Pest & Disease Management - Aphids

With their pear-shaped bodies, long antennae and a pair of rear-end siphunculi -- or exhaust pipes as they are sometimes described -- aphids are one of the most easily recognised and common glasshouse pests.

Aphid on Philadelphus - image: Dove Associates
Aphid on Philadelphus - image: Dove Associates

All aphid species are sap-sucking. Some have a wide host range while others are restricted to specific plants or plant types.

In most aphid species, females can produce live young without mating, which condenses the life cycle, as well as lay fertilised eggs. Live young are born fully active and can mature to adults in as little as one week. The variety of ways that aphids can wreak plant damage — distorting and reducing growth, transmitting viruses and producing sticky honeydew — also contributes to their economic importance as pests.

Aphids feed by probing plant cells with their filamentous mouthparts, sucking up sugar-rich sap from phloem tissue. Because they have to ingest large amounts of sap to obtain enough nitrogen, the excess sugar is excreted as honeydew, which provides the ideal environment for sooty moulds.

Biology

Identification of the correct aphid species is important because some of the biological control agents are species-specific.

• Most aphid species have two types of plant host, one on which they overwinter in some form, such as eggs, and the second to which adults fly in spring and on which much of the feeding damage is done. New generations of winged aphids migrate between seasonal host plants or fly to find fresh feeding grounds when colonies have become overcrowded.

• Temperature plays an important role in determining the speed with which aphids complete life cycles and populations build up.
Treatment: biological control

• Peach-potato and melon-cotton aphids — Aphidius colemani parasitic wasp. Best used as a preventive treatment, introduced early in the season.

• Glasshouse-potato and potato aphids — Aphidius ervi or Aphelinus abdominalis parasitic wasps. Introduce these at the first sign of aphids. Aphelinius is slower acting than Aphidius ervi.

• Aphidoletes aphidimyza predatory midge larvae. The adults need dark periods for mating, whereas the larvae need 15 hours of daylight to avoid triggering diapause, the mechanism by which pupae overwinter.

• Chrysoperla carnea, a native lacewing. Introduced as larvae that are avid predators of aphids. Best used against established populations in hot spots and as complementary control to Aphidius and Aphidoletes.

Treatment: cultural control

• Monitor for first signs of pest or damage.
• Use yellow sticky traps to monitor the adult flying stages.
• Spectral-filter polythene claddings are available, which may modify aphid feeding behaviour.

Treatment: chemical control

Although the active ingredients imidacloprid and thiamethoxam were included in the 2013 neonicotinoid ban, some exemptions were made for selected glasshouse-grown ornamental plants.  Check revised labels and the EAMU for Actara before applications take place.

All retail products containing these active ingredients will be completely withdrawn from the market by 30 November.

Note that some ornamental crops may also be seen as edible including almond, apple, apricot, peach, nectarine, pear, plum, quince, sloe, blackberry, blueberry, gooseberry, raspberry, cherry, Castanea sp., currants, grapes, hazelnut, Actinidia, citrus, olives and some outdoor herbs.

 

Other products available

1 Gazelle SG (acetamiprid): insecticide with contact, systemic and translaminar activity. Not included in neonicotinoid ban. Compatible with most biological controls.
2 Naturalis-L (Beauveria bassiana): primarily for whitefly and thrip control with a limited effect on aphids. Compatible with biological controls.
3 Toppel 100* and others (cypermethrin): contact and stomach-acting pyrethroid insecticide. Not compatible with biological controls.
4 Decis and others (deltamethrin): contact pyrethroid insecticide with residual activity. Not compatible with biological controls.
5 Danadim Progress (dimethoate): contact and systemic organophosphorus insecticide. Not compatible with biological controls.
6 Dursban WG and others (chlorpyrifos): contact and ingested organophosphorus insecticide. Not compatible with biological controls.
7 Sumi-Alpha (esfenvalerate): contact pyrethroid insecticide with residual activity. Not compatible with biological controls.
8 Savona (fatty acids): contact-acting insecticide. Compatible with most biological controls.
9 Imidasect 5GR, Intercept 70WG, Couraze (imidacloprid): compatible with most biological controls. Subject to restrictions from the neonicotinoid ban.
10 Hallmark WZT* and others (lambda-cyhalothrin): fast-acting, persistent, contact and residual insecticide. Not compatible with biological controls.
11 Majestik (maltodextrin) and Eradicoat (maltodextrin): contact insecticide with physical action. Use as an overall spray 24 hours before introducing biological control agents.
12 SB Plant Invigorator: contact insecticide with physical action. Compatible with most biological controls.
13 Aphox and others (pirimicarb): contact and translaminar activity. Compatible with most biological controls.
14 Chess WG*: prevents aphids feeding, killing them in one-to-four days. Compatible with most biological controls.
15 Pyrethrum 5EC and others (pyrethrins): short-term, contact insecticide extracted from natural pyrethrins. Compatible with most biological controls.
16 Calypso*, Biscaya*, Exemptor (thiacloprid): Not included in neonicotinoid ban. Compatible with some biological controls.
17 Actara* (thiamethoxam): contact and systemic properties. Not compatible with biological controls. Subject to restrictions from the neonicotinoid ban.
18 Mainman* (flonicamid): Feeding inhibitor.  Systemic and translaminar activity.  Compatible with biological controls.’
19 Movento* (spirotetramat): Translaminar.  Contact-acting with ingestion activity.  Compatible with some biological controls.’

Fully updated by Dove Associates.

* Extension of Authorisation for Minor Use (EAMU) required for use in ornamental plant production outdoors and/or under protection.

Dove Associates shall in no event be liable for the loss or damage to any crops or biological control agents caused by the use of products mentioned.


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