Volunteer potatoes left behind from the previous year’s crop are one of the major sources of blight inoculum and growers are being advised to think ahead to prevent the problem happening again future years. Growers are also being advised to plan an integrated control programme, including the application of the only in-potato crop solution, Fazor.
"A foliar application of Fazor in second earlies and maincrop potatoes reduces the viability of small daughter tubers and suppresses volunteers developing in the field after harvest. When applied at the right time and under the right conditions, data shows that Fazor will give 75% control or more of potato volunteers in following crops. It will also inhibit sprouting in store," says William Corrigan, Agronomist for Dow AgroSciences.
"The timing of Fazor is fast approaching and there are a number of criteria that need to be met in order to optimise performance. The effectiveness of Fazor is a function of application timing, growing conditions at application, accuracy of application, variety and storage conditions," he advises.
"In terms of application timing, growers should calculate back at least three and not more than five weeks from their intended burn down date. This allows the chemical sufficient time to be taken up by the leaves and translocated to the tubers where it acts. The optimum timing is five weeks before harvest."
Each field needs to be checked for maturity and tuber size, using test digs. The smallest tubers required to reach marketable size should be greater than 25 mm across. If too many tubers are going through, it is worth waiting a week and re-sampling in five days time," William advises.
The ideal timing for Fazor is when the crop is actively growing and the haulm is mostly green, but with a few of the lower leaves turning yellow and most of the flowers having fallen, he adds. William also indicates that the crop should not be stressed by drought, pests, diseases or high temperatures (in excess of 26ºC).
"Potato volunteers are a significant problem, brought about by shorter rotations. They arise when undersized tubers fall through the harvester webs or become detached from the plant at harvest. You can get up to 300,000 volunteers per hectare and they can remain viable for up to eight years. Not only are they an important source of blight inoculum but they also act as a reservoir for other diseases, viruses and pests including Potato Cyst Nematodes. A planned and integrated approach to their control across the rotation is necessary, using wider potato rotations, other herbicides such as Dow Shield in sugar beet, Starane in cereals and glyphosate in non-crop situations, but Fazor is still the only solution that can be applied in potatoes," says William Corrigan.
He points out Fazor is included in the Assured Produce Protocol. It is recommended that growers check with their supplier before making an application.
Growers and advisors can use the e-learning module for Fazor in order to get best results this season. The e-learning module can be found on-line at www.fazor.co.uk .