Other cone rusts are similar in many ways to the one we described. Cronartium conigenum, for instance, infects cones of Chihuahua pine (Pinus leiophylla) in Arizona and New Mexico. The fungus kills up to 50 percent of the cones on groups of trees and up to 90 percent on single trees. Alternate hosts are Quercus emoryi and Q. hypoleucoides. Melampsora Farlowii infects cones of eastern hemlock (Tsuga canadensis). Infected cones turn yellow and die.

Chrysomyxa pyrolae infects cones of black spruce (Picea mariana), blue spruce (P. pungens), Engelmann spruce (P. engelmannii), Norway spruce (P. abies), red spruce (P. rubens), and white spruce (P. glauca). Infected cones turn yellow and produce no seed. Alternate hosts are species of Pyrola and Moneses.

Among diseases that affect the seed crops of deciduous trees are a blight (Taphrina) and powdery mildew (Erisiphe aggregate). Both damage female catkins of alders (Alnus). The blight Taphrina pruni causes plum pockets on wild plum.

MANY INSECT pests prey on the flowers, fruits, and cones of most commercial forest trees in North America.

Insect depredations are nearly always completed by the time seed is extracted; rarely is seed damaged during storage. Dynamics of insect populations coupled with seed crop fluctuations result in considerable variation of seed losses in successive years, among stands of the same tree species, and even between neighboring trees.

The average extent of insect damage, however, is large enough to cause concern to managers of seed orchards and seed-production areas.

The seedworm Laspeyresia youngana can infest as much as 79 percent of the cones on white spruce and Sitka spruce (P. sitchensis) in Alaska.

Up to 64 percent of the seed in cones of white spruce (P. glauca) can be destroyed by the fly larva, Pegohylemyia anthracina, in Saskatchewan and Ontario. This insect appears to do more damage when the white spruce cone crop is small.

Surveys in California have shown cone moths (Dioryctria) to damage 17 to 73 percent of Douglas-fir cones.

Seed chalcids (Megastigmus) in the same State have destroyed as much as 21 percent of Douglas-fir seed.

A beetle, Conophthorus lambertiana, can destroy 25 to 75 percent of the cone crop of sugar pines over large areas in the West.

The white pine cone beetle (Conophthorus coniperda) in 10 years destroyed more than 95 percent of the white pine cone crops on the Massabesic Experimental Forest in Maine.

Cone moth larvae damage 10 to 60 percent of maturing slash and longleaf pine cones in many seed-production areas in the South. Two species of pine seedworms have infested up to 90 percent of the slash pine cones in some localities of north Florida and destroyed as much as half of the seed in damaged cones. A small sucking insect, Gnophothrips piniphilus, has killed up to 20 percent of the slash pine flower crop in Florida.

The major insect pests that affect seed of forest trees belong to four large orders the beetles (Coleoptera), the moths (Lepidoptera), the flies (Diptera), and the wasps (Hymenoptera). Nearly always are the insects in the larval stage when they destroy seeds.

Seed chalcids, seedworms, and acorn weevils feed almost exclusively within seeds. The Conophthorus beetles, Barbara moths and Dioryctria moths feed throughout the cone. The Conophthorus beetle, attacking coniferous trees, bores an egg gallery in the cone axis about the time cones start their second year of development. Developing larvae then proceed to destroy internal scale and seed tissues. Cone moths produce more than one generation in the South. Their larvae feed on pine flowers, cones, vegetative buds, shoots, and tree trunks at different times throughout the year.

To protect seed crops from insect damage in seed orchards and seed-production areas, we must have detailed knowledge of their life histories and habits. Much of this essential information is still lacking. Results from several tests with insecticide sprays indicate, however, that chemical control can give at least partial protection to seed crops.

A measure of protection of sugar pine cones from the cone beetle has been obtained by application of 2 pounds of DDT in 2 gallons of diesel oil sprayed from a helicopter. First and second-year cones of slash and longleaf pine in the South have been protected cone moth larvae with a 0.5-percent water emulsion of benzene hexachloride, applied by hydraulic sprayer or mist blower.

During the period of establishment, seed orchards may need protection from insects other than those attacking seeds or cones. Grafts of southern pine, for instance, need protection from the beetle, Pityopthorus pulicarius, which bores in at the graft union and kills the scion. Monthly sprays with benzene hexachloride or DDT, applied until the graft union heals over, have controlled the insect. Pine tip and shoot moths hinder the development of young planted pine in many parts of the country. These insects can be controlled in newly established seed orchards with emulsions of DDT or benzene hexachloride.

P. E. HOEKSTRA, a research forester; E. P. MERKEL, an entomologist; and H. R. POWERS, JR., a plant pathologist, are employed at the Southeastern Forest Experiment Station of the Forest Service.