{"id":4493,"date":"2011-01-27T15:58:42","date_gmt":"2011-01-27T20:58:42","guid":{"rendered":"http:\/\/extension.umaine.edu\/ipm\/"},"modified":"2023-02-07T12:16:15","modified_gmt":"2023-02-07T17:16:15","slug":"5042e","status":"publish","type":"page","link":"https:\/\/extension.umaine.edu\/ipm\/ipddl\/publications\/5042e\/","title":{"rendered":"White Pine Weevil"},"content":{"rendered":"

\n \n \"Print\n <\/a>\n <\/div><\/h3>\n

Pest Management Fact Sheet #5042\u00a0
\n<\/strong><\/span><\/span><\/h3>\n

James F. Dill, Pest Management Specialist
\nClay A. Kirby, Insect Diagnostician
\nCharles D. Armstrong, Cranberry Professional & Staff Entomologist
\n<\/em><\/p>\n

For information about UMaine Extension programs and resources, visit extension.umaine.edu<\/a>.
\nFind more of our publications and books at extension.umaine.edu\/publications\/<\/a>.<\/strong>
\n<\/span><\/strong><\/p>\n

Description & Biology<\/h3>\n

The white pine weevil (Pissodes strobi<\/em>), which kills the tops of conifers, is the most serious insect pest of white pine in Maine. The weevil also attacks Norway spruce, Colorado blue spruce, jack pine, red pine, Scotch pine, mugho pine and native spruces. On rare occasion, Douglas fir may also be attacked.<\/p>\n

Adults become active in late March to mid-April and are found mating and feeding on the bark of terminal leaders.\u00a0 Eggs are laid from mid-April through June in the bark of the previous year\u2019s leader.\u00a0 Upon hatching, grubs start tunneling downward under the bark.\u00a0 As they progress, the grubs gather in a feeding ring which effectively girdles the leader.\u00a0 Typically, the top 1\u00bd to 2 feet of the main stem is killed, although severe attack may result in the loss of two to three years of growth.\u00a0 Weevils usually do not attack trees less than four or five years old, or less than three feet tall.\u00a0 Infested trees exhibit a wilting and browning leader, usually by July.\u00a0 Weevil-damaged trees eventually develop two leaders and a bushy appearance, thus reducing the value of ornamental trees.\u00a0 Trees are rarely killed by the weevils.<\/p>\n

Mature grubs bore slightly into the woody stem where they form fibrous chip cells in which they pupate.\u00a0 By mid-July, some weevils have matured to the adult stage and emerge from the infested leaders.\u00a0 These new adults feed on the new shoots from late September to early October in the upper third of the crown.\u00a0 Usually by November, all weevils have entered the ground litter (often at the base of host trees) in order to overwinter.<\/p>\n\n\t\t