The biggest plant protection challenge of this year is the spread of phytoplasma of grape yellows, and although it is "still" rare in home gardens, we would like to give our readers an idea of the disease.
What is phytoplasma?
Phytoplasma is the name of a genus of bacteria. They have in common that they are viable only in the tissues of host plants and in a single living organism that transmits them from one plant to another. These vectors are called vectors. Therefore, we cannot transfer them from one plant to another, for example, with pruning shears. They have no cell wall, only a 3-layer cell membrane to protect them.
The grapes golden jaundice phytoplasma
It is named after its food plant (grapes) and the characteristic symptom it causes (jaundice). It was first detected in Hungary in 2013 on the outskirts of the town of Lenti in Zala County. Now the pathogen is confirmed in 13 counties and is spreading rapidly. The vector animal is the American grape vine, which was first found in Hungary in 2006 and is now widespread everywhere. In addition to grapes, willows, hazelnuts, honeysuckle and palmetto can also be host plants for the disease. However, it only causes economic damage to grapes. For this reason, it is advisable to plant the vines at a distance from these species and to weed and kill the wild-growing holly and hollyhocks.
The American grape berry
It produces one generation a year. The eggs are laid from August to October by the imagoists, either singly or in groups, under the fleshy bark of the vine where they overwinter. The larvae take 7 to 8 weeks to develop, from mid-May to mid-July, once the warmer weather arrives. The larvae usually remain on the plant where they hatched from the eggs and suckle on the lower, shady leaf bracts. The imlarvae pupate from early July to late September and live and reproduce for about a month.
Why is phytoplasma dangerous?
- the infection can reduce vine yields by 20-50 %
- in a short time, up to 80-100 % of vines can be infected with phytoplasma, and susceptible varieties (e.g. Olaszrizling) can die within a few years
- there is currently no suitable pesticide treatment available to control the disease and it is incurable
Symptoms
The disease has many symptoms, such as shortening of the spacing, rubbery texture of the shoots, uneven russeting or browning and shrivelling of the berries. But the most easily noticeable of all is the triangular leaf drift towards the backhand from mid-summer. These leaves are also harder to the touch than usual. Then the subsequent leaf colouring, which is yellow on white berry varieties and red on blue berry varieties. In weaker infections, only the veins of white berry varieties start to yellow.
The symptoms can easily be confused with another, less common phytoplasma (Ca. Phytoplamsa solani), which is also incurable. The right thing to do is to pull out and burn the symptomatic vines to prevent further infestation.
How can we protect ourselves?
- Destruction of other host plants
- Only buy propagating material from a safe source
- Vector animal control
- Pulling out infected plants
- The American grape berry beetle can be effectively controlled with conventional insecticides.
Chemical-free:
- Oils and oil-containing preparations (sunflower, orange, etc.)
- Insect repellent/repellent with simple materials (Softguard)
- Plant-derived insecticides (neem oil, natural pyrethroids)
- With yellow sticky tabs
- By destroying pruning waste
To protect yourself, combine different methods, the timing of which can be helped by the diagram below.
Source: Nébih (link)
💚 SoftGuard two of its active ingredients are chitosan and the enzyme chitinase. Chitosan, as a chitin derivative, scares the plant a little before the real problem is present, and the plant turbocharges its own immune system. The enzyme chitinase, on the other hand, has a chitin-degrading effect, which can have a contact effect on the more sensitive organisms with softer outer coat (larval stage) and can be used as a repellent on adults. Use is recommended in the early period May-July, repeated every 3 weeks.
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