Timothy Grey

By William Vencill, Timothy Grey and Stanley Culpepper

Part of the book: Herbicides and Environment

By Timothy Grey and William Vencill

Part of the book: Herbicides

By Timothy Grey and Theodore Webster

Part of the book: Herbicides

By Timothy Grey and Theodore Webster

The phase out of methyl bromide (MBr) challenged vegetable growers’ abilities to control weeds in low-density polyethylene (LDPE) mulch production systems. The herbicides halosulfuron, fomesafen, S-metolachlor, and clomazone are needed as part of the pesticide program in LDPE vegetable production to control weeds including Cyperus species. Experiments were conducted during the spring and autumn of 2012, evaluating Cyperus rotundus, bell pepper, and cucumber response to these herbicides applied to soil immediately prior to LDPE laying. Halosulfuron, fomesafen, S-metolachlor, and clomazone applied to soil under LDPE mulch did not negatively impact stand and growth of bell pepper in spring or autumn experiments, or cucumber in spring trials. However, there was significantly less growth in the autumn experiment as halosulfuron, S-metolachlor plus clomazone plus halosulfuron or fomesafen, reduced vine length. Cyperus rotundus suppression and control was achieved with halosulfuron alone and when used in combinations with S-metolachlor plus clomazone, and combinations of S-metolachlor plus clomazone plus fomesafen. These herbicides provided weed control that were comparable to MBr plus chloropicrin (MBrR-C). Using herbicides for control and suppression of Cyperus rotundus in combination with safety for pepper and cucumber will allow growers to implement new control strategies into their vegetable production systems.

Part of the book: Herbicides

By Timothy L. Grey and Larry J. Newsom

Italian ryegrass has become one of the most common and troublesome weeds of wheat production in the Southern United States. There are multiple reports in this region of Italian ryegrass herbicide resistance to acetyl-CoA carboxylase (ACCase), acetolactate synthase (ALS), and glyphosate herbicides. One commonality for Italian ryegrass resistance in this area is that most of these mechanisms of action for these herbicides are all postemergence (POST) applied. In order to have profitable soft red winter wheat production, applications of preemergence (PRE) herbicides with residual control of Italian ryegrass and other winter weed species would benefit growers. There are a very limited number of herbicides that can be applied at the time of wheat planting, primarily only when pyroxasulfone is registered for this timing. Research was conducted to establish weed control information when herbicides were applied to soft red winter wheat PRE, at wheat emergence (AE), or POST at Feekes stages 1.0–1.9, depending on herbicide label recommendations. Injury from any pyroxasulfone PRE treatments up to 120 g a.i. ha−1 was transient and did not affect wheat yield for any experiment. Italian ryegrass control was variable depending on location and year. Susceptible and diclofop-resistant Italian ryegrass control was 86% or greater with pyroxasulfone at 60 g a.i. ha−1 and greater with applied PRE. Italian ryegrass control was variable ranging from 27 to 49% with pendimethalin ME-applied PRE, diclofop at Feekes sage 1.0, and pinoxaden applied at Feekes stage 1.9.

Part of the book: Wheat Improvement, Management and Utilization

By Timothy L. Grey, Charles Y. Chen, Russell Nuti, Walter Scott Monfort and George Cutts III

Experiments evaluated the genotype by environment effects on seed germination and vigor of the peanut runner-type cultivars ‘Georgia Green’, ‘AT3085R0’, ‘AT271516’, ‘Georgia 03L’, and ‘FR458’ grown under similar production practices, for three planting dates: April, May, and June in Georgia and Alabama. Objectives were to determine if time of planting and harvest dates would subsequently affect germination and vigor when tested using a thermal gradient devise (temperature range14 to 35 °C). Runner-type peanut seed grown in Dawson Georgia in 2008 had the strongest seed vigor with Germ80 of 22 to 40 growing degree days (GDD), and maximum incidence of germination rate 84.8-95.7% when planted April, May, and June 2008 across 15 seed lots. In contrast, seed harvested from plantings of May 2009 at Dawson Georgia exhibited Germ80 of 24 to 40 GDD with maximum incidence of germination rate 79.8-93.6%, but seed from April 2009 plantings had poor vigor of 56.8-72.8% and no amount of GDD could achieve Germ80, with similar results for June 2009 plantings for this location. For Headland April, May, and June 2009 plantings of the same cultivars, all seed had poor vigor, ≤75.6% maximum incidence for germination rate, and none obtained a measurable Germ80.

Part of the book: Seed Biology

By Timothy L. Grey and Kayla M. Eason

Herbicides are necessary for successful vegetable production in the Southeastern United States. Along with bare-ground production, low density polyethylene (LDPE) mulches are often utilized to produce multiple crops (2–4) by rotation over the course of a 12-to-24-month period. These include fresh market tomato, pepper, cucurbits, eggplant, and cabbage. For LDPE mulch vegetable production, between each crop growers must apply contact and residual herbicides to mitigate weeds. However, these herbicides can remain on the mulch and injury transplants. Herbicides are often soil applied for bare soil production as well as under the LDPE mulch. Herbicide carryover in soil using these vegetable production methods can also result in management issues. Proper quantification analyzing the dissipation is critical in the decision-making process for growers to prevent unnecessary crop losses. A series of experiments have been conducted to quantify the dissipation of the herbicides flumioxazin, fomesafen, ammonium-glufosinate, glyphosate, halosulfuron-methyl, paraquat, S-metolachlor, and sulfentrazone over time using UPLC/MS and bioassay methods. These methods are presented.

Part of the book: Pesticides