Spring is the season when a host of pest organisms come to feed and life hugely on our garden crops. Foremost amongst them are species of tiny flying insects, known commonly as aphids, which while not generally fatal, cause a lot of visual damage to a wide range of plants.
The first symptom of aphid activity is the secretion of sugary substances on new leaves, stems, and flowers. This can be extremely disagreeable with honeydew dripping on to paths, parked cars, and other crops. More harmful to the plants’ health is the sooty mould, which is a complex of fungi which develops from the honeydew. Left unattended, the soot blocks out light from reaching the plants’ foliage, thereby depriving the plant of its own vital energy source.
Before going into how to handle aphids, do not forget that the purpose of pest control isn’t the complete eradication of the offending organisms, but instead the control of their population levels to manageable proportions. The indiscriminate use of insecticides only succeeds in clearing the way for pest populations to explode, as the insecticides decrease the population of natural predators. For this reason, quite apart from environmental considerations, it is ideal to avoid applying pesticides in your home garden entirely.
As intelligent pest management is about control rather than elimination, non-poisonous, “environmentally friendly” insecticides, such as insecticidal soaps, can do a decent job. Better still is to use the good old-fashioned garden hose at high pressure to wash off the aphids, with a little help from your thumb and forefinger. Will this be 100% effective?
Since aphids in the spring tend to attack young juicy growth, they are largely found on the plants’ growing tips, which makes it easy to eliminate them by simply clipping the plants gently. This works perfectly for foliage plants such as Artemisia or Ivy, but of course might prove very disappointing for flowering ornamentals and fruit trees. Additionally it is possible to let nature take its turn. In the Mediterranean region for example, periodic hot, dry winds kill aphids just as effectively as insecticides.
With pests generally and aphids in particular, timing is all-important. Finally, we should be striving to turn the backyard into a balanced eco-system, but this is easier said than done. In the meantime, aphids should be treated in the first signs of infection.
Aphids produce a range of generations within one spring, so there’s every chance that the gardener is spraying the symptoms rather than the cause itself.
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