543 



Sandground (J). The Economic Value of a Study of the Nematodes, 

 with Remarks on the Life History of Heterodera in South 

 Africa.— 5. African Jl. Sci., Bulawayo, xvii, no. 3-4, July 1921, 

 pp. 322-334. 



In this list of Nematodes the following are of importance to 

 agriculture : — Aphelenchus ornierodis, on violet buds ; A . cocophilus, 

 causing serious injury to coconut palms in the West Indies ; A. pyri, 

 causing decay of pears ; A . fragariae, destructive to strawberries ; 

 Tylenchus acutocaudatits, in coffee trees and causing disease of bananas ; 

 T. hiformis, infesting the roots of sugar-cane in Hawaii ; T. dipsaci 

 {devastatrix) (of which T. scandens is regarded as a synonym), widely 

 distributed over Europe, Australia and other countries, causing damage 

 to onions, narcissus bulbs and buckwheat, and also producing stem 

 rot of clover and making the cultivation of lucerne almost impossible 

 in many districts in South Africa ; T. oryzae, infesting rice in Java, 

 with which T. angusfa, infesting rice in Bengal, is possibly identical ; 

 T. mahogani, causing disease in mahogany trees ; T. penetrans, 

 infesting violets, potatoes, cotton and camphor tree roots ; T. semi- 

 penetrans, infesting roots of Citrus in California, Algeria, Australia, etc. ; 

 T. similis, in roots of sugar-cane and banana ; T. sacchari, the probable 

 cause of a sugar-cane disease ; T. tritici, infesting wheat ; Heterodera 

 schachtii, attacking sugar-beet and causing galls on maize, barley, 

 rye, oats, winter and spring wheat, and the disease known as nettle- 

 head in hops ; and H. radicicola, attacking more than 500 plants of 

 economic importance, including orchard trees and ornamental shrubs, 

 vegetable and cereal crops, tea, coffee, tobacco, cotton, flax, okra, 

 lucerne, rubber, sugar-cane, etc. 



The actual financial loss due to the last-named species is incalculable. 

 The peculiarities in its development are discussed, with special reference 

 to sexual differentiation. 



GowDEY (C. C). The Citrus Black Fly { Aleurocanthus woglumi, 

 Ashby). — Jamaica Dept. Agric, Kingston, Ent. Circ. 3, 1921, 

 11 pp.. 2 plates. [Received 22nd September 1921.] 



Aleurocanthus woglumi, Ashby, has been recorded on 75 food- 

 plants ; those reported from Jamaica are here classified under the 

 three headings : favourite, occasional, and supplemental food-plants. 

 The eggs are deposited on the lower surface of the leaves in spirals. 

 They hatch in from 7 to 10 days ; the larval stage lasts from 23 to 

 40 days, and pupation 16 to 48 days, giving a total life-cycle of from 

 46 to 98 days. The generations overlap, and their number is influenced 

 by climatic conditions. 



Natural enemies include Chrysopa sp., at least three Coccinellids, 

 and the ant, Cremastogaster brevispinosa, Mayr, var. minutior. For. 



A section of this bulletin by Mr. S. F. Ashby deals with the action 

 of the fungi, Aschersonia aleiirodis and Aegerita webberi [R.A.E., A, 

 viii, 480, etc.]. The cinnamon fungus, Verticellium hetcrocladum, 

 also infests A. woglumi, but is of less importance than the others. 

 Co-operation is essential to the success of such remedial measures 

 as spraying. The best results have been obtained with whale-oil 

 soap, kerosene emulsion, or Black-leaf 40, for which formulae 

 are given. 



