What are the control measures for Cypress leaf blight?

The branches and leaves of the Cypress are dense, the tree shape is graceful, it stays green through all four seasons, and it has strong resistance and a long lifespan, making it an excellent landscaping and ornamental tree species. However, the Cypress is prone to leaf blight, so what are the control measures for Cypress leaf blight?

1. Symptoms of Cypress leaf blight

1. Symptoms

It mainly harms the scale leaves and green young twigs of the current year. In the early stage of the disease, the scale leaves change from green to yellow-green, lose their luster, and then turn dead yellow, causing the scale leaves to fall early. The lesions on the scale leaves spread downward and harm the young twigs; the affected young twigs fade in color, turn yellow-green, and then dead yellow, and are not easy to fall off, being blown off by the wind the following spring. In severe cases, the crown is covered with dead yellow diseased and dead branches and leaves, and when it occurs year after year, the crown becomes sparse and the growth vigor is weak, reducing its ornamental value.

2. Pathogen

Through isolation and culture of diseased plants, the pathogen was identified as the genus Alternaria, belonging to Deuteromycotina, Hyphomycetes, Moniliales, and the genus Alternaria.

3. Occurrence pattern

The pathogen overwinters as mycelium on diseased branches, and in the following spring produces conidia, which become the source of primary infection. The conidia are spread by airflow and invade through wounds. The disease period is April to May, and the peak period is July to September. Light rain favors the formation, release, and invasion of conidia.

2. Control measures for Cypress leaf blight

1. Eliminate overwintering pathogens

After the Cypress sheds its leaves, remove the dead branches and fallen leaves, especially the diseased and dead branches remaining in the crown, and treat the removed diseased and dead branches centrally. In addition, spray once with 100-200 times copper sulfate solution; before bud break in March of the following year, spray once more. As a pre-bud eradication agent, 3-5 degrees Baume lime sulfur mixture can be sprayed on the dry branches for sterilization.

2. Strengthen management

While doing winter pruning well, strengthen summer pruning, with the premise of improving light and reasonable load, promptly thin out branches that hinder ventilation and light penetration, and worsen the conditions for pathogen breeding; apply more organic fertilizer, use formula fertilization, strengthen tree vigor, and improve resistance to the disease.

3. Chemical control

Starting in mid-June, alternately spray systemic and protective fungicides, once every 5-7 days, ensuring that before each continuous cloudy and rainy period lasting more than 2 days, the leaves and branches are all under the protection of the chemicals. Considering the control of other diseases, when spraying dithiocarbamate fungicides, they can be mixed with other systemic fungicides.

Precautions:

Choose medicines produced and sold by legitimate enterprises that meet quality standards, and be sure to rotate the chemicals used. Spraying must be meticulous and thorough, not missing a single branch, especially when spraying the inner branches and trunk of the crown, ensuring that the front and back of the leaves and the fruit are evenly covered with the chemical. At the same time, the higher the degree of atomization of the spray liquid, the better the control effect.