This week in the garden plants are growing very rapidly as we approach mid summer, which is less than a month away. Not only are the plants growing fast, but the insects that live on the plants such as aphids are appearing everywhere! We are having a bit of a problem with orange aphids in the lower greenhouse. It is not difficult to imagine why aphids in a greenhouse are not a good thing! With so many plants close together in a contained space – greenhouses provide ideal places for aphids to multiply!
Firstly it is important to be able to identify aphids, so that you are aware when you have a pest problem. Aphids are soft bodied insects which live on the sap of a wide range of plants and flowers. You’ll see them on stems, inside flowers, and on the underside of leaves. Aphids can be green, black, orange, pink or shades of brown. The green aphids typically found on roses are usually called “greenfly”, and the fat black aphids often found on broad beans are called “blackfly”. Some aphids have wings so they can travel from plant to plant creating new colonies at any time. Aphids multiply extremely fast during warm weather by producing live young. These live young aphids already have the next generation of aphids developing inside them when they are born. They can go from nymph to adult in just 7 days!
Aphids suck the sap out of the leaves and stems of the host plants, weakening them and causing distortion to emerging flowers and leaves. Bad aphid infestations are very debilitating. The buds don’t swell fully, and often the flowers and fruit are small.
So how can we control aphids? We have been using what gardeners call a ‘natural predator’. Natural predators are a way of controlling pests without using chemicals.
Aphidius, (a tiny parasitic wasp) are the most popular, and least expensive way of controlling common aphids. Aphidius colemani tend to tackle the smaller aphids. Aphidius look like very small flying ants, about 2-4mm long. These tiny insects lay their eggs inside aphids and the aphid is then paralysed and the new Aphidius hatches from the body leaving behind a dead aphid “mummy”.
Last week we released around 500 Aphidius into the lower greenhouse where hope they will be working their way through the aphid population.
Out in the garden our kale plants, Cavalo Nero are large enough that we can start to harvest a few leaves each week. We choose, then cut away the middle size leaves on the plants leaving the lowest leaves to continue to produce the resources needed for the rest of the plant to keep on growing. When harvesting it is really important not to cut out the plant’s central growing tip as this would seriously stunt the plants’s growth.
We are feeding our outside cordon tomatoes, and tending all other vegetable beds, keeping the plants weeded and watered, awaiting the time when they will be ready to harvest.