Six-spotted mite - a pest of grapevines and avocados

Page last updated: Thursday, 22 March 2018 - 2:47pm

Six-spotted mite can defoliate grapevines and avocado trees in the lower south-west of Western Australia.

Natural enemies tend to keep numbers in check, but occasionally chemical intervention may be required especially in avocado orchards.

Origin

Six-spotted mite, Eotetranychus sexmaculatus (Riley), is native to central America. It was first recorded in WA in 1986 on avocado seedlings from eastern Australia.

In the same year and presumably from the same source, the mite was recorded for the first time on avocados in New South Wales, Queensland and South Australia. It also occurs in New Zealand where it is also important in avocado orchards and is also present in parts of Asia and the Middle East.

Damage

The mite feeds primarily on the lower surface of leaves, concentrating its activity adjacent to leaf veins. This feeding is characterised by discolouration of leaf tissue, leaf death and premature defoliation.

Yellowing adjacent to leaf veins on underside of white grape variety by feeding of six-spotted mite
Feeding by six-spotted mite on white grape variety

Yellowing adjacent to leaf veins on upper side of white grape variety by feeding of six-spotted mite
Leaf feeding by six-spotted mite on white grape variety

Reddening of area adjacent to leaf veins on underside of red grape variety from feeding by six-spotted mite
Leaf feeding by six-spotted mite on red grape variety, underside of leaf
Reddening adjacent to leaf veins on upper side of red grape variety from feeding by six-spotted mite
Leaf feeding by six-spotted mite on red grape variety

Signs of feeding on white and red grape varieties are yellow or red shadows respectively, on either side of the veins and visible from both sides of leaves.

Purple discolouration adjacent to veins on underside of an avocado leaf by feeding of six-spotted mite
Feeding by six-spotted mite on underside of avocado leaf

Purple discolouration adjacent to veins on the upper side of an avocado leaf by feeding of six-spotted mite
Feeding by six-spotted mite on avocado leaf

On avocado, six-spotted mite feeding appears as brown to purple discolouration next to leaf veins.

In citrus, primarily grapefruit but also oranges, feeding on the leaf stems and occasionally the fruit stems will cause the fruit to yellow and fall. Six-spotted mite has not been recorded on citrus in WA.

Kiwifruit is also a host for six-spotted mite, but this has not been observed in WA.

Near panel of grapevines defoliated by six-spotted mite with next panel protected with a miticide
Defoliation of grapevines by six-spotted mite next to protected vines

Heavy infestations result in severe defoliation. This results in delayed ripening or failure of grapes to ripen and reduced quality and yield of fruit.

Defoliation of avocado tree by six-spotted mite
Defoliation of avocado tree by six-spotted mite

Avocados are particularly susceptible to the mite and low numbers can defoliate trees, exposing fruit to sunburn.

Awareness of whether the mite is present is the first step in minimising its potential for damage.

Contact information

Stewart Learmonth
+61 (0)8 9777 0167

Author

Stewart Learmonth