Site and Stand Conditions Associated with Pine False Webworm Populations and Damage in Mature Eastern White Pine Plantations

The influence of site and stand conditions on pine false webworm (Acantholyda erythrocephala [L.], Hymenoptera: Pamphiliidae) population densities and host damage was evaluated in 22 eastern white pine (Pinus strobus L.) stands in northern New York State. Mean pine false webworm density was positively related to stand size (ha) and inversely related to soil silt content (A-horizon) after holding stand size constant. Percent radial growth loss (during the first five years after defoliation began) was inversely related to soil carbon content (B-horizon) and inversely related to fine sand content (A-horizon) after holding B-horizon carbon constant. Severe radial growth suppression (missing or discontinuous growth rings) and white pine mortality were inversely related to live crown ratio. The frequency of trees with missing growth rings was inversely related to soil nitrogen (A-horizon) after holding live crown ratio constant. Stands located on sandy glacial lake shoreline/delta deposits had more coarsely textured soils with lower levels of organic matter and nitrogen and had slower height growth rates, lower tree diversity, greater relative dominance of white pine, and higher levels of pine false webworm defoliation than stands on adjacent landforms. These results may be useful to foresters managing eastern white pine stands in areas where similar site and stand conditions predominate and pine false webworm occurs.

A brief review of the past use of baculoviruses for the management of eruptive forest defoliators and recent developments on a sawfly virus in Canada

An overview is presented of the state of knowledge on the use of baculoviruses—a family of virulent insect viruses exhibiting narrow host ranges—for the suppression of insect outbreaks in Canadian forests. Emphasis is on recent investigations using NeabNPV against the balsam fir sawfly and the pine false webworm. Key words: Acantholyda erythrocephala, Baculoviridae, Baculovirus, balsam fir sawfly, biological control, forest protection, insect outbreak, Neodiprion abietis, pine false webworm

Radial growth impact of pine false webworm defoliation on eastern white pine

The impact of pine false webworm (Acantholyda erythrocephala (L.), Hymenoptera: Pamphiliidae) defoliation on the radial growth of mature eastern white pine (Pinus strobus L.) during an outbreak was assessed using a stem analysis comparison of two stands (defoliated vs. control) and increment cores collected from 21 defoliated stands and 5 control stands in northern New York State. Stem analysis revealed that whole-stem standardized annual volume increment (AVI) in a defoliated 67-year-old white pine stand (n = 10 sample trees) was reduced significantly below the AVI in the nondefoliated control stand (n = 8 sample trees) by the second year of moderate to heavy defoliation, and AVI was reduced by 97% by the fifth year of defoliation. No time lag between upper-bole and lower-bole impact was observed, and annual growth rings were more frequently missing or discontinuous at lower stem heights. The standardized latewood tracheid index was not reduced significantly below control stand levels until the third year of defoliation. Increment-core analysis revealed growth losses that corresponded with reported periods of defoliation in nearly all stands; sustained suppressions (5–16 continuous years) below a growth index of 0.5 occurred in over half of all defoliated stands. These results are discussed in relation to pine false webworm biology, comparisons with other conifer defoliators, environmental factors, and methods employed.

Control of conifer defoliators with neem-based systemic bioinsecticides using a novel injection device

A systemic tree injection tube was designed to introduce the required volumes of neem-based bioinsecticides into conifer trees. The device consists of plastic tubing attached with hose clamps to a maple sap spile at one end and a tubeless automobile tire valve at the other end. A hole is drilled in the tree, the spile is hammered into the hole, the device is filled with the systemic insecticide, and the system is pressurized by attaching a bicycle pump to the tire valve. The parts are readily available, the device is simple to construct and easy and quick to install on a tree, application volumes are adjustable, and the device is reusable. This device has been used successfully to inject 188 trees representing four conifer species in either spring or fall, primarily with neem formulations but also with dimethoate, imidacloprid, and acephate. In most cases, all of the material was injected into the trees without leakage, although neem formulations were characteristically slow to enter the trees and certain neem formulations were not injected completely at volumes above 15 mL per injection tube. Dosages of 0.2 g azadirachtin/cm of diameter at breast height (dbh) or less provided control of pine false webworm, spruce budworm, cedar leafminers, gypsy moth, and introduced pine sawfly on red pine, white spruce, eastern white cedar, white pine, and white pine, respectively. Dosages as low as 0.005 g active ingredient/cm of dbh applied with injection tubes in either one or two holes per tree resulted in a 95% reduction in defoliation of mature (mean dbh ± SD = 23.4 ± 3.3 cm) red pine caused by pine false webworm.