GROWTH ACCELERATORS AND INHIBITORS IN LEMON BUDS INFESTED BY ACERIA-SHELDONI (EWING) (ACARINA - ERIOPHYIDAE)

The biological activities of growth accelerators and inhibitors in lemon buds both infested and uninfested with the citrus bud mite, Aceria sheldoni (Ewing), were examined by the Avena test. The growth-promoting activity of the purified ether extract containing the auxin was diminished in proportion to the degree of infestation. Paper chromatography fractions of extracts obtained from infested buds exhibited a strong inhibiting activity on Avena coleoptile elongation in the presence of 0.1 ppm indol-3yl-acetic acid. This inhibiting activity seems to be due to the presence of a high level of phenolic compounds.The phenol level and its biological activity in both infested and uninfested buds were examined. Infested buds exhibited a higher amount of phenols than uninfested ones, the level of the phenols increasing with bud age. The phenols from infested buds inhibited Avena coleoptile elongation to a much greater extent than those from uninfested buds.Our results suggest that the presence of the citrus bud mite in lemon buds can increase the level of phenols and possibly other growth depressors in the buds, and that they, in turn, may cause the observed inhibition of growth and development of the infested citrus plant. © 1969 Oxford University Press.