THE WATER-CRESS SOWBUG, 



13 



& Son, who are practical cress growers and liave had several years' 

 experience with the pest: 



A METHOD OF GROWING AVATER CRESS TO DISPOSE OF THE SOWBUG. 



The (lamaj^o done by tho sowbug to wator cress lias made it our greatest 

 enemy in cress growing, and only after fighting it for four years have we suc- 

 ceeded in finding a way to keep down its numbers so as to be sure of a crop. 

 As cress is ordinarily grown — in lakes or streams of spring water anywhere 

 from G inches to 3 feet in depth — it seems impracticable to apply any insecti- 

 cide. At first we tried to catch the bugs with wire-netting traps placed where 

 the whole stream of water had to pass through them, but the bugs remained 

 among the cress, and we cMught only alxjut 20 per cent. 



Later, in using copper sulphate to kill moss in the cress, we found that it 

 also killed tho sowbugs, snails, etc., when jipplied freely. Further e.xperinients, 

 however, proved that bluestone could not be applied in deep running water any 

 better than the insecticides previously tried, and when applied in shallow or 

 still water it injured the cress. 



The method we are employing at present to fight the sowbug is largely a 

 matter of arrangement of cress beds (see fig. 4), and can be used only where 

 the bottoms of the beds can be graded and drained or where level land adjoins 



TROUGH 



Fig. 4. — Cross section of cress pond showing arrangement for avoiding damage by the 



water-cress sowbug. 



the source of the water supply. We dug long trenches in level land, making 

 them IG feet wide and about 15 inches deep. Lengthwise they were graded to 

 give a fall of 3 inches in 100 feet, and crosswise to make the center of the 

 trench several inches deeper than the sides. In the center and running the full 

 length of the trench a trough made of three 10-lnch boards was sunk below the 

 bottom of the trench in such a way that all of the water might be drained out 

 of the trench through it. Then, with the ui»per and lower ends of the trench 

 and trough arranged to be oijened or closed, the trench could be filled or emptied 

 at will and the flow of water regulated up to 8 inches in depth over the cress. 

 Of course fertile soil was put in the trenches and the cress could be planted 

 either before or after the water was turned in. 



With cress beds arranged as above, manipulation to dispose of the sowbugs 

 is simple. By cutting off the water supply and allowing the water to pass out 

 at the lower end of the trench, the sowbugs will collect in the trough, following 

 the receding water, as they can live only in water. No little puddles should 

 remain among the cress, as the bugs will collect in them instead of in the trough. 

 It will bo found necessary, also, to use boards to walk on in gathering the cress, 

 as prints of one's boots in the beds would make holes for the bugs to shelter iu. 

 The bugs do not move until nearly all of the water is drawn out of the trench. 

 Thus they are collected in a small amount of water in the trough and can then 

 be readily killed with a liberal amount of bluestone. either solid or iu solution. 



