The chemical nets rapidly and death can occur 

 within 1 hour after ingestion; animals apparently 

 run for cover at the onset of symptoms, and few 

 reappear. Compound S-6999 appears to be prac- 

 tically nonhazardous to animals other than rats 

 when exposed in a bait at a concentration of 1 per- 

 cent or less. No accidental poisoning of any wild 

 or domestic animal occurred in any of the 134 

 field trials, although in a few instances baits were 

 known to have been consumed by dogs, cats, hogs, 

 and chickens. 



Registration of DRC-71!, as <i pocket gopher 

 control. — A highlight of the year was further de- 

 velopment of the promising pocket gopher toxi- 

 cant and rodent icicle DRC-714. Personnel of the 

 Denver Center, cooperating with the Chemagro 

 Corporation, have, decided to develop the chemical 

 as a rodenticide and will undertake steps neces- 

 sary for registration. The Denver Center will 

 expand its testing program on field rodents and 

 will gather data on the effect of the chemical on 

 nontarget species of wildlife. These efforts should 

 soon clarify the potential of DRC-714 in mammal 

 control, and lead to its eventual availability to the 

 public. 



Nutria studies progressing. — Laboratory tests 

 in evaluation of zinc phosphide as a candidate toxi- 

 cant for use in nutria control have been completed. 

 Favorable results were obtained at the 20-mg/kg 

 level. Followup held tests to evaluate zinc phos- 

 phide treated baits on nutria in or near sugarcane 

 fields are being made. 



Nutria population studies are in progress near 

 Houma, La., and Beaumont, Tex. A method of 

 nape-tagging nutria with a %- by 214-inch Saflag 

 tag and safety pin is being used. Data from ob- 

 servations and trapping are beginning to yield 

 valuable information on nutria populations and 

 movements, necessary to the development of bait- 

 ing techniques. 



Pocket gophers injurious to Christ/mis trees. — 

 The Mississippi Valley pocket gopher is respon- 

 sible for serious mortality in Christmas tree plant- 

 ings over much of Minnesota and western Wis- 

 consin. Losses to gophers arc most prevalent in 

 the central pine region and the Twin City area. 

 Since Minnesota is one of the top Christmas tree 

 States in the Nation, the loss is regarded as serious. 

 For example, in 1962 more than 5.5 million trees, 

 valued at more than $6 million, were harvested. 



Case-history studies of red pine and Scotch pine 

 plantations, in cooperation with the Minnesota 

 School of Forestry, have demonstrated losses 

 ranging from 13 to 16 percent by the time plan- 

 tations are 10 years old. The greatest damage 

 usually occurs in plantings between the first and 

 sixth year. The "burrow builder," a Bureau- 

 developed tool, has been effective in controlling 

 gophers, but while the loss has been materially 

 reduced, it is still in excess of $200,000 annually. 



New method of testing seed protectants. — Bu- 

 reau biologists, in cooperation with the University 

 of Florida Agricultural Experiment Station, 

 evaluated a newly developed method for field-test- 

 ing candidate blackbird repellents in 1963. The 

 tests were designed both for distinguishing bird 

 damage from other types of damage to germinat- 

 ing seeds, and for isolating side effects of candi- 

 date bird-repellent chemicals on germination. 

 This was accomplished by comparing the total 

 damage in identical companion rows of sprouts in 

 which alternate rows were protected. To insure 

 bird pressure, some test plots were grown inside a 

 large enclosure containing captive birds. Con- 

 sistent differences between candidate materials, 

 and agreement between measurements of sprout- 

 ing success and observed damage, indicate that 

 this technique may have the sensitivity and relia- 

 bility long needed in field-testing repellents on 

 planted seed. 



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