Table 4. — Number of trees in the Forest Preserve District of Cook County showing each of several degrees of 

 chemical damage following treatment of 400 trees with improved SD-3562, each lot of 100 trees at a dosage of 1, 1.5, 2, 

 or 1 + 1 ml per inch of trunk dbh, May, 1961. Observations were made in June and September of the same year. 



•Damage classifications the same as under table 3. 



was by the injection method on May 5, when the buds 

 of the trees were swollen. A fourth randomized lot 

 was treated with a split dosage--l ml per inch of tree 

 dbh on May 5 followed in 2 weeks with 1 ml per inch. 

 A fifth randomized lot of 100 trees was left untreated 

 as a control. 



No Dutch elm disease was evident in either the 

 treated or control lots in 1961. However, considerable 

 chemical injury was noted in the treated trees. A 

 summary of the observations, table 4, shows that there 

 was injury at all dosage levels. By mid-September 

 the trees killed ranged from 13 per 100 at a dosage of 

 1 ml to 29 per 100 at a dosage of 2 ml per inch of tree 

 dbh. The observations indicate the ability of many 

 trees to overcome the toxicity of the chemical when 

 the damage is slight or even severe. Trees of 3 inches 

 dbh or smaller appeared to be more easily killed by 

 the chemical than larger trees. The larger trees re- 

 covered more readily from nonfatal injury than the small 

 ones. Chemical injury in the Forest Preserve District 

 of Cook County was much more severe than at Sinnis- 

 sippi Forest or in the Wisconsin areas included in 

 some tests by Norris (1960:1035), who reported only 

 to 5 per cent injury following a dosage, applied in 

 May, of 6 grams per 3-inch tree (equivalent to 5 ml per 

 3-inch tree or 1 2/3 ml per inch of tree dbh). 



TESTS AGAINST OTHER PESTS WITH SD-3562 

 APPLIED TO TREES BY SEVERAL METHODS 



Sixteen honey locust trees were divided into four 

 groups of four trees each, the groups were designated 

 A, B, C, and D, and the trees were designated as in 

 table 5. One tree in each group was set aside as a 

 control. On June 14, 1961, three trees in each group 

 were treated with improved technical SD-3562 at dos- 

 ages of 1, 2, or 3 ml per inch of trunk dbh by one of 

 the four methods described below; methods A, B, C, 

 and D were used on groups A, B, C,and D, respectively. 



A. The chemical was injected into four holes, 

 each five-sixteenths inch in diameter, drilled in the 

 trunk of a tree, fig. 3. The holes were then plugged 

 with dowels. 



B. The chemical was applied with a syringe to 

 the surface of the bark entirely around the trunk about 



3 feet above the ground and allowed to rundown, fig. 1. 

 This method of application was similar to methods 

 employed by Jeppson et al. (1952:669). 



C. The chemical was applied to the bark as in 

 method B. It was then loosely covered with thin plastic 

 to reduce weathering. 



D. The chemical was applied as in method B to 

 bark that had been striated with a razor blade at 

 intervals of about one-fourth inch to a depth of one- 

 eighth inch. 



Some yellowing and dropping of leaflets was noted 

 on trees treated with dosages of 2 and 3 ml by method 

 A and with a dosage of 3 ml by method D. The damage 

 was not severe. No damage was noted in 1961 on trees 

 treated by methods B or C. 



Bagworm on Honey Locust. — In the second week 

 after treatments by methods A, B, C, and D described 

 above, about 25 larvae of the bagworm, Thyridopleryx 

 ephemeraeformis (Haworth), were confined in sleeve 

 cages, fig. 4, one cage on each of the four trees that 

 had previously been treated with a dosage of 3 ml of 

 SD-3562, and one cage on the control tree in group A, 

 table 5. Extent of the kill showed that the chemical 

 had been translocated to the foliage in all but one of 

 the trees in sufficient quantity to be highly toxic to 

 the bagworms. 



Each week, from the third week through the ninth 

 week after application of the chemical, a cage with 

 about 25 bagworm larvae was placed over a branch of 

 each of the 16 trees. After a period of 1 week, each 

 caged branch was clipped from the tree, and branch 

 and cage were taken to the laboratory for examination. 

 A new group of bagworms was caged on another branch 

 of each tree for the following week. 



The chemical applied by each of the four methods 

 of treatment and at each of the three dosages was 

 highly toxic to the bagworms, table 5. The most con- 

 sistent and persistent effect was obtained by method A. 

 that is, with the chemical injected into holes in the 

 trees. Here, with one exception, a complete kill of 

 bagworms was obtained at each of the three dosages 

 through the ninth week after treatment. Method D, with 

 the chemical placed on striated bark, gave the next 

 best results. This method gave high, although not 

 always complete, kills through the ninth week. When 





