Whitefly and Pest Control
Wet, warm summers are the most favorable time for the development of homoptera proboscis insects with a delicate and beautiful name for whiteflies. A delicate miniature butterfly (0.5-3.0 mm) of a white color, whose wings and body is dusted with a white powdery substance, could touch people, if not for its harmfulness. Whitefly first appeared as a pest of protected ground crops (1870, England), but later occupied its niche in the open ground.
Whiteflies in the course of phylogenesis formed more than 200 species, and became one of the most common pests of vegetable, flower and berry-fruit crops of open and closed ground. They are permanent residents of greenhouses and apartments, houses in which there are indoor plants. Whiteflies are quarantined pests. About 150 plant species of 53 families inhabit. They are carriers of viral, fungal and bacterial diseases. They hibernate on plant debris, under the bark of trees in the form of eggs, larvae, puparia.
Types of Whiteflies
In June, a massive flight of whiteflies begins. When you approach a bed with eggplant, tomatoes, cucumbers, you wave your hand a little, and a white cloud rises above the planting - these are whiteflies. Whitefly species specialized in the development process and prefer to lay eggs and spend a significant part of their life on host fodder plants.
Especially common and most familiar to greenhouses and summer residents are Cabbage whiteflies (Aleyrodes proletella) Tobacco Whitefly (Bemisia tabaci), Greenhouse, or greenhouse, whitefly (Trialeurodes vaporariorum) Strawberry whitefly is the most commonly inhabited fruit and berry plant (Aleurodes fragariae) and citrus whitefly (Dialeurodes citri) The latter is considered a quarantine pest of citrus fruits. In Russia, it is most common on the Black Sea coast of the Caucasus.
Of vegetable and flower crops, a miniature pest most damages plants with loose (large-cell) 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 pest development cycle, the most vulnerable periods of life, so as not to once again poison plants with treatments.
Whitefly development cycle
The sizes of adult insects (adults), depending on the species, range from 0.5-3.0 mm. In its development, whitefly passes through three stages - eggs, larvae and nymphs. An adult adult comes out of a nymph. It is spread by foci. On one plant can be representatives of all stages of development and adult insects, which complicates the effectiveness of pest control. In the links of the development of eggs and nymphs, pests are practically not vulnerable to protectants. Whitefly larvae are most active in plant damage. In their development, they go through 6 stages of maturation, of which 3 are accompanied by molting. Each larval stage of larval development lasts from 2 to 4 days. Only the larva of the first age (slider) is actively moving. By the last molt, a VI-instar larva (puparia) ceases to feed, covers itself with a wax-like substance, and passes into the nymph stage, from which whiteflies emerge after 6 days. The cycle is completed. The imago mates with the male 12-20 hours after departure. Mating during the life of the imago occurs several times. Duration of egg development is 9 days.
Multiple Averaged Digits
Since each species of whitefly, depending on the feed host, has its own periodicity of the stages of development and the life of the pest in general, we present the averaged data characterizing its periods of greatest severity.
In the population settled by a separate outbreak, the main part is whitefly eggs (40-50%) and larvae (up to 40%). The imago lays eggs on the lower side of the leaf in an amount of 20-280 pieces, of which 80-94% survive to an adult insect. The development of adults from egg deposition to the emergence of larvae depends on the feed plant and optimal temperatures. On average, females and males of different types of pests can live at temperatures ranging from +18 .. + 24ºС, respectively, from 18 to 24 (and even up to 60) days and from 12 to 17 days. Raising the temperature to +24 .. + 30 ° C reduces the life of an adult whitefly up to 4 days.
Duration of oviposition of fertilized whitefly females lasts 18-22 days. The development of the larva lasts 7-15 days. From the nymph to the exit of the imago - 10-15 days. The development of one generation is completed in about 26-28 days. Under such conditions, the amount of imago per 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 when the whitefly larvae of the first age pass to the second, and the smallest - during egg laying and during the development of the nymph. But when processing plants, it is necessary to observe the weather. If the weather is optimal, then even with a minimal amount of imago, a high breeding rate will increase (and significantly) the number of pests. So, it will be necessary to increase the number of treatments from 4 to 6-7.
Ways to protect crops from whiteflies
Separate use of certain drugs will not bring the expected effect. Against whiteflies, comprehensive protection is needed, including preventive and household work with agrotechnical ones, including the use of plant treatments with drugs.
- During the growing season and at the end of the season, carefully remove all plant residues from crops and weeds so that adult eggs and other pests do not lay eggs on them.
- Be sure to disinfect the greenhouse and soil in the fall.
- Carry out the agrotechnical measures stipulated by technology in the open ground.
- During the growing season, do not overfeed the plants, especially with nitrogen fertilizers, clearly follow the irrigation regime.
- If you are engaged in organic farming, then in order to protect crops from whiteflies, you can be planted on the culture of predatory bedbugs of the macrolofus and the mite of amblyseus, especially in greenhouses and greenhouses. They significantly reduce the number of whiteflies. You can buy them at specialized outlets and populate according to the recommendations.
- During the growing season, sometimes it is 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 whiteflies?
Biological protection measures are most acceptable in personal subsidiary plots and in small dachas. Biochemical preparations developed on the basis of living beneficial microflora effectively destroy whiteflies without harming animals and humans.
Of the common and long-mastered biological products, it is best to use the bio-insecticide actophyte, which destroys (except for whiteflies) a fairly large list of pests. During the growing season of vegetable crops, 2 to 4 treatments are sufficient. Aversectin C and Avertin-N are effective from the same group. They are especially effective in killing young whitefly larvae and other sucking pests. Recently, bicol and bitoxibacillin have become more widely used. In Russia, bio-insecticides Nemabakt and Antonym-F have been created, which are the best drugs against a wide range of pests, but their release has just begun and is still being sold in limited quantities.
It should be noted that bioinsecticides begin to work at elevated temperatures and humidity. Therefore, the processing is carried out at + 18 ° C and above. Before processing, plants must be moistened or treated after watering. Rain washes away solutions of bioinsecticides, so you have to repeat the treatment. 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 owners of organic farming.
Folk remedies for whiteflies
Biological remedies include the use of decoctions of insecticide plants for whiteflies (onion husk, yarrow broth, garlic infusion). Decoctions of the plant are sprayed from a small spray. The use of decoctions requires frequent repetition - after 2-3-4 days for a long time.
The use of chemicals in the cultivation of garden crops in open and, especially, closed ground is not recommended. In some cases, when the vegetable wedge occupies a vast area, and the whitefly has epiphytotically propagated, 1-2 treatments can be performed at the beginning of the growing season. The last processing is carried out no later than 20-25 days before harvesting.
Of the chemicals that are allowed on vegetable crops against whiteflies, you can use mospilan, int-vir, spark-M and others. When choosing a drug, you need 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, a dressing gown, a hat, glasses, a respirator or a multi-layer dressing).