Tuesday, 22 July 2014

Erinose Mite

acenia hibisci (Syn. Eriophyes hibisci)

If you have severe pimpling of young leaves and developing vegetative buds on your hibiscus, you most probably have a problem with erinose mite. It is very widespread now through South East Queensland and northern New South Wales (unconfirmed reports suggest that the mite may have become established in NSW as early as 1978).

This microscopic mite was most probably introduced into Australia on illegally imported hibiscus cuttings from Brazil, Hawaii, Tonga or Fiji where the mite is found. Upright and weeping forms and Indian and Hawaiian types of Hibiscus rosa-sinensis are affected. Okra, another member of the Malvaceae plant family has been affected overseas but as yet it has not been seen in Australia.

Transmission occurs on cuttings or perhaps via transfer in wind currents. Neglected plants appear to be at greater risk of infestation. Generally, pruning of affected tissue does not provide control without an appropriate spray program. Growers who have cut back damaged foliage and allowed them to regrow often report that the new leaves are still infested with erinose.

To effectively manage this mite in high risk areas, spraying at monthly intervals throughout the year may afford some protection with more frequent sprays during the main growth period. There is not, however a registered chemical control for A. hibisci. Miticides with a generic registration against mites, such as wettable sulphur or maldison may do the trick. It will also help if you prune early so that new growth has hardened before the erinose mites hatch and start feeding. Also as the season progresses, you might also consider using fertilisers that are not too high in nitrogen so that soft leafy growth is minimised during the time the mites are at their peak.

It is imperative as gardeners that we do not spread this problem - we should not move cuttings from infested areas into other districts and badly affected shrubs and prunings should be removed and either burnt, buried or taken to the dump in an enclosed plastic bag.

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