Agapanthus gall midge

Agapanthus gall midge is a new species of fly affecting Agapanthus that can cause buds to become deformed and discoloured and fail to flower. It was first noticed in the UK in 2014 but may have been present for several years.

Affected buds with agapanthus gall midge larvae

Quick facts

Common name Agapanthus gall midge
Latin name Not yet described
Plants affected Agapanthus species and cultivars
Main symptoms Deformed and browning flower buds that fail to open
Caused by Larvae of a small fly
Timing Currently unknown

What is agapanthus gall midge?

Agapanthus gall midge is a tiny fly that lays eggs on the developing flower buds of Agapanthus. The feeding activities of the larvae inside the buds cause abnormal bud development and infested buds can fail to open.

    Low level symptoms of agapanthus gall midge – distorted buds on lower left side of flower headModerate symptoms of agapanthus gall midgeSevere symptoms of agapanthus gall midge – flower head mostly abortedAgapanthus gall midge larvae 2-3mm in lengthAffected buds with agapanthus gall midge larvaeAdult agapanthus gall midge

    Research

    The species of midge causing this problem is unknown as it is an undescribed species (i.e. new to science). Consequently, very little is known about the biology and lifecycle of this insect. The Plant Health team at RHS Garden Wisley have launched a project to study it, and are asking for help from gardeners who have seen agapanthus gall midge or damaged flowers.

    By Post: Please send samples of infested flower heads in sealed bags or containers to: Entomology, RHS Garden Wisley, Woking, Surrey GU23 6QB

    By Email: Alternatively, photos including postcode of location of the plant, will help us to map how widespread the midge is in the UK and can be emailed to advisory_entomology@rhs.org.uk.

    The RHS confirms that your information will be stored in compliance with the Data Protection Act and your address will not be shared with third parties, other than for data processing purposes. If you prefer not to have your information used in this way, please indicate when submitting your record.

    Symptoms

    If the foliage of Agapanthus appears healthy but the flowers are abnormal in the ways described below, then agapanthus gall midge is most likely the cause:

    • Infested flower buds are deformed in shape and may have patches of brown discolouration 
    • Affected buds fail to open and either dry up or rot
    • If the infestation occurs as the flower spike is developing, the entire flower head may collapse or fail to develop
    • Numerous creamy yellow or orange maggots, up to 3mm long, may be found inside the buds, crawling around in a watery liquid

    Control

    Currently the RHS does not know which control methods may be effective against agapanthus gall midge. Practical countermeasures and advice on this pest will result from the on-going studies at the RHS.

    Gardeners may wish to pick off and destroy galled flower heads as soon as they are seen but there is no evidence yet to show how effective this may be.

    Biology

    The tiny gall midge lays eggs on the plant and the larvae develop inside the individual flower buds or inside the flower head sheath. The larvae can then cause the bud to be deformed and discoloured and often fail to open. The severity of this can range from a couple of buds failing to collapse of the entire flower head.

    Infestation can be confirmed by opening the buds or flower heads and looking for the presence of small maggots 1-3mm in length which are a creamy yellow colour. The midge larvae leave the flower head to overwinter and pupate in the soil.

    Our research should help us to understand the lifecycle of the midge and determine when the adults are ovipositing (laying eggs).

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