Common diseases and pests of Green Yuanbao and their control methods

Common diseases of green yuanbao: powdery mildew

Symptoms

Powdery mildew of Green Yuanbao usually infects the leaves first. The symptoms of the disease mostly occur on the back of the leaves. In the early stage, there are chlorotic spots on the leaves. When the disease is serious, it is covered with powdery coal layers. In the later stage, the diseased leaves are covered with small black spots, which are the cleistothecia of the pathogen.

The pathogen is phyllactinia corylea karst, which belongs to the genus Phyllactinia, family Erysiphelaceae, class Pyrocomycetes, subphylum Ascomycota. The hyphae grow on the surface and extend into the epidermal cells. The diameter of the closed theca is 70-119um, with 5-10 appendages, which are hyphae-like, brown, and have septa.

Occurrence pattern

The occurrence pattern of powdery mildew of Green Yuanbao: the pathogen overwinters on the diseased remains in the form of closed ascocysts. When the spring is warm the following year and conditions are suitable, ascospores are released for initial infection, and then conidia are produced for secondary infection, spreading through wind and rain. The disease has a long duration and can occur from May to September, but is more severe in August and September.

Prevention and treatment methods

The agent can be 1500-2000 times diluted 25% triadimefon wettable powder, or 1000 times diluted 70% thiophanate-methyl wettable powder. Spray once every 10 days, and the number of sprays depends on the progression of the disease.

During the dormant period of plants in winter or early spring, 3-5 degrees Baume lime sulfur mixture can be used to spray the nursery ground. During the germination period in early spring, 0.3-0.5 degrees Baume solution can be used. When using eradicants, the effect will be better if combined with the removal of pathogens.

Common pests of green yuanbao: spiny moth

Pest symptoms

The larvae feed on the leaves. Young ones eat the leaf flesh; older ones form notches and holes. In severe cases, the plant will be eaten down to the bare stalks.

Occurrence pattern

There is one generation per year in the north, two generations in the lower reaches of the Yangtze River, and three generations in a few areas. The mature larvae overwinter in the cocoons in the 3-6cm soil layer under the trees before pupating. In the first generation area, pupation begins in mid-May, and pupation and egg-laying begin in early June. The occurrence period is irregular, and newly hatched larvae can be seen from mid-June to early August. The damage is most serious in August. From late August, they begin to mature and bury themselves in the soil to form cocoons to overwinter.

Prevention and treatment methods

During the peak period of larvae, spray 1200 times diluted 80% DDT EC, 1000 times diluted 50% phoxim EC, 1000 times diluted 50% malathion EC, 1000 times diluted 25% phosmet EC, 1500 times diluted 25% Acumin EC, 3000 times diluted 5% Levofloxacin EC.