Pests Have Favourites - Usually Mine!

Most garden pests can be tolerated, at least to a large degree. And, if left to its own devices Nature has its own methods of dealing with most of them.

I am absolutely fascinated by the ways in which plants can not only resist attack by pests, but also communicate with both insect predators and with other plants, in the process. There has been much research of late, most of which has already been outlined, for example in this review by Sophie Wilkinson.

PESTS HAVE FAVOURITES - USUALLY MINE
If you were with us last year, you will recall the problems I had with snails on a hosta and on some dahlias. But it was only on certain plants, not them all.

This is typical of pest attack. They usually tend to attack just certain varieties and leave others. And these seem to remain attack-free, year after year. So the obvious way would be to keep the ones which survive without protection and discard the rest. This, I do - and given the problems I had with snails on one of the hostas last year, I am also thinking of doing the same here. Problems arise when favourites are attacked. What then?

As you know, I don't like using chemicals for pest control. I know I recommend them, but this is to show that pests can be controlled this way, and also that it's not a closed shop - although I would prefer natural control, I am open to any means possible to control them, especially to preserve my favourites.

But, more than this: There are certain pests and certain types of attack which I am not confident can be left alone. I am thinking of slugs, snails and vine weevils, which attack the roots. I have lost endless plants this way.

I know there are nematodes (these look like tiny worms and enter the pest to destroy it from the inside) which will work in the soil. But these are expensive and will only work in warmer conditions - not now when the slugs are doing the worst of their damage on the tender young delphinium roots, and vine weevil grubs are attacking azaleas, primulas and pansies the same way.

Vine Weevil Damage on Pansies in Containers

Vine weevils love to over-winter plants in containers, especially if they have some nice fresh pansy leaves (and later, roots) to feed on. The semi-circular chunks missing from the edges of the leaves reveal their presence. However, they do not usually chew holes in the centre of the leaves.

A dose of 'Provado Vine Weevil Killer' (9g/litre thiacloprid, mixed at 30mls per litre of water) will protect containers until spring.

Vine weevils (especially the grubs, which chew through the roots) are also a problem for primroses, often used in winter containers as a source of bright colours. 'Provado' protects these as well.

Sneaky Vine Weevil

Look what I found overwintered with a begonia tuber. Before planting, it is best to remove as much peat or soil as possible from around the tubers. I only just spotted this vine weevil. I must remember to treat the plant later in the year in case I missed any others.

It is unusual to find grubs at this time year. Normally they would have pupated into adult weevils by now, ready to lay a fresh lot of eggs in the autumn. It really is a strange season.

Vine Weevil Spraying

Sprayed Rhododendrons and Pieris(Forest Flames) with 'Thiacloprid' ('Provado Vine Weevil Killer 2'). The idea here is to kill the adult weevils before they lay eggs and before they do too much cosmetic damage to the plant leaves (adult Vine Weevils chew out semi-circular chunks from the leaf edges).

Although it might still be a little early, I don't want to give them any chance. I have sprayed up under the underside of the leaves so that the chemical will dry on there, not get washed off, and produce lasting protection. This chemical is also systemic (it is taken into, and moves around, within the plant), so spraying the underside also helps uptake, because it is sprayed directly onto the leaf pores through which it can enter the leaf.

It might still be a little early. I find that adult Vine Weevils prefer tender young leaves, which are only just developing on the Pieris but only develop after flowering in the Rhododendrons. At this time it is difficult to spray without some spray getting onto the flowers and thus poisoning the bees. By the time it is safe to spray, it is too late; the damage has been done.

Ideally, I like to spray the leaf buds just as they are opening. This way, the chemical is on the leaf edges where the weevils feed.

This treatment is not the standard one, which is pouring the insecticide onto the roots to kill the grubs (which can do the real damage). But I find the cost of doing this to be prohibitive. Spraying the leaves is far more cost-effective, provided all the adults can be killed.

However, it is worth treating pots of Fuchsias and other vulnerable plants by douching the roots.

This chemical provides long-lasting control for up to 2 months.

I will treat them again in a few weeks.