PRELIMINARY REPORT UPON WORK WITH 

 THE STALK BORERS IN MINNESOTA. 



Papaipeiiia species. 



These disgusting pests, "worms" they would be called by gardeners, 

 bore into and ruin many of our choice flowering plants, and also work 

 in the stalks of barley, corn, oats, tomatoes, etc. They have been found 

 boring in Dahlia, Hollyhock, Golden Glow, Gallardia, Phlox, Delphin- 

 ium, Aster, Daisy, Peony, Rose and Sunflower, and have been referred 

 to frequently in previous reports from this department, detailed di- 

 rections being given in the annual report for 1906, for combating them 

 during the summer, by reiuoval and by the use of carbon bisulphide. 

 They are so common and so destructive that they seem worthy of care- 

 ful work on the part of the Entomological Division, particularly since 

 the life histories of the various species have not been worked out 

 for this part of the country. 



The presence of the larva of Papaipcriia may be detected in such 

 plants as Golden Glow, Peony and Hollyhock by a noticeable wilting 

 of the top of the plant, often followed by the portion of the stalk 

 above the entrance hole breaking down. A careful search around the 

 bases of such partially wilted plants, or an examination of the stalk 

 itself will usually reveal a quantity of caterpillar excrement. This 

 having been found, it is an easy matter to locate the entrance hole of 

 the caterpillar. Burdock and Giant Bur-elder having thick stalks, show 

 but little wilting, but the presence of a caterpillar in a stalk of these 

 plants is usually indicated by the stalk being somewhat swollen, and 

 the caterpillar excrement is always present. Stalks of these plants 

 never break over after being attacked, as do the stalks of Golden Glow 

 and other equally delicate growths. 



Golden Glow and such small stalked plants rarely, if ever, harbor 

 more than one larva. One stalk is usually sufficient for the develop- 

 ment of a single caterpillar. Burdock, on the other hand, often has 

 more than one caterpillar in a single stalk. The larv?e of cataphracta 

 and iiitela work in the center of the main stalks of their food plants, 

 and they often work out from the main stalks into the branches, and 

 sometimes enter the branches first and work into the main stalk later. 



For the purpose of getting all the information possible along these 

 lines, and of making a study of the life histories of the various species 

 of this genus, upon which treatment of plants largely depends, Dr. 



