To be most effective, apply applications in October, March or early April to allow time for tree roots to absorb the insecticide and move it up into the tree. During outbreaks, the combined damage caused by adults and larvae results in reduced growth and usually in the total loss of the previous and current years’ terminal shoots. Grow evergreen trees under a canopy of 50% shade to make the leader shoots less attractive to the white pine weevil. Boxelder bugs. Use a persistent product because the adult weevils don’t all warm up at the same rate. White Pine Weevil (Pissodes strobi) is a native conifer pest with a wide host appetite. Direct control through the use of pesticides may be necessary but is not advised without first consulting a specialist in tree pest control. If you need to control white pine weevil, your best opportunity is early in spring. Insecticides labeled for application on spruce trees to control bark beetles or wood-boring beetles probably also would kill white pine weevils, but it is University of Idaho policy only to recommend products that specifically include both the target plant (spruce trees) and the target pest (white pine weevil). Adult weevils are brown with white spots; they occur in spruce and pine ecosystems throughout Canada. Small oviposition punctures covered by blackish fecal caps can also be seen, usually near the top of the previous year's leader.Tree mortality due to the white pine weevil is rare, however. Insecticide should be applied to the terminal leader once it begins to warm up, somewhere around 25 to 65 growing degree-days base 50. They remain on the host tree to feed until the temperature drops in fall, when they seek shelter in the litter to overwinter. Winter mortality due to poor litter quality and ground predation was also observed in jack pine plantations. The adult weevils overwinter on the ground, protected and insulated by the litter (fallen needles). MSU is an affirmative-action, equal-opportunity employer. This usually coincides with the ripening of wild raspberries around mid-July. White Pine Weevil Damage. Adults overwinter in the forest litter and, in early spring, they emerge when the temperature rises to 2-4oC. Destruction due to a white pine weevil is very distinctive. Dave Smitley, Michigan State University, Department of Entomology -
Other biological control agents, such as predators and parasitoids, play an important role in additional brood mortality. Symptoms are usually noticeable by late June. Jeffrey W. Dwyer, Director, MSU Extension, East Lansing, MI 48824. An alternative method for pine weevil suppression is the application of entomopathogenic nematodes to tree stumps harbouring developing pine weevils. In both cases, insecticide selection depends on the product label. White Pine Weevil Control Tips Attacks white pines, spruces More common in pure plantings Adults emerge in early spring when T > 50 F (as early as March in PA), Treat in early spring when adults emerge with borer pesticide Mechanically remove Shepard’s Crooks before August 1. It is also very effective for ornamental trees. April 13, 2018. The larvae are white, legless, C-shaped grubs with a medium brown head and several long, silken hairs on the body. Changing the environment can help prevent or reduce infestations. It will absorb into the bark of the tree and offer both immediate control of active weevils … Chemical Control (Planning Ahead) Conifers may be protected against white pine weevil in two ways: by spraying the tops of the trees in early spring or by making a fall application of a systemic insecticide. The white pine weevil may significantly hinder the growth of young trees. Plantations on unproductive sites are the most susceptible to outbreaks. Studies have shown, however, that in Norway spruce, the impact on volume productivity can be negligible when the trees reach commercial size. Indeed, the weevil's love of spruce is exemplified by its alternate common name, Engelmann Spruce Weevil, or simply Spruce Weevil. This is happening now around Lansing, Michigan, and will probably not happen until the end of April around Cadillac, Michigan. Protection of seedlings with chemical insecticides for up to two years after planting. First a few trees are attacked, then the population grows rapidly, resulting in rates of 20-50% of trees attacked per year. Native to North America, the white pine weevil occurs throughout the range of white pine in eastern Canada. PINE WEEVIL CONTROL. Pruning of infested terminals should begin as soon as wilting (i.e., the characteristic shepherd’s crook) is detected. Reference to commercial products or trade names does not imply endorsement by MSU Extension or bias against those not mentioned. The presence of the insect is easily detected by the dropping, wilted appearance of the current year’s leader, which resembles a shepherd’s crook. Its host range includes Scotch, jack, red, pitch, and eastern white pines as well as Douglas-fir and all spruces. Check out the MSU Landscape and Nursery Management Certificate Program! In western Canada, its distribution coincides with that of various species of spruce. A white pine weevil is also referred to as a spruce weevil or an Engelmann spruce weevil. In the springtime, female weevils begin laying eggs and feeding on branch tips at the top of their favorite tree hosts. The rapid increase in this initial stage is due to the large proportion of trees available for attack and to the fact that many attacks result in multiple leaders. At the end of their feeding period, the larvae burrow in the pith or directly under the bark, forming pupal cells lined with strands of wood chips.