By Joe Traynor
The California almond industry has been trying to develop a commercial self-fruitful almond variety – a high yielding variety that produces a quality nut – for more than 50 years. Such a variety would reduce or eliminate the almond grower’s dependence on honeybee pollination. Although progress has been made in developing self-fruitful varieties, the light at the end of the tunnel is still barely visible.
The recent run-up in almond acreage is putting increased pressure on a bee supply that is static or decreasing. Some growers have reduced their bee needs by planting alternate blocks of early and late-blooming varieties. The five to seven day gap in bloom dates allows these growers to get close to double duty from their bees. There is, however, a limit to the acreage of such early-late plantings since the market for late-blooming hardshells is limited (prices for hardshells are about 10 cents per pound below Nonpareil prices and a significant increase in hard-shell acreage would widen this price differential).
Currently, late-blooming varieties comprise about 14 percent of California’s bearing almond acreage. Interestingly, 25 percent of the non-bearing acreage in 1998 was late blooming if one includes the Butte variety; 22 percent of this non-bearing acreage was Butte, which is currently being included in Nonpareil plantings as well as with Mission (and Ruby and Padre) plantings. Butte blooms a few days before Mission and few days after Nonpareil, thus occupying a “no-mans land” between early and late-blooming varieties.
Pollination prices plummet in March because of the exodus of bees from early-blooming almonds (see diagram). If the almond industry were to develop varieties that bloom in March, the potential bee shortage problem would be solved and almond pollination costs would drop.
Three weeks later, the risk of poor weather during bloom would be greatly reduced and there would be a much more stable supply of almonds. Currently, almond yields are directly correlated with weather conditions during the seven to 10 day period of Nonpareil bloom; this results in significant variations in year to year crops. March-blooming varieties would greatly reduce such year to year variations (and would reduce or eliminate the potential for frost damage for most growers).
There are three ways to develop almond varieties that bloom in March:
- Breed new varieties – probably the best long-term solution, but will take time.
- Delay bloom on current varieties with chemicals – Dormex and calcium nitrate are currently widely used by cherry growers to get cherry trees to bloom earlier. There are chemicals (e.g. ethrel, gibberellin) that will delay bloom in almonds but limited tests done a number of years ago gave erratic results. More work should be done in this area and new chemicals should be looked at.
- Use a late-blooming rootstock and/or interstock – Late-blooming rootstocks or interstocks will delay the bloom of the top variety. It might be difficult to develop a late-blooming root-stock that has the desirable characteristics of current rootstocks, but an interstock – a sandwich variety between the top and rootstock – could be used (see figure).
Late-blooming interstocks are being used on apples and peaches to delay bloom past the period of greatest frost hazard. Late-blooming almond varieties (e.g., Tardy Nonpareil, which blooms in March) are available for interstocks on almonds (the potential of virus or disease transmission via the interstock would have to be addressed).
It is likely that a late-blooming interstock would give only a five to seven day delay in bloom at best (although this should be determined) – not enough for a March-blooming Nonpareil, but if used in conjunction with bloom-delaying chemicals, a March-blooming Nonpareil could become a reality.
A possible concern with a March-bloom Nonpareil (or other varieties) is a late harvest; however, UC. data show that the Tardy Nonpareil variety harvests only a short time later than Nonpareil and well before Mission.
If March-blooming almonds were developed, beekeeper income would decline, but for many beekeepers March-blooming almonds would provide the benefit of providing a food source during a time when money must be spent to feed bee colonies.
The significant benefits to the almond industry of March-blooming almond varieties certainly warrant further work in this area. Such work should be initiated before a diminishing supply of bees has a significant impact on almond yields and/or before rental prices for bees become unaffordable.
Joe Traynor is the manager of Scientific Ag, a bee brokering firm in Bakersfield, Calif