356 EXPERIMENT STATION RECORD. [Vol.43 



In the field tests made to deteriuine the repellent effect of the usual spray- 

 ing mixtures upon leaf hopi^ers, us compared with mixtures (jf heavier con- 

 sistency, the heavy washes composed of china clay or lime were a little more 

 effective than the other spraying mixtures. Because of serious damage to the 

 foliage, the heavy lime wash was the least satisfactory of the various mixtures 

 tested. 



"Although the Bordeaux mixture alone or in combination with lead did not 

 prove as effective a repellent as the sprays of heavier consistency, it should be 

 enipluisized that thorough spraying of all surfaces of the leaves of potato plants 

 prevented serious damage by leaf hoppers. Furthermore, this spray withstood 

 the washing effects of the rains much better than china clay or lime, the 

 combination with lead proving somewhat superior to Bordeaux mixture alone." 



What per cent of tipburn is caused by the potato leaf hopper? E. D. Ball, 

 and F. A. Fenton {Jour. Econ. Ent., 13 (11)20), No. 2, pp. 218-221, pi. Jj.— This 

 is a report of work carried on in Iowa during 1919 in an attempt to ascertain 

 the relative proportion of dilferent factors in causing tipburn. 



Plants inclosed in cages continued to grow with green and healthy foliage 

 when all the rest of the plants in the field were dead. In a test in which 50 

 males were placed in a wire gauze cylinder on a potato tip and 50 females in 

 another, the females produced serious burning while the males produced none. 

 A repetition of the experiment gave the same results. In an expefiment in a 

 shaded greenhouse burning developed on the leaves on which young nymphs 

 were placed, although those that were free from nymphs remained green and 

 normal. 



I'orms of the oyster-shell scale In Illinois, P. A. Glenn {Jour. Econ. Ent., 

 13 {l'J20), No. 2, pp. 173-178). — Observations made during the last six years 

 have led the author to I'ecognize three forms of the oyster-shell scale as occur- 

 ring in Illinois. The brown form which infests apples appears to be identical 

 with the European species {Lepidosaphcs ulmi L.) and has been successfully 

 transferred to lilac, a^li, and Coi-nus, but an attempt to transfer it to poplar 

 was unsuccessful. This form is double-brooded, the first brood hatching be- 

 tween the first or second week in May at Urbana, the second brood during the 

 latter part of July. It is usually very heavily parasitized. 



The grayish-brown or bamled form is the one that is generally and de- 

 structively abundant on poplar, ash, willow, lilac, cornus, and Rosa rugosa in 

 Urbana and Champaign, and at numerous other places in the northern half of 

 the State. American elm, soft and hard maple, ailanthus, and linden growing 

 near heavily infested ash and poplar may become infested and seriously in- 

 jured by the large number of young which are carried to them annually from 

 the infested trees, but in other situations they do not become infested and it 

 is doubtful whether the scale can maintain itself on them. This form can not 

 live on apple, pear, peach, plum, hackberry, and horse chestnut. It is single- 

 brooded and hatches at Urbana during the third or fourth week in May. This 

 form is not parasitized. 



The yellowish-brown form has been taken on Cornus, lilac, soft maple, and 

 R. rugoaa at Urbana. This form is double-brooded and is usually heavily 

 parasitized. While little difference can be found in the structural characteris- 

 tics of the three forms, the author finds that there is a striking and quite 

 constant difference in the average number of circumgenital pores. The dif- 

 ferences noted are summarized in tabular form. 



Recent tests of materials to control San Jose scale, J. S. Housek {Mo. 

 Bui. Ohio Sta., 5 {1920), No. 2, pp. 49-51). — While during the past few years the 

 San Jose scale has lost some of its virulence in some sections of Ohio, sections 



