This article is the third and final in a series on choosing almond varieties.
This third article (see Part 1 and Part 2) continues to look at the “checklist” of issues to consider when choosing almond varieties. At the 2009 Almond Industry Conference, a panel of experts gave growers assistance in this choice by reviewing variety development, evaluation and selection, balancing both field and market considerations. The panel included Tom Gradziel (UC Davis almond breeder), Joe Connell (UC farm advisor, Butte County), Bruce Lampinen (UC Pomology Extension specialist), Ned Ryan (past Almond Board chair and almond industry consultant) and Roger Duncan (UC Davis farm advisor, Stanislaus County).
This last installment looks at disease and insect susceptibility, kernel quality and “fit” for your farming operation and style.
A comprehensive chart summarizing varietal resistance to several diseases and insects is included on page 11 of the UC publication “Integrated Pest Management for Almonds,” Second Edition (UC Agriculture and Natural Resources publication 3308, published in 2002). While this is a good resource, some of the information has been updated since publication as a result of findings from the Regional Variety Trials (RVT) funded by the Almond Board and other sources. For instance, Nonpareil is among the more tolerant varieties to Alternaria, rather than being very susceptible. An updated version of the RVT findings can be found at the link mentioned in the last paragraph.
In addition to these findings, farm advisor Joe Connell provided his own disease summary, noting the RVT plots have been valuable for identifying newer test varieties that are highly susceptible to certain diseases that are “bad standouts” during wet years such as occur during an “El Niño.” These observations are included in Connell’s presentation, which can also be found by following the link at the end of this article.
Among the newer and more popular varieties not listed in the UC IPM publication is Winters, which is very susceptible to anthracnose, Alternaria and scab. Farm advisor Roger Duncan additionally cautioned that a variety such as Winters that is partially self-compatible and has set and performed well in the more rainy north may not be appropriate for southern plantings where Alternaria is a persistent problem.
Almond breeder Tom Gradziel underscored this by saying location is critical to assessing performance, which should be done under different conditions. A valuable aspect of the RVT plots is they have been planted in three distinct almond-growing regions: north, central and south.
Worm pressure — primarily, navel orangeworm and secondarily, peach twig borer — varies by region, according to Duncan, but the relative tolerance-susceptibility ranking of different varieties is stable and is dependent on both shell seal and hull split/harvest timing in relation to insect flights.
One source of data supporting these conclusions is the RVT plots, particularly the Kern County 1993–2006 trial. Another resource is the industry-wide percent inedible (reject) data published by the Almond Board. A five-year (2006–2010) recap ranking rejects of the top varieties and Winters is available through the Varieties page accessed by the link near the end of this article. This recap parallels the RVT observations and research, and the data shows Nonpareil is susceptible to worm damage, while a number of key varieties sustain less damage, and some varieties, such as Sonora, have somewhat more damage than Nonpareil.
The RVT reports also have data on percent double kernels and twins (two kernels within the same pellicle). The data should be assessed over a number of years to look for a consistent trend within a variety, such as is found with doubling occurrence in Monterey. Even so, as Roger Duncan noted, it is important to check with your handler to determine if doubling and twins are important factors in light of applications such as dicing or consumer end uses such as in-shell.
“Fit” for farming operation and style
Farm advisor Duncan explained how operation size can impact decisions on the mix of varieties. Growers farming several hundred acres may want to spread out cultural operations, such as bloom sprays and harvest. Small growers may want to minimize the number of varieties, grow varieties that can be harvested within a short time frame and either mixed together or kept separately, or grow what a neighbor has in order to share equipment. These bloom and harvest considerations were covered in the second article of this series, which can be found online at www.farmpress.com/tree-nuts.
Lastly, variety choice may be a matter of style. Are you a risk taker? As Duncan pointed out, there are plenty of new promising varieties: Sweetheart, Avalon, Durango, Folsom, Independence, Kochi, Marcona and Supareil. For several of these, there are no long-term data spanning both a number of years and locations. Nevertheless, you may want to diversify your “risk portfolio” by trying out a new variety, which may turn out a winner. In doing so, almond breeder Tom Gradziel noted, you may experience the “Tiger Woods Effect,” in which no matter how promising a new variety is, it is performance over the life of an orchard that makes money. Connell concluded by saying the final test is if, after 20 years’ experience, you would choose to replant with that same variety.
For information on almond varieties, including the complete conference panel presentations and reports from the Regional Variety Trials sponsored by the Almond Board, go to AlmondBoard.com/farmpress22. Another valuable resource is the chapter “Evaluation and Selection of Current Varieties” in the Almond Production Manual (UC Division of Agriculture and Natural Resources, Publication 3364, published in 1996).