varieties can be changed at a high level by a simple procedure for dormant T-buds on fruiting .

Fbud grafting of grapevines Curtis J. Alley

fast, easy, foolproof method is stocks that are too large for chip-budding inch) to a few at about 180 cm (7 feet); A needed for topworking fruiting (over 1 inch in diameter). There is also a most were 75 to 90 cm (30 to 36 inches) grapevines to a better variety high above way to T-bud dormant mature vines at a long. ground level (that is, just below the bot- high level. Vines with buds inserted 2 to 3 cm tom trellis wire). High-level grafting with (V4 inch) from the top grew the most. the graft or the wedge graft re- T-budding experiments Those with buds inserted 10 to 15 em (4 quires time, considerable skill, and two to 6 inches) below the top usually had one or more applications of a good grafting In 1975, it was reported that grow- strong shoot; the second bud either re- compound. Usually, less than 90 percent ers in Mexico were successfully using a mained dormant or produced a weak of the grafts take. dormant T-bud wrapped with plastic tape shoot. T-budding has been the common on fruiting vines at a high level. The The heavy growth of watersprouts practice for years to change varieties in technique was developed in Argentina. at the top of the vines and on the trunks young deciduous trees, either in the On June 11, 1976, we started re- was removed after the July 28 inspection. fall, when the bark is still slipping, or in search at the Kearney Horticultural Field Those vines that had been budded 10 to the spring. Branches budded in the fall Station, Parlier, California, to see if the 15 cm (4 to 6 inches) below the top were are cut off above the bud the following T-budding method of topworking was topped to within 2 to 3 cm (% inch) of spring to force the bud. Branches or better than the wedge-grafting technique. the buds. young scaffolds budded in the spring may Six-year-old vines of St. Emilion were T- By August 31, 90 percent of the be cut off 25 to 30 cm (10 to 12 inches) be- budded to Carignane. The budwood, col- grafts had taken and produced shoots. As yond the bud at the time the bud is insert- lected in December 1975, had been wetted workers become more familiar with the ed, and cut back to 2 to 4 cm (1 to 1% thoroughly, placed in 6-mil, 90-cm by 150- technique, the 95 percent rate of takes inches) about 10 days later. cm plastic bags, and refrigerated at Oo to reported by Mexican growers can prob- T-budding is also the most common 1.5O C (32O to 34O F) until used. The tops ably be achieved. form of budding in the nursery row in of the vines were cut off about 90 cm (3 May and June on seedling fruit tree un- feet) above the ground, or about 30 cm (12 Tobudding procedure derstocks or rooted cuttings of resistant inches) below the bottom wire of a two- rootstocks. wire vertical trellis. Vines were 3.7 to 5 The was decapitated, and all loose On grapevines,'T-budding has been cm (1 '/z to 2 inches) in diameter. bark was removed from the area on the used primarily in breeding work. Green Two T-buds were inserted into each vine trunk where the incision was to be buds are inserted into the base of green vine-on opposite sides, in line with the made. A vertical cut 2 to 4 cm (3/4 to 1% shoots in early summer so that seedlings row. Buds were inserted 10 to 15 cm (4 to inches) long was made, 2 to 3 cm (% inch) will fruit early. T-budding is not satis- 6 inches) below the cut-off tops of most below the top. A knife designed for T- factory on grapevines under 1 inch in di- vines and 2 to 3 cm (3/4 to 1 inch) below budding (not chip-budding) was used ameter, because the bark is very thin and the cut-off tops of a few others. (fig. 1). tears easily, and most grape buds are too On July 28,76 of the 100 buds that The second cut was made at a right large to be easily inserted under the bark. had been inserted were growing. On most angle (or slightly less) to-and crossing Dormant mature buds may be used of the vines, both buds were growing. the top of-the first cut. When cutting for T-budding at ground level on - Shoots varied in length from 2 to 3 cm (3/4 through the bark, the knife was held at

4 CALIFORNIA AGRICULTURE, JULY 1977

an angle so that, as the blade crossed the vertical cut, it tended to peel open one of the corners of the bark where the two incisions crossed (fig. 2). The high point of the knife blade (quill) was then used to peel open both corners (fig. 3). The trunk was now ready for the bud to be inserted (fig. 4). lower ethephon rates With a bud stick about 1 em (Vz inchlin diameter, the budder made a cut effective in walnut harvest angled downward into the stick, from about 2 cm (Y4 inch) above the bud to about 2 cm below the bud (fig. 5). A sec- ond angled cut made downward about 1 to 2 cm (VZ to Y4 inch) below the bud met the first cut and severed the bud from the stick (fig. 6). The second angled cut below the bud exposes more cambium revious research results have clear- Each trial was replicated three surface (fig. 7) for better callusing, which P ly demonstrated that early walnut times with an average of 20 trees per first occurs at this point. harvest provides for the maximum quan- replicate. Ethephon was applied at PTB The bud was inserted under the tity of lightoolored kernels as well as (harvest commencing approximately 10 open corners of bark, and the base of the the minimum amount of navel orange- days later) at the following rates per acre: bud shield was pushed well below the worm damage. 3 pints in 100 gall^^ of water. bottom of the vertical cut with the point Walnut kernels are mature, light- 3 pints in 300 gallons. of the knife blade (fig. 8). The bud was est in color, and of most value when the m 4 pints in 100 gallons. then covered with tightly pulled, over- packing tissue surrounding the kernel 4 pints in 300 gallons. lapping wraps of white, 4-mil, plastic halves has just turned brown (PTB). m 6 pints in 100 gallons. flagging tape. Since the understocks were This usually occurs 2 to 3 weeks before 6 pints in 800 gallons. about 5 cm (2 inches) in diameter, a 2.5cm sufficient hull splitting for harvest occurs. 0 pints (untreated check). (I-inch)tape was used, starting below the By applying the growth regulator ethe- In each trial care was taken that bud (fig. 9) and wrapping up to about 2 to phon at PTB, hull dehiscence is acceler- ethephon-treated hsreceived thorough 3 cm (1 inch) above the horizontal cut ated, and walnut harvest can be advanced spray coverage. The walnut crop removed (fig. 10). by 6 to 10 days. Not only is harvest ad- from each treatment during each best The final few wraps were brought vanced, but in many cases, a complete operation WM accurately weighed to down to just above the bud and tied by harvest is obtained in one operation. Pro- determine the percent of the crop re- tucking the end of the tape under the last per we of ethephon has made it possible moved with each harvest.. wrap and pulling tightly to stretch the to maintain kernel quality of harvested Harvest began for all treatments, tape. walnuts at a much higher level. including the untreated check, on the Tape wrapped in this way can be In spite of benefits provided same date. In this way, date of harvert partially removed later if there is evi- through earlier harvest with ethephon, was eliminated as a factor governing dence of constriction or girdling of the growera have been somewhat reluctant completenessof harm& shoot. Cutting across the tape up to the to use the growth regulator. Of particu- bud on the side of the vine relieves pres- lar concern has been the expense of Rerub sure below the bud. The tape will unravel applying ethephon at the registered rate below but not above the bud because of of 6 pints per acre and uncertainty about Ethephon applications increased the percentage of removal in the harvest the overlapping last tie just above the the material's effectiveness in providing first in all locations (5g. 1). In the San Joaquin bud. The tape should not be cut or re- an early, single harvest. moved above the bud until fall, unless Valley, nut removal was Increased by 15.8 to 21.8 points, in the Sacra- there is evidence of girdling above the HOWOSMCIIS percentage bud. mento Valley by 11.3 to 15.7 percentage The tape held the buds tightly in The purpose of these trials was to points, and in the coastal region by 24.0 place and prevented the shoots from compare ethephon's effectiveness at 6 to 413 pertentage points over tbe un- breaking away. When the shoots were pints per acre with that at 3 and 4 pints treated check. about 45 cm (18 inches) long, they were per acre at dilute and semieoncentrate Although the Payne variety used fastened to the bottom wire for support. gallonage. in tbe cosstal region resulted in the low- To provide the more flexible established Replicated trials were established est percentage of nut removal in the first cordon needed for mechanical harvesting, during 1976 in three areas of California harvest, it also resulte&in the greatest each shoot was crossed over the top of with different climates: the San Jquin response in terms of percentage of re- the stock so that it was established on Valley, the Sacramento Valley, and moval over the untreated check. In no the side opposite the bud insertion. the coastal region. In each location a case was 100 percent nut removal ob different walnut variety was used in the tained in the firat harvest. However, in Curtis J. Alley is Specialist, Depart- trial: Marcbetti in the San Joaquin the Sacramento Valley trial, well over 90 ment of and Enology, Uni- Valley, Ashley in the Sacramento Valley, percent of the nuts were removed with versity of California, Davis. and Payne in the coastal region. one harvest, leaving M) few nuts that the i 6 CALIFORNIA AGRICULTURE, JULY 1977