Aphids in Conifer Hedges/Trees

This year has seen an increase in reports of damage to conifers from Aphids. Trees used as hedging seem especially at risk. Brown areas appear in the foliage, which spreads killing the plant in the areas infected. Large areas can be killed quite quickly.

Treating the Aphid responsible can be quite difficult, due to their location often deep within the Tree. They reproduce very quickly, sucking sap from the trees. Ants often appear after an infestation starts. They will milk some of the honeydew produced by the Aphid. They are not a pest in this respect but will often protect the Aphid from natural predators such as Ladybirds.

What can be done to stop the damage and pest? Predators such as Ladybirds can be added to the damaged areas, however large numbers need to be introduced if it is not caught early. Lacewing larvae are not suitable for use in Trees or hedging, as they prefer low growing plants.

Traditional systemic insecticides can be used but Just Green does not support or recommend the use of toxic substances. Contact based non-toxic sprays can also be applied. Suitable contact sprays include Just Bug Killer ,Savona, Block Out and SB plant invigorator. These are all available from Just Green. The key to their success will be coverage and frequency of application. They generally work by smothering the aphid, suffocating and killing them. None of the products have any toxic poisons in them. Once the area is dry, beneficial insects such as Ladybirds can re-populate the area. They need to be applied at least every 5-7 days, as the aphid reproduce very quickly. One problem to over come is how to get the contact spray onto the Aphid? They will often be deep within the Tree. The only way to get to them is with a hand sprayer which has pressure, such as a knapsack sprayer or sprayer with pump handle. Just Green has several products that are suitable.

For future protection, try putting up ladybird houses. These will act as winter shelters for Ladybirds. This helps increase Ladybird populations in your garden, which may prevent or reduce future attacks.