Why are my potatoes full of circular holes?
Liz Shearer, by email
Stefan says: Masses of circular holes, especially late in the season, suggest to me that the damage is caused by wireworms. These are the larvae of various kinds of click beetle, which are so called because they flip themselves into the air when lying on their backs. In general, wireworms are most troublesome when kitchen garden crops are grown on grassland; they’re often a problem in new gardens when housing developments are made on old pasture.
One effective way to diminish them is by regularly cultivating the soil so they are brought to the surface where birds will eat them. It’s also a good idea to ensure that main crop potatoes are lifted early when wireworms are less likely to be present. If compost bins become infested, the compost should be turned and exposed to the weather and to birds, which will help to reduce the numbers of wireworms before the compost is used.
Stefan says: You tell me you live in south west Scotland where there has been a drier than normal summer, although not unduly sunny and hot like most of the country. Early in the season the leaves on your Kilmarnock willow developed a yellow powdery coating, which would come off if you brushed against the leaves. Since then it’s looked, as you put it, ‘a poor soul’.
The powdery coating you describe comprised the spores of a rust fungus, of which several kinds affect willows, although not often as a serious problem on garden trees. I see them more commonly on wild native plants and in plantations. Nonetheless, rusts in general tend to be most serious in years with a damp beginning and dryness later. My advice is to spray with an approved fungicide such as RoseClear Ultra and repeat as the manufacturer directs. Then, next season, give a foliar feed from to time.