What about grape rust spots?
Consultation content
Some of my grapes look like rust spots, and there are rotten fruits. What caused it? What pesticides and fertilizers should be used now?
Consultant Mr. Wang
Consultation time 2008-06- 17
Contact number
Reply content
Occurrence regularity and control of grape anthracnose
Reply content
Hello, Mr. Wang! Welcome to the online consulting column of agricultural technology 1 10 of Zhejiang Lin 'an Agricultural Information Network.
Regarding your question about "grape rust spots and rotten fruits", according to the analysis of the situation, your grapes have been damaged by anthracnose. Below I will introduce "the incidence law and prevention methods of grape anthracnose" as follows:
Occurrence regularity and control of grape anthracnose;
Occurrence regularity: the main filaments of grape anthracnose overwinter on diseased fruit grains, annual technical vines and iron filings. In June and July of the following year, when the conditions are suitable, a large number of molecular spores are produced and spread by insects such as wind, rain and wasps, which leads to the first infection. Generally, most areas begin to get sick in mid-July, and then it becomes more and more serious. Every time it rains, a batch of conidia will be produced. This strain is very parasitic. Spore germination produces appendages and invading filaments, which directly penetrate the pericarp and invade. Generally, after an incubation period of 10 days, lesions appear. The length of incubation period varies with infection time and species. Some varieties of bacteria invade in the young fruit stage, and only show symptoms in the mature stage, with an incubation period of about 20 days. The closer to mature infection, the shorter the end time of incubation period, and some only need 2-4 days. The conidia produced on the lesion are constantly reinfected.
Pathogenic causes: The temperature range of pathogenic bacteria development is 8℃-37℃, the optimum temperature is 20℃-25℃, and the suitable temperature for producing spores is 28℃-30℃. Spores will appear after 24 hours at suitable temperature, which is an important factor.
During this period, the daily rainfall is 15-30 mm, and conidia can appear in the field after 10. Therefore, the high temperature and rainy weather when grapes are approaching maturity often leads to the epidemic of this disease. The incidence of fruit grains is closely related to the expansion of pH value of sugar content. When the sugar content of fruit juice reaches 7%-8% and the pH value is 2.8-2.9, grapes are seriously infected. Therefore, rainy years and orchards with low terrain, poor drainage, low shelves, poor ventilation and light transmission, and many shelf residues are seriously ill.
(1) preventive and control measures
① Eliminate overwintering germs. Combined with pruning, secondary branches, ear stalks and hard fruit vines on plants and supports are removed, and the ground is cleaned and destroyed centrally to reduce the number of pathogens in the garden;
② Strengthening cultivation management. Timely topping, tying vines, intertillage weeding, paying attention to drainage, reducing the temperature in the garden, rationally fertilizing and enhancing the tree potential;
③ Chemical control. Spray protection is an important measure to control grape anthracnose. Because mycelium overwinters mainly by annual biotechnology, spraying 50% carbendazim-jingmycin mixture or 800 times carbendazim-jingmycin mixture before germination can achieve good results. Spraying 50% carbendazim or 50% carbendazim 800 times solution before conidia appear from late May to early June; Spraying 75% chlorothalonil 500 times every 10 to 12 days after the rainy season; Or spray 200 times the same amount of Bordeaux; Or spraying 25% carbendazim solution 400 times continuously for 3-5 times can control the occurrence of the disease.
The above contents are for reference only, because I haven't been to the field for diagnosis.
Lin 'an, Ji Nong 1 10