Timing of Chopper Herbicide Site Preparation on Bedded Sites

Vegetation control after different application timings of Chopper herbicide (active ingredient imazapyr) relative to bedding was examined at four lower Coastal Plain study locations. Two bedding regimes, midseason and late-season, were examined at each location. Midseason bedding occurred between May and July and late-season bedding occurred between September and November. Results indicate that many of the historical application timing limitations placed on imazapyr are not necessary. Chopper herbicide in combination with methylated seed oil can be applied as early as February and as late as November, up to the day before bedding and immediately after bedding. Seasonal timing of application also was found to have a major impact on pine growth. For those treatments that provided good vegetation control, earlier season treatments resulted in the best pine growth. Optimal application timings were (1) June through September at least 3 weeks after midseason bedding, (2) February to the day before midseason bedding, and (3) February through July followed by late-season bedding. An exception is that if deciduous woody species such as hardwood or blackberry are targeted, early season applications (February–April) should not occur until these species have leafed out. The optimal timing windows are wide, allowing forest managers plenty of flexibility in scheduling operations. Use of optimal timing windows has the potential to substantially increase productivity without increasing costs.