Table of contents:
- Whitefly species
- Whitefly development cycle
- Several averaged digits
- Ways to protect crops from whitefly
- Preventive actions
- How to get rid of a whitefly?
A humid warm summer is the most favorable time for the development of homoptera proboscis insects with a delicate and beautiful name for whitefly. A delicate miniature butterfly (0.5-3.0 mm) of white color, whose wings and body are powdered with a white powdery substance, could touch people if not for its harmfulness. Whitefly appeared at first as a pest of protected ground crops (1870, England), but later occupied its niche in the open ground.
In the process of phylogenesis, whiteflies have formed more than 200 species, and have become one of the most common pests of vegetable, flower and berry-fruit crops in open and closed ground. They are permanent residents of greenhouses and apartments, houses that have indoor plants. Whiteflies are a quarantine pest. Inhabited by about 150 plant species of 53 families. They are carriers of viral, fungal and bacterial diseases. They overwinter on plant debris, under the bark of trees in the form of eggs, larvae, puparia.
Mass flight of whitefly begins in June. When you come up to a bed with eggplants, tomatoes, cucumbers, wave your hand a little, and a white cloud rises above the landing - these are whiteflies. Whitefly species have specialized in the process of development and prefer to lay eggs and spend a significant part of their life on forage host plants.
Especially common and most familiar to greenhouses and summer residents are Cabbage whitefly (Aleyrodes proletella), Tobacco whitefly (Bemisia tabaci), Greenhouse, or greenhouse whitefly (Trialeurodes vaporariorum). Strawberry whitefly (Aleurodes fragariae) and Citrus whitefly (Dialeurodes citri) are most often found on fruit and berry crops. The latter is considered a quarantine pest of citrus fruits. In Russia, it is most common on the Black Sea coast of the Caucasus.
Among vegetable and flower crops, the miniature pest most of all damages plants with loose (large-celled) tissues: tomatoes, cucumbers, zucchini, fuchsia, pelargonium, abutilon, nightshade, gloxinia and many other plants. For a successful fight against whitefly, it is necessary to know the development cycle of the pest, the most vulnerable periods of life, so as not to poison the plants with treatments once again.
Whitefly development cycle
The sizes of adult insects (adults), depending on the species, range from 0.5 to 3.0 mm. In its development, the whitefly goes through three stages - eggs, larvae and nymphs. An adult adult emerges from the nymph. It is spread by foci. One plant can contain representatives of all stages of development and adult insects, which complicates the effectiveness of pest control. In the developmental links of eggs and nymphs, pests are practically not vulnerable to dressing agents. Whitefly larvae are most active in plant damage. In their development, they go through 6 stages of maturation, of which 3 are accompanied by molts. Each larval stage of larval development lasts from 2 to 4 days. Only the first instar larva (creeper) moves actively. By the last molt, the VI instar larva (puparium) stops feeding,covers itself with a wax-like substance and passes into the nymph stage, from which the whitefly imago emerges after 6 days. The cycle is complete. The imago mates with the male 12-20 hours after departure. Mating occurs several times during the life of the imago. The duration of egg development is 9 days.
Several averaged digits
Since each species of whitefly, depending on the food host, has its own periodicity of developmental stages and, in general, the life of the pest, we present the average data characterizing its periods of greatest harm.
In a population that has settled in a separate outbreak, the bulk of it is whitefly eggs (40-50%) and larvae (up to 40%). The imago lays eggs on the underside of the leaf in the amount of 20-280 eggs, of which 80-94% survive to the adult insect. The development of adults from egg laying to larval hatching depends on the host plant and optimal temperatures. On average, females and males of different pest species can live at temperatures ranging from +18 to + 24 ° C, respectively, from 18 to 24 (and even up to 60) days and from 12 to 17 days. An increase in temperature to +24.. + 30 ° C shortens the life of an adult whitefly to 4 days.
The duration of oviposition of fertilized whitefly females lasts 18-22 days. Larva development lasts 7-15 days. From the nymph to the emergence of the imago - 10-15 days. The development of one generation is completed in about 26-28 days. Under such conditions, the number of adults in one generation can increase 30-40 times. During the growing season, 8-15 generations develop.
According to the observations of scientists, the greatest death of the pest is observed during the transition of the first instar larva to the second, and the smallest - during the laying of eggs and during the development of the nymph. But when processing plants, you must also observe the weather. If the weather is optimal, then even with a minimal number of adults, a high reproduction rate will increase (and significantly) the number of pests. This means that it will be necessary to increase the number of treatments from 4 to 6-7.
Ways to protect crops from whitefly
Separate use of certain drugs will not bring the expected effect. Comprehensive protection is needed against whitefly, including preventive and economic work with agrotechnical, including the use of plant treatment with drugs.
- During the growing season and at the end of the season, carefully remove all crop residues and weeds so that adults of whiteflies and other pests do not lay eggs on them.
- Be sure to disinfect the greenhouse and the soil in the fall.
- Perform the agrotechnical measures provided by the technology in the open field.
- During the growing season, do not overfeed the plants, especially with nitrogen fertilizers, strictly follow the irrigation regime.
- If you run organic farming, then to protect crops from whitefly, you can add the macrolophus bug and the amblyseius mite to the crops of the predatory bug, especially in greenhouses and greenhouses. They significantly reduce the whitefly population. They can be purchased at specialized retail outlets and populated according to the recommendations.
- During the growing season, it is sometimes enough to prepare a strong solution of laundry soap (not bleaching) and sprinkle the plants or rinse with a stream of cold water.
How to get rid of a whitefly?
Biological protection measures are most acceptable in personal subsidiary plots and small dachas. Biochemical preparations, developed on the basis of useful living microflora, effectively destroy whitefly without harming animals and humans.
Of the widespread and long-established biological products, it is best to use the bioinsecticide Aktofit, which destroys (except for whitefly) a fairly large list of pests. During the growing season of vegetable crops, 2 - 4 treatments are enough. From the same group, Aversectin C and Avertin-N are effective. They are especially effective at killing young whitefly larvae and other sucking pests. Recently, bicol and bitoxibacillin have become more widely used. Bioinsecticides Nemabact and Antonym-F have been created in Russia, which are the best drugs against a wide range of pests, but their release has just begun and is still on sale in limited quantities.
It should be noted that bioinsecticides begin to work at elevated temperatures and humidity. Therefore, processing is carried out at + 18 ° C and above. Before processing, it is necessary to moisten the plants or process after watering. The rain washes away the bioinsecticide solutions, so the treatments have to be repeated. The last treatment with bioinsecticides is carried out 2-3 days before harvesting. Solutions for treatments are prepared strictly according to the recommendations of the manufacturers. Increasing the concentration of the solution will not increase the processing efficiency. The use of bioinsecticides is recommended for organic farmers.
Folk remedies for whitefly
The use of decoctions from insecticide plants for whiteflies (onion husks, yarrow decoction, garlic infusion) should also be attributed to biological remedies. Plants are sprayed with decoctions from a fine spray bottle. The use of decoctions requires frequent repetition - after 2-3-4 days for a long time.
The use of chemicals when growing garden crops in open and, especially, closed ground is not recommended. In some cases, when the vegetable wedge occupies a large area, and the whitefly has epiphytotically multiplied, 1-2 treatments can be carried out at the beginning of the growing season. The last treatment is carried out no later than 20-25 days before harvesting.
Of the chemicals allowed in vegetable crops against whitefly, you can use Mospilan, Inta-Vir, Iskra-M and others. When choosing a drug, it is necessary to pay attention to the decomposition period, duration of action, hazard level and other indicators. The selected drug must be used strictly according to the instructions with all protective measures of a personal nature (gloves, gown, hat, goggles, respirator or multi-layer dressing).