A Phyllobius Species, a new Pest and Its Control on Arborvltae.
AbstractSevere injury by some insect to the roots of arborvitae (Thuja occidentalis) in a nursery in Rhode Island was reported in late April 1947, and on 5th May a few larvae and many pupae of an undetermined species of Phyllobius and a few pupae of Barypeithes pellucidus, Boh., were found in the soil round the roots. Pupae of both species transformed to adults within 72 hours when kept at room temperature in the laboratory. In the field, a few Phyllobius adults appeared during the middle of May and all had emerged by 26th May. Both sexes were present until 16th July, but they were rarely seen in flight, particularly after late May, and the weevil is probably disseminated chiefly in balled nursery stock. They fed on the newly formed leaves of arborvitae, generally at the terminal end of branches on the top third of the plant. They remained on the foliage at night, but it was not determined whether they fed then. They were also taken on species of Juniperus and Chamaecyparis. No eggs were found in the field, but caged adults laid eggs singly, or occasionally in groups of 2-5, at a depth of 2-3 mm. in the soil. These hatched in 10-11 days at 73-77°F., but failed to hatch at 80°F. In the field, larvae in the earlier instars were not found until 6th October 1947, when they were feeding on the roots of arborvitae with larvae of Otiorrhynchus (Brachyrrhinus) ovatus, L., and Barypeithes sp.
In field tests, sprays of 3 lb. lead arsenate, 2 lb. 50 per cent. wettable benzene hexachloride (6 per cent. γ isomer) and 2 lb. 50 per cent. wettable DDT per 100 U.S. gals, water applied to heavily infested arborvitae on 27th May, gave 31.7, 98 and 99.8 per cent. reduction, respectively, in adults of Phyllobius after two days and 88, 97.5 and 100 per cent. after 17 days, whereas the numbers on untreated plots had increased by 2.4 per cent. after two days and decreased, owing to natural mortality, by 82.3 per cent. after 17 days.