Common diseases of the dwarf ...

Common diseases of the dwarf jasmine: leaf spot

Symptoms

The Pieris japonica suffers from leaf spot disease, with oval and long light reddish-brown spots on the leaves, surrounded by chlorotic circles, which later expand into large irregular patches with black spots on them.

Prevention and treatment methods

Remove diseased leaves and spray pesticides in time. It can be sprayed with 500 times diluted 50% thiophanate wettable powder.

The leaf spot disease of the jasmine tree is easy to control. After cutting off the diseased leaves, spraying pesticides can prevent and control it.

Common diseases of the jasmine tree: dieback

Symptoms

The dieback disease harms the buds, leaves, tips and branches of the Pinus sylvestris, causing dieback. It can also harm the rhizomes, causing rot, and the sapwood, causing blue discoloration. In severe cases, it can cause the pine tree to die.

The pathogen of dieback disease can directly invade the intact tissue of young trees or tender shoots. For older trees, after causing dieback and cankers, the affected parts often ooze resin, the sapwood turns blue, and conidiophores form on the surface of dead tissue.

In the early stage of the disease, ulcer spots appear on the infected young shoots, the cortex cracks and resin oozes out, and the nearby needles die. Later, some of the ulcers healed, while others continued to expand, causing the top of the shoot to bend and form dead branches, similar to the damage caused by pine tip borer. After the ulcers on the branches and trunks continue to expand, the diseased parts will ooze fat for a long time. Once the lesions surround the branches, the entire plant will die.

Pathogen analysis

The pathogen of dieback disease is Sphaeropsis sapinea (Fr.) Dyke et Sutton, which belongs to the subphylum Ascomycota, class Coelocystis, and order Sphaerosporales.

The pathogen overwinters in the form of mycelium or conidia on diseased shoots or leaves. Conidia are produced in the spring of the second year and are spread by wind and rain.

Poor tree growth due to reasons such as poor soil, insect pests, and waterlogging can all contribute to the aggravation of dieback disease.

Prevention and treatment methods

Remove diseased branches and leaves promptly and burn them in a concentrated manner to prevent reinfection.

Spraying of chlorothalonil oil, carbendazim, mancozeb, Bordeaux mixture, 0.2% boric acid water, etc. has a certain preventive and therapeutic effect on the dieback disease of the jasmine tree.