Detailed Explanation of Key Early Spring Grape Management Techniques
Early spring management generally means doing five tasks well:
1. Clean the orchard thoroughly; combined with winter pruning, cut off pest-infested canes to reduce damage from anthracnose, black pox, cane blight, and pests overwintering on the canes. Cleaning the orchard thoroughly together with winter pruning, and completely removing diseased wood, diseased fruit, fallen leaves, and weeds from the trees and between the rows, has a marked effect on preventing white rot, black rot, downy mildew, brown spot, and other diseases.
2. Water thoroughly once. In northern regions, for orchards with poor soil moisture in early spring due to drought and frequent wind, water once after the Rain Water solar term in the first lunar month. Then, before topdressing base fertilizer, around the Spring Equinox on about the 20th day of the 2nd lunar month, irrigate again with a bud-stimulating water, applying 15 kg of urea or 25 kg of ammonium bicarbonate per mu, and cultivate and weed to loosen the soil; raising the soil temperature can make new shoots grow faster.
3. Spray thoroughly once. No matter what kind of disease or pest, to control its occurrence, two points are key: First, resolutely implement the principle of giving priority to prevention. From bud break to before leaf expansion, the prevention targets are black pox, white rot, anthracnose, downy mildew, and powdery mildew. The key time is the woolly bud stage of grape bud break, when 5 degrees Baume lime sulfur mixture should be sprayed once. The spraying range, in addition to the canes and trunk, must also cover the ground, especially the soil surface under the trees. This spraying can eradicate many kinds of overwintering diseases and pests and lay a good foundation for disease and pest control throughout the entire grape growing season.
4. Rub off buds thoroughly. This is the first operation for regulating tree nutrition. Grapes have many buds that sprout in early spring. In order not to waste tree nutrition, therefore when the buds grow to 1—2 cm, keep 1 plump, relatively large and flat main bud at each bud eye and remove the rest, doing this 1—3 times, which is called bud rubbing.
5. After bud break, the key is to achieve the second of the two points: in chemical prevention, the focus should be on prevention before and after flowering, which can achieve twice the result with half the effort. From leaf expansion to before flowering, after grape bud break, spray 10 ppm gibberellic acid to noticeably accelerate new shoot growth; it has the same effect on flower clusters. For varieties with relatively tight clusters, application can lengthen the rachis and make the clusters looser. At the 3—4 leaf stage, spray 25% difenoconazole EC at 3500 times (or 20% difenoconazole water-dispersible granules at 3000 times) plus 2.5% cyhalothrin at 2000 times plus foliar fertilizer 300 times urea, 500 times manganese fertilizer, 600 times Shanghao potassium, and 600 times peptide protein. This spraying prevents and eradicates various pathogens and pests just after overwintering and sprouting, with emphasis on preventing white rot, anthracnose, black pox, rachis withering blight, black rot, green plant bug, spotted lanternfly, and so on.
Pre-flowering management: from leaf expansion to before flowering, focus on doing six tasks well:
1. Shoot thinning should be early. To save tree nutrition, when new shoots grow to 20—40 cm, select thick new shoots with flower clusters and cut away weak shoots, water sprouts, and overly dense vegetative shoots, that is, shoots without flower clusters, so that new shoots grow evenly. Generally, each fruiting mother cane keeps only 1 fruit cluster. To prevent downy mildew, anthracnose, white rot, and black pox, spray mancozeb at 500—800 times. The focus of spraying should be new shoots and flower clusters. The zinc and manganese ions in mancozeb can be absorbed by grapes as trace elements and are beneficial to grape growth. When spraying, add foliar fertilizer 200 times urea, 300 times zinc sulfate, 500 times manganese fertilizer, 500 times Shanghao potassium, and 500 times peptide protein.
2. Tie the canes well. When new shoots grow to 40—50 cm, tie the new shoots promptly to prevent wind breakage. When tying new shoots, make the branches evenly distributed on the trellis; generally, a branch spacing of about 20 cm is appropriate. Grasping the timing of topdressing base fertilizer for fruit trees has a very good promoting effect on fruit tree growth, fruit quality improvement, and high yield. The first topdressing of base fertilizer should be around April 20 before flowering, applying 25 kg of nitrogen-phosphorus-potassium compound fertilizer, 30 kg of Saizhong 28 fertilizer, and 30 kg of humic acid organic fertilizer per mu, then irrigate after application.
3. Correct the flower clusters. About seven days before flowering, correct the flower clusters to reduce the number of flower buds. To improve berry quality, for (Hutai No. 8), remove the upper 4—6 spikelets of the rachis and keep only the lower spikelets, keeping only 15—20 spikelets per cluster, that is, keeping 60—80 flower buds.
4. Pinching and lateral shoot treatment. Generally, for varieties prone to flower and fruit drop (such as Hutai No. 8), pinching should be carried out from 4—5 days before flowering to the beginning of flowering. The degree of pinching is generally to leave 10 leaves above the flower cluster before pinching, and all other lateral shoots are removed. Later, when terminal winter buds appear, leave 2—3 leaves and repeatedly pinch.
5. Spray gibberellic acid and boron, zinc, manganese fertilizers, etc. About seven days before flowering, spray 10 ppm gibberellic acid once to promote the growth of new shoots and flower clusters. Add foliar fertilizer 300 times urea, 300 times borax, 300 times zinc sulfate, 400 times manganese fertilizer, 400 times Shanghao potassium, and 400 times peptide protein. Spray continuously 2—3 times at intervals of 5—7 days, which can promote flower organ differentiation and overcome uneven berry size.
6. Prevent and control diseases and pests. At 3—5 days before flowering, to prevent downy mildew, powdery mildew, black pox, black rot, rachis withering blight, gray mold, and white rot, spray once a long-lasting multifunctional fungicide 25% azoxystrobin at 1500—2000 times, plus insecticide and acaricide sprayed once, plus foliar fertilizer with high active content and a balanced full-element ratio, Green Giant High-Calcium Boron Zinc Potassium at 600—800 times, 300 times manganese fertilizer, 400 times Shanghao potassium, and 400 times peptide protein. To reduce costs as above, if referring to orchards with not serious disease conditions in the previous year, one may also spray 68% Jinlei at 800 times, foliar fertilizer Green Giant at 500 times, 300 times manganese fertilizer, 400 times Shanghao potassium, and 400 times peptide protein, focusing on eradicating downy mildew, but the preventive effect on other diseases is not as good as 25% azoxystrobin.