The Pine Tree Lappet Moth (Dendrolimus pini) is an important pest on pines, spruce, fir, and other trees in Europe and other regions. Overwintered Pine Tree Lappet Moth larvae typically emerge in late winter/ early spring and the first adults may be seen soon after. There can 1 or 2 generations in a year, depending on the weather and climate.  The Pine Tree Lappet Moth Growing Degree Day Model, developed by researchers, and available on the Pest Prophet app, is a tool growers can use to predict adult emergence, based on field-specific temperature data.

Initiating the Biofix

To properly use the model, the biofix must first be set. This is the date that will serve as the starting point for growing degree day accumulation. For Pine Tree Lappet Moths, this biofix is usually set to January 1st for the Northern Hemisphere. Once adult moths have been trapped for a few weeks in a row, the date of the first catch can be used to reset the biofix, and improve accuracy of later predictions.

Growing Degree Day Accumulation and Treatment

After the biofix is set, growing degree day accumulation can begin, using a lower threshold of 45F and an upper threshold of 86F. This can be done using daily high and low temperatures, or using hourly temperature data using the Pest Prophet app. The first adults from overwintered larvae will occur at about 662 GDD (F) in colder regions and for all other regions at approximately 1035 GDD and peak at 1752 GDD(F). Adult moth Flight for the second generation, which only occurs in the warmest areas, will begin at approximately 4074 GDD after the Jan. 1 biofix date. Traps and mating disruption pheromones should be placed to coincide with adult moth flight stages.

Source:

Hardin, J.A. and A. Suazo. 2012. New pest response guidelines: Dendrolimus pine moths. USDA-APHIS-PPQ-CPHST