T.E.R:R.A.I.N - Taranaki Educational Resource: Research, Analysis and Information Network


Mite (Eriophyes paratrophis) Witches broom gall

Kingdom: Animalia
Phylum: Arthropoda
Subphylum: Chelicerata
Class: Arachnida
Subclass: Acaromorpha
Infraclass: Acari
Superorder: Acariformes
Order: Trombidiformes
Suborder: Prostigmata
Family: Eriophyidae
Genus: Eriophyes
Species: Eriophyes paratrophis

Eriophyes paratrophis is an Eriophyid mite. These tiny mites which cannot be seen by the naked eye typically overwinter on their host plant. They begin feeding and initiate the accelerated growth of gall formation in spring as leaf or flower buds open.  The mite’s mechanical damage or salivary secretions initiate increased production of normal plant growth hormones and enzymes. These cause localized plant growth results in increases in cell size (hypertrophy) and cell number (hyperplasia). The outcome is an abnormal plant structure called a “Witches broom gall”. Sometimes there is also a powdery mildew fungus associated with these galls.
The galls are growing plant parts and require nutrients just like other plant parts. Once gall formation is initiated, many galls will continue to form even if the insect dies. It is possible that galls steals vital plant food and adversely affect plant growth. This is most likely a problem when galls are numerous on very young plants. Mature plant tissues are usually unaffected by gall-inducing organisms. Injury may also occur if galls are numerous on branches or if abundant for several consecutive years. In most cases, however, galls are not abundant enough to harm the plant.

All the galls photographed below and on the same Streblus heterophyllus (Turepo)