Response of Lagerstroemia x ‘Tuscarora’ to Multiple Applications of Pistill

Abstract

Abstract Profuse flowering, followed by heavy fruit set and cessation of vegetative growth, extends the production cycle of many crapemyrtle cultivars, particularly ‘Tuscarora’. A study was conducted in 2002 to determine the effect of multiple applications of 1000 ppm Pistill (ethephon) on flower abortion and subsequent axillary shoot growth in Lagerstroemia indica xfauriei ‘Tuscarora’ when applied to open flowers in July and August before fruit set. In one experiment, Pistill was applied 0, 1, 2, 3, 4, or 5 times during the two flowering periods, and at 7-, 14-, and 21-day intervals (DI) during each period in a second experiment. In the first experiment, two applications made during the July flush led to 48% flower abortion, whereas by the fifth application, made during the August flush, the abortion rate had increased to 58%. Axillary shoot formation occurred predominantly following the July flush, with 34 and 60 new shoots developing on plants receiving one and two applications, respectively. Pistill applications every 7, 14, or 21 days to open flowers during the first floral flush prompted flower abortion of 81, 51, and 18%, respectively, compared to no abortion in untreated trees. The same Pistill treatments applied during the August flush resulted in 96, 96, 54, and 0% abortion, respectively. Trees receiving Pistill at 7 DI, 14 DI, and 21 DI, respectively, formed 96, 108, and two new shoots following the July flower flush and 13, 27, and two new shoots following the August flush.