Page:Some recent developments in white pine weevil research in the northeast (IA CAT31009844).pdf/5

 for spray materials that have a brief residual effect.

The distances weevils may fly is very important when considering the degree of isolation required for small experimental spray plots, and also for large control operations. Barnes (1) has done considerable work on the flight habits of the weevil. To get more specific information on dispersal we tried tagging weevils with radioactive isotopes. We released 1,600 weevils tagged with Scandium-46 in September in a small plantation and traced them the following spring (4). While the lengths of individual flights were not measurable, the distinct stratification suggested that weevil movement of 300 to 400 feet was the result of direct uninterrupted flight from the release trees.

We feel that still further studies should be made of weevil dispersion. If weevils could be tagged in the spring, there would not be the loss of treated weevils during the winter. Present plans are to use Scandium-46 again but at a lower specific activity than was used in the fall, and to tag some 3,000 to 4,000 weevils for release in a large plantation in the spring.

E ARE also studying egg-laying habits. It has been reported that the weevils issuing in August do not mate until the following spring, and that insemination does not take place in the fall. In laboratory tests, 84 percent of the females isolated from male weevils in early November produced viable eggs in the spring.

To determine to what extent fall insemination occurs in the field, female weevils were collected in early October and were immediately placed in an overwintering cage by 3