IN YOUR ORCHARD
The loss of fruiting wood, especially in the lower parts of the tree, can negatively affect yield. The disease is caused by two fungal pathogens that enter the hulls after split and release a toxin that can kill leaves and twigs. Vigorous, heavily cropped, five to ten-year-old, well-watered and fertilized orchards suffer the most damage. Irrigation management is the only practical control for hull rot, although many growers apply a fungicide to their hull split NOW sprays. Research has shown that hull rot can be reduced by inflicting mild water stress on trees during early hull split. Mild water stress does not negatively impact long
term productivity and may even reduce unwanted vegetative growth in mature canopied orchards. In order to achieve mild water stress we recommend using a pressure chamber to monitor midday stem water potentials (SWP) through the season in order to keep fully irrigated trees between stem water potentials of -7 to -9 bars. Then during hull split we try to irrigate less to achieve stem water potentials between -14 to -18 bars, with the larger negative number having more stress. Without a pressure chamber growers can try putting on 50% of their normal irrigation water during the week before and the first two weeks of hull split. For flood or furrow, you can irrigate every other row if solid irrigation was used normally. Unfortunately, without a pressure chamber it is easy to over stress trees at exactly the hottest time of the season when there is a ‘fine line’ or ‘happy medium’ between yield, disease, and imposing regulated deficit irrigation at hull split for every orchard. Pushing trees too hard for maximum growth and yield may ultimately lead to increased disease severity and reduced long term productivity. Stressing trees too much in June and July can reduce nut size, spur growth, and the developing buds for next year.
Fan-Jet Microsprinklers ®
Add a line of Fan-Jets ® Precision Rain - Rain when you want it, where you want it. Frost Protection - Fan-Jets can help provide frost protection by raising the ambient temperature by 2-3 degrees. Fan-Jets will allow you to push salts away from the root zone. Fan-Jets will help your pre-emergents penetrate the soil.
Good luck!!!
Brent Holtz, Ph.D., Orchard Systems Advisor, University of California Cooperative Extension in San Joaquin County baholtz@ucanr.edu
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ALMOND FACTS
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