ISHS Acta Horticulturae 726: IV International Symposium on Pistachios and Almonds
AN INVESTIGATION OF SOME CAUSES OF DIE-BACK DISORDER OF PISTACHIO TREES AND ITS CONTROL THROUGH BALANCED FERTILIZATION IN IRAN |
| Authors: | V. Mozzaffari, M.J. Malakouti |
| Keywords: | pistachio (Pistacia vera L.); salinity; sodium; canker; potassium; calcium; zinc-fertilizer and pistachio yield. |
| Abstract:
The incidence of die-back in pistachio (Pistacia vera L.) occurs extensively in pistachio orchards of Iran where it has caused yields to be low. In order to evaluate the spread per cent occurrences and to determine the causative factor(s) of this incidence, some 203 pistachio orchards located in Rafsanjan, Kerman, Yazd and Khorasan regions were visited during the period 2002-2004. It was noted that 4-90 per cent, or on average 28 per cent of the trees had been affected and that the rate of this incidence had increased by 60% during the ten-year period from 1994 to 2004. Soil samples from profile depths of 0-40, 41-80 and 81-120 cm were collected in 31 randomly selected orchards for physicochemical analysis. Likewise, leaf samples as well as samples of irrigation water were collected in those orchards for chemical analysis. Then, correlations between the incidence of die-back and the examined factors were calculated. It was noted that the incidence of die-back in pistachio was positively correlated with soil EC, Na, K, SAR, Na/Ca and Na/K values. A stepwise regression analysis yielded this equation: Y= 51.799-0.194 (K)soil+0.946 (SAR)soil , R²= 0.737. On the basis of our research and reports by others, the fungus Paecilomyces variotti was found to be a causative agent of die-back in pistachio. A randomized complete block design experiment was conducted with 4 treatments and 6 replications on a total of twenty four, 25-year old trees of the pistachio variety Fandoghi, of which 40% was affected by the die-back problem in order to investigate the effect of balanced fertilizer application on preventing this incidence. The treatments included T1= the growers’ conventional method (ammonium sulfate+triple superphosphate at the rate of 3 kg each per tree); T2=T1+ potassium at the rate of 3kg potassium sulfate per tree; T3= T2+calcium applied as gypsum at the rate of 40 kg/tree; and T4=T3+zinc applied as zinc sulfate at the rate of 1500 g/tree. The direct fungal inoculation of the trees followed two years of the fertilizer treatments. The results showed a significant decrease (at 1% level) in the incidence of die-back with treatments T2, T3 and T4 as compared with the farmers’ conventional fertilization method. In other words, the application of potassium, calcium and zinc-fertilizers reduced this problem by 63 percent. | |
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