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Diclofop-resistant Italian ryegrass has become a major problem throughout the southeastern United States. AE F130060 plus AE F115008 are herbicides currently under development that are equally effective on diclofop- susceptible and -resistant Italian ryegrass. Field and greenhouse experiments were conducted to investigate the use of these herbicides in North Carolina. In a cultivar tolerance study conducted at weed-free locations, the cultivars 'Coker 9663', 'Coker 9704', and 'Pioneer 2580' were most tolerant of AE F130060 plus AE F115008, the cultivars 'FFR 555', and 'Pioneer 2684' were intermediate in tolerance, and the variety 'Jackson' was least tolerant. Yield reductions were attributed to fewer kernels per spike in treated versus non-treated wheat. AE F130060 plus AE F115008 injured weed-free wheat 27% and reduced yield 7% when the safener, AE F107892, was not included. Yield reductions were not observed with herbicide:safener ratios of 1:1 or 1:3 applied to 3-leaf, 2-tiller, or 6-tiller wheat. Increased Italian ryegrass control was noted when AE F130060 plus AE F115008 was applied with nitrogen as the carrier, however increased crop injury was a concern in trials conducted on weed-free wheat. Italian ryegrass control by AE F130060 plus AE F115008 was not affected in a tank mixture with thifensulfuron plus tribenuron. Reduced control was noted in the field and greenhouse when AE F130060 plus AE F115008 was mixed with 2,4-D or dicamba. No tank mixture affected wheat injury. In an adjuvant comparison study, the inclusion of an adjuvant with AE F130060 plus AE F115008 accelerated Italian ryegrass control 3 WAT compared to application without an adjuvant. Control by the herbicides was similar with or without an adjuvant at 6 and 10 WAT. The adjuvants tested included nonionic surfactants, an organosilicone surfactant, and crop oil concentrate. Both weed-free and Italian ryegrass-infested wheat treated with the herbicides alone and mixed with adjuvants produced similar yields. A wash-off study conducted in the greenhouse suggested the rainfree requirement for AE F130060 plus AE F115008 was 2 h.

Italian ryegrass is the most problematic weed of small grains in North Carolina. This weed has traditionally been controlled in wheat with diclofop. However, after many years of continuous use, much of the Italian ryegrass in the state is now resistant to diclofop. A field experiment was conducted at three locations to determine control of Italian ryegrass and response of imidazolinone-tolerant wheat to imazamox and other herbicides. Imazamox ammonium salt applied POST in the fall to 3- to 4-leaf Italian ryegrass at 35 to 53 g ae/ha controlled Italian ryegrass 90 to 100% 10 weeks after treatment. Late-season control ranged from 83 to 98% at two locations and 24 to 55% at the third location. Late-season control from spring-applied imazamox on 1- to 3-tiller ryegrass ranged from 53 to 58% at one location and 7 to 16% at the other locations. Split application of imazamox at 27 g/ha in the fall and 27 g/ha in the spring was less effective than fall-applied imazamox at 53 g/ha at two of three locations. However, split application was more effective than spring application. Fall-applied imazamox was less effective than fall-applied diclofop on diclofop-susceptible Italian ryegrass but more effective on mixed populations of diclofop-resistant and -susceptible biotypes. Pendimethalin applied PRE at 1120 g ai/ha increased late-season control 10 to 33 percentage points when used in combination with fall-applied imazamox at 35 g/ha. Imazethapyr ammonium salt at 70 g ae/ha was less effective than imazamox, while imazethapyr at 47 g/ha plus imazapyr isopropylamine salt at 16 g ae/ha and imazamox were similarly effective. Imazapic ammonium salt at 70 g ae/ha and imazamox at 53 g/ha were similarly effective at two locations, while imazapic was more effective at the third location. Imidazolinone herbicides caused only minor, temporary chlorosis on the wheat. In greenhouse experiments, a diclofop-susceptible biotype of Italian ryegrass was more sensitive to imazamox than a diclofop-resistant biotype. Imazamox controls Italian ryegrass in imidazolinone-tolerant wheat but is only marginally effective on some broadleaf species. A fallow-area field experiment was conducted at three locations in North Carolina to determine control of Italian ryegrass by imazamox as affected by imazamox rate, weed size at application, and mixtures with the broadleaf herbicides 2,4-D, dicamba, and thifensulfuron plus tribenuron. Interactions of imazamox rate, weed size, and broadleaf herbicides were not observed. Italian ryegrass control 56 days after treatment increased as imazamox rate increased. Pooled over weed sizes at application and mixtures, imazamox at 27, 35, and 44 g/ha controlled Italian ryegrass 44, 53, and 67%, respectively, at two locations and 83, 86, and 91% at the third location. Control decreased as weed size at time of application increased. Pooled over imazamox rates and mixtures, Italian ryegrass was controlled 86, 54, and 24% at two locations when herbicides were applied to 2-leaf, 4-leaf, and 2-tiller weeds, respectively. At the third location, Italian ryegrass was controlled 95, 94, and 71% when treated at the 2-leaf, 4-leaf, and 2-tiller stages, respectively. Small increases in control were sometimes noted with mixtures of imazamox and 2,4-D dimethylamine salt at 530 g ae/ha or thifensulfuron plus tribenuron at 18 plus 9 g ai/ha, while minor decreases were sometimes noted with mixtures of imazamox and dicamba diglycolamine salt at 140 g ae/ha. In a greenhouse experiment, mixing 2,4-D with imazamox did not affect Italian ryegrass control. Dicamba reduced control, while thifensulfuron plus tribenuron increased control.