Advice on timing Fazor applications for effective volunteer control

UK - July 20, 2006

A foliar application of Fazor (maleic hydrazide) to 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 it looks to be a hot summer, growers need to be extra careful when applying this product for best effect, advises Dow AgroSciences.

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

"The timing of Fazor is critical to its effectiveness but you just have to follow a few simple ground rules to get it right.  Fazor is applied alone through a conventional sprayer to the growing crop, when the crop is at the correct growth stage and the environmental conditions are suitable.  In terms of application timing, growers should calculate back at least three weeks and no more than five weeks from their intended burn down date : this allows the chemical sufficient time to be taken up by the foliage and be translocated down to the tubers where it acts.  The optimum timing for Fazor is five weeks before harvest.  Each field should then be checked for maturity and tuber size by using test digs.  Marketable tubers must be at least 25 mm across.  If too many tubers are going through the 25mm riddle, it is worth waiting a week and re-sampling," advises Andy. 

In terms of the crop stage, the ideal timing for Fazor is when the crop is actively growing, with the last few flowers still apparent but most having already fallen.  The haulm should still be vigorous with the bottom leaves starting to senesce.  The effectiveness of Fazor is a function of all these factors, according to Dow.

"Volunteers are a 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 available," says Mr. Leader.

Fazor contains 60% w/w maleic hydrazide, formulated as a WDG.  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 5 kg/ha in 350-500 litres of water.  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.