Greenfly and shed skins on a chilli plant

6 tips on how to spot greenfly

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Greenfly, a menace to all, and particularly to chilli growers. Greenfly not only spread disease and drain a plant of its energy they often damage the fruit too. But how do you find them in the early days before they take hold and decimate your plants? Here are 6 tips for early detection.

1/ Look in the new shoots. Although they are commonly found on the underside of leaves, early in the year before the sun gets hot, they get into the tender new shoots where they damage flowers and leaf growth while the are still forming, so look there first.

2/ Use a magnifying glass or zoom in with your phone camera. It is so much easier to find and kill two or 3 today than 300 a week from now. In the picture below you can clearly see two fatties tucked into the new leaves plus a couple of smaller ones. The scars from their bite marks will cause the leaves to be contorted.

Early greenfly infestation on chilli plant

Early greenfly infestation on chilli plant

 

3/ When the sun gets hotter they seem to take shelter. This is when you start to find them lower down the plant among the shady lower leaves. Look for the white shed skins, they are often the most obvious sign of a greenfly infestation.

 

Greenfly and shed skins on a chilli plant

Greenfly and shed skins on a chilli plant

 

4/ Look for twisted shoots as they emerge, this almost always  a sign of greenfly, not some other disease. The greenfly that caused the problem may have long since been eaten by predators, but it is best to give the tip a spray with an organic insecticide to be on the safe side.

 

Greenfly causing twisted leaf growth on a chilli plant

Greenfly causing twisted leaf growth on a chilli plant

5/ Look inside newly forming flowers, if the greenfly get hold before you stop them they will scar the flower tissue and this results in bent and badly formed fruit, more on that here. As soon as the bud starts to open they will get inside. A quick spray with a soapy organic insecticide should do the job, or there are lots in there you should nip the flower off and scrap it. There is no point in allowing the plant to put its energy into growing a malformed fruit, there will be plenty of other flowers.

6/ Look for white shed skins in spider webs or on the soil around the plant. This is the tell tale sign that greenfly are lurking on the leaves above. The shed skins are often mistakenly diagnosed as white-fly when they are just empty skins shed as the greenfly fatten ready to give birth to the next generation.

Fungus Gnats (or Sciarid Flies)

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I have never really had a problem with these before, occasionally I have seen them in chilli plants that are overwintered indoors, or other house plants. But mostly they tend to stick to indoor plants with old neglected soil.

For those that don’t know about them, they are a tiny black fly that hangs around the soil in a pot, you often don’t see them until you water it and they all fly up in a panic. Their even tinier grubs will be living in the soil, feeding on algae, rotting organic matter, and according to some experts but not others, the roots of your plant.

This year, however, I seem to have been inundated with them in the greenhouse. I think this is most likely due to the very mild winter. Where I live in South Devon we only had a couple of very light frosts, and the greenhouse never went below zero, hence poor sterilization of the soil. I had a couple of chilli plants out there which developed fungus gnats in their pots but I wasn’t too worried, normally they would die and be discarded before spring. I also had a bag of compost left over from the previous year which had a few in. I didn’t want to use it for potting so I dug it into the beds in the greenhouse. I foolishly thought the flies wouldn’t survive in natural soil because other bugs would kill them off. This was wrong, and before I knew it the beds were crawling, along with some other pots.

I am a big fan of biological controls, Nemaslug etc. and I urge people to use them whenever I can, but it is only recently that I have seen a control for Fungus Gnats. In my Growing Chillies book I deal with Fungus Gnats, but don’t mention a biological control for them as, at the time, there didn’t seem to be one available, hence this update. I have always used the old fashioned method of sticking a piece of potato in the soil which attracts the grubs and can later be discarded. Luckily now there is a biological control widely available, it is inexpensive, easy to use and very effective. It is microscopic nematode worms that infect the fly grubs. It comes as a light powdery substance in a small sealed tray. Dilute it in a watering can and water it into the soil of infected pots. It seems to me that the results are obvious within just a day or two. I suppose the grubs are infected almost immediately and the adults don’t live more than a day or two, so their life cycle is immediately halted.

This will be my first port of call in future, I might even order it as a matter of course every spring when I order my Nemaslug, you can get them shipped together from ‘all good purveyors biological controls’ I use www.greengardener.co.uk