EXPERIMENT STATION BULLETINS. 



175 



to celery, but on occasion, it has been known to overspread a celery field 

 in late July, collecting in little clusers on the leaves, and playing sad 

 havoc with the commercial fields. The outer leaves of the stalk suffer 



first, but later the inner, feathery 

 ones that go to make the market 

 head. 



The cause of all this trouble is a 

 small, shining black bug, very con- 

 vex and quite broad comparatively, 

 the length being a little less than 

 one-eighth of an inch. The insect 

 is said to rear only one generation 

 each year. It is known to work on 

 strawberry, raspberry, grape, wheat, 

 some grasses, and a number of 

 weeds, including red root and 

 ground-nut, beggar-tick, plaintain, 

 rag-weed and smart weed. 



Fig. 25. — Celery Aphis, enlarged, after 

 G. C. Davis. 



REMEDIES. 



Mr. Davis recommends crude carbolic acid and water used at the 

 rate of a teaspoonful to two gallons of water and sprinkled over the 

 plants or else crude carbolic and air-slaked lime used at the rate of a 

 teaspoonful of the acid to a bushel of lime, and dusted over the plants. 

 The emulsion of carbolic acid described on page 06 and diluted so 

 that the same amount of the acid is found in two gallons of water, will 

 make a more even preparation and one would expect less danger from 

 burning the plants than with the plain mixture. The writer has never 

 had an opportunity to try this, however, Mr. Davis found that hot 

 water killed the bugs when used at 155 degrees Fah. and that the plants 

 were killed at 175 degrees. On a small scale, this can be applied with a 

 sprinkler if care be taken to test the water with a thermometer carefully 

 and at short intervals. 



Clean culture. — The long list of weeds which serve as food-plants for 

 this little nuisance, shows plainly that the removal of weeds from the 

 vicinity of the celery fields will be the most effective preventive measure 

 at our command. Clean culture is, after all, a measure which pays well. 



Tarnished Plant-bug (see Insects affecting Beets). 

 Leaf-hoppers (see Insects affecting Beets). 

 Grass-hoppers (see Insects affecting Sweet-corn). 



Celery Thrips {Coleothrips trifasciata) . 



Related to the onion thrips, and in many respects, closely resembling 

 it, is the celery thrips. It is said to be the same species as the one 

 so common in clover heads. Very small and active, this insect jumps 

 and flies away on the slightest disturbance. For a more complete de- 

 scription of thrips, see Insects affecting the Onion. 



Celery-looper or Plusia {Plusia simplex). 



Closely related to the cabbage-looper is the celery-looper. The naked, 

 green larva is marked by eight white lines. The moth closely resembles 



