Timing Fazor applications for effective volunteer control

UK - July 22, 2005

Volunteer potatoes are a difficult and important problem to control on most farms growing potatoes, particularly with the increased use of rented land under the SFP scheme.  A foliar application of Fazor (maleic hydrazide) in second earlies and maincrop potatoes will reduce the viability of small daughter tubers and suppress volunteers developing in the field after harvest.  But this year, because planting was extended and it looks to be a hot summer, growers need to be extra careful when applying this product for best effect, advises Dow AgroSciences.

"The timing of Fazor is critical to its effectiveness but it is a simple case of following a few ground rules.  Fazor is applied through a conventional sprayer to the growing crop, when the crop is at the correct growth stage and environmental conditions are suitable.  In terms of timing, growers should work 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 translocate to the tubers where it acts.  The optimum timing is five weeks before harvest.  Each field should then 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 the 25mm riddle, it is worth waiting a week and re-sampling.  As different varieties mature at different rates and there was a spread of planting dates this year, there will be more variation in crop development and this, in turn, will mean a spread of Fazor timings.  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," advises Andy Leader, Principal Biologist for Dow AgroSciences.

"Because of the hot weather we are experiencing this summer, extra caution may be needed particularly in unirrigated crops that are likely to be suffering from moisture stress.  The label states that crops should not be treated under drought stress or if suffering from pest and disease attack.  Also Fazor should not be applied when temperatures are above 26°C.  Even irrigated crops should be treated only when the temperatures have fallen in the evening," says Andy.

Volunteers are a key problem in most arable rotations as they act as a source of blight inoculum and as a reservoir for other diseases, viruses and pests including Potato Cyst Nematodes.  They appear to becoming more of a problem, due to shorter rotations.  A planned and integrated approach to their control across the rotation is necessary, but Fazor is the only in-crop solution," says John Sellars, Marketing Specialist for Dow AgroSciences.

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, garlic and shallots.  It also has SOLAs in parsnips and carrots.  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.