Growth Stage and Time of the Year Effects on Nursery Crop Tolerance to Diuron

Abstract Four experiments were conducted to evaluate the tolerance of three landscape crops to over the top spray applications of diuron. Rates ≥ 0.56 kg ai/ha (0.5 lb ai/A) provided excellent (100%) yellow woodsorrel control regardless of the time of year the treatment was made. Diuron applications ≤ 1.12 kg ai/ha (1.0 lb ai/A) in fall and spring caused slight to no injury to dormant abelia, barberry, and spirea. Plants leafed out normally in the spring after application and there was no difference in growth 180 days after treatment (DAT). Application at 2.24 kg ai/ha (2.0 lb ai/A) caused slight to no injury on abelia, moderate injury to spirea, and severe injury to barberry by the following spring. Spring application to actively growing abelia and spirea caused slight to moderate injury from which plants treated with ≤ 0.56 kg ai/ha (0.5 lb ai/A) completely recovered by 90 DAT. Abelia treated with 1.12 kg ai/ha (1.0 lb ai/A) were slightly injured 90 DAT, and spirea were moderately injured 90 DAT. Abelia and spirea treated with 2.24 kg ai/ha (2.0 lb ai/A) were severely injured with many dead plants 60 DAT. Actively growing barberry treated with 0.28 kg ai/ha (0.25 lb ai/A) remained moderately injured by 90 DAT. Rates ≥ 0.56 kg ai/ha (0.5 lb ai/A) caused death to actively growing barberry by 60 DAT.</jats:p

Weed Control in Container-Grown Crops with Herbicide-Coated Fertilizers

Abstract Nursery Special 12N-2.6P-5.0K (12-6-6), Osmocote 17N-3.1P-10.0K (17-7-12), and Polyon 24N-1.7P-10.0K (24-4-12) were coated with Ronstar 50WP (oxadiazon) at 4 concentrations and compared to spray applied Ronstar 50WP and broadcast Ronstar 2G. With Osmocote and Nursery Special-coated fertilizers, the lowest Ronstar rate resulted in less weed control than traditional herbicide application methods. Ronstar-coated fertilizers applied at the recommended rate or higher provided similar weed control to broadcast-and spray-applied pre-emergence herbicides.</jats:p

Weed Control With Herbicide-Coated or -Blended Fertilizer in ‘August Beauty’ Gardenia

Abstract Prostrate spurge (Euphorbia maculata L.) control and injury to container-grown ‘August Beauty’ gardenia (Gardenia jasminoides Ellis) were evaluated using Ronstar 50WP (oxadiazon) or Pennant 7.8E (metolachlor)-coated or Ronstar 2G (oxadiazon) or Pennant 5G (metolachlor)-blended Nursery Special 12N–2.6P–5.0K (12–6–6) fertilizer. Herbicides were applied at 4 rates, 2.3, 4.5, 9.0, and 18.0 kg ai/ha (2, 4, 8, and 16 lb ai/A) and compared to broadcast and spray applied pre-emergence herbicide applications at 4.5 kg ai/ha (4 lb ai/A). Ronstar (oxadiazon)-coated or -blended Nursery Special at all rates, except 2.3 kg ai/ha (2 lb ai/A) provided similar weed control to the broadcast or spray applied controls. Pennant (metolachlor)-coated or -blended fertilizer controlled spurge only at 18.0 kg ai/ha (16 lb ai/A). Weed control was similar when comparing herbicide formulation (coated vs. blended). Gardenia growth was similar among treatments and no injury symptoms were observed with any treatment.</jats:p

Effect of Pre and Post Moisture Level on Preemergence Control of Hairy Bittercress (Cardamine hirsuta L.) with Flumioxazin

Moisture is an important component to activate preemergence herbicides; however, this aspect had not been investigated in soilless substrate. The objective of this study was to evaluate the influence of pre-application moisture levels and post-application irrigation levels in the preemergence control of hairy bittercress with flumioxazin in a pine bark substrate. Three similar experiments were conducted over a 13-month period. Treatments were a factorial arrangement at the following variables: three pre-application moisture levels (dry, medium and wet), two flumioxazin formulations (granular and spray), two flumioxazin rates [0.28 and 0.42 kg ai·ha−1 (0.250 and 0.375 lb ai·A−1)] and four levels of single-event, post-application irrigation [0.6, 1.3, 2.5 and 5.1 cm (0.25, 0.50, 1.00 and 2.00 in)]. Treated pots were overseeded with 25 hairy bittercress at 1 week after flumioxazin application. Pre-application moisture did not affect the flumioxazin efficacy at any time and treatment. The spray formulation (SureGuard) provided maximum fresh weight control (≥ 99%) in weed counts up to 12 weeks after application, regardless of rate, pre-moisture level or post-irrigation level. The granular formulation (BroadStar) was less effective than spray formulation, and efficacy was improved with the higher rate and higher levels of post-application irrigation (Experiments 1 and 3).</jats:p