A Complete Analysis of the Key Technical Points for Grape Pest and Disease Control
Grapes are woody climbing plants of the genus Vitis in the family Vitaceae, native to western Asia and now cultivated throughout the world, though about 95% of the world's grapes are concentrated in the Northern Hemisphere. During grape cultivation, the main common diseases include black spot disease, powdery mildew, downy mildew, mealybugs and aphids, among others. Let's take a look at grape pest and disease control techniques below!
Grape Anthracnose
1. Symptoms: Grape anthracnose can infect fruits, canes, leaves and tendrils. Infected areas develop small brown round spots that gradually enlarge and become sunken; the lesions produce concentric ring-like nearly circular lines and bear neatly arranged small black dots. These black dots are acervuli, and in humid weather the acervuli exude pink gelatinous masses of conidia. The lesions can expand to cover the entire fruit surface; diseased fruits gradually shrivel into mummified fruits, and sometimes an entire cluster shrivels into a mummified cluster.
2. Occurrence pattern: Infection generally begins in June, with the peak period from July to August, and damage gradually intensifies as fruits approach maturity. According to observations in Suzhou, diseased fruits appear half a month after petal fall (around June 10-15), forming the first disease peak of the year. Around August 10, as large numbers of fruits ripen, the disease enters its peak period with every spell of muggy thunderstorms, causing the most severe damage of the year.
3. Control methods
① Thoroughly remove diseased clusters, diseased canes and diseased leaves to reduce sources of inoculum. In areas south of the Yangtze River, bagging can be carried out immediately after petal fall.
② Strengthen cultivation management by timely pruning, tying canes and pinching tips to ensure ventilation of the trellis surface. Increase phosphorus and potassium fertilizer and control the amount of nitrogen fertilizer.
③ At the bud-swelling stage, spray once with 0.3% sodium pentachlorophenate plus 4 degrees Baumé lime sulfur, or 150 times thiram, or 100 times Tuzet as an eradicant.
④ Spray for control starting in late April in the south and late May in the north, then generally spray once every 10-15 days, using 80% anthracnose Formet at 700-800 times dilution, 50% chlorothalonil at 600-700 times dilution, 50% Tuzet or mancozeb at 800 times dilution. In the south where there is abundant rain, add "6501" at 1500 times dilution or 0.03-0.05% skin glue and other stickers to the spray solution.
Grape White Rot
1. Symptoms: On fruit stalks and cluster stems, infected areas first produce light brown water-soaked nearly circular lesions; later, grayish-white small granular pycnidia form on the surface of diseased berries and the diseased parts of cluster stems. When humidity is high, grayish-white conidial masses overflow from the pycnidia. Diseased fruits drop easily, and when shriveled they become brown or grayish-white mummified fruits. On canes, early infection shows water-soaked light brown lesions of irregular shape; the lesions mostly extend longitudinally into large brown sunken spots, with grayish-white granular pycnidia on the epidermis. Later, the epidermis of the diseased part splits longitudinally and separates from the woody tissue, the epidermis peels off, and the vascular bundles appear brown and tangled like hemp. When a lesion extends around the entire circumference of a cane's epidermis, the part of the cane above it dies. Leaf infection mostly occurs at the leaf margins, initially producing brown water-soaked irregular lesions that gradually enlarge into slightly circular spots with brown concentric rings.
2. Occurrence pattern: The disease favours occurrence at 28-30°C with atmospheric humidity above 95%. It is severe in hot, humid and rainy seasons, with a disease peak after rain. In the north, it can occur from June through the harvest period; it increases during the fruit colouring stage and peaks after storms. The disease is severe near the ground and under conditions of heavy clay soil, low-lying terrain and poor drainage; it is prone to occur where weeds are overgrown, branches and leaves are dense, or humidity is high, and is prone to occur on excessively vigorous and leggy plants.
3. Control methods
① Thoroughly remove diseased canes, diseased clusters and diseased leaves.
② Prune in time, raise the fruiting position, weed promptly, pay attention to drainage, and strictly prohibit the application of nitrogen fertilizer before flowering on leggy plants.
③ In the north, after the vines are uncovered, spray 5 degrees Baumé lime sulfur or 100 times chlorothalonil; starting from the young fruit stage (early June), spray once about every 15 days for prevention until harvest. In the south, focus control efforts on the inflorescence separation stage (late April to early May), 7 days after petal fall, and half a month before maturity. The main chemicals include half-strength, equal-strength or double-strength Bordeaux mixture, 75% chlorothalonil at 800 times dilution, 50% carbendazim wettable powder at 700 times dilution, 70% thiophanate at 700 times dilution or 50% Tuzet at 800 times dilution.
④ White rot is relatively mild on Kyoho grapes; in the south, develop varieties that mature earlier than Kyoho as much as possible, or use forcing culture to avoid the peak period of white rot occurrence.
Grape Downy Mildew
1. Symptoms: Grape downy mildew mainly damages leaves, new shoots and young fruits. Infected leaf areas first produce small light yellowish-brown water-soaked spots with indistinct edges; the lesions gradually enlarge into irregular or slightly circular large yellowish-brown spots. The lesions become reddish-brown or yellowish-brown; in severe cases the lesions and the leaf tissue outside them dry up, or the entire leaf dries up and drops off. Infected new shoots produce water-soaked brown spots; in severe cases the new shoots become distorted, stop growing or even die, and in high humidity a frost-like mold layer forms on the lesions. Tendrils, petioles and cluster stems can also be infected. After infection, young fruits produce water-soaked light brown spots; in high humidity a grayish-white mold layer forms on the young fruits and fruit stems, and second-crop fruits in autumn suffer more severely. After the fruits colour, damage is relatively mild.
2. Occurrence pattern: This disease is prone to major outbreaks in autumn with abundant rain, heavy dew and low temperatures. Poor ventilation in the orchard, high humidity and excessive nitrogen fertilizer favour occurrence. In the north it can generally occur from June, with the peak period from August to September. South of the Yangtze River, there are 2-3 disease peaks in the year: the first during the plum rain season, the second in mid-to-late August. In some years a further peak appears from mid-September to early October.
3. Control methods
① Remove fallen leaves and diseased branches by burying or burning. Timely pinch tips, prune, drain and weed, and increase phosphorus and potassium fertilizer.
② Spraying should begin at the early stage of disease; in the north it generally starts in early-to-mid June, spraying once every 15 days. 25% metalaxyl or domestic mefenoxam at 600 times dilution gives the best control effect; 40% fosetyl-aluminium at 300 times dilution, 90% fosetyl-aluminium at 500 times dilution or 1:0.5:200 Bordeaux mixture also have relatively good control effects. South of the Yangtze River, before early autumn spraying can in principle be combined with control of black spot disease; before disease occurrence Bordeaux mixture gives the best control effect, and if downy mildew occurs, spray 25% mefenoxam at 700 times dilution or 90% fosetyl-aluminium at 500 times dilution promptly.
Grape Black Spot Disease
1. Symptoms: The disease damages young fruits, new shoots, leaves and tendrils and other green tender parts. On infected young fruits, small brown round spots first appear on the fruit surface, then gradually enlarge, and later the centre of the lesion becomes grayish-white. On infected new shoots, tendrils, petioles and fruit stalks, brown circular or irregular small spots first appear, then enlarge into nearly oval shapes. On canes, canker spots form; diseased shoots stop growing and eventually wither, dry and turn black. On infected tender leaves, brown or black spots the size of a pinhead initially appear.
2. Occurrence pattern: The pathogen overwinters as mycelium in canker spots on diseased canes and can also overwinter in diseased fruits and diseased scars. In May of the following year it produces conidia, which spread by wind and rain to cause primary infection. Long-distance transmission is mainly through nursery stock and cuttings. After grapevines bud in spring, the disease can occur until September.
3. Control methods
① In combination with summer pruning or throughout the entire growing season, thoroughly cut off diseased shoots and remove diseased fruits and diseased leaves; after autumn pruning, thoroughly clean up dead branches and fallen leaves, burn them in a centralized manner and bury them deeply, so as to reduce sources of inoculum to the greatest extent.
② Reasonably increase potassium fertilizer to prevent leggy growth, strengthen the tree vigour and improve disease resistance; the trellis surface should be reasonable to maintain good ventilation and light transmission conditions.
③ In spring, before the vines are uncovered and sprout, spray sodium pentachlorophenate at 200 times dilution, or 3-5 degrees Baumé lime sulfur; during the growing season, spray 1:0.5:200-240 Bordeaux mixture once each before and after flowering. Other chemicals include 75% chlorothalonil at 500 times dilution, or 50% carbendazim at 1000 times dilution.