How to prevent and control pests and diseases of Gongju chrysanthemum? Key points for cultivation and management of herbaceous perennial

(1) Symptoms and control of major diseases

DamageChrysanthemumhas many diseases, among which the main disease symptoms are as follows: ① Powdery mildew (downy mildew), which damages chrysanthemum leaves, petioles and tender shoots. The diseased parts look as if sprinkled with a layer of white powder, namely conidia and hyphae. Diseased leaves are often distorted and deformed; on severely affected plants, the flower buds cannot open normally, growth stops, and the whole plant may even die. ② Brown spot disease (leaf blight), which mainly damages leaves; the round or oval lesions turn from purplish brown to dark brown, and in severe cases multiple lesions join together and spread over the entire leaf; the diseased leaves wither and turn black but do not fall off. The diseased plant dies successively from the lower leaves upward until the whole plant is killed. ③ Sclerotial rot (southern blight), which mainly damages the stem. It generally occurs first at the stem base on the soil surface; the lesions become soft and rotted, and white mycelium appears when moist. When a lesion encircles the stem, the leaves turn yellow, droop and wither, and finally the whole plant dies standing; inside the diseased stem there are mouse-dropping-like sclerotia.

Comprehensive disease control measures: ① After autumn, thoroughly remove dead branches and fallen leaves, promptly remove diseased plants and diseased leaves, and burn them in a centralized manner; ② Strengthen soil, fertilizer and water management as well as topping and pruning work, pay attention to selecting strong seedlings, and plant at a reasonable density, not too dense, so as to maintain good ventilation and light conditions in the chrysanthemum field; ③ Use chemical agents for control. During the disease period from April to October, rotate the use of effective agents, such as: 1:1:200 Bordeaux mixture, 20% triadimefon 3000-fold solution, 70% phosethyl-Al mancozeb 500-fold solution, 58% metalaxyl mancozeb 1000-fold solution, 70% kocide 1000-fold solution, 40% dimethachlon 1000-fold solution, as well as chlorothalonil, carbendazim, meibingwei, mancozeb, thiophanate-methyl, etc. Determine the number of sprays according to the disease condition.

(2) Major insect pests and control

① White grubs, the larvae of scarab beetles, damage chrysanthemum young roots and buds underground; they can be controlled by drenching with 1000-fold phoxim solution. ② Chrysanthemum aphids, leafhoppers and stink bugs, which mainly pierce and suck to damage leaves and tender branches. Control can be carried out by rotating the use of agents such as buprofezin (imidacloprid), haonian dong, yaqingling, kuai shaling, dagongchen, dimethoate, etc. ③ Leaf roller moths, which roll leaves to cause damage; control can be carried out with agents such as tianwangxing, beta-cypermethrin, kung fu, decis, etc.

When controlling chrysanthemum pests and diseases, pay attention to selecting pesticides with high efficiency, low toxicity and low residue. From 20 days before chrysanthemum harvest until the harvest period, pesticide use is prohibited to prevent pesticide contamination of chrysanthemum.