Richard's Ramblings August 10th - Pests and Diseases

head grower richard richard mee richards ramblings

Everything seems a little more normal now, the soil is moist and the cooler temperatures suit both gardeners and our common crop plants. The work seems less frenetic as we prepare our beds for the autumn/winter cropping. It’s again possible to enjoy having a tool in your hand as you progress steadily through what needs doing.

Though along with a return to more normal conditions we also have a return to more normal pest and disease problems. Pests and diseases are a natural part of growing, though how we respond to them depends on what sort of grower we are. If you want to grow organically you have to accept a certain level of damage, crops will rarely look perfect; if this bothers you then it’s probably better to use some chemicals. The range available to domestic growers is quite limited though you will find a chemical to use in most situations. The restricted range available is certainly a good thing though as until relatively recent times various highly toxic chemicals, such as mercury compounds, were available to domestic growers. The potential hazards to both user and the environment don’t bear thinking about. If however you value having a harvest free of pesticides and a garden with good biodiversity (as we do at GROWHQ) then an organic approach is needed. I thought it might be useful to go through the problems we have at GROWHQ at the moment and how we are dealing with them.

Potato blight started appearing on the leaves of our Orla potatoes, although the variety has some resistance to blight it is certainly not immune. This was not a major problem however as the crop was ready and we harvested them for the kitchen. If we had intended to leave them in the soil any longer then we would have cut off the foliage and left them in the ground. If they were a variety for storage then we would have left them in the soil for two or three weeks, for the blight spores to die off, then dug them up.

Caterpillars have appeared on some of the brassica (cabbage family) plants, despite our netting them (butterflies sneak in through any little gaps around the edge). I will use an organic biological control – Bacillus thuringensis – which are bacteria that only attack caterpillars (it rots them from the inside out!)

Our final major problem is powdery mildew on our courgettes and pumpkins. This can be treated with spraying on milk diluted 10/1 (use skimmed if you don’t want your courgettes smelling of vomit!). However, I won’t bother spraying the pumpkins as they have completed most of their growth and will happily limp on into the Autumn. The courgettes are worth treating to ensure a good harvest into September. Another approach is to make a second sowing of courgettes in June as the young plants will be much more vigorous at fighting off any infection. Maybe it’s just a natural part of ageing for things to get infected and drop off?

Anyway, I look forward to seeing some of you on the garden class next Saturday- you can come and look at my interesting collection of pests and diseases!

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