Two types of herbicide efficacy trials were initiated in five locations across Atlantic Canada. One product* (DUQ254), that has been of particular interest to cranberry producers for some time was investigated at five different rates with the objective of isolating the lowest effective rate.

The other type of trial was an initial herbicide screening trial with nine treatments. The objective of this trial was to investigate products that have potential for weed control in cranberries.

Products were applied at labeled rates and efficacy on specific weed species, as well as crop tolerance to the product was recorded. Products were selected based on the potential for involvement in existing cranberry integrated pest management strategies.

The dose response trials revealed no crop damage from the herbicide DUQ254. Weed control ratings were variable depending on the species investigated. DUQ254 had high efficacy against rushes and sedges (approximately 80%), however weed control ratings on other weeds were not as high. The distribution and density of rushes and sedges at one Nova Scotia site provided excellent conditions for demonstrating the ability of this herbicide at controlling these weeds.

Other products demonstrated good potential for weed control (DWE235, SYN278 and DUQ246) and had acceptable tolerance. It is important to note that the sulfonylureas performed well even though the eastern Canadian spring was very cold and wet.

Within the herbicide screening trial some products (FMC279, VAL596) did result in high crop injury at several locations. FMC279 and VAL596 also resulted in a reduction of berry yield, which was likely due to a reduction in fruit set rather than a reduction in fruit size. FMC279 and VAL596 however had high weed control ratings, and with the potential for alternative use patterns to avoid crop damage, are still of interest for future research. In addition this was the first season of screening these products and several seasons of experimentation are generally recommended before making conclusions. This would eliminate the possibility of overlooking a product which should not have been overlooked.

* Actual product names of herbicides used are coded as these products are not yet registered for use in cranberry pending minor use registration. Providing efficacy data is one component of the registration process, which is the aim of our research. Remember to always carefully adhere to label instructions on all products.