IMPROVEMENT IN EFFICACY OF GIBBERELLIC-ACID TREATMENTS IN REDUCING SUSCEPTIBILITY OF GRAPEFRUIT TO ATTACK BY CARIBBEAN FRUIT-FLY

Efficacy of the plant growth regulator, gibberellic acid (GA3), in reducing 'Marsh' grapefruit susceptibility to Anastrepha suspensa was increased through use of the surfactant, L-77 Silwet.(R) In addition, it was found that the duration of protection of grapefruit could be extended by use of two consecutive GA3 treatments a month apart. Corresponding effects on peel color and resistance to mechanical puncture were noted, but peel oil content was not affected by treatment and declined at the same rate as that of untreated fruit. The implications of these results in the further development of the fly-free concept and for fruit fly control are discussed.