PESTS AND PROBLEMS - Vegetable, Fruit and Herb Growing in Small Spaces - page 44

Spidermite
The red spidermite is just half a millimetre across and often hard to spot with the naked eye.
The leaf damage it causes is usually the first thing noticed. Leaves become bronzed, wither
and die. Use a magnifying glass to check if spidermites are the cause: you're looking for tiny
red or yellow spiders. A specific biological control, Phytoseiulus persimilis, is available but
only of use in a greenhouse. Outdoors washing with insecti-cidal soap is moderately effect-
ive. Usually a few are not too damaging but heavy infestations require action to avoid signi-
ficant crop damage.
Blight
Potato blight (see Potatoes, here ) isn't usually a problem when growing early potatoes in pots
unless you are very unlucky. Unfortunately blight also affects tomatoes and this is quite likely
to be a problem if you're not growing under cover.
The spores of the mould Phytophthora infestans float in from miles around when the
weather is warm and humid and land on your tomato plants. The first sign is small brown
patches on the leaves but in as little as a day the whole plant can be affected and dying. The
chances are that any tomatoes developing on the plants will be affected and inedible as well.
The first line of defence is to prevent the spores from getting onto the crop, which is why
greenhouse crops are rarely bothered. Even partial cover is protection; if you keep the rain
off, then the blight is probably kept off.
If you spot blight starting on the leaves, then immediately removing them may save the
day but, to be honest, the chances are not good.
You can get various fungicidal sprays for blight which are most effective if applied as a
preventative before it strikes. Sometimes fungicides can rescue the situation if applied at the
first sign of trouble, but you have to be really fast. Blight spreads incredibly quickly and
hours make a big difference.
The traditional spray was Bordeaux mixture. This isn't such a good idea in my opinion as
it contains copper and that is hardly good for your diet although it is organically approved.
Inorganic Dithane 945 is effective as long as it is applied before blight has hold, but once
again you are adding a chemical residue to your diet.
Rather than spray, once the blight has struck I remove any reasonably developed tomatoes
and store them so they are not touching. The green ones will ripen up (see Tomatoes, page
100). Dispose of the plants in the council green waste bin.