Cabbage heart mosquito
| Cabbage heart mosquito | ||||||||||||
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| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Contarinia nasturtii | ||||||||||||
| ( Kieffer , 1888) |
The cabbage-heart mosquito ( Contarinia nasturtii ), also called cabbage-heart mosquito and cabbage- gall mosquito , is a species of gall mosquito that occurs moderately often as a pest on cabbage species. If the infestation is severe, the growth point will atrophy and there will be a significant loss of yield.
description
features
The cabbage heart mosquito is 1.5 to 2 mm long. The fly is light yellow to light brown. This fly also has swinging arches instead of the hind wings. The antennas are built like pearls on a string. The eye bridge, a connection across the crown between the eyes, is typical of this fly. The eggs are 0.3 mm long and 0.08 mm wide. They have a sausage-like curved shape. The clutches are deposited in groups of (8 to) 15 to 25 eggs. The maggots are beige with a white head and also up to 2 mm long. They have no feet and the head is not detached, but shows only a minimal head capsule. The larvae can jump in order to advance faster.
Way of life
The cabbage heart mosquito loves a more humid microclimate. Therefore, the hatching of the mosquito can be prevented or delayed by dry weather conditions. Temperatures below 15 ° C will render the doll inactive. Cabbage heart midges prefer an optimal temperature of 22 ° C. The mosquitoes fly into the fields from May to August, mate and the males die immediately afterwards. The adults do not consume any further food after hatching. Even the females do not live long after oviposition. At a temperature of 20 ° C, the adult animals are four to five days old. A female can lay up to 200 eggs, which corresponds to 8 to 25 clutches. The optimal temperature range for laying eggs is between 16 and 26 ° C. From this it follows that the first flight begins during the first warm period in May with optimal temperatures. Eggs are deposited at the growth point in the heart of the plant and at the base of the petiole. A part is also placed on leaf surfaces. The eggs have no external structure and are smooth. The clutches consist of groups of sometimes only eight, mostly 15 to 25 eggs. Many white to yellow maggots hatch from the clutch. Depending on the temperature, four to ten days pass between egg laying and hatching of the maggot. When they have hatched on the leaf surfaces, they work their way to the growth point. The larvae join in groups. By eating and sucking on the upper side of the leaf stalks and in the heart of the plant, they also excrete toxins with the saliva for food intake. The saliva dissolves the cuticle and upper cell layers, making it easier to eat. At a larger stage, around 10 to 12 days after hatching, the maggots crawl into the ground towards the roots, where they pupate at a depth of around 5 cm. If the larva is already in the ground, but the microclimate is hot and dry, it will not pupate. The cabbage heart mosquito hatches about two weeks after pupation. It forms the second generation, which begins with the flight in June to July. This development cycle repeats itself again for a third generation, which then damages in August. The second and third generation flights can sometimes overlap in time. In 2001, five generations could be counted in the Vorderpfalz region despite the overlap of the individual generations. After all, the maggot hibernates in the ground and the mosquito hatches in the spring of the following year. However, the maggot does not pupate until spring after it has overwintered in an earth cocoon.
Meaning and occurrence
The pest is naturally present and therefore cannot really be introduced. The cabbage heart mosquito occurs mainly in the damp Alpine foothills. The pest particularly looks for cauliflower and broccoli , as well as head cabbage, Brussels sprouts and ground kohlrabi as host plants. But it also occurs on wild herbs of the cruciferous family. In recent years, the pressure of infestation has increased due to higher annual average temperatures.
Enemies
Dancing flies of the genus Platypalpus and small spiders are known as naturally occurring enemies . They prick the maggots and suck them out.
Plant damage
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Symptoms
As the larvae eat and suckle, cork forms on the young plant, causing deformations. Food is absorbed on the upper side of the leaf stalks and in the heart of the plant, where toxins are excreted with saliva, which attack the cuticle, epidermis and uppermost cell layers of the plant and thus liquefy them. This hinders the growth of the leaf stalks and the leaf heart. This means that the undamaged side of the stem continues to grow while the other remains. This leads to twisted growth of the leaves and the so-called torsion with spiral-shaped leaves, in cauliflower to twisted growth of the tip of the shoot and flower. If the plant is attacked at an early stage of development, the growth point can wither completely. There is a feeling of jamming or heartlessness. In individual cases there is also a multitude of heads. Secondarily, bacteria ( Erwinia ssp., Xanthomonas campestris or Pseudomonas ssp.) Can penetrate through the injuries , which then lead to heart or stem rot. If the plants are not attacked until later during the bloom formation and flowering, the cabbage heart mosquito causes compressed flowering shoots that are branched like tufts. With broccoli, the missing heart leads to increased side shoots with many small individual flowers. In this type of cabbage, damage is visible from the 4-leaf stage to the formation of flowers. This makes the flower umbrella misshapen and bumps or depressions can form. The midsummer generation (2nd generation, in June) is the most damaging because, on the one hand, optimal temperature conditions prevail and, on the other hand, there are usually young plants as hosts. If larger areas are grown next to each other on several planting dates, the existing pests are distributed over the entire area, which speaks against edge infestation.
Countermeasures
Crop planning and management: If no host plants are grown for two years , the pest will almost completely disappear. In this context, the term local pest is also used, which only damages in the closer, optimally suitable environment. Multiple cultivation of cabbage species on the same area promotes the pest, as does insufficient field hygiene.
Choice of location: Since the mosquitoes are very small and can be carried away by the wind, they prefer less windy locations. This can be taken into account when choosing the field for cultivation. The cabbage heart mosquito is almost impossible to find in eastern Austria due to drought and high temperatures.
Mechanical: The pest can be repelled with fine-meshed insect nets. They are placed over the culture and the edges of the net are weighted down so that no pests can slip through below. Depending on the season, insect nets result in higher temperatures and higher humidity , which promote fungal and bacterial diseases in the culture and can lead to physiological heat damage in summer.
Control and prognosis: With cauliflower , precise control is necessary, especially at an early stage of development, because this is where the greatest damage can occur. For this purpose, yellow traps are set up in the stock and adhering cabbage heart midges are counted. The yellow traps are yellow glued plastic boards or bowls colored yellow on the inside, filled with water and a little washing-up liquid.
Chemical treatment: Since the presence and flight time of the cabbage heart mosquito lasts only a few days, very precise control is a prerequisite for the success of a chemical treatment. Otherwise the mosquitoes will not really be hit and the treatment will be unsuccessful. It is also important to treat the heart of the plant because mosquitoes and larvae are there, but depending on the size of the plant, they are shielded by foliage. The treatment is most sensible if the inflow is to be expected in the most sensitive development stage of the respective culture. In seed production, treatment takes place before the flower fully develops. Since the adult animal takes no more food, are treating agents that act only as ingested and Sauggift or against Imagines useless. Usually 1–3 targeted treatments are necessary. Active ingredients from the group of pyrethroids and phosphoric acid esters are used . It is important to work with large amounts of water and to add wetting agents because of the pronounced wax layer on the cabbage plants . 100% treatment success is not possible.
swell
Individual evidence
- ↑ a b c d e A. Kahrer, M. Gross: Vegetable pests - recognition, way of life, control. 1st edition. AV-Druck, Vienna 2002, ISBN 3-7040-1569-5 , pp. 24-26.
- ↑ a b c d e f A. Gemmar, I. Koch: Occurrence of the cabbage heart mosquito on broccoli in the Vorderpfalz. In: vegetables. No. 3, 2002, pp. 12-13.
- ↑ P. Appelman: Koolgalmug komt altijd na 20 mei. In: Groenten & Fruit. Week 22, 2005, p. 47.
- ↑ A. Leroy: LES CHOUX - choux pommés, choux-fleurs, choux de bruxelles, choux-raves. Librairie Hachette, 1943, pp. 82-83.
- ↑ a b c d A. P. Everaarts, S. Zwanepol: teelt van BROCCOLI. In: teelthandleiding. No. 54, Proefstation voor de Akkerbouw en de Groenteteelt in de Vollegrond Lelystad, drukkerij Belser, Lelystad April 1993, pp. 53-54.
- ↑ CP de Moel, H. Bosch, S. Zwanepol: teelt van BLOEMKOOL. In: teelthandleiding. No. 51, Proefstation voor de Akkerbouw en de Groenteteelt in de Vollegrond Lelystad, drukkerij Belser, Lelystad April 1993, p. 83.
- ↑ a b Anonymous: Aanpak koolgalmug in broccoli onderzocht. In: Groenten & Fruit. Week 5, 2008, p. 28.
- ^ R. Verdonk: Broccolitelers test Schots insectengaas. In: Groenten & Fruit. Week 15, 2008, p. 30.
- ↑ R. Verdonk: wapen tegen mogelijk koolgalmuk in aantocht. In: Groenten & Fruit. Week 29, 2008, p. 26.
- ^ A. Pollini: La difesa delle piante da orto - sintomi, diagnosi e terapia , 4th edition. Edagricole, Milano 2008, ISBN 978-88-506-5296-9 , p. 117.
literature
- G. Crüger among others: Plant protection in vegetable growing. 4th edition. Ulmer Verlag, Stuttgart 2002, ISBN 3-8001-3191-9 , pp. 59-62. (Lifestyle, symptoms, countermeasures)
- R. Fritzsche, R. Keilbach, H. Thiele: The plant, storage and material pests of Central Europe with references to countermeasures. Gustav Fischer Verlag, Jena 1994, ISBN 3-334-60531-0 , p. 301. (Symptoms, countermeasures)