Treesearch

Zectran, a carbamate insecticide, is being field-tested against the spruce budworm. Taken in sufficient quantity, it can induce cholinesterase (ChE) inhibition in mammals. In laboratory experiments, Zectran was fed orally to mice. Results indicated that maximum ChE inhibition occurred 15 to 30 minutes after ingestion of Zectran, and that a ChE test is unreliable in the case of Zectran poisoning unless taken while symptoms are apparent.

A study at the Institute of Forest Genetics, Placerville. Calif . showed that dwarfmistletoe could spread from infected overstory ponderosa pine into planted Jeffrey pine--a maximum distance of about 145 feet. About one-third of the trees within this distance were infected after 22 years. The level of infection in the trees remained low. however and the parasite had intensified only slightly. Dwarfmistletoe did not appear to have affected height growth. Differences in degree of infection were noticed among blocks of trees from different altitudinal zones.

Lists 97 references. Includes most of the available citations on the species, with major emphasis on injurious agents, wood strength, and seasoning characteristics.

A survey of 104 old-growth stumps on the Redwood Experimental Forest, in northern California showed that (a) probability of a stump sprouting varied inversely with its diameter; (b) number of sprouts per sprouting stump and height of tallest sprout were not related to stump diameter; (c) lower portions of stumps sprouted more often and produced more sprouts than did higher parts; (d) height of tallest sprouts varied directly with number of sprouts; and (e) different kinds of damage produced different sprouting responses.

Xylem resin samples, obtained from 72 freshly cut pine stumps at the Institute of Forest Genetics, Placerville, Calif., were analyzed for monoterpenes by gasliquid chromatography. Very little or no qualitative or quantitative variation could be attributed to annual ring, time of securing sample, and period of storage of sample up to 1 year. The 34 hybrids sampled generally had resin properties that were intermediate between those of their parents. Several pines had terpenes whose presence hitherto has been unreported.

Three plantations of knobcone X Monterey pine hybrids were established on marginal timber sites at elevations of 671 m.(2,200 ft.) to 991 m. (3,200 ft.) in northern California in 1964. After 3 years, the hybrids appear more promising than either parent species. Damage from snow and windthrow suggests high risk of storm damage to hybrids planted at higher elevations.

Eleven air attack experts were asked to rate 12 models of fixed-wing tankers and light helitankers for effectiveness ill delivering chemical fire retardants under 21 typical situations. They rated fixed-wing tankers as more effective in strong wind crosswinds, and downwind approaches, but helitankers as more effective in narrow canyons and on steep slopes. Certain models were considered better performing than others in specific situations. The study provides the dispatcher with some guidelines on the type and model of aircraft to send out in given situations.

Since it first appeared in Tanganyika in 1957, red band needle blight has become a major forest disease around the world. Apparently spread by high altitude winds, the blight has been found killing Monterey and other pines in California's northwest coastal counties. About 30 pine species are susceptible. Caused by the fungus Dothistroma pini (sexual stage Scirrhia pini), the disease usually damages only young trees. Climate may hold the disease in check in most of California.

Panels of Douglas-fir and robusta eucalyptus blocks showed little seasonal variation in Equilibrium Moisture Content (EMC) of wood at 19 indoor locations on Oahu, Hawaii. Differences in EMC between locations were more variable. Minimum EMC at nonair-conditioned locations was 10 percent;at air-conditioned locations. 8 percent. Maximum EMC at nonairconditioned locations was 16 percent; at air-conditioned locations, 12 percent.

As an aid to aerial photo interpretation, a Crown Closure Comparator has been developed. Printed as a positive film transparency, this device shows tree crowns as open dots on a black background. The Comparator is used to stratify I-acre plots into broad volume classes on single aerial photos using 4 crown-diameter and 9 crown-closure classes. It can also be used for stereo classification with mirror-type stereoscopes.