What are the common methods for preventing and controlling cherry blossom pests and diseases?
There are many types of cherry blossom pests and diseases. The common ones are described below:
Perforation-type brown spot disease It occurs in May and June. Small purple-brown spots appear on the leaves, then gradually expand into circles. After the diseased spots dry and shrink, they become small holes. The pathogen mostly overwinters on diseased branches and leaves. The optimum temperature for its development is 25°C to 28°C. It spreads by wind, and rainy seasons favor infection and disease development. When the tree is weak, drainage is poor, and ventilation and light penetration are poor, the disease occurs severely.
Control methods:
(1) Strengthen cultivation management, prune and trim reasonably, and pay attention to cutting off diseased shoot tips, promptly clean up diseased leaves and burn them, creating clean growing conditions for the plant.
(2) Before new shoots sprout, spray 3 to 5 degrees Baumé lime sulfur mixture. During the disease period, spray 160 times Bordeaux mixture or 50% benomyl wettable powder 1000 to 2000 times solution, or 15% zineb 600 times to 800 times solution.
Leaf blight In summer, yellow-green round spots appear on the leaves, then turn brown, with scattered small black granules. The diseased leaves die but do not fall off.
Control methods:
(1) Remove and burn diseased leaves, and spray Bordeaux mixture before budding.
(2) In May and June, spray 65% zineb wettable powder 500 times solution again, once every 7 to 10 days, for 2 to 3 consecutive sprays.
Crown gall disease It mainly occurs at the base of the main trunk, and sometimes also on the root collar or lateral roots. Tumors form on the diseased part, initially milky white or flesh-colored, gradually turning brown or dark brown, spherical, with a rough surface, unevenness, and cracking. After infection, the root system develops poorly, with very few fine roots, aboveground growth is slow, and the tree vigor is weak. In severe cases, the leaves turn yellow, fall early, and even the whole plant dies.
Control methods:
(1) Saplings infected with crown gall disease must be centrally destroyed. Before planting, saplings are best soaked in 1% copper sulfate for 5 to 10 minutes, then washed with water, and then planted.
(2) When diseased plants are found, the galls and surrounding tissue can be thoroughly removed with a knife or saw.
(3) The soil around diseased plants can also be disinfected by scattering sulfur powder at 50 grams to 100 grams per square meter. At the same time, pay attention to soil improvement.
Scale insects There are many types of scale insects that harm cherry blossoms, mainly including waterwood hard scale, chaff scale, long white scale, and Japanese wax scale. Adults and nymphs pierce and suck the sap of branches and leaves, weakening plant growth. At the same time, some species secrete large amounts of excrement, which easily induces sooty mold and affects growth and flowering.
Control methods:
(1) The most favorable period for controlling scale insects is the peak hatching period of the nymphs. Spray 25% phosmet 600 to 800 times solution or 40% omethoate emulsifiable concentrate 1000 times solution.
(2) In winter and spring, spray 5 degrees Baumé lime sulfur mixture, or 3% to 5% diesel oil emulsion, to eliminate overwintering nymphs. The effect is relatively good.
Pear lace bug
It mainly harms the underside of cherry blossom leaves, piercing and sucking sap. The damaged areas have many speckled brown excrement and black flyspeck-like marks left during egg laying. The entire underside of the damaged leaf appears rust-yellow, while the upper side forms pale white spots. When the damage is severe, the spots on the leaves merge into patches, the whole leaf loses its green color and becomes pale white, and defoliation occurs early.
Control methods:
(1) In winter, clear weeds and dead branches and fallen leaves, and destroy them centrally.
(2) When individual newly emerged white adults are found among the nymph clusters on the leaves, it indicates that the first-generation nymphs have basically hatched and pesticides should be sprayed promptly for control. This is a favorable period for control. Use 90% trichlorfon 1000 times solution or 50% malathion emulsifiable oil 1500 times solution, or 40% omethoate 1000 times solution.
Small clearwing moth
The larvae bore into and feed on the inner side of the bark of cherry blossoms. The adult body is blue-black. It occurs once a year. The larvae overwinter under the bark, so they can cause damage from early spring. They emerge in August and September. Eggs are laid in bark crevices or wounds on the bark.
Control methods:
(1) Apply lime coating on cherry blossom branches and trunks to prevent egg laying.
(2) In spring, when gum oozes from holes on dry branches or there is insect frass, use a hammer to tap and crush the larvae inside, or use a small knife to cut open the bark and kill the larvae. Then apply a fungicide.
(3) Apply 50% phoxim emulsifiable concentrate 700 times solution to the bore holes or spray the entire branches and trunk to kill young larvae.
Red spider mite
Red spider mites reproduce rapidly and increase sharply in number during high temperature and drought in June and July. At this time, the damage is severe. They mainly pierce and suck the sap of cherry blossom leaves, causing the damaged leaves to lose green and show gray-yellow spots, resulting in scorching and early defoliation. The damaged young buds turn yellow and scorched, cannot unfold leaves, affecting normal growth and ornamental value, and can also lead to attacks by other pests and diseases.
Control methods:
(1) When red spider mites are found on individual cherry blossoms, remove them promptly.
(2) Before cherry blossoms bud in early spring, spray the trunk with crystal lime sulfur mixture 300 to 500 times solution to eliminate overwintering female adults and eggs.
(3) During the damage period, spray 50% bromopropylate emulsion 2500 times solution or pesticides such as omethoate and dicofol.
(4) Because mites easily develop resistance, pay attention to alternating the use of acaricides.
Aphids
Aphids mainly harm cherry blossom buds, new leaves, and flower buds, sucking sap from the plant with piercing-sucking mouthparts. The affected plant parts grow slowly, and the leaves wrinkle and curl. In severe cases, they fall off. When flower buds are damaged, they cannot develop normally and drop off. This insect can also secrete large amounts of honeydew, inducing severe sooty mold and greatly reducing the ornamental value of the damaged cherry blossoms.
Control methods:
(1) When the number of insects is not large, spray clean water to wash them off or combine with pruning, cutting off insect-infested branches for disposal.
(2) In mid-to-late April, bury and apply 15% aldicarb granules around the cherry tree where there are the most fibrous roots, using 1 to 2 grams per tree buried 2 cm deep in the soil. The effect is good.
(3) Spray 1000 to 1500 times 50% menazon emulsifiable concentrate or 4000 to 5000 times 2.5% deltamethrin emulsifiable concentrate, or 2000 times 20% fenvalerate emulsifiable concentrate.