Broom gall mite

The broom gall mite (Eriophyes genistae) is a microscopic pest belonging to the Eriophyidae family. These mites are worm-like in shape, translucent or yellowish, and are distinguished from other mites by having only two pairs of legs, which makes them highly specialized for living within plant tissues.

Because they measure only a fraction of a millimeter in length, they are invisible to the naked eye. Their survival strategy relies on inducing the plant to create a protected environment, known as a gall, where they can feed and reproduce shielded from external predators and environmental changes.

This mite specifically attacks plants within the Genista genus, often referred to as broom. It primarily targets the terminal buds and developing shoots, injecting saliva that alters the plant's hormonal signaling, forcing it to produce abnormal vegetative tissue.

The damage is systemic in nature regarding the affected shoots. The energy that the plant would normally allocate to healthy growth is diverted into the formation of useless, disfigured gall tissue, leading to a significant loss of vigor in the infested plant.

The most prominent sign of infestation is the presence of galls, which appear as dense, fuzzy, or warty growths replacing normal buds. These structures may be spherical or irregular and often appear in clusters on the tips of the branches.

Infested branches stop growing normally and become severely stunted or twisted. In severe cases, the entire terminal end of the shoot may die back, negatively affecting the aesthetic quality and overall health of the shrub.

Effective management begins with strict sanitation practices. As soon as the characteristic galls are spotted, they should be pruned off and destroyed, ideally burned, to eliminate the source of the infestation before the mites migrate to healthy parts of the plant.

Chemical control can be challenging due to the protection offered by the gall structure. Acaricides should be applied during the period when mites are moving between shoots, typically in early spring, using systemic or contact products to reduce the population levels significantly.