Identification and Control Methods for Common Cherry Blossom Diseases and Pests

There are many types of cherry blossom diseases and pests. The common ones are described below:

Perforation-type brown spot disease It occurs in May and June. Small purplish-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. In rainy seasons, infection and disease development are favored. 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, carry out reasonable pruning, and pay attention to cutting off diseased shoots, timely clearing diseased leaves and burning them, creating clean growing conditions for the plants.

(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 granular spots. The diseased leaves wither 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 It mainly occurs at the base of the main trunk, and sometimes also on the root crown or lateral roots. Tumors form on the diseased parts, initially milky white or flesh-colored, gradually turning brown or dark brown, spherical, with a rough surface, uneven and cracked. 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 yellow, fall early, and even the whole plant dies.

Control methods: (1) Nursery stock infected with crown gall must be centrally destroyed. Before planting, it is best to soak the nursery stock in 1% copper sulfate for 5 to 10 minutes, then wash it with water, and then plant it.

(2) When diseased plants are found, the galls and surrounding tissues 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 sq m. At the same time, pay attention to soil improvement.

Scale insects There are many types of scale insects that damage cherry blossoms, mainly including water wood 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 stage 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 emulsion, to kill overwintering nymphs. The effect is relatively good.

Pear lace bug It mainly damages the underside of cherry blossom leaves, piercing and sucking sap. The damaged areas have many mottled brown excrement and black flyspeck-like marks left during egg laying. The entire underside of the damaged leaf appears rusty 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 turns pale white, and defoliation occurs early.

Control methods: (1) In winter, remove weeds and dead branches and fallen leaves, and destroy them centrally. (2) When individual white adults that have just emerged are found among the nymph clusters on the leaves, it indicates that the first-generation nymphs have basically hatched, and pesticide 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.

Lesser clearwing moth The larvae bore 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 damage can begin in early spring, and 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 holes are seen on dry branches with gum flowing out or insect frass, use a hammer to strike and crush the larvae inside, or use a small knife to cut open the bark to catch and kill the larvae. Then apply a fungicide.

(3) Use 50% phoxim emulsifiable concentrate 700 times solution to smear the entry holes or spray the entire branches and trunks to kill young larvae. Red spider mite When the temperature is high and drought occurs in June and July, red spider mites reproduce rapidly and their numbers surge, causing severe damage at this time. 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 and cannot unfold leaves, affecting normal growth and ornamental value, and can also lead to infestation by other diseases and pests.

Control methods: (1) When red spider mites are found on individual cherry blossoms, remove them promptly.

(2) Before cherry blossoms sprout in early spring, spray the trunks with crystalline lime sulfur mixture 300 to 500 times solution to kill overwintering female adults and eggs.

(3) During the damage period, spray 50% bromopropylate emulsifiable concentrate 2500 times solution, or omethoate, dicofol, and other pesticides.

(4) Because mites easily develop resistance, pay attention to alternating the use of acaricides.

Aphids Aphids mainly damage cherry blossom buds, new leaves, and flower buds. With piercing-sucking mouthparts, they suck the sap inside the plant. 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, leading to dropping. 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 by cutting off 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 into the soil. The effect is good.

(3) Spray 50% menazon emulsifiable concentrate 1000 to 1500 times solution, or 2.5% deltamethrin emulsifiable concentrate 4000 to 5000 times solution, or 20% fenvalerate emulsifiable concentrate 2000 times solution.