A comprehensive pest control plan is necessary to combat white pine weevil infestations. Insecticide should be applied to the terminal leader once it begins to warm up, somewhere around 25 to 65 growing degree-days base 50. With the years, the insect became very common due to the increased number of plantations and the absence of control methods. This resin originates from special structures called resin canals found in the bark of the leader. Although it occurs naturally in our forests, in eastern Canada, it is considered to be the most serious pest of white pine, jack pine and Norway spruce plantations. Mechanical control, which entails the pruning and destruction of infested leaders, is considered effective and is being used increasingly in private plantations. Damage from white pine weevil can be prevented by spraying the upper trunk and terminals of spruce and pine in early to mid-April and again two weeks later with products that contain bifenthrin, permethrin or cyfluthrin. 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. It’s better to be a bit early than to be late with this application. They crawl up the trunks of nearby host trees to the terminal shoot and begin to feed before mating. In both cases, insecticide selection depends on the product label. Its host range includes Scotch, jack, red, pitch, and eastern white pines as well as Douglas-fir and all spruces. Pruning of infested terminals should begin as soon as wilting (i.e., the characteristic shepherd’s crook) is detected. Debarking Weevils. Damage from the pest was first reported in the early 20th century in eastern Canada. How can I prevent weevils invading? Use a persistent product because the adult weevils don’t all warm up at the same rate. Apply these products at rates given on the label for bark beetles or borers. PINE WEEVIL CONTROL. Grow evergreen trees under a canopy of 50% shade to make the leader shoots less attractive to the white pine weevil. Diversification of the tree population can also prove effective. Changing the environment can help prevent or reduce infestations. The larval stage, which lives beneath the bark, is white with a distinct brown head. White Pine Weevil Damage. If you need to control white pine weevil, your best opportunity is early in spring. This article was published by Michigan State University Extension. Damage was variable, depending on the region. It has irregularly shaped patches of brown and white scales on the front wings. White pine weevil is the smaller of the two pests, measuring about ¼ inch (6–7 mm) long; males are slightly smaller than females. Is the weevil that you are dealing with the white pine weevil (Pissodes strobi) that feeds under the bark on the upper leaders of the conifer trees and that cause a "shepherds crook" to form and kills the new growth?If that is the pest, then it is too late to spray topical insecticides on the trees to prevent the weevils from putting the next generation of eggs under the bark. 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. During the weevil life-cycle, different mortality factors affect the eggs, larvae, pupae and adults. The female lays her eggs in feeding cavities in the bark made with her rostrum. Those eggs will hatch within a few weeks and the larvae chew their way through the bark. The pales weevil, Hylobius pales, (Figure 14) prefers loblolly, shortleaf, pitch, and white pine seedlings. Since then, regular outbreaks have occurred. Dave Smitley, Michigan State University, Department of Entomology - April 13, 2018. After this initial period of invasion, the rate of attack diminishes and the percentage of trees attacked each year stabilizes at relatively high levels, with annual fluctuation due to the variable effects of mortality factors operating on the population: weather, natural enemies, larval crowding, and others. During the summer, predation by larvae of the fly Lonchaea corticis may cause the death of up to 85% of the new generation. The leader is eventually killed. How can the large pine weevil be controlled? However, when too many eggs are laid, there is intense larval competition and mortality occurs. The adult weevils damage seedlings by chewing small holes on the stem above and below the ground. Feeding punctures made by the adult weevils can also damage the leader. White pine weevil or spruce leader weevil (Pissodes strobi) is a weevil in the family Curculionidae (weevils or snout beetles) in the order Coleoptera. Michigan State University Extension programs and materials are open to all without regard to race, color, national origin, gender, gender identity, religion, age, height, weight, disability, political beliefs, sexual orientation, marital status, family status or veteran status. Populations are monitored by the provincial departments.Damage is caused mainly by the larvae, which feed under the bark of the tree’s terminal leader. Issued in furtherance of MSU Extension work, acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture. 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. Overwintering mortality of the weevil is considered a key factor in the reduction of the weevil population in white pine plantations. 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. Boxelder bugs. Weevil adults could feed on the terminals for three weeks or perhaps longer. Pruning should be done while the larvae are still active under the bark and before the emergence of the new generation of adults. The adult is a small rust-colored weevil that is about 4-6 mm long. In British Columbia, it hinders the regeneration of Sitka spruce, white spruce and Engelmann spruce and is considered a major pest of most other species of spruce. In the springtime, female weevils begin laying eggs and feeding on branch tips at the top of their favorite tree hosts. After the eggs hatch, in about 10 days, the larvae burrow into the bark, feeding on the cortex (inner bark). Jeffrey W. Dwyer, Director, MSU Extension, East Lansing, MI 48824. Infected leaders should be cut back at the level of the topmost whorl of unaffected branches. If you had weevil damage last year and need to control the weevils, do it early this spring. If you have young pine trees and want to ensure they don’t get targeted by pine weevils or other wood borers, spray them each spring with MAXXTHOR EC. 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. Check for weevil grubs in stored food, Monitor grains for mould and humidity, Choose insect-resistant foliage and trees, Store food in tightly sealed containers. The adult weevils overwinter on the ground, protected and insulated by the litter (fallen needles). It will absorb into the bark of the tree and offer both immediate control of active weevils … A white pine weevil is also referred to as a spruce weevil or an Engelmann spruce weevil. Damage from white pine weevil can be distinguished from other types of injury by the somewhat curled shape of the leader, sometimes referred to as a “shepherd’s crook” (see photo). Adult weevils are brown with white spots; they occur in spruce and pine ecosystems throughout Canada.
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