326 INSECT PESTS OF FARM, GARDEN AND ORCHARD 



Control. Inasmuch as the aphides spread from peas to clover, 

 the latter crop should not be planted near peas when avoidable. 

 In the spring the aphides should be carefully observed on the 

 clover and if they become excessively abundant, the only way to 

 prevent their migration to peas is to plow under the clover deeply 

 and roll the field. 



Highly fertilized land in which the moisture is retained by fre- 

 quent cultivation very often enables a crop to mature in spite of 

 moderate injury. Peas sown broadcast or planted in 8-inch 

 drills have been much more seriously injured than those planted 

 in rows 18 to 30 inches apart and cultivated, and those planted 

 close together afford no opportunity for brushing or cultivating 

 as described below. ' ' 



Early varieties of peas have practically escaped injury where 

 late varieties have been wholly destroyed, so that it is obvious that 

 only the earliest varieties should be grown where injury is antici- 

 pated. 



Early in 1900 Professor W. G. Johnson found that when peas 

 were planted in rows that the aphides could be readily knocked from 

 the vines by means of brushing with a branch, and that by follow- 

 ing the brushes with cultivators, the aphides would be covered with 

 earth and destroyed, either by suffocation or by the heat of the 

 soil. Where the air temperature is 95 F. the soil will be nearly 

 120, and aphides brushed onto it will be actually roasted to death 

 in a few minutes. The cultivation should not be repeated for 

 about three days, as it requires about that time for the destruction 

 of the insects covered with earth, if it is not hot enough to kill 

 them at once. By this method large areas of. peas have been saved 

 from destruction, but it was found that where the soil was moist 

 it would form small clods after cultivation and that the aphides 

 would merely crawl out from under them. 



To meet this difficulty Professor Johnson devised a pan into 

 which the aphides might be brushed and destroyed. This pan is mod- 

 elled after the hopper-dozers used in the West for catching grass- 

 hoppers, and consists of a long, shallow pan, the width of the dis- 

 tance between the rows and 5 or 6 inches deep. A little water is 



