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And although until recently we could say that these pests did not reach Lithuania, this summer became a turning point: the specialists of the Botanical Garden receive letters, messages, photos and videos of invasive butterflies, their caterpillars and plants destroyed almost all the days. Unfortunately, the professionals do not have comforting knowledge.
Letters from scared Kaunas residents flooded
“I’m sending you a video, what is it? For me, where I live in Aleksotas, the beeches were destroyed. I fight by all means: I destroyed some, sprayed others with Actara, but it doesn’t work. Mavrik has stopped for now, but the creature is not multiplying them yet. What to do? I see the same with my neighbors. “
“Invasive butterfly worms have already arrived in Lithuania, they will eat beech leaves in a few months if you don’t destroy them. Check and store your beech trees as only bare twigs will remain. The beech trees have already been bitten by me and everyone I know. in Aleksotas and A. Šančiai. Worms are hard to find because we didn’t notice any of them. “
These are just a few letters that have been flowing into the boxes of VMU Botanical Garden specialists lately. The beech trees of all of them were attacked and condemned to Cydalima perspectalis by the moths that were spreading due to the hot weather.
And although the natural region of distribution of these butterflies is the humid subtropics of East Asia, Japan, China, Taiwan, Korea, the Far East of Russia, India, these butterflies were introduced to Europe from the East Asian region several decades ago and now they are invasive. species. is spreading successfully, penetrating deeper and deeper into the northern regions.
Butterflies spread not only by the plants they carry, but also naturally, traveling around the wind between 5 and 10 km a year.
“What amazes the residents of Kaunas this summer has long been a very serious problem of loss of boxwood in other countries, especially in southern Europe. Officially discovered in Europe in 2006, the butterfly has already been practically caught in everywhere from Croatia, Turkey, Georgia to Germany, Sweden and Poland.
In Lithuania in 2018. B. Paulavičiūtė, an employee of the Kaunas T. Museum of Zoology that time, ”says dr. Antanina Stankevičienė.
What is it?
Greenish with bright vertical stripes and black dots. Cydalima perspectalis butterfly caterpillars grow for about a month, up to 35-50 mm. Initially, those that feed on the lower part of the plant are difficult to see until the first signs of damage become evident and the secretions of brown caterpillars hanging from the lower leaves in cobwebs. Only the central vein of the leaf and the outer part of the leaf remain after the feast of the caterpillars. Also, caterpillars can gnaw on the bark of shoots. Plants damaged in this way generally do not recover and die.
Pests that have reached the pupal stage are also difficult to detect: they are 25 to 30 mm long, first green with brown longitudinal lines and then increasingly brown. In early summer, they hatch active at night, so ugly butterflies are rarely seen in white, with a slightly purple and brown border, with wings. The length of the outstretched wings is 45 mm.
In late August, 1mm egg clusters are laid at the bottom of beech trees, and the butterflies hibernate in the cocoons of young larvae between two closely joined leaves of beech trees. In early spring, the cycle repeats, generally generating 2-3 generations of butterflies per year, and in warm areas, up to 4.
What to do?
“It is extremely mobile, so it is difficult to kill pests. As soon as the damage caused by C. perspectalis is noticed, the caterpillars must be removed and mechanically destroyed first, and most importantly, not spread near the growing plants, since this will undoubtedly propagate the butterfly itself ”, say the specialists.
If you only grow a few beech trees, harvesting caterpillars can be an effective control measure, every 2-3 days. You can try washing larger areas with a strong jet of water; it is true that caterpillars stick to leaves very tightly, so they may not be easy to shake off or spray with water.
It should be noted that insecticides are most effective in killing younger caterpillars: for example, spraying cypermethrin, synthetic insecticides containing deltamethrin very carefully inside the bush and under the leaves, when the caterpillars are most active.
“Ways to control this butterfly have been tried in various ways: entomopathogenic nematodes (Steinernema carpo-capsae) tested in the laboratory, unfortunately, without success.” As in the case of the vengeful moth that destroys our chestnuts, pheromone traps have been tried, but in the same way without much success. It has been noted that even birds do not find these caterpillars: after feeding on the old leaves at the bottom of the plant, the caterpillars also consume the toxic alkaloids accumulated there, thus becoming poisonous to the birds themselves.
Attempts were made to use these butterflies to kill Asian predatory wasps (Vespa velutina Lepeletier) in their natural range, but again the problem was that it turned out that when they were brought to southwestern France, these wasps began to kill local bees intensively. ! ”The searches are counted by dr. A. Stankevičienė. According to her, if summers – and especially night temperatures – remain so hot, C. perspectalis will spread in our country without major obstacles, destroying boxwood in all regions of Lithuania.
Advises to look for alternative plants
C. perspectalis has been observed to damage 8 species of beech, and in its natural range it damages Japanese and climbing goats, horned hollyhocks, aphids and marmosets.
And, despite all protective measures, butterflies are successfully spreading, damaging more and more valuable plants, hedges and carp. German scientists working with particular diligence on this pest warn that it is necessary to look for what would replace beech trees in vegetation.
Saulius Galvanauskas, director of the Vytautas Magnus University Botanical Garden Arboretum, says that small evergreen shrubs that could become a substitute for beech trees destroyed by butterflies could be holly, shiny honeysuckle, or slow-growing yew; It is important that the plants are resistant to frost, According to the specialist, the yew is more suitable in a shady place, yours in a sunny place, which now has the most expressive shapes, colors and textures.
