Scaffolds 01 index

(Jim Schupp, jrs53@cornell.edu, Horticultural Sciences, Highland)

Apogee (<Greek.> apo- far from + gaia- earth). 1. The point in a satellite's orbit that is highest or furthest from the earth. 2. A new plant growth regulator for apples that has just been registered for use in New York State.

Apogee plant growth regulator for apples has been registered for use in New York for the 2001 season. Apogee blocks the synthesis of gibberellins, the naturally occurring plant growth substances that promote shoot elongation. When Apogee is applied, the actively growing shoots on the apple tree slow down over the following 10—14 days, then stop elongating altogether. The result is shorter shoots with fewer leaves. This arrested growth lasts for three to six weeks, depending upon the dose used, and the natural vigor of the tree. By making one or two repeat applications of Apogee, you can control growth for the entire season, under New York growing conditions.

Reducing shoot growth increases the penetration of sunlight to the interior of the tree canopy, improving fruit color and fruit quality. Dormant pruning time is reduced by 40—50%, and the need for summer pruning may be eliminated. Treatment with Apogee also reduces the severity of the shoot blight phase of fire blight.

Over the next three issues of Scaffolds, we will cover the keys to success with Apogee, starting with the decision of where to use it, then discuss rates and timing, followed by application advice. The goal of these articles is to enable growers to make informed decisions and to get optimal cost-effective performance from this exciting new product.

Where to use it.

In relation to tree vigor and tree size: If orchard vigor is low, shoot length will be short and there is little reason to apply Apogee. Apogee will be very beneficial in those orchards with average vigor, where annual terminal growth is 18—24 inches. Blocks with excessive vigor, especially those where the combination of close tree spacing and high vigor creates overcrowding, are great candidates for Apogee.

Apogee will probably provide the greatest amount of economic benefit in vigorous semi-dwarf and dwarf orchards. Yes, Apogee will reduce growth and pruning time for trees on standard rootstock, but one is still left with total canopy volume that is too large for optimal fruit color. It will also take more Apogee per acre to effectively treat larger trees, resulting in greater cost per acre.

In relation to pruning: Apogee will reduce pruning time, but it will not replace annual dormant pruning. It will provide the greatest benefits on trees that have been dormant pruned. There are some benefits from pruning that Apogee will not provide.

Dormant pruning removes damaged and diseased limbs and maintains the proper canopy shape by eliminating limbs that have grown too large for their position in the canopy. Pruning reduces the number of spurs and the number of growing points, and so it is important for maintaining a healthy balance between growth and fruiting. Renewal pruning selectively removes older, less productive wood, and stimulates new branches with younger, more productive spurs. Pruning is a fruit grower's first crack at thinning too. Removing competing fruiting spurs and their potential fruits increases fruit size and quality. In short, Apogee is a new tool to help the professional grower do a better job of canopy management with reduced labor, not a crutch for poor management practices!

In relation to varieties: Apogee has been effective on all the varieties tested, including most if not all of the commercially important ones. McIntosh is perhaps the toughest variety to manage with Apogee, but even Mac can be tamed with timely sprays and good coverage. Vigorous, blight-susceptible varieties such as Gala, Gingergold, and Fuji should be right at the top of the list for Apogee.

Apogee applications have caused fruit spotting/corking and cracking on Empire in some trials. For 2001, the Apogee label will carry a caution statement to advise growers about the possibility of cracking on Empire and Stayman. This damage doesn't always occur, and researchers are actively searching for the cause and its cure.

I'm not sure Empire needs Apogee. Empire is a relatively low vigor cultivar, so I see the primary benefit of Apogee to Empire as eliminating summer pruning to improve fruit color. The damage has been observed in NY in wet, cloudy years (1998 and 2000), but not in a dry sunny year (1999). It's possible that this problem is worse with poor drying conditions, so that may also be a factor for growers to consider.

Should you use it this season? In many orchard blocks, Apogee would increase fruit color and reduce growing costs. I would encourage growers to try Apogee in a few such blocks, and to leave check trees to allow a firsthand comparison. High levels of fire blight inoculum are present in some orchards; so using Apogee to supplement streptomycin sprays in these orchards will make a lot of sense if the weather favors fire blight infection during bloom.

Apogee may eliminate the need for summer pruning, and our studies show it reduces dormant pruning by 40—50%. Since pruning is one of the largest labor expenses in apple growing, the pruning labor that can be saved with Apogee justifies the expense of this product in many orchards. Each block has different pruning requirements based on tree size and vigor, so I encourage growers to use the estimated 40—50% savings to identify those blocks where Apogee will give them the most benefit.

Next installment: Rates, timing, and scheduling

Scaffolds 2001 index