White Clover (Trifolium repens) Control and Flower Head Suppression in Apple Orchards

Abstract

White clover is a weed in apple orchards that competes with the crop; also, flowers of this weed are unwanted attractants of honey bees at times when insecticides, which are harmful to these pollinators, are being applied. In 1997 and 1998, white clover flower head and plant control by clopyralid alone and with 2,4-D and apple tolerance to these herbicides were determined. Treatments consisted of clopyralid at 0.10 and 0.21 kg ae/ha, 2,4-D at 1.1 kg ae/ha, and 2,4-D at 1.1 kg ae/ha plus 0.03 or 0.05 kg ae/ha clopyralid, which were applied 2 wk before full apple bloom and 2 wk after full apple bloom, and a nontreated check. No crop injury occurred with any treatment. All herbicide treatments provided some white clover control and flower head suppression. No differences in white clover bloom reduction were observed through May among treatments containing clopyralid. As summer progressed, the effect of clopyralid rate became more apparent. Clopyralid at 0.21, regardless of application time, provided 99% vegetative control and 100% flower head reduction through July. Clopyralid plus 2,4-D controlled white clover better than 2,4-D alone. However, vegetative control and flower head reduction with clopyralid at reduced rates (0.03 or 0.05 kg ae/ha) plus 2,4-D were not acceptable (76% or less and 78% or less, respectively). Thus, clopyralid at 0.10 and 0.21 kg ae/ha will be necessary for acceptable white clover vegetation control and flower head reduction.

Seletividade de herbicidas em trevo-branco no estádio fenológico de expansão do primeiro trifólio

“…A tolerância a 2,4-D imazethapyr, bentazon foi sugerida também em outros experimentos (MACRAE et al, 2005;MCCURDY et al, 2013) pela menor redução na produção de massa seca e em outras espécies do gênero Trifolium (CEBALLOS et al, 2004;CELEN et al, 2006).…”

The bumblebee Bombus ardens ardens (Hymenoptera: Apidae) visits white clover in orchards before Oriental persimmon blooms

“…However, T. repens flowers might compete with D. kaki flowers for pollinators and reduce pollination of the crop. In fact, negative effects of T. repens flowers on crop pollination in kiwifruit, apple, and cherry orchards have been reported (Clinch 1984;MacRae et al 2005;Holzschuh et al 2012). Therefore, further studies should examine whether growing T. repens on the ground of D. kaki orchards has a positive effect on sustaining the local population of B. ardens ardens and any significant effect on pollination of D. kaki by this species.…”

Differential Response of FourTrifoliumSpecies to Common Broadleaf Herbicides: Implications for Mixed Grass-Legume Swards

“…Selective weed control in grass-clover swards is hampered by the lack of effective herbicides that are tolerated by clovers. Many effective broadleaf herbicides are reported to control clover, including 2,4-D, carfentrazone, clopyralid, dicamba, and triclopyr (MacRae et al 2005;Neal 1990;Neal and Mascianica 1988;Willis et al 2007). Yet few herbicides are labeled for postemergence application to various clover species, and most are restricted to states where clovers are cultivated for seed production or forage.…”