CHRYSANTHEMUM MIDGE. 19 
successfully and continually. Hence, it was decided to test out 
the efficiency of several applications when made two and three days 
apart. The test is given in the next paragraph. 
EXPERIMENT 2. 
In the treated lots five plants were used for (a), (b), (e), and (f), 
and six plants for (c) and (d) for each test. The plants used had 
been growing in pots. Only two plants were used in both checks. 
The dipping was done as indicated every two or three days. Obser- 
vations were taken daily. 
TABLE VI.—Results of experiment 2. 
| | 
| Percent- 
Started. Closed. Treatment. erent aoe eaae Remarks and conclusions. 
ciency. 
1919. | 
(a) May 1...| May 10..| Nicotine sulphate (1-500), 217 123 | 56.6 | Greatest efficiency with- 
fish-oil soap 1 ounce to in 24 hours of treat- 
1 gallon. ment. 
{b) May 1...| May 10..| Nicotine sulphate (1-800), 152 86 56.5 | Same as above. 
fish-oil soap 1 ounce to 
1 gallon. | 
(c) May 19. .| May 23..| Nicotinesulphate (1-1,000), 45 30 66.6 | Lower leaves turned yel- 
fish-oil soap 1 ounce to 1 | low and died on most 
gallon. plants. 
(d) May 19..| May 23..| Volatile nicotine sulphate 72 35 48.6 | Slight blackening of tips 
(1-1,000), fish-oil soap 1 | on larger leaves. 
ounce to 1 gallon. 
(e) May 1...| May 10..| Linseed-oil emulsion plus 80 2 2.5 | Not efficient. 
nicotine sulphate(1-800). 
(f) May 7....| May 9...| Fish-oilsoap 1 ounce to1 | Many. 0 0 Allemerged successfully; 
gallon | | not efficient. 
(2)iMayn1e =) | Mayall O=s| (Check. $322. 3h es oe | Many. | 0 | 0 | Allemerged successfully. 
Gap PMaystOns e Mave23=a|3@heckcsse 45> sce = oe Many. | 0 0 | Same as above. 
Discussion of resulis—The data represented in Table VI are 
self-explanatory as to the relative value of the various strengths 
and combinations of insecticides. The mathematical representation 
of the first two lots does not clearly define the actual state of affairs. 
It was repeatedly observed that on the day following treatment the 
number of adults killed was usually larger than on the second or 
third day. In other words, the effectiveness of such practices de- 
pends entirely on the interval which elapses between applications, 
and the conclusion to be drawn is that nightly or daily applications 
are absolutely necessary to get the maximum killing. The insecti- 
cide proved to be effective in killing the adult in the act of emer- 
gence, but did not sufficiently penetrate the tissues of the leaves to 
kill the immature stages within the galls. The column ‘‘Total 
killed’”’ is understood to mean the killing of the adult in the process 
of emergence (Pl. II, B). It is also important that the treatment 
should be applied when the adults are almost ready to emerge from — 
the galls. 
