Uptake and persistence of soil applied paclobutrazol in ‘Alphonso’ mango and soil in the Konkan region of Maharashtra, India

Abstract

‘Alphonso’ mangoes from the coastal Konkan region of Maharashtra, India, are popular in domestic as well as international markets. Paclobutrazol, a plant growth regulator, has been successfully used on a commercial scale in soil application to counter the alternate bearing habit of mango in this area for more than a decade. Residue analysis of paclobutrazol in mango fruits at harvest was carried out by field survey to evaluate whether such applications of paclobutrazol for a long time has resulted in any residue persistence of paclobutrazol in mango and whether these mangoes are safe from the human health risk perspective. Paclobutrazol residues were also analyzed at harvest in surface soil from tree basins where paclobutrazol had been applied, to evaluate the extent of paclobutrazol contamination of the surface soil in this region. Irrespective of the number of total paclobutrazol applications in the last 10 years or the orchard type (laterite rock cultivation or conventional soil cultivation), the residues of paclobutrazol were not found above quantifiable levels (limit of quantification = 0.01 ppm) in 80% of the whole mango fruit and 100% of the mango pulp samples. No residues of paclobutrazol could be detected in tree basin surface soils where paclobutrazol had been applied continuously for 5 or more years. However, in orchards where less than five applications of paclobutrazul had been made in relatively more recent years, residues could be detected (0.02–0.34 ppm) in soil. The high application rate of paclobutrazol (20 g a.i./tree) made the previous year in an orchard resulted in its high residues in tree basin soil (0.34 ppm) the next year.

Keywords:

• alternate bearing
• paclobutrazol
• plant growth regulator
• mango
• residues
• soil
• uptake