Acariformes

Commonly referred to as mites, members of the Acariformes include two main orders: Trombidiformes and Sarcoptiformes. Trombidiformes include the plant-feeding mites, but some are also predatory. Sarcoptiformes can be found in the soil, leaf littler, understory plants, and forest canopies.

Morphological characteristics of mites:

• adults are very small, sometimes microscopic, arthropods with an oval or elongated body;
• adults have two body parts or regions consisting of an unsegmented abdomen (also called the idiosoma) and a cephalothorax (fused head and thorax, also called the gnathosoma);
• adults usually have four pairs of legs, although some have only two or three pairs; and
• the mouthparts, called chelicera, are adapted for piercing, sucking and lacerating.

General biology and ecology

The number of developmental stages vary amongst each mite family. As a rule, the nymph and the adult are similar, except for the number of pairs of legs found on a newly hatched larva. The diet of mites is highly varied. They may be plant feeders (phytophagous), predators or parasites (zoophagous), or detritus feeders (detritivorous or saprophagous). Some are also considered plant pathogens because they cause disease (interfering with normal tree physiology) or act as vectors transporting other pathogens that cause disease, but for the purposes of this database they have been included with the Arthropoda (insects and mites). Mites can be found in large numbers in a wide variety of habitats, depending on their diet. Most mites are terrestrial, but some live in ponds and even salt water. In agricultural and forest environments, phytophagous species feed mainly on foliage and succulent plant stems. A very large number of saprophagous species live in the litter on the forest floor and in dead and decomposing trees, thereby playing an important role in recycling organic matter. Predatory species are beneficial because they feed on the eggs and young stages of some phytophagous insects and mites. In some cases, the predatory species can be used as biocontrol agents in greenhouses and orchards.

Important families in the order Trombidiformes that contain tree pests

Listed below are families from this order found in this database. Species listed within the families are linked to the site’s pest fact sheets.

Eriophyidae

Eriophyid mites are very small, only about 0.2 millimetres in length, and worm-like. Unlike the Tetranychids, mites of this family have only two pairs of legs. Eriophyid mites cause biochemical and physiological changes in their plant hosts. These changes can be both specific and non-specific. The species of this family within this database all form galls on leaves, succulent shoots, flower buds, and vegetative buds. 

• Ashflower gall
  Scientific name: Eriophyes fraxiniflora Felt
• Birch budgall mite
  Scientific name: Acalitus rudis (Canestrini)
• Crimson erineum mite
  Scientific name: Aceria elongatus (Hodgkiss)
• Galls of hardwoods
  Scientific name: Eriophyes sp.
• Maple bladdergall mite
  Scientific name: Vasates quadripedes Shimer
• Poplar bud gall mite
  Scientific name: Aceria parapopuli (Keif.)

Tetranychidae

Commonly referred to as spider mites because they produce silk webs, species within this family are very small, measuring about 0.35 millimetres to 1 millimetre in length, and coloured red, orange, green or yellow, and have four pairs of legs. There about 100 species in several genera that cause economic losses in agricultural crops and forests. The damage to hosts is typically to their leaves or needles and results from mites sucking and removing the contents of palisade cells on the leaf or needle surface. Only one species is of concern to Canadian trees within this database.

• Spruce spider mite
  Scientific name: Oligonychus ununguis (Jacobi)