23 



settle on the underside of the leaves. For the same reason they 

 prefer the north side of trees. This is particularly marked on small, 

 and hence well-liizlitod trees. Insects are not important natural 

 enemies of the whitefly ; the twice-stabbed lady-beetle destroys 

 some of the crawling larvae and occasionally older ones. The 

 larvae of Syrphidae and Chrysopidae also destroy many crawlers 

 and a species of thrips eats the eggs. The most efficient work is 

 performed by some parasitic fungi [see this Review, Ser. A, ii, p. 

 129], especially by the brown fungus, Aegerita webberi, because it 

 does not depend upon the dispersal of the spores to reach other 

 larvae on the leaf. Its thread-like mycelium radiates from each 

 dead larva far over the surface of the leaf and unless checked by 

 cold or drought is sure to infect any other whitefly larvae present 

 These hyphae often extend down the leaf-stalk, over the twig and 

 up the stalks of other leaves. A. webberi seldom appears before 

 August, but often continues to grow well into November if the weather 

 is sufficiently humid. The red fungus, Aschersonia aleurodis, develops 

 earlier in the season than A. webberi and is more easily introduced 

 into a citrus plantation. It does not, however, kill all the larvae on a 

 leaf and usually is not so vigorous in autumn. A third species that 

 often does great execution, particularly on the larvae of A. nubifera, 

 is a M/crocem (^u.9an'(«»), also called the "white-fringed fungus" [see 

 this Review, Ser. A, i, pp. 26G-267]. The cinnamon fungus, Verticil- 

 lium heterocladum, also proves useful. 



The best method of controlling whitefly under Florida conditions 

 is to aid in the spread of the parasitic fungi during the rainy season 

 and to spray with miscible oil emulsion in spring and autumn. The 

 fungi should be introduced as soon as possible after the appearance 

 of whitefly because the pest is usually most harmful w^ithin a year or 

 two of becoming firmly established, which is only possible in the 

 absence of the fungus. Artificial dissemination at the beginning of 

 the rainy season will usually result in a much more satisfactory spread. 

 Fungus can be obtained commercially and the preservation of a supply 

 of fungus is recommended [see this Revieiv, Ser. A, ii, p. 129]. 

 In the case of severe infestation during the dry season, contact in- 

 secticides should be used and Yothers' formula is advised [see this 

 Review, Ser. A, i, p. 187]. The lime-sulphur spray is very useful 

 against mites, but its use is incompatible w4th that of fungi parasitic 

 upon the whitefly or upon scale-insects, so that prevailing conditions 

 must guide the grower in deciding which pest is more urgently in need 

 of control. Another control against whitefly consists of fumigation 

 with hydrocyanic acid gas. 



A. cifri has been observed to mature on the following plants, 

 arranged approximately in order of preference : — Chinaberry and 

 umbrella tree, all varieties and species of citrus, Cape jessamine 

 (Gardenia Jlorida), privet, prickly ash, Japanese and native persim- 

 mons. Less severely infested plants include, among others, cherry 

 laurel, coffee, pomegranate, honeysuckle, blackberry and oleander. 

 The destruction of the wild and useless plants, particularly the 

 chinaberry, is advisable when they grow near citrus plantations. 



