Effects of Naphthalene Acetic Acid and Carbaryl on Fruit Thinning in ‘Kinnow’ Mandarin Trees


1 Department of Horticultural Science, Collage of Agriculture, Shiraz University, Shiraz, Iran

2 Department of Horticultural Science, Collage of Agriculture and Natural Resources of Darab, Shiraz University, Shiraz, Iran


Several fruit trees including some cultivars of citrus tend to develop irregular bearing. Fruit thinning has been used for hundreds of years to manipulate blooming and crop load to improve the alternate bearing process. Frequently, combination sprays of two or more chemical thinners are used in various fruit trees and the thinning responses were additive and more effective than individual compounds. In this study, we investigated the effects of Naphthalene acetic acid and carbaryl alone and in combination in thinning of ‘Kinnow’ mandarin (Citrus reticulata Blanco) trees. Some characteristics such as fruit weight, diameter and volume, total soluble solid (TSS), titrable acidity (TA), TSS/TA, vitamin C and peel thickness were measured prior to harvest for 2010 and 2011 as a complete randomized block design with 13 treatments and four replications. Results showed that the application of NAA and carbaryl alone in June drop stage of fruit growth increased fruit thinning percentage, TSS of fruit juice, fruit weight, volume, diameter and length. These chemical thinners improved fruit size significantly by increasing the leaf/fruit ratio. Combination sprays could not effectively thin fruits than individual chemicals and thus had no effect on fruit size. Fruit characteristics such as TA, ascorbic acid, TSS/TA ratio and peel thickness were not affected by our treatments.     


  1. Dennis F.J., 2000. The history of fruit thinning. Plant Growth Regul. 31(1-2), 1-16.
  2. Davis K., Stover E., Wirth F., 2004. Economics of fruit thinning: A review focusing on apple and citrus. Hort Technology. 14 (2), 282-289.
  3. Guardiola J., García-Luis A., 2000. Increasing fruit size in Citrus. Thinning and stimulation of fruit growth. Plant Growth Regul. 31(1-2), 121-132.
  4. Monselise S., Goldschmidt E., Golomb A., 1981. Alternate bearing in citrus and ways of control, Proc. of the International Society of Citriculture. Tokyo, Japan. Nov. 9-12, 1982. pp. 239-242.
  5. Gallasch P., 1978. Control of alternate cropping of Valencia orange with ethephon and napthalene acetic acid. Anim Prod Sci. 18(90), 152-157.
  6. Ortola A., Monerri C., Guardiola J., 1991. The use of naphthalene acetic acid as a fruit growth enhancer in Satsuma mandarin: a comparison with the fruit thinning effect. Sci Hortic. 47(1), 15-25.
  7. Van Rensburg P., Shung-Shi P., García-Luis A., Fornes F., Guardiola J., 1996. Increasing crop value in Fino Clementine mandarin with plant growth regulators. International Citrus Congress , Sun City, South Africa. International Society of Citriculture. 1996. Pp. 970-974.
  8. Wheaton T.A., 1981. Fruit thinning of Florida mandarins using plant growth regulators, Proc. of the International Society of Citriculture. Tokyo, Japan. Nov. 9-12, 1982. pp. 263-268.
  9. Nawaz M.A., Ahmad W., Ahmad S., Khan M.M., 2008. Role of growth regulators on preharvest fruit drop, yield and quality in kinnow mandarin. Pak J Bot. 40(5), 1971-1981.
  10. Jacobs M.B. The chemical analysis of foods and food products. , 2nd ed., Van Nostrand Company: New York, 1951.
  11. Agustí M., Zaragoza S., Iglesias D.J., Almela V., Primo-Millo E., Talón M., 2002. The synthetic auxin 3, 5, 6-TPA stimulates carbohydrate accumulation and growth in citrus fruit. Plant Growth Regul. 36(2), 141-147.
  12. Stover E., Ciliento S., Ritenour M., Counter C.,
  13. NAA thinning of ââ‚‌˜Murcottââ‚‌™: comparison of small plot and commercial harvest data. Proc. Florida State
  14. Hort. Soc. Florida. Usa. 2002. Pp. 287-291.
  15. Stover E., Wirth F., Robinson T., 2001. A method for assessing the relationship between cropload and crop value following fruit thinning. Hortscience. 36(1), 157-161.
  16. Ouma G., 2012. Fruit thinning with specific reference to Citrus species: a review. ABJNA. 3, 85-100.
  17. Greene D.W., Autio W. R., Miller P., 1990. Thinning activity of benzyladenine on several apple cultivars. J Am Soc Hortic Sci. 115(3), 394-400.
  18. Prieto V.M.G., 2008. Apple fruit chemical thinning in chihuahua, México. Rev Fitotec Mex. 31(3), 243-250.
  19. Marini R.P., 2002. Thinning'Golden Delicious' and spur 'delicious' with combinations of carbamates and NAA. Hortscience. 37(3), 534-538