Prevention technology of common pest mites in landscape plants
Mites can also be called spider mite, yellow spider and so on. It is not a kind of insect, but belongs to arachnoidea and acarina. Pest mites have various species, in which the Eotetranychus smithi, wheat stone mite, Eriophyes disoar Nal, tetranychus cinnabarinus, Aculops niphocladae Keifer and Tetranychus viennensis will cause serious damage on landscape plants. They respectively belong to tetranychidae and eriophyidae and will mainly damage apples, peaches, poplars, willows, hawthorns, euonymus japonicus, Chinese scholartree, sycamore, lawn, Chinese rose, rose, trifolium repens, pepper and many other landscape plants.
Pest mites will mostly gather in the blade back. The imago and nymph usually suck the leaf juice by piercing the leaves with mouthparts, which will damage the landscape plant chlorophyll and influence photosynthesis. The damaged leaves will usually have grey white spots or white patches. Besides, it will even lead to the cell proliferation of damaged parts, thus the blade will appear to be gall shape or gall ball shape, or the leaves will become curl and will shrink. Even sometimes the whole leaves will be withered, just like being roasted by fire, therefore, it also can be called “fiery dragon pest”. Under serious condition, leaves will wither and fall off. Besides, plant will even die when the leaves all fall off. In addition, many pest mites can also transmit plant virus diseases and fungal diseases.
b. The morphological characteristics
Pest mite is usually very small, which will not exceed 2mm. The imago and nymph both have 4 feet, while the larva has 3 feet. It usually appears to be round or oval shape as well as mostly appears to be orange yellow or red brown. Therefore, it can be called red spite. The species will be different according to different food types, food amount and plant colors. Pest mite is a kind of pest that will mainly do harm to the blade and can pierce and suck plant leaves.
c. Occurrence regularity
Pest mites can breed by sexual propagation and apomixia, which usually wintering in the form of egg or fertilized adult female in the bark crack or the soil. They have extremely strong fertility, which can breed more than 10 generations or even 20-30 generations in one year. It mainly damages the back of leaves as well as can spin and net. The eggs are usually laid on the upper pulse of back leaves and the silk net. They can even breed rapidly under high temperature and dry conditions, in which 20-30 degrees Celsius will be the most appropriate air temperature. Besides, they can breed one generation in every five days and will repeat this behavior generation by generation.
In one year, pest mite will breed most from May to June and August to September; as the air condition is dry in autumn and the rainfall is little, it can breed fast and the population number will rapidly increase, however, if it continuously rains for several days, the population number will obviously reduce. As the wintering population cardinal number is large, the population number will greatly increase in the second year; in addition, the unreasonable drug delivery will cause environmental degradation and reducing of natural enemy.
d. Prevention methods
a. Make good forecast, check blade surface and blade back in time and observe the pests with microscopes. Before the occurrence of serious damages on the leaves, spray the drugs ahead of time. By preventing the damage in the early stage, it will have important effect on controlling rampant in the later period.
b. Seize the critical period. By spraying the pesticide in May to June every year when the first generation young mites largely hatch (which can be called the pest mite damage peak season) together with the second damage peak season from August to September in autumn, it can achieve double effect.
c. Clear the withered grass layer, insect-plague branches and weed in the green belt in time and intensively burn them up. As the wintering mites will usually inhabit under the eaves around the greenbelt, these places should be checked carefully so as to control the pest mites.
d. Spray 5 baume degree lime sulphur before the plant germination; or inject 40 percents of omethoate EC on the trunk with 1ml every 1cm DBH.
e. Irrigate in time so as to improve the insect resistance and reduce damage.
f. If mites only do little harm on the tree growth in summer, it can be washed by clear water.
g. When the insect attack becomes serious, it can be controlled by spraying 1.8 percents of abamectin insecticide EC in 7000-9000 times liquid; or spray 1.2 percents of matrine in 800-1000 times liquid; or spray 15 percents of pyridaben EC in 2500-3000 times liquid; or spray 73 percents of propargite EC in 2000 times liquid; or spray 5 percents of hexythiazox EC in 1500-2000 times liquid. By using the above pesticides alternately, it can avoid drug resistance of pest mites and extend the service life of pesticides. By continuously spraying the pesticides and insecticides in 3-4 times, it will have good prevention effect.
h. The pesticides should be sprayed both on the front and back side of the blade so as to avoid the reducing of pesticide effect. DDVP should not be used in killing mites, as it will stimulate the proliferation of mites. Besides, pyrethroid and imidacloprid are also prohibited to use, as they almost have no prevention effect on mites.
i. Protect the natural enemies, such as ladybird, lacewing and so on.