Home and Garden Orchard
Utah State University Extension
Western tentiform leafminer populations can vary tremendously between years or even between generations within a single year. A large population in Utah's commercial fruit districts hasn't been observed since the early 2000s. Increasing resistance to organophosphate insecticides and variable effectiveness of at least six parasitic wasp species that attack the leafminer can influence the population size.
Alston, Diane G. and Reding, Michael E., "Western Tentiform Leafminer Phyllonorycter elmaella" (2011). All Current Publications. Paper 1923.