50 NATURAL CONTROL OF WHITE FLIES IN FLORIDA. 



fungous leaf, the authors conchide that showers and abundance of 

 larvse and pupae are conditions most favorable to successful pmnmg. 

 Good infections have been secured at times when there were no adults 

 on the leaves. 



Wliile there are cases on record where very good results in intro- 

 ducmg fungus have followed the pinning method, this nmst be 

 regarded as second in importance to the introduction of spores m 

 water mixtures, especially when Aschei-sonias are concerned. On the 

 other hand, mfections with the brown fungus have been secured with 

 more certainty by pmning than by spraying, although with no more 

 certainty and in a less widespread manner than by the dippmg of 

 mfested shoots mto ground brown-fungus leaves and water as de- 

 scribed elsewhere. Infections with brown fungus by pimimg have 

 been secured as late in season as November 6 (1908). 



Infections secured by rubbing fungus-uifected leaves, as described 

 under experimental methods, have proved of more value in connec- 

 tion with the brown fungus. Although success has attended the 

 mtroduction of the Aschereonias by this method, they are too easily 

 introduced by water mixtures to warrant attempts at introducmg 

 them by rubbing. Under favorable weather conditions the rubbing 

 method is many times superior to the pinnmg. At most, rubbing, 

 even for brown fungus, is a veiy uncertain method, as only a very 

 small percentage of leaves rubbed become mfected. In a hammock 

 grove at St. Augustme, Fla., in August, 1907, the senior author 

 rubbed about 1,200 leaves on four trees, the leaves averaging about 75 

 citri larvae and pupae. Infection resulted only on about two twigs. 

 Later m the season slightly better results have been obtained. When 

 only a few brown-fungus-infected leaves are obtauiable, they can best 

 be used for rubbing and then pimimg. Frequently leaves that appear 

 to have been rendered worthless by riibbmg have caused infections 

 when pinned. Fungous leaves should be kept wet or moist durmg 

 rubbing by frequently dipping m water. Good mfections with 

 brown fungus have been secured as early as June 5, 1907, and as late 

 as October 31, 1908, although September and October have proved 

 more favorable months than the three ])receduig. While Prof. Faw- 

 cett reports ^ success m obtaining infections by means of the brown- 

 ish sporodochia, which are found dusted over the surfaces of the 

 mfected leaves, several similar tests by the authors made at various 

 times since June, 1907, have all been without results. 



WATER MIXTURES OF SPORES AND MYCELIA. 



Preparation of mixture. — Wliichever of the three most promismg 

 methods of introducing the fungi in water mixtures is to bo followed, 

 viz, spraying, dipping, or brushing, the initial steps in the preparation 

 of the mixture, with few exceptions, are the same. The "fungous 



1 Science, vol. 31, no. 806, p. 913, 1910. 



