About a month ago, as the weather warmed up, I could see aphids and thrips starting to multiply on my pepper plants. Now I know that aphids give birth to live young and can multiply exponentially, so I thought I would keep an eye on it. Every so often I would brush some off with a paintbrush and relocate them, but I wasn’t going to panic. I did consider whether I would need to reluctantly use a soap spray, but an observation made me decide against it. I noticed that on one of the plants there were a few bloated motionless aphids (see picture).
These aphids had been parasitised by an inconspicuous little black wasp (see picture). It is only 1-2 mm long, but moves very quickly, injecting its eggs into the poor unsuspecting aphids. Most of us aren’t aware of them, because they don’t have the bright ‘look at me I am a predator’ uniforms of ladybirds or hoverflies. The eggs hatch out inside the aphid, and the larva starts munching on its insides. Within a few weeks, the larva pupates, then the adult bursts out in true ‘alien’ style. If you look at the picture, the aphid on the right has a small hole where the wasp has made an exit. Within a few weeks, the plants were littered with these empty shells. Aphidogeddon had struck!
To add to their woes, I also found another visitor – a ladybird larva, which was wandering around, scooping up and munching thrips. To me, the markings on its back look like a harlequin ladybird larva. These have got a bad name for themselves as they are a non-native species that outcompete native ladybirds for food. I still think they are doing a useful job, so leave them alone. Have a look at this video of one having a feed on thrips on my pepper plants.So aphid numbers are definitely on the decrease in my peppers as we head towards July. I am glad that I didn’t waste resources, using the soap spray, as it would have obliterated everything, leaving no food source for these valuable predators. Instead, I let them exist at low levels, which caused no harm to the plants, and then nature did its work on the rest. This is a pattern I observe repeatedly. Aphid numbers are worst in May and June, but numbers crash in July. This ‘July aphid crash’ is a well-known, phenomenon (amongst plant nerds anyway) that is not completely understood. What is observed is an increase in numbers of ‘natural enemies’ that attack pests during this period, including predators and parasites. There are even fungi that attack insects – if you though the parasitic wasp was gross, just try looking up entomopathogenic fungi online!