The use of carfentrazone (Shark) has recently become popular for suppression of primocanes in raspberry. It is a good option for growers because it is substantially less expensive than the standard hand pruning and also a lot safer and more effective than gramoxone (Paraquat).
It is worth the while to review the application of Shark in caneberries. As an herbicide, Shark must be applied differently from other pesticides in raspberries to reduce the risk of damage (see photos below) to the non-target floricanes and maximize its efficacy.
First, growers must direct the material toward the base of the plant where the primocanes are growing. Full coverage of the target is not as important as prevention of drift into the upper canopy, damage to leaves and subsequent reduction of fruiting potential.
Raising application gallonage and pressure, while an excellent idea for fungicide or miticide applications, is not recommended for application of Shark in raspberries, since both increase the risk of spray drift and damage to the upper canopy. Forcing a lot of water through a small opening over a short period of time raises pressure and creates small droplets, which travel further than large droplets, and increase the risk of carrying the herbicide off target and causing damage. Application gallonage does not need to exceed 35 gallons per acre, and pressure of application should not be over 40 psi. Nozzles should be of a TeeJet size 8004 or greater.
The usual recommendations regarding mitigation of spray drift hold very true when using Shark herbicide in raspberries. Sprays should take place in the windless conditions of early morning, and it is a very good idea to add a drift retardant to the tank mix. Any conditions arising which will favor drift should be a signal to cease the application.
There are several herbicides mentioned for primocane management in raspberries mentioned in this article. Before using any pesticide, check with your local Agricultural Commissioner's Office and consult product labels for current status of product registration, restrictions, and use information.
Phytotoxicity of Shark herbicide on non-target leaf. Since the droplets landing on the leaf were very small, damage is limited.
Severe damage caused on mature cane caused by direct application of Shark herbicide. Plant will not die, but fruit production will be delayed and quite probably reduced.