Small aphid populations are generally not serious. Aphids can, on rare occasions, be a vector for viruses, but in a garden situation that usually is not a concern. They can also be the cause of distortion of leaves or buds, but under normal conditions they cause no permanent harm to plants.
Most pesticides sold for killing aphids are very effective; unfortunately, they not only kill the aphids, but many of the beneficial insects that feed on aphids as well.
Aphid predators always appear on the garden scene after the arrival of the aphids. Pesticides either kill the predators (along with the aphids) or eliminate the predators’ food source (the aphid). Either way, the end result is the same: a serious disruption of the garden’s insect ecology.
Instead of an active insect ecology where the predators keep the aphid numbers low naturally, pesticide use disrupts the natural balance between friend and foe. Because of their resilience, the aphids, as well as other pest insects, are quick to repopulate the garden without interference from the beneficial insects, and pesticides use will have to be continued throughout the season.
Remember: the use of highly soluble synthetic fertilizers can cause the excessive growth that pests and pathogens are very attracted to. It is recommended that organic forms of fertilizers that are released slowly be used to promote strong growth and provide a host of benefits to the soil biology.
A positive step toward aphid and other insect management is to increase garden biodiversity by planting plants that attract beneficial insects. It is at the larval stage that most beneficial insects consume pest insects such as aphids. The adults rely on pollen and nectar for food. If you provide a source of the food, they will repay you by laying their eggs on aphid and other insect pests.
To control aphids without pesticides:
- Tolerate small populations of aphids.
- Wash aphids off with a stream of water.
- Increase the garden biodiversity to provide sources of pollen and nectar for the adult beneficial insects.
- If localized to a few tips, brush off by hand or prune off and compost clippings
- Use organic slow-release biodegradable fertilizer.