In a forest situation it is not unusual to see some trees more heavily affected than others. It is not known why some trees are affected more than others. Causes could be genetic, site related or a combination of both. This species of needleminer primarily infests older needles and this is quite evident when infested branches are examined up close. Feeding in individual needles causes the needle tip, not the entire needle, to discolor.
Infested needles are hollow as a result of the feeding.
Often life stages of the insect, including larvae and pupae, can be seen within the needle when held up to light. Outbreaks of this insect occur sporadically and as mentioned earlier have not been associated with significant tree mortality. It is thought that populations of the moth typically crash due to natural causes, particularly natural enemies. Control in a forest situation is typically not warrented.