In-crop control of volunteers with Fazor

Volunteer potatoes left behind from the previous year's crop are one of the primary sources of blight inoculum and growers are being advised to think ahead to prevent the problem happening again next year. Growers are also being urged to plan an integrated control programme, including the application of the only in-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 Andy Leader, Principal Biologist for Dow AgroSciences.

"The timing of Fazor is fast approaching but there are a number of criteria that need to be met in order to optimise performance. The effectiveness of Fazor is a function of growing conditions at application, accuracy of application, variety and storage conditions," adds James Maud, Technical Manager for the manufacturer, Chemtura.

"In terms of timing, recent trials work suggests that Fazor should be applied at least twelve weeks after planting, although this is not a specific label recommendation, just a guideline. This year with the spread of planting timings, this is perhaps one condition that hasn't been relevant for a few years. Growers should then look at the other end of crop development and 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 and a Fazorometer. The smallest tubers required to reach marketable size should be greater than 25 mm across. If too many tubers are going through the 25mm riddle, it is worth waiting a week and re-sampling in five days time. With the broader planting window this year, it may be more important to focus on this criterion," James 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.

James Maud also indicates that the crop should not be stressed by drought, pests, diseases or high temperatures.

"Potato volunteers are an increasing problem, brought about by shorter rotations and milder winters. 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 Andy Leader of Dow AgroSciences.

He points out Fazor is included in the Assured Produce. It is recommended that growers check with their supplier before making an application.

Fazor contains 60% w/w maleic hydrazide, formulated as a water-soluble granule. It is recommended on second earlies and maincrop potatoes (but not on seed or first earlies) as well as bulb onions. In potatoes, Fazor is recommended at a dose rate of 5 kg/ha in 350-500 litres of water. It should be applied to actively growing foliage, typically around 3 to 5 weeks before burn down. It has a maximum number of treatments of one per crop and a latest time of application of 3 weeks before harvest. It is packed in a 2.5 kg bag. Fazor also has a specific off-label approval for use in garlic, shallots, carrots and parsnips.

For further information, please contact

Andy Leader, Dow AgroSciences on 01462 457272 or 07802 225769 (mobile).