SPRAYING FLORIDA CITRUS FRUITS Q 
EFFECTIVENESS OF ONE AND ae APPLICATIONS OF BORDEAUX- 
The relative degree of effectiveness indicated by each of the 
several lines in Figure 2 has been calculated.’ The term “ percent- 
age of effectiveness ” is used for the final result. A 100 per cent of 
effectiveness means that no rot occurred. A 25 per cent of effective- 
ness means that one-fourth of the oranges that otherwise would have 
rotted were saved by the treatment; that is, a possible rot of, say, 
10 per cent of the fruit would be reduced to an actual loss of 71 per 
cent. A zero percentage of effectiveness indicates no contro] of rot 
whatever. 
Table 1 gives the percentages of effectiveness for the lots of fruit 
shown in Figures 2 and 5, as well as certain particulars about the 
scope of the tests. The table includes results for both one and two 
applications of spray. Each percentage of effectiveness 1s an aver- 
age for the number of seasons indicated and is based on the showing 
of rot from unsprayed check plots for these particular groups of 
seasons. With the natural fluctuations in the amount of rot from 
year to year, the figures of average percentage of rot do not give as 
accurate a basis of comparison as do the percentages of effectiveness. 
TABLE 1.—Results of spraying experiments with 3—-3-50 Bordeaux mixture plus 
1 per cent oil for control of rot in oranges 
Average abe se 
percent- bal 
Applications of spray pha age of rot ery q 
(36 day | (36 day 
period) period) 
Lappientiion.boelore:A pr. ths 252. - 22-2. 2 ee 2, 200 19.3 27 
1 application between Apr. 15 and May 5-_--.--------- 2, 050 17.7 33 
1 application between May 6 and June 15_._--------. 3, (97 23. 2 12 
application after Jume 15-2 222-2552 s =e 3, 860 24.6 6 
2 applications, starting before Apr. 15_-------------- 3, 350 15, 2 42 
2 applications, starting in period from Apr. 15 to 
IVER hee ee eo oe eee eee 3, 533 16.3 38 
Wmeprayed.ehecks ts. 6540 oe 2 See ees Up: toy 8,850: | 2 2s 0 
1 For each of the treated groups a special check was calculated, including the unsprayed plots for the 
particular seasons in question. 
= 
MODIFIED COPPER SPRAYS 
Preliminary tests were made with a representative group of copper 
sprays and dusts to determine whether any gave promise of supe- 
riority over the standard 3-83-50 Bordeaux-oil formula. The tests 
were not repeated over a period long enough to justify extensive 
statistical treatment. However, the indications seem to be definite 
5 The average height of each line is caleulated for any particular period, say 36 days, by 
adding the cumulative percentages of rot indicated at each 3-day interval along the line, 
and then dividing by the number of such intervals, in this case 12. This value would be 
the average percentage of rot developing in the lot of fruit represented by the line and 
would take into consideration the time at which the rot began to show as well as the 
total amount reached in the successive time intervals. The average percentage of rot 
thus obtained for each treatment is subtracted from that for the unsprayed check to deter- 
mine the saving effected by the treatment. This difference is then divided by the average 
percentage for the unsprayed check to determine the percentage of rot that has been 
eliminated by the treatment. 
