12 September 1997

Watch beet crops for red spider mite

CHECK sugar beet crops for red spider mite and think about lifting seriously affected fields first, advise Brooms Barn researchers.

A fair amount of current yellowing in crops could be caused by spider mite, which has become more prevalent in recent years, says Mike May. "A pest of southern European crops, it will have been encouraged by the warm August."

Key symptoms to watch for are interveinal yellowing with silvery-grey webs on leaf undersides. "You need a powerful lens to see the mites themselves, which at this stage are pale yellow with two dark spots, not red. They only become red later."

With no effective mite sprays the best approach is to consider rescheduling harvest, says Mr May. Very little of the discolouration is due to virus yellows, confirming earlier predictions, says colleague Alan Dewar. &#42