Fluazifop-P Reduces Strawberry (Fragariaxananassa) Tolerance to Terbacil

Abstract

Greenhouse and field experiments were conducted to characterize a synergistic interaction between fluazifop-P and terbacil in strawberry (FragariaxananassaDuchesne). In the greenhouse, injury from foliar terbacil applications generally increased two- or more fold when 75 or 150 g/ha fluazifop-P was applied foliarly 24 h later to either a terbacil tolerant (‘Veestar’) or sensitive (‘Kent’) strawberry cultivar. Synergism also occurred when terbacil was applied as a soil drench and fluazifop-P was applied 5 d later. There was little difference in effect between tank-mixed and sequential applications made 0.5 and 20 min apart. Increased injury was also observed with intervals up to 6 d between applications in the greenhouse, and the order of herbicide application did not affect injury level. Similar results were obtained in field experiments on newly planted ‘Honeoye’ and ‘Cavendish’ strawberry. An interval of 6 d or more between terbacil and fluazifop-P application is suggested to minimize the risk of increased crop injury.

Tolerance of Greenhouse-grown Strawberries to Terbacil as Influenced by Cultivar, Plant Growth Stage, Application Rate, Application Site and Simulated Postapplication Irrigation

“…Data from this experiment confi rm previous studies showing strawberry cultivars vary in their tolerance to terbacil (Jensen et al, 1996;Lindstrom and Swartz, 1987;Masiunas and Weller, 1986;Weller, 1984). In this experiment, 'Jewel' was less tolerant to applications of terbacil than was 'Mira', but similar in tolerance to 'Allstar' based on visual injury.…”

“…In our study 'Jewel' was more vigorous based on leaf dry weight but was damaged more severely by terbacil than the slower-growing cultivar 'Mira', refuting Masiunas and Weller (1986). However, strawberries have been shown to completely outgrow moderate foliar injury of terbacil within a few months (Jensen et al, 1996). It is likely that these plants would have responded in a similar manner.…”

“…The herbicide is applied preemergence for control of most germinating broadleaf and grass weeds and also controls some emerged weed seedlings that are less than 1 inch (2.5 cm) tall at the time of application. Terbacil is persistent in the soil and can provide residual control of germinating weeds for four weeks or more (Jensen et al, 1996). Terbacil molecules enter plants primarily though roots, and then move apoplastically in xylem tissues to their site of action in leaf mesophyll chloroplasts where they inhibit photosynthesis (Ashton and Monaco, 1991).…”

“…Metabolism of terbacil to nontoxic derivatives in strawberry is an important component of crop tolerance (Genez and Monaco, 1983b). Strawberry cultivars vary in their sensitivity to terbacil (Jensen et al, 1996;Lindstrom and Swartz, 1987;Masiunas and Weller, 1986;Weller, 1984). Masiunas and Weller (1986) found that vigorous cultivars were not affected by applications of terbacil nearly as much as less vigorous cultivars.…”

Fluazifop-P Inhibits Terbacil Metabolism in Strawberry (Fragaria×ananassa)1

“…We have previously reported that fluazifop-P and terbacil interact synergistically in strawberry (Jensen et al 1996). When applied alone, strawberry plants have a high tolerance of fluazifop-P, even when applied repeatedly at high rates (Clay et al 1990) and during sensitive crop stages like bloom (Doohan et al 1986).…”