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Summer pests!


The prolonged hot, dry weather this summer seems to have brought a new batch of pests to my garden. Here's what I've done about them.

Red Spider Mites

More often associated with greenhouses and indoor plants, these critters invaded my beautiful leycesteria formosa "golden lanterns. Unfortunately I initially mistook the symptoms - brown, powdery leaves - for stress from lack of water and simply started watering it. By the time I realised what was wrong the whole plant was infected and the mites had spread to a number of other plants in my garden.

With the leycesteria I felt I had no choice but to remove the infected leaves, leaving just the new growth on the plant:

I took similar action with a hydrangea but with most plants I hoped to address the problem without being so drastic.

Although I make no claims to being an organic gardener, I am not keen on using chemicals so I tried:

  • Soapy water - this had no obvious effect

  • Organic bug killer - this had no obvious effect

  • Inorganic - this had no obvious effect.

At this point I did some research and discovered that spider mites tend to be resistant to standard pesticides. A lot of people online seemed to recommended SB Plant Invigorator, which while not organic is a fairly gentle chemical spray which kills pests by suffocating them. It comes in a pre-mixed 1 litre spray bottle, but I used the concentrated version in my pressure sprayer which meant I could use the lance to get to the undersides of leaves and into the centre of plants. I have now thoroughly sprayed all of my affected plants and their neighbours with this and the problem does seem to have reduced. I think I'll have to re-spray a couple of times but hopefully this will finally address the problem.


At my garden club this week a friend commented that they had successfully used these sachets in their greenhouse. They contain immature predatory mites (Amblyseius andersoni) which emerge from the sachets over a 6 week period and kill the spider mites. I like the idea of a biological control of this sort, but I'm not sure how well they'd work outdoors:


Sawfly

This year has not been my first brush with sawfly. In the past I have had them on my gooseberries, you can see what I did about them here: https://www.seeingthefuchsia.com/single-post/2018/05/16/Gooseberry-Sawfly---update.

This time the sawflies were on my roses. They're in the ground, not pots, so getting rid of them was not a simple matter of washing off the soil and roots. Instead I've been going outside in the evenings - when they're at their most active - to remove the leaves which they're on, then carrying the infected leaves down to the "wild" area at the end of my garden. Not a perfect solution as although I think it's too far for the larvae to crawl they may still lay eggs in the soil and the flies could be back next summer, but I'm too squeamish to simply kill them.


Scale Insects

Our blackcurrant bushes often attract ants which farm aphids on their stems. This year however it's been a new pest, scale insects. As you can see below, these look like small growths on the stems:

Luckily I'm not so squeamish about these and they were simple to get rid of simply by picking them off the stems and throwing them away.

Other pests

Although they've been sparse I've still had a few greenfly and whitefly. Blackfly have not appeared this year which is very unusual, I can only assume they don't like the hot weather (or perhaps the spider mites have eaten them!). I've also had leaf miners and, for the first time, leaf curl:

I'm hoping the SB Plant Invigorator will take care of the whitefly. The leafminer and leafcurl are not yet widespread so I'm removing the affected sections in the hope that this will prevent them from spreading.


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