Control of citrus canker

Citrus canker Xanthomonascitri (Hasse) Dowson is a serious bacterial disease of citrus, which has been regarded as the object of plant quarantine at home and abroad. After the plant is damaged, the tree is weak, and the leaves and fruits are easy to fall early, so that the yield is reduced and the fruit quality is affected. After serious damage to seedlings and young trees, the leaves were bare and the branches withered, which hindered the development of citrus production.

[pathogens and symptoms]

The pathogen of citrus diseases and insect pests is a kind of Trichoderma, which mainly harms citrus and Fructus Aurantii of Rutaceae, and can also infect kumquat. The pathogen can infect the leaves, shoots and fruits of citrus. Needle large yellow oily spots appeared at the initial stage of leaf damage, and after expansion, they were raised on both sides of the leaf, corklike and rough, the central cracking was crater-like, and there was a yellow halo around the disease spot; the injured shape of the tip and fruit was similar to that of the leaf, and the disease spot on the branch had no yellow halo, which was often irregular, the disease spot on the green fruit had a yellow halo, and the halo disappeared after fruit ripening.

[condition of onset]

The pathogenic bacteria of citrus diseases and insect pests lie on diseased branches, leaves and fruits. In the next spring rain season, branches and leaves contact with each other and spread from wounds, stomata or lenticels with the help of wind and rain. The transfer of diseased seedlings can spread over a long distance. High temperature and heavy rain are conducive to the prevalence of the disease, and orchards with excessive application of nitrogen fertilizer, too many shoots and improper pruning are also prone to the disease. The peak period of the disease is from May to September every year, and the summer shoots suffer more seriously. In addition, there were differences in disease resistance among different varieties, oranges were more susceptible, pomelo was the second, and wide-skinned oranges were the lightest.

[prevention and control methods]

① strictly quarantines and forbids the transfer of seedlings and seeds from disease areas.

The ②-infected seeds were sterilized by soaking the seeds in 55 ℃ 56 hot water for 50 minutes.

When the garden was cleared in winter in ③, the diseased branches and leaves were cut off and burned and sprayed with 0.8-1 Baumedu stone flow mixture.

④ young trees were sprayed once in spring, summer and autumn and when the leaves were green, and the fruiting trees should also be sprayed once at 10, 30 and 50 days after falling flowers. The medicament can be selected as 4000-fold dilution of copper oxychloride, 72% agricultural streptomycin or-fold 50%DT wettable powder.