Aphid control

Chrysoline c

Chrysoperla carnea

 

 

 

 

 

How does it work?

Chrysoperla carnea is a predator which is best known for feeding on aphids. The larvae and adults are familiar sights in gardens.

Adults are usually pale green in colour, with membranous wings which they hold folded like a tent over their bodies. They often enter buildings during the autumn, whilst looking for over-wintering sites.

Larvae are very different in appearance, with three pairs of prominent legs which project outwards from the front third of the body. One of their most obvious features is the pair of pincer-like mandibles on the head. They use these mandibles to hold prey, and in some cases to lift it off the substrate to prevent escape. Once the mandibles have penetrated the prey, the lacewing larva injects enzymes which gradually digest the internal organs. When digestion is complete, the liquid body contents are sucked out through the mandibles.

Adult females lay single eggs on long stalks, usually on the underside of leaves. When the larva hatches, it immediately moves down this stalk until it reaches the leaf surface, where it begins to search for prey. When fully fed, the larvae spin a silken cocoon on a leaf or other surface, and form a pupa within this. During this non-feeding stage, the larval tissues are re-organised to form the adult, a process known as metamorphosis. At the end of this stage, an adult lacewing will emerge from the cocoon.

Larvae are predatory. and will eat many types of insects, not only aphids. They will even attack and kill caterpillars which are considerably larger than themselves. They can consume very large numbers of prey, and destroy quite large colonies of aphids. If food is not available, they are strongly cannibalistic.

One feature of lacewing adults is their tendency to migrate very soon after they become adults. For this reason, it is difficult to establish a permanent population within a greenhouse crop. Released larvae consume pests, but adults do not remain in the same area, and a second generation is rarely produced.

Chrysoperla carnea is now known to be part of a group of similar species. These species are morphologically similar, but have very distinctive "mating songs" which experts can use to confirm their identity.

 

When and where should you use it?

Chrysoline C can be used as a spot treatment to reduce localised outbreaks of aphids and other pests. It is normally used in conjunction with aphid parasitoids such as Aphidius colemani, Aphidius ervi, or Aphelinus abdominalis.

It will eat many species of aphids, and so can also be used when the identity of the aphids in uncertain, or when more than one species is present.

How should you use it?

Larvae should be used as soon as possible. Their cannibalistic nature means that they will begin to eat each other as soon as the food provided for them during transport is exhausted. Take care when releasing them that any carrier material does not fall to the floor: it is important that it remains on the leaves initially so that the larvae can move onto the plants.

Release larvae directly into the colonies of aphids which you wish to control. Rates of use will depend upon the level of infestation by the pest: high rates will give rapid reductions in aphid numbers, whilst lower rates may allow the aphids to persist and multiply. More than one release may be necessary, especially where larvae are used, because the first individuals may reach full size and turn into non-feeding pupae before the aphid infestation is controlled. Do not release fresh larvae whilst larger larvae from the previous release remain on the plants. The young larvae will mostly fall prey to the larger, existing ones.

 

When should you not use it?

Chrysoline c is not recommended for preventive use, not for control of very widespread colonies of aphids.

What will it do?

Chrysoline c will support control of aphids as part of an IPM programme using aphid parasitoids. It is ideally suited to the clean-up of localised outbreaks of aphids within an otherwise successful control programme, and can be used as an alternative to spot treatments with insecticides.

It will consume many species of aphid, some of which are not controlled by commercially available parasitoids such as Aphidius spp.

Chrysoline c can also be useful for the limitation of some other pests, including mealybugs, scale insects, and the larvae of Lepidoptera (caterpillars).

As a generalist predator, it will also attack and consume beneficial insects and mites.

What will it not do, and what are the control options?

Chrysoline c will not prevent aphid infestations, nor will it eradicate aphids in most situations. It is a specialist at exploiting the rapid growth of aphid colonies, arriving when the colony is large and plenty of food is available, and moving on to the next colony as the food supply diminishes. As such, some aphids normally remain in any colony, and populations can rapidly increase again unless other control measures are in use.

It should be used as part of a programme with aphid parasitoids and other aphid predators. Where the principal aphid is Myzus persicae or Aphis gossypii, use Aphidius colemani preventively or curatively. For Macrosiphum euphorbiae or Aulacorthum solani, use Aphidius ervi. Aphelinus abdominalis is also available for control of Macrosiphum euphorbiae. Where the aphid species is unknown, or mixed species are present, there are two options available:-

Aphiline ACE mix contains a mixture of all the three parasitoids mentioned.

Aphidoline a contains the predatory midge Aphidoletes aphidimyza, which has a broad host range and will attack and kill many species of aphids. Adults of this species are mobile, and can locate aphid colonies before they become troublesome.

The latter is the preferred option on crops such as strawberries, where several species of aphids occur which cannot be controlled adequately with commercially available parasitoids.

There are also a number of chemicals available for aphid control, which are compatible with other biological control agents. Amongst these are pirimicarb and, such as pymetrozine. Imidacloprid Neonicotinoids such as thiamethoxam may also be used effectively for spot applications, and areis best applied as a drench to the roots of the plants. The availability of insecticides varies between countries, as do formulations and methods of application permissible. Always check the availability of a particular compound on the crop and in the country concerned.