficiently. In addition to nematodes, spraying for beetles and watering the roots for larvae with Mospilan 20 SP with the active substance Acetamiprid is also partially effective. etc.
Tomatoes with a green hood
On tomatoes, part of the fruit remains as if unripe. I believe it is a fungus, but the plants are not attacked, they are beautifully green, with no signs of damage. I would like to know if the fruits are suitable for consumption. Thank you. Bohumil Drmla
It is most likely a disorder of genetic origin, nicknamed yellow collar or green hood. Malfunction non-ripening of the stem part of tomato fruits conditions of stress. There are more reasons that can cause it. It is most often the case insufficient or excessive lighting, temperature fluctuations, unbalanced nutrition (most often a lack of potassium or boron or an excess of nitrogen). This problem most often occurs with tomatoes grown in a greenhouse or foil plant, and especially with older varieties. New varieties of tomatoes usually do not suffer from this disorder as much. You can eat the fruit after removing the green parts.
Weird garlic
Hello, we harvested such a strange garlic this year. Can you tell us what is the cause? Thank you, Šoltys, Nový Jičín
It was most likely caused physiologically – unfavorable conditions (drought, heat) during growth.
How do aphids hibernate?
Hello, I heard somewhere that it is good to dust the ground with lime under fruit trees and bushes in autumn, and this will destroy aphids for the next season. I am asking for your opinion if this is true and if so, under which trees and small fruits it is suitable so that the lime does not harm them. Thanks for the advice. Jarmila from Hané
Aphids usually overwinter their eggs, which they lay on the shoots of trees and shrubs in autumn. So, by dusting with lime, you only fertilize the trees, and you can also do a lot of harm to some shrubs that require a more acidic substrate.
About the author
Josef Gall he has been engaged in plant medicine, as well as growing plants, since 1970, when he graduated from the University of Agriculture in Brno. He worked at the Central Agricultural Inspection and Testing Institute in the plant protection department, and is still an active member of the Czech Plant Medicine Society.
