306 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1953 



sprays may possibly root-kill these plants, but sucli costs are prohibi- 

 tive. I myself worked with foliage sprays in 1946, 1947, 1948, and 

 1949, and then gave them up, for though I was getting good kill-to- 

 ground results, I was not getting root-kill on enough species. Despite 

 these disadvantages, the very striking photogenic effects of these 

 sprays, the over-all browning of the foliage, and the clean and neat- 

 looking grassland the year after have all served to sell the treatment 

 on many thousand acres. 



Basal sjn-aying involves small quantities of spray mixture (averag- 

 ing between 10 and 50 gallons per acre) at relatively high concentra- 

 tions (in ratios of 1 part of commercial chemical to 20, 40, or more 

 parts of solute, usually oil). Application is generally by 5-gallon 

 pack-sack sprayers, equipped with special nozzles. Attempts to use 

 power equipment, either to cut costs or to avoid using human labor, 

 have not yet been satisfactory, either in the degree of kill obtained or 

 in the selectivity and gallonages used. Actually, the technique of 

 application is of considerable importance, for the basal bark must not 

 only be wetted, but soaked thoroughly for extensive rundown. This 

 rundown (downward movement within bark or wood is apparently 

 negligible) affects the crown collar, the source of future resprouting, 

 although in field practice such an aim may be thwarted by deposition 

 of soil, stones, logs, or leaves around the base of the plant. 



Again, the physiological effects on the plant of this spraying are not 

 known. Two separate phenomena seem to be involved. The first is an 

 upward movement of chemical through the wood. This movement is 

 evidenced in the field by a relatively early top kill, followed by kill 

 progressively downward. The second may possibly be related to a 

 chemical ringing, without chemical top-poisoning. In this instance, 

 effect is deferred often for a full season. Then the entire foliage of 

 the tree, from top to bottom, uniformly turns yellow and dries. In 

 this deferred killing resprouting seems less likely to occur than in the 

 more rapid top-poisoning, and there is thus an implication — though 

 unsupported at present by any research data — that if chemical ringing 

 does take place, it may be the roots that die first by starvation. In any 

 event, basal spraying requires a patient and understanding client. 



The spraying is usually done in winter. When spring comes the 

 buds may burst and the plant may grow vigorously through to mid- 

 summer. Only then may the leaves begin to curl and the plant show 

 signs of dying. By fall, kill-to-ground may or may not be complete,' 

 depending on the adequacy of the spraying and other as yet uncon- 

 trollable factors. Ultimate kill-to-ground may not occur until the 

 end of the second growing season, and instances are known where the 

 tree died in the fourth year, though appearing perfectly healthy in 

 the preceding years. To make the situation more exasperating, re- 

 sprouting may occur, sometimes abundantly. If the root collar was 



