Green Peach-aphis Black Beet-seed Louse 



With the approach of fall the winged lice of the late summer gen- 

 erations return to the peach and plum trees. The first lice to return to 

 these trees give birth to wingless females which lay eggs instead of giving 

 birth to young. About the time these females are mature the winged 

 males begin to arrive from the summer hosts. 



After mating the females deposit several greenish eggs, which later 

 become shining black. These eggs (Fig. 2, Plate VIII, Page 25) serve 

 to carry the species through the winter. 



(b) BLACK BEET-SEED LOUSE* 



(Figs. 6 and 7, Plate III, Page 15) 



The black beet-seed louse is notorious because of its injury to sugar 

 beet seed, both in Europe and America. In this country it has been par- 

 ticularly destructive in some of the western states where beet seed is being 

 grown on a commercial scale. 



NATURE OF INJURY 



In feeding upon beet seed plants the lice congregate in compact masses 

 at the tip of the growing seed branches. Their feeding so exhausts the 

 sap that the plants make very slow growth and in severe cases the infested 

 branches die. The yield of seed is very materially reduced as a result of 

 attack by this louse. 



METHODS OF CONTROL 



Hand Picking 



In Europe all infested branches are collected and carried from the 

 field, together with the lice, and destroyed. This method is hardly prac- 

 ticable except in the case of cheap labor and selected breeding plants. 



Black Leaf 40 



Spraying infested plants with black leaf 40 (See page 114), one part 

 to 600 to 800 parts of water, will destroy the lice and not affect the quality 

 of the seed. 



Winter Spraying 



Spraying the winter host with lime-sulphur mixture (See page 115) 

 to destroy the eggs before the buds open or with black leaf 40 (See page 

 114) as the lice are hatching in spring is undoubtedly the most effective 

 means of controlling this pest. 



Destruction of Summer Hosts 



When lice occur on wild plants during the summer these should be 

 destroyed, together with the lice on them. The destruction of all wild 

 host plants in the vicinity of beet seed fields, before they become infested, 

 is to be recommended. 



'There is some evidence that there may be more than one species of black louse attacking beet 

 seed in the United States. This Bulletin discusses but one. the species damaging beet seed in Northern 

 Co'orado. 



1 17 



