61 



inclosed. A tablespoonful serves for ordinary tubs. This treatment 

 does not injure the plant, and if the tub fits tightly to the ground 

 the vapor of the bisulphid is retained and the lice will all be killed. 

 This remedy is much used b}^ growers of melons and cucumbers who 

 watch their vines carefully, removing and destroying affected plants 

 and fumigating those which can be saved. 



THE BEET APHIS. 



{Pemphigus hetw Doane. ) 



This insect is a root-louse and comparatively new as a pest. Atten- 

 tion was first drawn to it in 1896, and for three or four 3'ears after- 

 wards it did considerable injury to sugar beet in Washington." We 

 do not know its full life history nor its distribution, but it occurs 

 also in Oregon and probabl}^ in California. In Oregon a thousand 

 tons or more of beets were ruined in a year in a single valle}". This 

 insect is one of many which may be seemingl}^ harmless up to a certain 

 point, but, with a changed environment, become of more importance 

 economically. 



The smaller rootlets of beets are first attacked and, when the aphis 

 occurs in large numbers, the}^ are soon destroyed. The loss of these 

 so weakens the j)laut that it is not able to withstand further attack, 

 and, as a result, the leaves wither and the beet shrivels and becomes 

 spongy. Wild yarrow {AchUlea lanulosa) appears to be a normal host 

 plant, and when its roots are examined in localities where the insect 

 abounds, they will frequently be found covered with the white woolly 

 excretion of the insect, while the louse itself is feeding on the smaller 

 rootlets. This species also lives on knotweed or door-mat weed {Poly- 

 gonum amculare)^ on grasses, and some other plants. It is likely to 

 increase its range, but this may be a matter of slow accomplishment, 

 unless it is introduced from one localit}^ to another on beets in 

 shipment. 



METHODS OF CONTROL. 



Owing to the large acreage which is planted in sugar beet in many 

 portions of our countr}^, it does not seem probable that we can treat 

 satisfactorily an insect like this root-louse, which feeds underground, 

 by means of insecticides. Kerosene emulsion and bisulphid of carbon 

 will no doubt kill it, but the expense would be excessive were either 

 used on a large scale. Nor can we hope entirely to eradicate the pest 

 when it has taken up quarters in our fields by means of cultural meth- 

 ods. Additional observations on its life history and experiments look- 



«Cordes: Sugar Beet Gazette for November, 1899; Doane: Bui. 42, Wash. State 

 A'gr. Expt. Sta., 1900, pp. 3-11. 



