THE SLENDER SEED-CORN GROUND-BEETLE. 



25 



check (not treated) ; plat 5, oil of mustard; plat 6, carbolic acid. The 

 plats were planted May 21, 1908. 



All plats were examined on June 1,2, and 3, 1908. Every hill that 

 contained no live plants, or that had only one plant, was dug up and 

 examined carefully. Two hundred hills in both the experimental 

 and check plats were inspected. The results are summed up briefly 

 in the following table : 



Table I. — Results of experiments in treating seed-corn with repellent oils to ward off 

 attacks of the slender seed-corn ground-beetle. 



Plat 

 No. 



Number 

 hills ex- 

 amined. 



Destroyed by 

 Clivina. 



Total. 



Destroyed by 

 other pests. 



Total. 



Per cent 

 affected 



by 

 Clivina. 



Per cent 



affected 



by other 



pests. 



Number 

 hills en- 

 tirely de- 

 stroyed. 



Number 

 hills 

 with 

 only 1 

 plant. 



Number 

 hills en- 

 tirely de- 

 stroyed. 



Number 

 hills 

 with 

 only 1 

 plant. 



1 



2 



2a 



3 



4 



4a 



5 



6 



200 

 200 

 200 

 200 

 200 

 200 

 a 200 

 200 



11 

 8 



11 

 7 



12 



10 



8 

 11 

 21 

 11 

 16 

 20 



19 

 19 

 32 

 18 

 28 

 30 



25 

 15 

 28 

 21 

 36 

 21 



27 

 42 

 30 

 35 

 49 

 38 



52 

 57 



58 

 56 

 85 

 59 



9.5 

 9.5 



16 

 9 



14 



15 



26 



28.5 



29 



28 



42 



29.5 



10 



12 



22 



21 



20 



49 



11 



24.5 



a In plat 5, a very large percentage of the seed did not germinate and it is to be inferred that the kernels 

 were injured by the oil, therefore this plat was not included in the table. 



No attempt was made to ascertain the number of hills destroyed by 

 each individual pest other than the Clivina. A cutworm, probably 

 Agrotis ypsilon, caused a large amount of injury. Wireworms and 

 the seed-corn maggot were also responsible for a part of the trouble. 

 The oil of wormseed probably injured the kernels, as a much larger 

 number of plants in plat 4 were missing than in some of the others. 



EXPERIMENTS IN 1909. 



After looking over the results of experiments conducted during the 

 year 1908 it was decided to use the oils of cajeput, citronella, and 

 lemon, as these promised the best results. Two small plats (Nos. 5 

 and 6) were planted later than the others, one (No. 6) with and the 

 other (No. 5) without fertilizer, the fertilizer being placed directly 

 on the corn. 



The plats were in the same place as those of the year 1908, and con- 

 ditions were the same as regards the size of the plats and the quanti- 

 ties of materials used. The treatments given the several plats were 

 as follows: Plat 1, oil of cajeput; plat 2, oil of citronella; plat 3, oil 

 of lemon; plat 4, check (not treated); plat 5, 95 hills planted June 2 

 (unfertilized); plat 6, 93 hills planted June 2 (fertilized). Plats 1 

 to 4 were planted May 22, 1909. 



