What are the types of whitefly, whitefly and whitefly?

Whitefly whitefly is a new important pest invading Hainan, which has the characteristics of various modes of transmission, many host species and fast reproduction speed. Do you want to know about its shape, life history and harm? it is very helpful to control spiral whitefly.

The morphology of spiral whitefly (Fig. 1-4)

Egg: about 0.29*0.11mm in size, long oval, smooth surface, with a handle at one end of the egg. The eggs are translucent and colorless.

Nymph: a total of four years old. The age of each age is 0.28-0.12, 0.48-0.26, 0.67-0.49 and 1.06*0.88mm. At the beginning of each age, the molting was transparent and colorless and flat, but gradually became translucent and raised on the back with the development. The shape of each age is similar, but it changes from slender to oval with the degree of development. The first instar nymph has segmented antennae and functional feet, while the antennae and feet of other instar nymphs degenerate. The wax powder secreted by the nymphs from the first instar to the third instar was small and short, and the wax powder secreted by the nymphs increased greatly at the fourth instar, and its floc could reach 8mm.

Adult: the body length of female and male is 1.97and 2.10mm respectively. The wings are transparent at the beginning of Eclosion, and a few hours later they are covered with white powder. The male worm has a mating grip at the end of the abdomen.

The life history of whitefly whitefly

The emergence of males is earlier than that of females, and the peak of Eclosion is at 6: 8 a.m. in the morning. The ratio of female to male is 1.5. Mating occurs in the afternoon, when the male spreads his wings and flaps up and down quickly to attract the female to approach, and then mate. The peak time of adult migration occurs at 5: 00 to 7: 00 in the morning, but the activity time is delayed when the temperature is low or on a cloudy day. Generally speaking, the migration ability of males is weaker than that of females and mostly stays on the leaves of the original host plants. The maturity of the eggs in the ovary of the female was related to the age, and it was not until the third day that the female began to spiral upward from the original host plant to find the tender leaves of the new host plant to lay eggs. The female lays eggs on the back of the leaves, the eggs are scattered in a special spiral, and there is white wax powder. The number of eggs in each circle varies from 11,53 to 53. The egg has a small stalk that inserts upright into the stomata of the leaves. At 25 degrees, the lifespan of female and male were 15 and 12 days respectively, the male produced parthenogenetic per unit area, and the final egg production was 65.2 eggs. The nymph has a total of four years old, and only the first instar nymph can move. After initial hatching, the nymphs crawl to the nearby veins and feed on them. The development period and survival rate of a generation depend on the temperature. It takes 26.5 days to complete a generation at 25 degrees on kidney beans, and the survival rate is 91.9%. The egg and nymph stages from the first instar to the fourth instar took 7.0 and 5.1, 3.4, 4.4 and 5.5 days respectively, and the survival rates were 100 and 98.2, 100, 97.3 and 96.2%, respectively. The suitable temperate zone for adult activity is 12.3-32.3 degrees. The occurrence and harm of spiral whitefly host plant species are seasonal. In Taiwan, spiral whitefly occurs in autumn (October-December), followed by spring and winter, and rarely in summer. The species of host plants damaged by spiral whitefly were the most in autumn, followed by spring and winter, and the least in summer. Because females like to lay eggs on new leaves, the application of nitrogen fertilizer and pruning can often promote the increase of population density of spiral whitefly. However, heavy rain and low temperature will reduce the population density of the insect.

The harm of spiral whitefly

There are five ways of harm to humans and plants caused by spiral whitefly, which are described as follows:

1. Nymphs and adults directly suck the sap of the host plant with an oral needle on the back of the leaf, which can make the host leaf fall ahead of time when the insect occurs seriously, but it will not kill the host plant.

two。 A large amount of white wax powder and floss secreted by nymphs not only affect the appearance of host plants, but also their secretions are disgusting when blown away by the wind.

Even in Hawaii, the adult or its secretions or both have not been shown to cause allergies and dermatitis, but people are frightened and complain about it.

3. Honeydew secreted by nymphs induces coal disease, which not only affects the photosynthesis of host plants, but also affects the appearance of plants and attracts insects such as ants and flies.

4. It was suspected that the cocoa coconut virus (lethal yellow disease) was a vector, but now it has been confirmed that the worm does not have the ability to do so.

5. It not only affects the yield of food crops and economic fruit trees, but also leads to the potential threat of export quarantine of ornamental plants. In Taiwan, whether 1-year-old guava or 4-year-old guava was damaged by spiral whitefly for 4 months, the fruit yield loss was as high as 7380%, but if 90% nano-wettable powder (methomyl WP) was applied 1800 times every 7 and 14 days, the fruit yield loss was sharply reduced to 0 and 60.7%.

The mode of dispersion of spiral whitefly

Apart from the migration of adults, spiral whitefly can also be transmitted by infected plants, other animals, or vehicles (cars, boats), such as plants on both sides of major roads, stations and car parks in Hawaii. However, it has not been confirmed that the worm can spread over a long distance by means of upper airflow.

The economic importance of spiral whitefly: spiral whitefly is an omnivorous pest of vegetables, fruit trees, grain, ornamental plants, street trees and forests. In Hawaii, there are more than 27 families and more than 100 species of host plants, including avocado, banana, bread tree, pepper, citrus, coconut, Jasminum, guava, Leucaena leucocephala, Australian walnut, lemon fruit, papaya and rose. In Africa, whitefly whitefly becomes an important pest in agriculture and forest if not controlled. If the tree aspect includes banana, papaya, guava, citrus, avocado, coconut and lemon fruit, the forest aspect includes Acacia sp., Eucalyptus sp. And Terminalia sp., have cassava as food crops. In Taiwan, there are 156 host plants belonging to 65 families, among which guava, Christmas red, olive kernel, mulberry, amaranth, papaya, pepper, eggplant, hibiscus, poinsettia, lychee, maple, Chinese wolfberry, bauhinia, marble, rhododendron, jasmine, canna and cherry suffer more seriously.