56 HOPS. 



as Heterodera Schachtii. When infested with these pests the 

 yQung hop loses its dimbing powers, and the tendrils grad- 

 ually languish, remain small, and put forth peculiarly shaped 

 leaves resembling those of the stinging nettle. No nema- 

 todes were found at all in the parts of the plant above ground, 

 but the young tender rootlets exhibited knotty swellings, 

 forming the habitation of the lemon-shaped females of the 

 Heterodera. Isolated cases of nettle sickness have been 

 observed in Oberhofen, near Bisweiler (Hagenau district).^ 



The foliage of the hop plant is infested by a larger num- 

 ber of pests, different from those attacking the roots : — 



1. Tetrcmychus telarius L., the red hop spider or mite (T. 

 daoius Koch, T. humuli Fleischm., T. lintearicus Dufour, Trom- 

 hidium telarium Herm., Gamasus telarius Lotz.), is the dreaded 

 foe that causes "copper brand". This minute pale red or 

 orange yellow animal, which is barely -V inch in length, in- 

 habits the under side of the leaves, and also infests the cones, 

 covering the lower surface of the leaf with a fine grey web 

 in which the eggs are laid. The infected leaves are covered 

 with brown patches, which, starting from the angles of the 

 veins, spread over about one-half of the entire surface ; the 

 leaves then wither up and fall off, as is also the case with 

 infected cones, Owing to the circumstance that this spider 

 occurs on man.y other plants, such as the lime, the oak, the 

 bean, hemp, poppy, flax, rose, acacia, strawberry, etc., it is 

 very difficult to eradicate. When present in force it always 

 means a considerable loss of crop. 



The insecticide used is a 1^ per. cent, solution of green 

 soap mixed with 1^ per cent, of quassia extract ; and the 

 washing of the plants with a IJ per cent, solution of alum 

 hasrecently been recommended. Both are highly efficacious, 

 but, as the spider attaches itself firmly to the under side of 



'Prank and Sorauer, Jahresbericht des Sonderausschusses filr Pflanaen- 

 schuU, 1895. 



