in effectiveness came the self-prepared mixture with a 20 percent increase; and then the two other brands used, with 18 and 16 percent increases respectively. The sprays were purposely applied at long intervals in order to give a thoro trial to the sticking qualities of all. Frequent rains after application helped in the test. Therefore the yields did not represent the actual increases possible following treatment with these insecticides under optimum conditions. These experiments showed that under Iowa conditions such as were experienced in 1922 at least three types of commercial bordeaux mixtures were effective in controlling the leafhopper and preventing hopperburn. Whether they will be as effective as the self-prepared mixture in the long run, is still a debatable question. INSECTICIDE TESTS In preliminary tests it was shown by the writers (20), that bordeaux mixture was toxic to the nymphs of Empoasca mali Le B. In further experiments, three different combinations of self-prepared bordeaux and three types of proprietary mixtures of this compound were tested. As shown in table XIX, the commercial brands acted somewhat more rapidly than the other, but all were toxic without exception. The average length of life of the nymphs when feeding from leaves covered with these materials varied from two to three days. In contrast the cheeks lived for an average period of one week. Over 500 individuals of this species were kept under observation on sprayed potato leaves, and in not a single instance did one mature, unless very near the transformation stage when placed in the vial. Approximately a sixth of them moulted once, and in two cases two moults were observed. The majority died before eedysis. On the other hand a relatively large proportion were reared to maturity in the vials on unsprayed leaves. TABLE XIX. EFFECT OF BORDEAUX SPRAY UPON EMPOASCA MALI Treatment 4-4-50 NYMPHS TABLE XX. EFFECT OF BORDEAUX SPRAY UPON DIFFERENT INSTARS OF EMPOASCA MALI It was also demonstrated that the five instars varied in susceptibility to this spray compound, the first succumbing the most rapidly, the fifth being the most resistant (table XX). Adults appeared to be comparatively immune to this mixture, several often living 15 days while feeding from sprayed leaves. The effect at this stage was chiefly deterrent. SUMMARY OF CONTROL TESTS The data from four years' spraying with the insecticides discussed, showed that the whale-oil soap-nicotine sulfate combination was entirely unsatisfactory. It gave temporary relief by killing 60 to 70 percent of the nymphs on the vines at the time of application, but it did not affect many of the adults. It neither repelled the adults nor had any action on the thousands of young that hatched from the plants within the following 24 hours. Furthermore, usually enough old nymphs escaped to continue the production of hopperburn. The same difficulties were experienced with the kerosene emulsion, except that with this preparation there was always a possibility of foliage burning caused by the spray as severe as the hopperburn itself. On the other hand, three sprays of home-made bordeaux mixture 4-4-50 formula gave good control. If applied properly during June or July at intervals of ten days to two weeks under favorable conditions, the thin film of bordeaux remained on the plants for some time. Many nymphs that escaped drowning when this spray was applied, or hatched afterwards, died as a result of feeding from leaves covered with this preparation. Furthermore ovipositing females avoided plants sprayed with this compound. Nicotine sulfate appeared to add nothing to the effectiveness of the spray and only increased the expense. Commercial brands of bordeaux mixture were reliable as a rule, but they were non-adhesive. They washed off easily in a heavy rain and were more expensive. (1) (2) (3) ACKERMAN, A. J. 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