APHIDS 



55 



BEET 



The Beet Apliis 



Pemphigus betae Doane 



This is a robust greenish-wliite or 

 white mealy louse infesting the roots of 

 the lieet on the Pacific coast. When in 

 abundance it becomes very injurious, its 

 presence being indicated first by wither- 

 ing and stunted growth of the leaves. 

 The lice attack first the small roots, later 

 moving to the main root and causing it 

 to become spongy. Agamic winged and 

 wingless females occur on the plant the 

 year around and the se.xed forms have 

 yet to be found. This species also in- 

 fests the roots of pigweed, dock and kin- 

 dred plants. The only known remedy is 

 to discontinue for at least one year plant- 

 ing beets on infested land and to de- 

 stroy the wild host-plants. 



The Beet-root Aphis 



Tychea brevicornis Hart. 



This occurs in Colorado on the roots of 

 beets and may be controlled by the dis- 

 continuance of planting beets on infested 

 land until such time as is required for 

 the lice remaining in the soil to die of 

 starvation. 



The California Beet-root Aphis 



Trifirlaphis radicicola Essig 

 The food-plants and control of this 

 species are similar to that of the Beet 

 Aphis. 



CUCURBITOrS CROPS 



The Melon or Cotton Aphis 



Aphis gossypii Glover 



This aphis inhabits a large variety of 

 plants including cotton, orange, straw- 

 berries and most of the Cucurbitaceae. Its 

 life history is yet imperfectly known. In 

 early spring it migrates from various 

 weeds and shrubs to cultivated plants. 

 Later migrations follow during summer 

 and fall. The progeny of the migrant 

 lice settle in colonies on the under side 

 of the leaves of the cucurbits and soon 

 cause considerable curling. Control 

 measures should be initiated as soon as 

 the pest makes its appearance. Under 

 spraying the foliage with oil emulsions 

 or tobacco extracts is often satisfactory 

 or the plants can be fumigated with 



carbon bisulfid or tobacco paper. The 

 carbon bisulfid should be evaporated un- 

 der a tub or similar tight-fitting recep- 

 tacle placed over the plant. A dram of 

 liquid may be used for each cubic foot of 

 space. The plants can be fumigated suc- 

 cessfully by burning tobacco paper under 

 a canvas frame fitted over the plant. 

 The amount of tobacco paper to be used 

 varies with the cubic measurement of 

 air space under the frame. If the leaves 

 are badly curled fumigation is prefer- 

 able to spraying. 



COTTON 

 Two species of plant-lice occur on 

 young cotton plants. These are the 

 Melon or Cotton Aphis {Aphis gossypii 

 Glover! and the Bur-clover Aphis (Aphis 

 medicaginis Koch). Both are small black 

 or dark brown species and inhabit nu- 

 merous weeds, migrating thence to the 

 cotton plant. The best ■ means of con- 

 trol lies in the prevention of the lice 

 from reaching the cotton and this may 

 be done by ridding the fields of weeds. 

 If melons are planted near the cotton 

 they will prove a continuous source of 

 infestation. 



COR\ 



The Corn-root Aphis 



Aphis maidi-ratlicis Forbes 

 This aphis is a small bluish-green 

 mealy species. Besides corn it infests 

 sorghum, broom-corn, cotton and grasses. 

 The eggs are laid in the late fall in ants' 

 nests, the egg-laying females having been 

 carried thither by the ants. The young 

 hatching in spring attack the roots of 

 grasses, later migrating to cultivated 

 plants. As the Corn-root Aphis is chiefly 

 troublesome where corn has been planted 

 on the same ground for several years in 

 succession, a rotation of crops will greatly 

 check its ravages. Fertilizing the land 

 with barnyard manure will help the corn 

 to withstand injury, and deep plowing and 

 harrowing in winter will destroy the ants' 

 nests in which the winter eggs are stored 

 besides getting rid of the ant protectors. 



The Corn-leaf Aphis 



Aphis maidis Fitch 

 With the exception of the cotton plant 

 this species has the same range of food- 



