414 Report of the Department of Entomology of the 



Commercial tests with tar pads during 1912: Test No. 1. — This 

 test was located north of Geneva on the truck farm of Mr. Henry- 

 Cook. On May 14 tar pads were placed about four hundred and 

 thirty plants on five alternate rows of a small field of cabbage. 

 The intervening rows were left as checks. There was no injury 

 by maggots, and on July 8 there was no difference in size or appear- 

 ance of the plants in the check and treated rows. 



Test No. 2. — This test was located east of Geneva in a cabbage 

 field on the truck farm of Mr. Charles Scofield. Four hundred 

 disks were applied to four alternate rows of plants on May 22. 

 The period of oviposition commenced somewhat before this date, 

 and as the plants had been set two days before treatment it was 

 possible for them to become infested with eggs before the papers 

 were applied. The injury by maggots, as evidenced by the wilting 

 and death of some of the plants, was very noticeable on June 21. 

 At this time 10 per ct. of the checks and 1 per ct. of the treated 

 plants were either killed or badly wilted. In addition to this differ- 

 ence in the percentage of plants seriously injured, there was also 

 another perceptible result, namely, the cabbages in the protected 

 rows averaged slightly larger than those of the check rows. The 

 smaller size of the checks was attributed to the work of maggots, 

 which were generally observed about the roots of the untreated 

 plants. It appeared that while the insects were not sufficiently 

 numerous to kill the cabbages, enough of them were present to 

 retard their growth. 



Test No. 3. — This was located near Geneva in one of the plantings 

 of Mr. Geo. Gasper. Four hundred disks were placed on four 

 alternate rows on May 15, the day following the setting of the plants. 

 The soil was a clay loam and was somewhat lumpy because of the 

 unfavorable conditions at the time of cultivation, and in addition 

 the plants were set low in the ground, which made it difficult to 

 attach the tarred disks. The cards were soon covered by a half 

 inch or more of earth, due to the washing of the soil during a heavy 

 shower. By June 20 many of the plants were wilted and some 

 were dead as a result of the injury by the maggots. Careful counts 

 on this date showed that 5| per ct. of the treated plants and 16 

 per ct. of the checks were either killed or missing. In addition 

 to this difference the protected plants were slightly larger than the 

 checks. 



