A specific off-label approval has been granted for SumiMax (flumioxazin) in vining peas to control volunteer potatoes.

Since approval for Fortrol (cymazine) was removed in 2007, chemical control of potato berries (apples), which are toxic and difficult to remove at the factory, has been very difficult, Jim Scrimshaw of PGRO says.

In trials flumioxazin gave suppression of volunteer potatoes and helped prevent flower and berry formation with acceptable levels of crop damage. Adequate leaf wax is essential to ensure crop safety and it should not be applied to wet foliage.

Rainfall shortly after application may enhance residual activity, but may increase crop damage also. It must also not be used with any partner products or adjuvants as these might increase contact activity and cause severe spotting on the crop.

As well as volunteer potatoes, SumiMax, also sold as Digital and Guillotine, will control a wide-range of broadleaved weeds, including charlock, cleavers, chickweed, poppy and pansy, when small, and particularly when soils are moist.

The product also has a SOLA, applied for by the Horticultural Development Council, for use in carrots, parsnips and bulb onions for the control of volunteer potatoes. Again, growers need to take care with applications because of the risk of damage to crops.