تاثیر عناصر غذایی ارقام مختلف نخل روی جمعیت زنجرک خرما Ommatissus lybicus (Hem. Tropiduchidae)

Ommatissus lybicus is one of the key pests of Iranian groves. This study aimed to evaluate the effect of different palm cultivars on O. lybicus. The experiment was carried out in a randomized complete block design with 3 treatments (except in Kerman) and 4 replications plus control on same-age palm trees. The treatments in Hormozgan province were the Mazafati, Khasoui, and Piarom. The Mazafati, Zahedi, and Shahani cultivars in Fars province and the Karout and Mazafati cultivars in Kerman province were chosen as treatments. Bio2 (0.3% EC) (1.25 ml/L) was spraying when the second and third instars of O. lybicus nymphs emerged in the winter generation. Nymph and honeydew droplets were counted before and 14 days after spraying. The percentage of calcium, nitrogen, potassium, crude fiber, and sugar were measured in date palm leaves. The dubas quantity ratio (DQR) was used to show differences in the relative preference of the pest compared to the cultivars. Pearson correlation analysis and the complete clustering method were used to compare the dubas numbers among cultivars, then the complete clustering method was also used to divide the cultivars into different groups. The most effective variable in the nymph of O. lybicus population was determined by stepwise multiple regression. Analysis of variance of nymph and honeydew droplet counting in 14 days after spraying on different cultivars showed no significant difference between the cultivars in the three provinces. The comparison of the mean of elements percentage and the weight of leaves in Fars province showed that the Shahani cultivar had the highest rate of calcium (0.52), potassium (1.42), and sugar (0.19). In Kerman province, the rate of nitrogen and weight showed significant differences. The Karout and Mazafati cultivars had the highest rate of nitrogen (1.91) and weight (2.45), respectively. In Hormozgan province, the highest rate of calcium (0.61), nitrogen (1.93), and potassium (1.49) were in Khasoui cultivar while the highest rate of crude fiber (23.60) and sugar (0.11) were observed in the Piarom cultivar. The correlation between different date palm cultivars and the average of O. lybicus nymphs showed a highly significant negative correlation (-0.947 and 0.910 one day before and 14 days after spraying, respectively). The correlation between different date palm cultivars and the percentage of elements revealed that there was a significant negative correlation (-0.714) only between the weight of the leaves and the cultivar. Among the examined parameters, crude fiber was the most effective variable (R2=0.70) in the population of O. lybicus nymph with a negative correlation (-29.72).