Volunteer Potatoes

Key Points

Volunteer potatoes are becoming an increasing problem in sugar beet crops
The major potato and sugar beet growing areas in the UK overlap significantly
Control is best achieved by integrating agrochemical and cultural techniques
Dow Shield^† 400, in conjunction with ethofumesate containing products, is the best treatment

Introduction

An integrated approach the management and reduction of volunteer potatoes is particularly important where less competitive crops, such as sugar beet, are part of the rotation.

Potato tubers left in the field at harvest lead to problems in following crops from volunteer potatoes. These volunteers compete with the crop for light, space and nutrients leading to reduced yields and quality. They are often also the source of potato blight infection. The problem can be particularly troublesome in crops such as sugar beet, where the crop is relatively uncompetitive during early stages of establishment and growth.

Biology

In general, potatoes reproduce both vegetatively and by true seed. The latter, though viable at an early stage of berry development, is generally a less extensive source of weed potato infestation. The greatest increase in volunteer potato problems arises as a consequence of vegetative reproduction. Varieties such as Cara and Maris Piper are renowned for their capacity to produce large numbers of small tubers.

The sugar beet crop, with its slow development and low competitiveness is the crop most likely to allow volunteer potato numbers to flourish. In the UK, there is a significant geographic overlap between the major potato and sugar beet growing areas, confirming the extent of the potential volunteer potato problem in these shared cropping regions. Volunteer potatoes can only be controlled successfully by complete integration of agrochemical and husbandry techniques.

Product Choice

To reduce the burden of volunteer potatoes in following crops Fazor^~ (active ingredient maleic hydrazide) can be applied to the growing potato crop. Application of Fazor should be made after natural cell division of the tubers has ceased and when translocation of nutrients from the leaves to the tubers is most active. To learn more about Fazor read about sprout suppression in potatoes.

In the sugar beet crop the single most important product to use in controlling volunteer potatoes is Dow Shield 400 (active ingredient clopyralid). Dow Shield 400 is selective to many arable and horticultural crops, whilst causing distortion of stems and foliage of potato plants. Efficient translocation to the daughter tubers results in reduced weight, number and viability.

Dow Shield 400, applied in tank mixture with ethofumesate containing products, is the very best treatment against volunteer potatoes in sugar beet. The effect on progeny tubers is carried through to succeeding generations, thus reducing the threat from volunteers in the second year after treatment. The extent of haulm control from Dow Shield 400 varies with variety, as shown below.

Most Susceptible

Pentland Dell
     Desiree
          Marfona
               Maris Piper
                    Nadine
                         Estima
                              King Edward
                                   Sante
                                        Romano
                                             Record
                                                  Cara
                                                       Wilja
                                                            Least Susceptible

Potato control is consistently enhanced by tank mixing with ethofumesate or products formulated with ethofumesate. To increase flexibility, Dow Shield 400 has recommendations for tank mixing with many ethofumesate containing products.

The first application of Dow Shield 400 at 0.25 litres per hectare should be made when the volunteer potato shoots are between 5cm and 10cm tall, providing the sugar beet crop is at the correct growth stage. The second application, again 0.25 litres per hectare, should be made when volunteer potatoes are between 10cm and 20cm tall. This is the size of an untreated potato so, for an accurate guide to when this stage is reached; it is advisable to leave a small area of untreated volunteer potatoes in the field. Typically the second application is made 7 to 14 days after the first.