Integrated control is the way forward for volunteer potato control

UK - May 10, 2005

Volunteer potatoes are a perpetual concern for growers and advisors, with 77% reporting that they were "very concerned or concerned" about volunteers and 46% saying that the problem was increasing, according to a survey conducted by Dow AgroSciences.

"Volunteers remain a difficult problem on the majority of farms that grow potatoes.  In the survey, only 4% thought that the problem was actually decreasing.  Shorter rotations, use of rented land and growing certain varieties, such as Maris Piper, Saturna and Cara, that tend to produce chats are all conducive to the increase in the volunteer problem," reports John Sellars, Marketing Specialist for Dow AgroSciences.

"The survey showed that 71% of those interviewed regarded volunteers as an important source of potato blight.  Volunteers need to be controlled as not only do they act as a source of disease inoculum but also as a reservoir for other diseases and viruses including spraing, PCN, silver scurf, black scurf, black dot, powdery scab, aphids and aphid-transmitted viruses.  The survey showed that growers and advisors were adopting an integrated approach to volunteer potatoes, using chemical and cultural methods.  On average at least four actions were being taken in the crop and in other crops within the rotation.  Over 70% of those interviewed used glyphosate pre-harvest, with 61% using this total herbicide in stubbles. Around 56% used Starane (fluroxypyr) in cereals to control volunteers and 46% avoided ploughing after the potato crop has been harvested.  Nearly 40% used Dow Shield (clopyralid) in sugar beet and 37% were using Fazor in the growing crop," adds John.    

According to John, every opportunity should be taken to control volunteer potatoes.  With potato planting underway and the threat of blight inoculum on volunteers acting as a primary source of infection to the newly emerged crop, growers should be utilising volunteer control methods in cereals and sugar beet now.  Later in the season a foliar application of Fazor (maleic hydrazide) at 5 kg/ha around 3-5 weeks before burn down in second earlies and maincrop potatoes will reduce the viability of small daughter tubers and so stop the volunteers developing in the field after harvest.  Fazor acts by inhibiting cell division and prevents eyes from sprouting.  "It is not possible to control volunteers in one shot. A planned and integrated approach is needed," concludes Mr. Sellars.

Fazor contains 60% w/w maleic hydrazide, formulated as a water-soluble granule.  It is recommended on second earlies and maincrop potatoes as well as bulb onions.  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 per hectare.  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.