Spruce spider mite

Systematic position: Oligonychus grypus is a member of the Trombidiformes order and the Tetranychidae family (spider mites). It is a significant pest of coniferous trees, recognized for its specialized feeding habits on evergreens.

Host plants: This mite primarily infests various spruce species, including Norway spruce, blue spruce, and white spruce. It is commonly found in both managed landscapes, ornamental gardens, and commercial forest nurseries where susceptible hosts are planted.

Biology and life cycle: The mites overwinter as eggs, typically attached to the base of the needles. Larvae emerge in the spring as temperatures rise. During warm and dry summer months, they can produce several successive generations, which often leads to rapid population outbreaks.

Damage and economic impact: The mites feed by piercing the needles and sucking out the plant juices. Initial symptoms include tiny yellow or light-colored speckles on the needles. As damage progresses, the foliage turns brown and eventually drops off. Severe infestations can cause significant stress, loss of tree vigor, and may lead to the death of young plants.

Control measures: Managing Oligonychus grypus involves a combination of cultural and chemical strategies. Key recommendations include:

• Maintaining tree vigor through proper watering and fertilization.
• Using overhead irrigation to increase humidity, which is unfavorable for mite reproduction.
• Applying specific acaricides or horticultural oils during the early season.
• Regular monitoring of the lower canopy, where infestations often begin.