Vegetative Growth and Citrus Leaf Miner Infestation as Affected by Different potassium Sources in East of Mazandaran

In order to study the effect of potassium fertilizers on vegetative growth and reducing citrus leafminer (Phyllocnistis citrella) damages, an experiment was conducted on 3 years old tamson navel orange in sari area. Three sources of K fertilizer were used in the form of soil and foliar application of K2SO4, foliar application of K2SO4, KNO3 and KCl in main plot and interaction between concentration and time in subplot. The experiment was done on the basis of split factorial de sign in 3 replication during 2 years. Summer and fall vegetation (included shoot length and number of leaf) and the percentage of injoury of leafminer were recorded from 4 June, each 15 days, to mid november. This was done through measuring the number of larva in the leaf and the area of the leaf surface, which was contaminated by larva. Result showed that in the first year of the experiment, the ratio of contaminated percentage/ leaf number in summer vegetative growth was lowest in the spraying of K2SO4 treatment and highest in the spraying of. KCl. Foliar application of K2SO4 was more effective than KCl and KNO3 in reducing of leaf contaminated area. In fall vegetation growth, Larva number, contaminated Leaf percentage, contaminated percentage/length ratio and contaminated percentage/length number ratio were minimum in the foliar application of high concentration of KCl. In the second year the treatment had not effect on the summer vegetation growth indices. Fall vegetation growth and the percentage of leaf contamination were significantly changed. The highest amount of contamination percent was produced in soil application of K2So4 and the lowest one produced in the foliar application of K2SO4 (along with soil application) and Kno3 with high concentration treatments. Combined analysis of data showed that sources of potassium had no significant effect on the growth indices and contamination percent, which produced on summer shoots. The highest number of larva and contaminated leaf number were produced in the KCl spray and the lowest one produced in the K2SO4 spray and soil and foliar application of K2SO4. The most important indices under study were the contamination percentage/length and contamination percentage/leaf number ratios, which were lowest in the soil and foliar application of K2SO4. Analysis of the time of foliar application showed that spraying in may had the best effect on the indices under study. Increasing in contamination had the favorable trends on fall growth because, in the highest concentration, the minimum of contaminated percentage, larva number, contaminated leaf number contaminated. percentage/length and contaminated P. /leaf number ratios were take placed. With increasing of K concentration, it is showed that, K had more effect on reducing of damage although K concentration in leaf was not increased significantly.