[NAFEX] FW: Combating a Pecan Disorder

Lon J. Rombough lonrom at hevanet.com
Thu Mar 6 10:18:11 EST 2003



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From: ARS News Service <NewsService at ars.usda.gov>
Reply-To: ARS News Service <NewsService at ars.usda.gov>
Date: Thu, 06 Mar 2003 07:17:18 -0500
To: ARS News subscriber <lonrom at hevanet.com>
Subject: Combating a Pecan Disorder

STORY LEAD:
Scientists Offer Suggestions to Combat Pecan Vivipary

___________________________________________

ARS News Service
Agricultural Research Service, USDA
Sharon Durham, (301) 504-1611, sdurham at ars.usda.gov
March 6, 2003
___________________________________________

Maintaining soil moisture levels may be one approach to combating pecan
vivipary, the premature germination of pecans, according to Agricultural
Research Service scientists.

Based on several years of study, ARS scientists at the agency's Southeastern
Fruit and Tree Nut Research Laboratory in Byron, Ga., are offering pecan
producers several suggestions to combat pecan vivipary. In addition to
controlling soil moisture levels, other useful actions could include using
an aphid pesticide and thinning tree nuts to prevent the disorder.
   
For growers trying to control vivipary, the scientists report, it's
important to ensure that soil moisture levels are near field capacity during
the kernel-filling stage (usually September and October for most U.S.
cultivars and locations). Growers also can take advantage of the
early-ripening effect of a commonly used aphid pesticide. And, along with
thinning excess fruit, they can harvest early to help avoid vivipary.

The scientists found that premature germination is closely associated with
high temperatures during the latter stages of kernel filling, but that high
temperatures alone do not necessarily lead to vivipary. It may be that a
combination of high and low temperatures, such as hot days and cold nights,
helps cause the disorder.

Vivipary also seems driven, at least partially, by an interaction between
nut temperature--the magnitude of that temperature change during a 24-hour
period--and nut moisture content. A genetic component may also contribute to
vivipary.

Nuts exhibiting premature germination quickly undergo a loss in quality and
become worthless, making vivipary disorder a major economic problem. While
many growers may never have seen the malady in their particular farming
operation, other growers in the U.S. pecan belt commonly suffer substantial
marketable yield losses, which can exceed 50 percent. Its impact is usually
greatest in the lower San Joaquin Valley of California, lower elevations in
Arizona, and portions of the mid- to lower Rio Grande Valley of Texas.

The Southeastern Fruit and Tree Nut Research Laboratory continues to look
for additional strategies and tools that growers can use to eliminate
vivipary. 

ARS is the U.S. Department of Agriculture's chief scientific research
agency. 
___________________________________________

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