400 Journal of the Department of Agriculture. 



Tobacco Slug : Spraying Devious I rations. — •Deinoiistratioiis have 

 been carried out during the past season at fouv different places in the 

 Piet Eetief District to show that the tobacco slug can be econoinically 

 controlled by spraying with arsenate of lead. On two of the plots the 

 slug was kept thoroughly under control by two sprayings, with an 

 interval of three weeks. At the other two places three sprayings were 

 given, and yet there was some slug present at harvest time. The 

 infestation was, however, considerably less than where no spraying- 

 was done. The difference in the results obtained seemed to be due to 

 insects coming in from unsprayed tobacco or from weeds at the last 

 two places, while at the first two places all the insects in the vicinity 

 were killed off by the spraying, and there was thus no subsequent 

 generation to give trouble. On the one farm the sprayed plot was 

 more or less isolated, and on the other the owner regularly sprayed his 

 whole field of tobacco. 



These results show the efficacy of spraying. They also show the 

 importance of thoroughly spraying the whole field, so that there will 

 be no beetles breeding in one part to infest the sprayed portion later 

 when the rains have washed off the poison. They also indicate that 

 weeds on which the pest breeds should not be left to grow in the 

 vicinity of the tobacco. 



It does not seem possible to state definite times when to spraj-. 

 The best advice that can be given at present is to keep watch and 

 spray as soon as slugs make their appearance, not neglecting a slight 

 infestation. In one case that came under observation there was an 

 infestation of slug about the time the tobacco flowers were beginning 

 to appear, which the owner did not think serious enough to spray for ; 

 but a more serious invasion followed when the tobacco was almost 

 ripe and spraying had become inconvenient. A thorough spraying 

 when the insect was first noticed would probably have prevented the 

 late infestation. If a crop is harvested with the slugs serious damage 

 in the shed is likely to occur. 



One pound of arsenate of lead jiowder to 32 gallons of water was 

 used for the demonstration spraying ; but one pound to 50 gallons has 

 been found amply strong to kill the insects. A knapsack pump was 

 used, and on the whole it proved satisfactory, though a far larger 

 mounted barrel pump would be better and do much quicker work. Some 

 tobacco growers have purchased automatic compressed air sprayers, 

 and are very pleased with them. It is evident that these pumps have 

 advantages over knapsack pumps, and would be preferable, if they 

 prove to last as long. Bucket pumps were given a trial, and it was 

 found that a convenient way of using them was to have one man 

 directing the nozzle, and another carrying the bucket and pumping. 

 In this manner the field can be got over as quickly as with a knapsack 

 pump, but it requires two men instead of one. Sprinkling with a 

 vsmall grass broom was found to take, on small plants, at least twice as 

 much material and time as spraying with a knapsack pump, and can 

 only be recommended where the need for treatment is urgent and a 

 pump is not available. 



With plants in rows, three feet apart and two and a half feet 

 apart in the rows, it was found that when the tobacco was about a 

 foot high, a quarter-acre plot could be sprayed with about fifteen 

 gallons. When the plants were about two feet high, with leaves 

 about two feet long, about 24 gallons would be required for the some 



