Plants are not the only organism coming into active growth in spring, insects are also taking advantage of the increasing warmth.
There are more than 900,000 known insect species in the world, but less than one per cent of those are pest species.
Insect pests fall into two main groups: the sapsuckers, and the chewers or leaf eaters. One of the most common sapsuckers is the aphids, which is quite small and can go unnoticed until numbers build. Aphids appear on the soft, new growth of many ornamental plants including fruit trees, citrus and vegetable crops.
They are soft-bodied pear-shaped insects about 2 millimetres in size with long antennae and a pair of abdominal tubes called cornicles. Depending on the species, they can be white, green, yellow, brown, black, grey or even pink. The grey cabbage aphid is a particularly notorious pest and can be found on the underside of the leaves of plants in the Brassicaceae family.
Aphids increase in population very rapidly through a reproductive process called parthenogenesis, basically overwintering eggs hatch as wingless females that can produce live young that are clones of the parent. Females can give birth to five to 10 clones every day.
As the population increases winged adults emerge to take flight and seek new host plants to start a colony. Managing aphids with soapy water, garlic and chilli sprays. Squash aphids with your fingers or blast them from plants with water. An old-fashioned solution for killing aphids is flour. A quick dusting of the infested plants with baking flour causes them to move on.
Aphids have many natural predators, such as hover flies, lacewings, parasitic wasps, and predatory ladybird beetles. Encourage these beneficial insects into the garden by planting a diverse range of flowering plants. Avoid yellow flowers as aphids are attracted to yellow - take advantage of this by installing yellow sticky traps among susceptible crops.
Another problem associated with aphids is the sticky, sugary honeydew excretion that can result in a secondary infection of sooty mould on plants. Ants also feed on the honeydew and protect aphids from predators.
Spring brings an abundance of new growth but a closer look at what's going on in the garden could reveal a sinister set of circumstances unfolding.
- John Gabriele is a horticulture teacher with a love for green spaces.