Birch Leafroller

Birch leafrollers were recorded in the Interior, Southcentral, and Southeast. Damage in the Interior was recorded during Ground Detection Surveys from south of the Brooks Range to Fairbanks, east along Chena Hot Springs Road, along the Alaska/Canada border on the Taylor Highway, and south along the Parks Highway between Fairbanks and Cantwell. An annual birch defoliator survey is conducted in Southcentral Alaska in late summer. Observations were made north to the Alaska Range, around Anchorage and south to Moose Pass on the Kenai Peninsula. Per the annual survey in Southcentral, leafroller damage was the highest it has been since 2018, with the observation records doubling from 2022. Leafrollers were observed on alder during ground surveys in Southeast but at low levels. Only 20 acres of birch leafroller damage were mapped during aerial detection surveys, all of which were in the Interior. 

Due to the pandemic, we were unable to conduct aerial surveys to map birch leafroller damage in 2020. However, Epinotia solandriana was observed throughout Interior and Southcentral Alaska, with 47 observations recorded during ground surveys. Nineteen ground survey observations of Caloptilia spp. were made throughout the Interior, with only three observations made in Southcentral.

Birch leafroller was not mapped during aerial survey in 2019, however 121,000 acres were aerially mapped in 2014 and 330,000 acres were mapped in 2013. Based on ground observations, the frequency (number of affected trees) of birch leafroller infestations in Interior and Southcentral Alaska has remained relatively constant; however, the intensity (number of leaves per tree) is low. Low intensity infestations are difficult to detect during aerial surveys.

Birch leafroller larvae roll leaves and subsequently skeletonize them through feeding, which cause them to curl, brown, and drop prematurely. This can cause branch dieback and occasionally tree mortality. Alaskan birch leafrollers are univoltine (have one generation per year) and overwinter in the egg stage. Larvae hatch in mid-May to early June and begin feeding in buds and as they develop into later-instars, feed in rolled leaves. Sub-adult instars leave their leaf rolls and pupate in fragile cocoons between the humus layer and the mineral soil. The adults emerge in late-July through August. After mating, eggs are laid singly on the previous year’s twigs, usually on roughened bud stalks. While birch leaf rollers (Epinotia solandriana) are the most common leafrollers observed on birch, there are other genera, including Clepsis, that are also associated with this host. Drastic and repeated defoliation by these insects can result in minor growth reduction and occasional branch dieback. Leafroller populations are naturally controlled by adverse weather, parasites, predators, and disease.