Agriculture Reference
In-Depth Information
Botrytis can spread quickly when conditions favour it, so if you spot it early, cut
away any affected material and compost it. If this is not possible, spray with
bicarbonate of soda solution every few days (see Chapter 7, page 58).
Cabbage root fly
This pest is hardly ever a problem in polytunnels, but if it is common in your area
you may wish to put protective collars around the stems of brassica seedlings.
These are discs with a straight cut running from the edge to a hole in the centre.
Alternatively, grow plants entirely under fleece.
Carrot fly
Again, this pest is hardly ever a problem in polytunnels. If it affects your outdoor
plot, grow your carrots under fleece using a cloche tunnel (see Chapter 7, page
58) to avoid squashing the fragile young seedlings.
Caterpillars
Growing brassicas organically without some sort of protection is a heartbreaking
exercise in futility. Give the seedlings a good start in clean compost, ideally pH
6.5 to 7, in modules high on a shelf or bench where most pests cannot reach
them. The cabbage white butterfly can be a problem for any brassicas between
late April and September.
Once the seedlings are planted in the beds, protect them with netting that is held
away from the leaves with some kind of support, or protect the whole tunnel by
screening the doorways (see Chapter 6, page 53, 'Pollinators or brassicas' box). If
you simply drape the net over the plants, you will find that butterflies can lay
their eggs through the holes perfectly well. Even if the plants are netted, it is crucial
that you check them at least once a week during butterfly season, because the
butterflies will soon find (and exploit) any gaps or holes.
Regardless of what manufacturers may tell you, horticultural fleece is less suit-
able than netting for excluding butterflies, in summer because of the heating
effect, and in spring because of the small but significant loss of light.
Cats
See Chapter 2, page 24.
Celery fly
This pest is rarely seen in polytunnels, but if you see blistering on the leaves it
may indicate an attack. Remove affected stems; the plants should be able to grow
back quickly, provided that they are otherwise healthy.
