Posted: Fri Apr 07, 2006 8:24 pm Post subject: Unidentified chlorotic dieback
I have a peach/nectarine/cherry/apricot grower who has been under my advanced fertility program for 10 years. He recently planted 1 ac citrus (Meyers lemons, blood oranges, others) - they are not responding. See pictures,
Here is the data & fertilizer history (my interpretations):
Soil is clay, CEC 24. Ratios of cations; Ca 65% (low): Mg 26% (v hi): K 5.9% (ok-hi): Na 2.1 (ok).
plenty of P2O5, K2O.
Micronutrients: Excess Zn, Cu, Ok levels of Fe, Mn, B
Tissue/Leaf: Nitrogen - 2.4% total, 48 ppm Nitrate (low-ok) K 0.9% (lo), Ca 2.3% (lo), Mg 0.3% (lo-ok), Zn 15 ppm (lo), Mn 31 ppm (ok), Fe 179 ppm (ok) Cu 15 (ok)
It looks like a calcium/boron problem to me; also like zinc deficiency.
Fertilizer history: We have added calcium, zinc sulfate to soil, N @ 10 #/ac using fish emulsion. No Zn applied to foliage.
Symptoms: Chlorotic leaves, yellow mid-ribs, brown spots on undersides. Die back/defoliation of shoots, small leaves, flattened shoots. See pictures.
If you can help identify the problem, thanks
--
Gregg Young, M.A.
Certified Professional Agronomist
Environmental Scientist
P.O. Box 246
Talmage, CA 95481
Posted: Fri Apr 07, 2006 8:36 pm Post subject: Spring twig dieback, weak roots
Hi Gregg,
I have seen this same problem developing over the last couple of years in an orchard I have been watching for 17 years.
I don't know what it is either, but I have a guess. The UC IPM manual for citrus describes "twig dieback" caused by a poor root system or scion-rootstock incompatibility, in combination with cool soil and increased water demand in the spring. I suppose this could also lead to symptoms of nutrient shortages.
My orchard has had some serious dieback.
I don't know what to do about this, except to try to strengthen the roots.
Devin Carroll