There is a huge army of small willing garden helpers out there, all they need is food and lodging and they will work day and night in your garden. No, not a Dickensian child labour scheme, but a myriad of tiny predators to help you in the battle against garden pests.
Whilst I not an organic gardener, I’ve always used herbicides and pesticides as a last resort. I’ve been aware of biological control for a while but only really started using them a few years ago. I get my biological army from greengardener.co.uk. Not only do they stock a microscopic predator for most plant pests they have a huge amount of useful information and resources. You can even ask their advice for tricky infestations.
My greenhouse and conservatory (where I grow peppers and aubergines) started to suffer very bad white fly and red spider mite infestations. The aubergines in particular seemed to suffer to the point of having to destroy the plants. Not to mention the sticky mess and lack of yield. I tried spraying but it was having very limited effect, and a quick google informed me that there was some pesticide resistance in white fly in particular.
I did a bit of research and went for Encarsia for whitefly control. Encarsia are tiny parasitic wasps, around 1mm in length. They are harmless to us, and you have to look really hard to even see them. What they are harmful to are whitefly, laying eggs inside them and eating them from the inside! These have been used commercially for many years and have the advantage that the whitefly cannot become resistant to them. I found them to be very effective, and have had no whitefly problems since starting to use them. However, they are not cheap – £20 for a medium greenhouse per year.
For red spider mite, I have used a mix of Amblyseius Andersonii and Phytoseiulus. These are both miniature predators which are applied at different times of the year. I have found that they almost eliminate red spider mite.
For greenfly and blackfly, the solution is likely to be already living in your garden; ladybirds, in particular their larvae, have a huge appetite for aphids and scale insects. The first time I used them I made the mistake of buying them, and then found out there was no need. Once you get to know what the larvae look like, simply look for them in the garden and relocate them to where they are most needed. I have a plum tree that seems to be a ladybird breeding colony; most days I move 5-10 larvae to a new home. Whilst they look tiny it is noticeable how quickly they make the aphids disappear. This year, I seem to have an early infestation of greenfly, so I have applied “Aphidius” in March, as the ladybirds have not fully emerged. Aphidius are another miniature horror story, they lay an egg in the aphid, and when the egg hatches the larvae munch away on the aphid’s insides. In addition, the greenfly are distressed by the predators activities and omit pheromones that cause their friends to panic and drop off the plants.
A few years ago, my bay trees got infested with scale insect. This was not much of a problem for the trees, they didn’t seem to care and grew regardless. The main problem was that the scale insects attracted wasps, who went after the sticky honey dew the scale insects produced. This made the garden a much less attractive place to be, having to share it with hundreds of wasps. I asked greengardener.co.uk and they advised a mix of scale nematodes and ladybird and lacewing larvae. Nematodes are microscopic worms that burrow into the scale insects and quickly destroy them. The nematodes are applied by mixing with water and spraying the infected plants. I was fairly skeptical but one treatment and the bay trees have been less infested by scale insects, and the squadrons of wasps have stopped visiting.
I still have a few pest issues, mainly asparagus beetle, codling moth and lupin aphids. I have spotted that a nematode is being marketed that targets asparagus beetle, which I will try this year. In previous years the biological control has been much larger, i.e. me. During the asparagus season you pick and squish the beetles. It is effective, but has to be done several times a day. This does not eliminate the beetle but does limit the damage they do.
Codling moth is the main culprit for maggots in apples. The non-biological control has been up until recently spraying with a pesticide. Unfortunately the pesticides used are not bee friendly, and it gets expensive to treat larger trees. A nematode solution is now available, and you spray the ground around the tree in autumn, I will try this later on in the year.
Last year I had a few infestations of lupin aphids. These are recognisable, they look like massive greenfly (and live on lupins!). Apparently soapy water sprayed on will work, and I suspect Bug Clear Fruit and Veg (which is diluted rapeseed oil) will work as well. I will try ladybird larvae as well, but these giant aphids may be too much for them.
Since starting to use biological controls I have had very few problems with whitefly, greenfly and red spider mite. An added bonus is that some of the predators will return of their own accord and continue to help you for many years.
Happy Gardening,
Robin
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