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The southern pine coneworm, Dioryctria amatella, is one of four Dioryctria species that is known to commonly attack 2nd-year cones on lollylob pine in east Texas. This pest has been reported to kill 2 to 5 percent of the commercially-produced east Texas Virginia pines grown for Christmas trees. Caterpillars commonly tunnel underneath the bark of two- to four-year-old pines, girdling the trees in the process. External evidence of attack includes large deposits of pitch at the base of the trunk or along the "handle".
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D. amatella has several generations per year in the south. Other than infesting first- and second-year pine cones, this species is known to damage male and female pine flowers, pine terminals (stems and shoots), southern cone rust (Cronartium strobilinum) infested cones and fusifonm rust galls (Cronartium fusiforme) cankers. They are often attracted to the host volatiles associated with wounds and feed in the cambium region of pine stems or trunks. On slash and longleaf pines, early-season infestations tend to occur in flowers and shoots or in rust-infested plant parts, while later generations occur primarily in cones. In east Texas, southern pine coneworms emerge in late summer or fall (September or October). This may be the time when females oviposit on Virginia pine Christmas trees.
Producers considering using insecticides to prevent or control this pest should be aware of several factors. First, although azinphosmethyl (Guthion®), fenvalerate (Pydrin®), permethrin (Ambush®) and carbofuran (Furadan®) are registered for the control of coneworms on pine cones in southern pine seed orchards, it is uncertain if these insecticides will control coneworms infesting the trunks of Virginis pine trees. Insecticides such as lindane and chlorpyrifos (Dursban®) normally used to control other bark-boring insects may be more effective for the control of Dioryctria stem and trunk attacks, although these products are not specifically registered for this use. Secondly, the cost of insecticide treatments applied in an attempt to prevent trunk girdling by coneworms is probably not justified in most cases since so few trees in a planting are usually attacked. Once a tree is infested by the caterpillars, the use of any insecticide will not effectively control larvae tunneling inside. Insecticides, if used, only prevent larvae from entering the tree.
A better approach for managing southern pine coneworms in a Virginia pine Christmas tree planting would be to properly manage Nantucket pine tip moth infestations and to avoid damaging young trees with tractors or other equipment used in production operations. Many of the same insecticides used for the control of Nantucket pine tip moth infestations are also labeled for southern pine coneworm control. Avoidance of damage to the trunks and lower branches will prevent young trees from being attractive to egg-laying female moths. Removal of severely damaged or infested trees may also help reduce the active population in the local area. Finally, monitor infestation levels to ensure that damage does not become sufficiently widespread to economically justify more severe control tactics such as a the use of insecticide applications.
I wish to thank Dr. Scott Cameron of the Texas Forest Service for his help in determining the species infesting Virginia pines in Texas and for his suggestions regarding possible control strategies.
The USER is always responsible for the effects of pesticide residues on his livestock and crops, as well as problems that could arise from drift or movement of the pesticide from his property to that of others. Always read and follow carefully the instructions on the container label.
The information given herein is for educational purposes only. Reference to commercial products or trade names is made with the understanding that no discrimination is intended and no endorsement by the Cooperative Extension Service is implied.
Educational programs conducted by the Texas Agricultural Extension Service are open to all people without regard to race, color, sex, disability, religion, age or national origin.
1989
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Last modified: March 18, 1997 by Edgar Cross