PITCH-EATING WEEVIL, Pachylobius picivorus (Germar)
In the Gulf Coast States the pitch-eating weevil is probably the most troublesome insect pest of pine seedlings. No accurate figures are available on the damage directly attributable to this pest, but mortality losses are estimated to average about 30 percent in susceptible areas. All of the southern hard pines and other conifers are probably suitable breeding and host material for the pitch-eating weevil. Its range overlaps that of the pales weevil, being reported from Labrador, Canada, south to Florida and west to Texas. It occurs in damage-causing numbers only in the Gulf Coast States.
Pitch-eating weevils breed in the roots of freshly cut stumps. The adults burrow down through the soil, sometimes a considerable distance from the stump, and lay their eggs in niches chewed in the root bark. On hatching, larvae mine the inner bark, packing their galleries with frass. Pupal cells are excavated in the sapwood, and a chip cocoon is constructed from the excelsior-like material removed during the cells’ construction. Development time varies from six to ten months depending on when the stumps are initially infested. Emerging adult pitch-eating weevils feed by night on the tender bark of seedlings. Small irregular patches of bark are removed, eventually girdling the seedling and causing its death. The pitch-eating weevil exhibits a population trend similar to that of the pales weevil, and is a threat mostly in early spring and in the fall.
The most effective control for pine reproduction weevils is to wait nine months before replanting or until the stumps in an area are no longer attractive to the weevil. Chemical control can be used when such a delay is considered impractical.
DEODAR WEEVIL, Pissodes nemorensis (Germ.)
This snout beetle is very similar to the white pine weevil both in appearance and habits. It is found throughout the south- and mid-Atlantic states from southern New Jersey west to Missouri. Although deodar cedar is the preferred host, Atlas cedar, Lebanon cedar, and several species of southern pines are also attacked.
Galleries and chip cocoons of the deodar weevil.
Adults emerge from April to May and feed briefly on the inner bark of leaders and lateral branches of host trees. Heavy feeding frequently girdles the stem and can kill small trees. The adults are dormant during the summer, but resume activity in the fall to lay their eggs. From one to four eggs are deposited in feeding punctures. The newly hatched larvae bore into the inner bark where they construct winding galleries which girdle the stem. Evidence of such infestations is often delayed until January when the branches begin to turn brown. Winter is spent in the larval stage. The larvae pupate in March or April and the cycle is complete.
Keeping shade trees in a vigorous condition by proper watering and fertilization helps reduce their susceptibility to weevil attack.