Aphids

The rosy apple aphid is one of the most damaging aphids of apples. They feed on apple foliage as well as fruitlets and can cause significant yield losses even in low numbers. Damaged fruits remain small with a wrinkled apperance making them unmarketable. Further, the damage caused on branches one year can negagtively affect the growth of the same branches and its flowers the following year.

The green apple aphid attacks the leaves of apple throughout the season but can be tolerated at higher levels than the rosy apple aphid because of no direct injury to the apples.

Aphids have several natural enemies such as earwigs, ladybirds, lacewing larvae, hoverfly larvae, and several parasitoids. Some of these natural enemies provide potential for supressing aphid populations in conservation biological control strategies.

However, the rosy apple aphid and the green apple aphid also have a natural protector, the black garden ant (Lasius niger), which protects the aphids from natural enemies, possibly impairing biological control strategies in some orchards.

Our research is focused on combining several strategies to avoid spraying aphicides in apple. The goal is to be able to enhance biological control of aphids by natural enemies.

In order to do so, the first step is to divert the ants from tending and protecting the aphids. To do this, we are working on developing a sugar solution that is more attractive to the ants than the aphid honeydew making. By doing so, the ants should stop/minimize tending of aphids and the natural enemies will have easier access to predate the aphid colonies.

A further step to this strategy is to combine it with lures and flower strips to attract and maintain the natural enemies.

The black bean aphid (Aphis fabae) has a wide range of hosts and is one of the most wide spread aphids. Crops that are typically attacked by the black bean aphid are sugar beets, beans, and potatoes

The bird cherry-oat aphid (Rhopalosiphum padi) is distributed world wide. It is often a pest of cereals in the temperate regions, especially in some Northern European countries.

The English grain aphid (Sitobion avenae) is, like the bird cherry-oat aphid, a serious pest of various cereals potentially causing great yield losses.

All the above mentioned aphid species have several natural enemies such as ladybirds, lacewing larvae, and parasitoids.

We are studying how far into cereal and sugar fields it is possible to attract lacewings as well as looking at the biological control in the vicinity of lures.