A hot July ended with a warm, damp and humid spell that stretched into August; ideal for the establishment of recently planted cauliflowers, leeks and cabbages. It also provided ideal conditions for blight to rampage through many of our potato crops. The disease is caused by the aggressive fungal pathogen phytophthora infestans, which can reduce a healthy crop to a field of blackened stumps in less than a week. Worse still, heavy downpours can leach infective spores down through the ridges to attack the tubers. The pathogen’s arrival in Ireland in 1845 wiped out their staple crop and, combined with woeful neglect from England, caused a famine that killed one million people and led another million to emigrate.
Non-organic growers spray with a systemic fungicide through summer until autumn; 8-10 sprays would not be uncommon. In organic crops, limited amounts of Bordeaux mixture (copper sulphate) can be used in some situations and can slow the spread of the disease. It is relatively innocuous, but only gives very temporary protection and some growers are concerned about its effect on soil life. There are more disease resistant varieties available now, but in most years, well before the crop has reached its potential yield, we still end up mowing off the tops and scorching the stumps to protect the crop below.
Fortunately, such aggressive pathogens are rare and are normally the result of relatively young relationships with their host. Over time the relationship typically evolves towards a slow, lingering death, then mere mild stunting of growth; why kill your host and move on if you can farm them and continue to reproduce indefinitely? It is likely that many symbiotic relationships were initially parasitic and slowly co-evolved towards mutual benefit.
On a more cheerful note, I hope you are enjoying our padron peppers. For me, most evenings start with a tapas of these delicious, if unpredictable, peppers quickly fried and salted. They take no more than five minutes to prepare. They are out-yielding expectations and it seems criminal to waste them, so, for the aficionados amongst you, we are now selling a 400g bag at £4.95.