Therefore, many generations occur each growing season. In addition, at any given time during the growing season, all stages from eggs to immatures to adults can be found. This can affect pesticide performance. Natural predators help control mites. With the SSM's ability to quickly reproduce, Fraser fir fields would soon be overrun with spruce spider mites if it were not for the underlying level of protection provided by natural predators including syriphyid fly larvae, larvae and adult lady beetles, spiders, and predatory mites.
Growers inadvertently affect predator populations through management practices.
Along dusty roads, SSM causes more damage because the dust on needles scratch the more active predators, causing them to desiccate and die. The predatory mites need high humidity to survive. On windy ridges, SSM damage is more common because predatory mites cannot survive. In fields surrounded by woods resulting in little air movement and higher humidity, the SSM almost never causes damage to Fraser fir. If groundcover is absent, natural predators have lost an important habitat, and their numbers will be reduced.