What are the control methods for apple Phytophthora fruit rot?
This spring, the temperature in my area was lower than usual and there was more rain than usual, causing severe outbreaks of apple Phytophthora fruit rot. Apple Phytophthora fruit rot, also known as apple Phytophthora disease, can harm apple fruit; the skin of affected fruit first looks as if scalded by hot water, then turns brown, and the flesh rots. It can also attack the root crown of trees, causing the bark to rot. Whether on fruit or root crown, when humidity is high, white short hairs grow. In some years it often occurs severely.
The pathogen of apple Phytophthora fruit rot has many hosts and is generally present in apple orchards. This pathogen prefers high humidity and low temperatures, and disease only develops when humidity approaches 100%. Once the temperature exceeds 25°C, disease generally no longer develops. In 2008, because of the rare low-temperature and high-humidity weather before mid-June, the most severe outbreak of apple Phytophthora fruit rot in 20 years occurred. When it attacks the root crown, it is mostly spread with irrigation water.
Control methods:
1. The Phytophthora rot pathogen overwinters in the soil in diseased residues, so clearing away diseased residues, promptly removing fallen fruit, and picking off diseased fruit and diseased leaves from the trees to bury them deeply together is an important disease prevention measure.
2. Because the Phytophthora fruit rot pathogen is mainly spread by splashing rain, the closer the fruit is to the ground, the more easily it is infected and develops disease. Fruit below 60 cm from the ground is affected the most, and generally the highest is no more than 1.5 m. Measures such as appropriately raising the fruiting position and laying grass on the ground can avoid infection and reduce damage.
3. Improving the orchard ecological environment, draining accumulated water, lowering humidity, and allowing the canopy to ventilate and receive light can effectively control the disease.
4. In severely affected orchard blocks, when low-temperature and high-humidity weather occurs in May to June, spray 100-fold dilution of copper sulfate on the ground, using wetting the ground as the standard. Spray for control before bagging, focusing on fruit at heights below one meter. Various pesticides used to control downy mildew can be used. When it attacks the root crown of the tree, irrigate with 100-fold dilution of copper sulfate.