12 CIRCULAR 241, U. S. DEPARTMENT OF AGRICULTURE 



been burned over a short time previously was practically free from 

 leaf hoppers while the adjacent unburnt area, under otherwise identi- 

 cal conditions, was abundantly infested with hoppers of several 

 different species. Even where the areas examined were closely adja- 

 cent or the burnt patches were surrounded by unburnt grass the 

 difference was very noticeable. This was evidently due to the fact 

 that the burning had been quite recent, and unfavorable weather had 

 kept the hoppers so inactive that there had been little migration from 

 unburnt to burnt portions. With so positive a case as this, along 

 with many others of nearly equal certainty, it seems entirely war- 

 ranted to recommend burning for such pasture lands and range as 

 can be burned over without causing other injury. 



CAPTURING THE INSECTS IN HOPPERDOZERS OR TAR PANS 



The direct treatment which has had the most thorough trial is the 

 use of the hopperdozer, which consists of a sheet-iron strip, 2% by 

 12 or 15 feet, coated with coal tar. The apparatus is drawn over the 

 grass ; and as the insects hop at its approach, many of them fall upon 

 the tar surface and are killed. In a number of tests of this method 

 at the Iowa Agricultural Experiment Station it was found that, in 

 pastures having a normal infestation of leaf hoppers, the insects 

 could be captured at the rate of from a half million to a million to 

 the acre, which very appreciably reduced the number occurring in 

 the treated fields. Probably three-fourths or more of the hoppers 

 occurring in any particular area were captured by one or two treat- 

 ments of this kind. It was found that this treatment could be applied 

 to best advantage during the latter part of the afternoon on sunny 

 days, when the insects jump most readily and could be caught in the 

 greatest numbers. In one experiment with this plan, a plat was 

 treated for a season, and a comparison of the hay from this plat with 

 that from an equal untreated area showed an increase for the treated 

 plat of more than 50 per cent. 



Two fenced lots of bluegrass, each containing about 1% acres, 

 were used in another experiment. One plot -was treated, leaf hop- 

 pers being collected from it by the hopperdozer in large numbers 

 at various times, and upon this plot cattle, varying in numbers, 

 had been pastured at different times throughout the season for a 

 period of about 73 days. On the other, untreated, a single cow was 

 pastured. A comparison of the number of available hours of pas- 

 turage per animal on each plot showed that the treatment gave a 

 gain of 68 per cent in the capacity of the pasture. However, it is 

 evident that migration of these insects from adjacent areas would 

 tend to reduce the advantage of the treatment, especially in a small 

 field, and that the greatest advantage could be secured from treating 

 an entire tract, so that there would be no opportunity for reinfesta- 

 tion from adjacent lands. The expense of this method of treatment 

 is not great, the cost of materials being very small, and the labor 

 of man and team, or tractor, dependent on locality or season. 



SPRAYING 



With the present spraying apparatus, it is possible to apply 

 broadcast sprays of insecticides over any pasture lands or meadows, 

 or even cultivated fields, where the crop is not so far advanced as 



