With warmer weather forecast it is important to be vigilant against the outbreak of Aphids. Aphids are a collective group of pests of which greenfly and blackfly are the best known. They are the most common of all pests and almost every plant form the smallest shrub to the tallest oak tree can be infested at one time or another.
Aphids are typically green or black but they may be pink, brown or yellow. They are usually 2mm long although some species are larger.
Lifecycle.
Their complicated life cycle makes them difficult to completely eliminate. At some stages they lay eggs, particularly to over-winter the species but they also give birth to live young, a process the female can manage without the involvement of a male. Some greenfly can begin producing offspring five days after being born.
Symptoms.
The little 'bugs' feed on the sap of the plant weakening it and reducing its rate of growth. Plant leaves will invariably become curled or distorted. The Aphid colonies gather on the underside of the leaves and as they suck the sap they excrete a sugary honeydew on to the leaves below thus developing a shiny glaze. Particularly in damp conditions, a sooty mould will grow on the honeydew glaze which is not only unsightly but will gradually deprive the leaf of light and eventually the plant will die.
Aphids also shed their skins as they increase in size and their cast off skins also gather on the leaf surface below forming a whitish dust.
Treatment and Control.
There is no shortage of insecticide that will kill aphids and prompt treatment at the first sign of infestation can make more difference than the choice of insecticide. Vulnerable plants such as dahlias and roses and especially plants such as lilies, where there is a high virus transmission, should be sprayed routinely from spring through to autumn. A persistent systemic insecticide is particularly useful for non-edible crops that are vulnerable. Pirmicarb is the insecticide to choose if you want to protect beneficial insects as it is selective and leaves most of the beneficial insects unharmed.
Organic Methods.
For an organic choice try one based on derris or an insecticidal soap. These insecticides have fatty acids as a control and need to be used more regularly, maybe twice a week. Spraying in winter with a winter wash is a useful way to control over-wintering eggs on fruit trees and roses but remember the tree or rose must be in a dormant state before this treatment is carried out. The best idea is to check your plants regularly to ensure that they are not under attack from Aphids and if they are, try to get them under control as quickly as possible.
JOBS OF THE WEEK.
* Check susceptible plants, particularly roses and lettuce, for Aphid attack and spray as necessary.
* Begin to support herbaceous perennials with bamboos or plant support rings.
* Water and feed plants in the greenhouse regularly.
* Feed trees and shrubs in the garden with a slow release fertiliser.
* Plant out alpines in well-drained ground incorporating sand or grit
