64 



NATURAL CONTROL OF WHITE FLIES IN FLORIDA. 



an average of 29.8 red-fungus pustules per leaf, the degree of white- 

 fly infestation agreeing quite closely M^ith rows 4 to 11 (Table X) of 

 the experimental grove. 



(2) Swindley grove, near Orlando, Fla. More than 80 'per cent 

 citrus white fly: less than 20 per cent cloudy-winged white fly. — In this 

 grove of 900 seedling oranges experiments were conducted during 

 the summer of 1908 to determine what advantage might follow two 

 introductions during the same season, and incidentally, one intro- 

 duction on each of two successive j^ears. About one-fourth of the 

 trees were sprayed with no fresh red Aschersonia,^ one-fourth with 

 fresh red-fungus mixtures varying to strength (300 to 625 pustules 

 per gallon) during July, and another fourth in a like manner during 

 July and August, The remaining fourth, wliich had been sprayed 

 during July, 1907, was again sprayed in August, 1908. The results 

 are given in Table XI. 



Table XI. — Red Aschersonia: Results of experiments in spreading the infection. 



Block 

 No. 



Fungous introductions. 



Leaves 

 exam- 

 ined. 



Pupa 

 cases x)er 



loaf, 

 average. 



Red As- 

 chersonia 

 infection, 

 average 

 per leaf. 



Unsprayed chock 



Sprayed once, July, 190S 



Sprayed twice, July and August, 1908 



Sprayed twice, July, 1907, and August, 1908 



120 

 120 

 120 

 120 



9.8 

 6.2 

 6.7 

 6.0 



0.01 

 6.1 

 7.3 

 2.9 



While the data presented show that more fungus developed on the 

 trees sprayed twice in one season, the spread of the fungus on all trees 

 during the season of 1909 was so rapid that it became impossible to 

 tell wliich trees had been sprayed once, twice, or not at all. All 

 developed an equally large amount of fungus which, supplementing 

 unexplained mortality, so held the fly in check that the fruit in the 

 grove was practically clean by the following fall. By the following 

 spring much of the fungus had fallen off and there were more specimens 

 of the fly in the grove during 1910 than the owner had noticed for 

 many years, and the trees became thoroughly sooted. 



(3) Drennen estate grove, near Orlando, Fla. The citrus and 

 cloudy-winged tvhite flies present, the latter comprising 0.8 per cent, 

 according to an estimate made in June, 1909. — In this experiment a 

 solid block of six rows of eight trees each was divided into two series, 

 one comprising the even and one comprising the odd numbered trees 

 of the six rows. Only a trace of red fungus (no yellow or brown) had 

 been found in this grove and none had been discovered near the 

 experimental block. After the first introduction, therefore, the 

 experiment is properly one of increasing the efficacy by spreading 

 the infection. An attempt was also made to introduce and spread 

 the yellow and brown fungi by including their spores and mycelial 



1 This fourth was composed of trees either not sprayed or sprayed with dried pustules of the Ascher- 

 Bonias later determined to be valueless. 



