J'U 
 
 ) 
 
NICOTINE SULPHATE IN A DUST 
 CARRIER AGAINST TRUCK- 
 CROP INSECTS 
 
 ROY E. CAMPBELL 
 
 Scientific Assistant, Truck-Crop Insect InvtwtiKations 
 
 UNITED STATES DEPARTMENT OF AGRICULTURE 
 DEPARTMENT CIRCULAR 154 
 
 Contribution from the Bureau of Entomology 
 L. O. HOWARD, Chief 
 
 Washington, D. C. 
 
 Issued February 21, 1921. 
 
 WASHINGTON : GOVERNMENT PRINTING OFFICE : 1921 
 
 ..vA.,..^aA,s^JJ: 
 
I \pwARv OF CON(jHtSi: 
 
 OCT 3 1933 
 
.C3 
 
 v\ 
 
 NICOTINE SULPHATE IN A DUST CARRIER AGAINST 
 TRUCK-CROP INSECTS. 
 
 INTRODUCTION. 
 
 The successful use of nicotine sulphate in dust form by Ralph E, 
 Smith, of the University of California, in 1916 in the control of 
 the walnut aphis Chroma pirn juglandicola. Kalt.), a serious pest 
 in the walnut sections of southern California, induced the writer to 
 test this insecticide against insects injurious to truck crops. As 
 first used by Prof. Smith, the dust was made by grinding up stems 
 and refuse tobacco, with the inevitable result of a variation in the 
 nicotine content. To this variation was laid the cause for the 
 diversity of results in different orchards where the amount of mate- 
 rial used and methods of application were the same. Since there 
 was no way to regulate the nicotine content in ground tobacco. Prof. 
 Smith decided to use a certain amount of prepared and standardized 
 nicotine sulphate in an inert dust carrier. After extended experi- 
 ments it was found that kaolin possessed the necessary character- 
 istics for fineness, lightness, and inertness for an ideal carrier. Fur- 
 ther experiment showed that a mixture of 2 per cent by weight of 
 40 per cent nicotine sulphate in kaolin gave a thoroughly satisfactory 
 kill of aphids. It was also found that by using 25 per cent of finely 
 pulverized unslaked lime in the carrier, the slaking and heat there- 
 from took up the moisture in the nicotine-sulphate solution and 
 that a chemical reaction took place, forming calcium sulphate and 
 .free nicotine, which latter proved to be much more toxic to the 
 aphids than the nicotine sulphate. 
 
 PROCESS OF MANUFACTURE. 
 
 The original process of manufacture was as follows : The material 
 was first run through a sifter and mixing box such as bakers use. 
 The proper amount of kaolin and lime was put in this box, wliich 
 was about 5 feet long by 2 feet square, and had a capacity of 400 
 pounds. At one end was a small tank into which the desired amount 
 of nicotine sulphate solution was placed, a 2 per cent mixture re- 
 quiring 8 pounds, a 5 per cent mixture 20 pounds, etc. So that the 
 mixing would be thorough this solution was blown into the mixing 
 box as a fine spray. From the mixer and sifter the dust went 
 20861°— 21 3 
 
4 Circular lofy, U. S. Dept. of Agriculture. 
 
 through an additional sifter, so that when the process was complete 
 the materials would be entirely blended into a fine dust, such as would 
 easily go through a 2()()-mesh screen. 
 
 At present the process is similar, but on a much larger scale. 
 
 The use of this dust was so successful and so universally satisfac- 
 tory that the California Walnut Growers' Association, one of the 
 large cooperative farmers' organizations of California, decided to 
 manufacture it, not only for its own members but also for outsiders. 
 During the 1920 season 10 tons of 40 per cent nicotine sulphate were 
 used in making approximately 450 tons of the dust. During the 
 season when the walnut apliis was at its height the one plant turned 
 out almost 100 tons per week. As a result of the marked success of 
 this method of control, spraying for the walnut aphis has been en- 
 tirely superseded by dusting. 
 
 The dust is easily carried by the wind, and hence the best results 
 are obtained when little or no air is moving, and also when there is 
 a slight amount of moisture on the foliage. Many dusters make a 
 practice of beginning at daylight and continuing up to about 10 
 o'clock. Since an acre can be covered in about one-half hour, a com- 
 paratively large area may be gone over. It is often possible to con- 
 tinue later in the morning, so that if an early start is made an aver- 
 age of 15 to 20 acres per day can be dusted, which is in decided con- 
 trast to the 3 or 4 acres which it is possible to spray in the same length 
 of time. Several operators have tried dusting at night, but although 
 this practice was successful, it has not been followed to any extent. 
 
 TYPE OF MACHINE USED. 
 
 In the commonest type of duster the hopper holds 100 pounds of 
 dust. A mechanical and easily regulated device allows the desired 
 amount of dust to feed into the pipe under the hopper, through which 
 the air is blown from the large, rapidly revolving fan. From the 
 pipe the dust passes into a hose 4 inches in diameter and about 12 
 feet long. The operator moves about under the tree with this hose, 
 directing the blast of dust, until the tree is covered. Power to run the 
 fan is derived from a gasoline engine. The duster and engine can 
 be mounted on a small wagon or sled. Such an outfit retails at about 
 $375 complete, while a walnut sprayer would cost not less than $900. 
 The duster requires a driver and one operator, while the sprayer 
 takes two operators, and sometimes a driver. An extra sack or two 
 of dust can be carried with the outfit and other sacks placed at the 
 ends of the tree rows, so that refilling the hopper is a matter of only 
 a few minutes' time, while with the sprayer it is necessary to stop 
 work and go to the source of water to refill, which often may be 
 some distance. 
 
Nicotine Sulphate in a Dust Carrier. 5 
 
 ACTION OF THE DUST. 
 
 The action of this dust on insects and mites is similar to that of 
 the nicotine sulphate in liquid spray, except that it is very much more 
 rapid. Within a minute or two after the application of the dust, 
 aphids or other insects show extreme distress. They become agi- 
 tated, elevate their abdomens as if they were trying to stand on their 
 heads, and soon fall. \^lien one is standing under an infested walnut 
 tree just after it has been dusted the falling of aphids reminds one 
 of a gentle rain. On other plants the effect is as immediate, but not 
 quite so striking. 
 
 The after effect has been observed to be quite lasting also, especially 
 on young aphids. If any young are produced by an adult which was 
 not killed, or by a migrant several days after the application was 
 made, they will immediately be overcome by the dust. 
 
 USE AGAINST TRUCK-CROP INSECTS. 
 
 When nicotine sulphate applied as a dust became so strikingly suc- 
 cessful in controlling the walnut aphis, it was decided to test it 
 against some of the insects, particularly aphids, affecting truck and 
 associated crops. 
 
 THE MELON APHIS. 
 
 Tlie melon aphis {Aphis gossypii Glover) has been a serious enemy 
 of the melon, squash, cucumber, and some other crops in southern 
 California for a number of years, the damage varying from year to 
 year, and in different localities, from slight and scattered infesta- 
 tions of little consequence to severe infestations causing a total loss 
 of the crop. From the fact that the insect feeds almost entirely on 
 the lower surface of the leaves, causing many of the latter to curl, 
 it has been difficult to obtain a satisfactory control with liquid spray. 
 If sufficient time and care are taken to insure the covering of all the 
 leaves, particularly the undersides, the operation is too expensive, 
 and if extreme care is not taken the percentage of aphids killed is too 
 low to make the spraying worth while. 
 
 Tests of nicotine sulphate dust did not give very good results at 
 first, but when a mixture containing more nicotine sulphate was used, 
 the results improved accordingly. It was soon discovered that while 
 the walnut aphis was easy to kill with a 2 per cent strength, for 
 practically all other aphids a higher strength was required. When 
 extreme care was taken and a very thorough application made, the 
 weaker strength gave good results, but in commercial practice it 
 was found that a 5 to 7j per cent strength of 40 per cent nicotine 
 sulphate was \Qvy much better. 
 
6 Circular 15^, U. S. Dept. of Agriculture. 
 
 The most satisfactory type of machine for melons was found to be 
 a hand-operated bellows duster such as is shown in figure 1. With 
 such a machine one man can cover not less than 2 acres of full- 
 grown cassabas or muskmelons a day, using about 50 pounds of dust 
 per acre, costing 12 cents a pound for 5 per cent strength and 15 cents 
 for the 7 J per cent. 
 
 It is characteristic of the melon aphis in southern California that 
 it appears early in the season, when the plants are small, and seri- 
 ously infests scattered portions of the field. If left unchecked the 
 plants will be sufficiently damaged to produce little or no fruit, and 
 often the aphids will spread to all parts of the field. Such infesta- 
 
 FiG. 1. — Hand-opeiated bellows type of duster used in applying nicotine sulphate 
 dust to melons for the melon aphis. 
 
 tions are a nuisance to spray with an outfit of any size, while knap- 
 sack, or small compressed-air sprayers, are almost equally unsatis- 
 factory. With a duster of the type shown in figure 1, however, it is 
 a simple matter to go over the field as often as necessary, dusting tlie 
 infested plants and thus stopping the damage and checking the 
 spread. 
 
 Figure 2 shows a power-operated fan blower which was used in 
 a badly infested cassaba melon field. This machine killed a large per- 
 centage of the aphids, and covered almost an acre per hour, but 
 was somewhat wasteful of material, using from 75 to 100 pounds 
 per acre. It was apparent that this amount could be reduced with 
 
Nicotine Sulphate in a Dust Carrier. 7 
 
 some mechanical changes and by using a smaller exit pipe. This 
 machine would be advantageous for large acreages and where it is 
 desired to get over a field in a very short time. The outfit, with 
 engine, costs about $150, while the hand duster does not cost over $20. 
 Dusting for the aphis was found to be equally successful on all 
 kinds of melons, cassabas, cucumbers, etc. 
 
 THE CABBAGE APHIS. 
 
 The cabbage aphis (Aphis hrassiccw Ij.) often does serious damage 
 in California. The bulk of the cabbage crop is grown in the winter. 
 
 Pig. 2. — Power-operated fan duster used with success in a badly infested melon field. 
 
 and usually the aphids are kept in check by rains and cold weather. 
 For several years, however, the early winter rains have been lacking 
 and the temperature very mild, Avhich has resulted in a serious aphis 
 infestation of thousands of acres of cabbage and cauliflower. 
 
 Here, again, because of the fact that the colonies of aphids are 
 usually on the undersides of the leaves, or are protected by the com- 
 pact foliage of the growing head, it is difficult to get a satisfactory 
 killing by spraying. The difficulty is further accentuated by the 
 fact that the aphis colonies cause the leaves to curl, making it almost 
 impossible to reach them with a spraj^ When the dust was tried in a 
 badly infested cabbage field, a high percentage of the aphids was 
 killed. The cloud of dust hovering over and about the plant pene- 
 
8 Circular 15^, U. S. Dept. of Agriculture. 
 
 trated to all parts, and in most cases e\eii re:iched the aphids in the 
 curled leaves. (Fig. 3.) 
 
 A preliminary experiment to determine the effectiveness of the 
 different strengths of nicotine sulphate in the dust gave the following 
 results (Table 1). A careful estimate of the aphids on a number of 
 different plants Avas made both before nnd after dusting, and the 
 percentage of killing taken from that. 
 
 Tahi.k 1. — Effc(tircnG>fs of different strenytlis of nirofiiir sulithaie in dunt 
 against the cahhafir niiUin. 
 
 Strength of 40 per cent nicotine sulphate, by 
 
 weight per cent__ 2 4 6 8 10 ' 10 
 
 Percentage of apliii Is killed <S2. S 92.4 96.7 97 9S. .S 91.8 
 
 ^' 
 
 
 '^^i^-Mm&mm^ "^ '^ 
 
 
 
 -• • - ■ ■ ■ n, 
 
 
 I'll.. :;. — Duf-tinj; liir tlir t',ililia.i,'c npliis. Note cloud ol' diisl lidsi'iiiii; about aud coiu- 
 plotely fovoiing all parts of infested plants. 
 
 P\irther experiments confirmed the above, indicating that the per- 
 centage of killing rose considerably from 2 to 6 per cent strength, 
 but above that the rise was small and did not justify the additional 
 expense of the extra nicotine sulphate. It was also determined that 
 for ordinary commercial purposes the 5 per cent strength was the 
 most satisfactory, considering both the killing obtained and the cost 
 per pound. 
 
 A badly infested cabbage field in Orange County was dusted by 
 hand machines such as that shown in figure 3. Mexican laborers were 
 employed, one man covering an average of 2 acres a day, using 30 
 
 'This dust was atxiut '.i monllis old. and. lla^■ini; Iweii ki'pl in a ic\inn.v sack. Intd lost 
 some of its .stienfrtli. 
 
Nicotine Sulphate in a Dust Carrier. 9 
 
 pounds of dust per acre, on cabbage less than half grown, while on 
 cabbage more than half grown one man averaged If acres a day, 
 using 50 pounds of dust per acre. (See Table 2.) The cost of the 
 dusting with 7^ per cent strength of dust was as follows : 
 
 Table 2. — Cost of (histing cabbage for the cabbage aphis. 
 
 On cabbage less than half grown: 
 
 Dust, 30 pounds, at 15 cents $4. 50 
 
 Mexican labor, * day at $3.25 1.65 
 
 Total cost per acre 6. 15 
 
 On cabbage over half grown : 
 
 Dust, 50 pounds at 15 cents 7.50 
 
 Labor, IJ acres per day ! 1. 85 
 
 Total cost per acre 9. 35 
 
 About the same time a field of badly infested cabbage was sprayed 
 with 40 per cent nicotine sulphate and soap by a commercial sprayer. 
 The work was done with a power outfit, two men following behind 
 with short spray rods attached to 25-foot lines of hose. With this 
 outfit it was possible to cover only 3 or 4 acres per day, at an average 
 cost of $12 per acre, including rent of machine and team. The per- 
 centage of aphids killed was low, averaging not over 70 per cent for 
 the entire field. On the other hand, an average killing of 90 per cent 
 or over is easily obtained with the dust when carefully applied. 
 
 THE ONION THRTPS. 
 
 Extensive plantings of onions in the Coachella Valley have often 
 been severely damaged by the onion thrips {Thrips tahaci Lind.). 
 
 Control by spraying with a nicotine sulphate and soap solution 
 has been successful from a standpoint of killing efficiency, but the 
 practice was unsatisfactory for the following reason : 
 
 Bulb onions are planted in rows 12 to 14 inches apart, and irri- 
 gating flumes cross the fields about every 660 feet, with the onion 
 rows reaching up to the flumes. On account of the closeness of the 
 rows and the irrigating flumes across the fields, the operation of 
 horse-drawn spray machines causes considerable damage to the 
 onions. As it is impossible to drive across the flumes, the frequent 
 turning around damages many onions. Practically all cultural work 
 is done with burros or ponies, having small feet, but a spray machine 
 of any size would require large horses, which would cause further 
 damage to the bulbs. 
 
 A trial of the nicotine sulphate dust on the onion thrips killed from 
 87 to 97 per cent. A trial on a commercial scale, using the hand- 
 
10 Circular ITA, U. S. Dept. of Agriculture. 
 
 operated bellows duster (fig. 4) showed that one man could cover 
 from 2i to 3 acres a day, using from 40 to 50 pounds per acre, which 
 made a total cost, including labor at $3.50 per da^J^, of from $6 to $7 
 per acre. . 
 
 A field of seed onions near by, of similar size but planted in 24-inch 
 rows, was sprayed with a traction sprayer, which had a stationary 
 boom covering five rows at a time. With this outfit it was possible 
 to cover up to 6 acres a day, although this depended on the dis- 
 tance it was necessary to go for water to refill the tank. An average 
 of 150 gallons of spray per acre was used (with a weight of 1,200 
 pounds) . The total average cost per acre, including hire of team and 
 
 Fig. 4 — Du«tiug ouious with banU-yperated bellows duster. 
 
 two men, was $4.40, and this amount would be approximately doubled 
 for the bulb onions, grown in the 12 to 14 inch rows. 
 
 A small power-operated duster that could be used in an infested 
 onion field has an arrangement of pipes from the blower so that eight 
 rows can be covered at a time, with one pipe discharging directly over 
 each row. With this outfit from 10 to 12 acres could be covered a 
 day using 50 to T5 pounds of dust per acre, at an average cost of from 
 $8 to $9.50 per acre, including material and hire of pony and one man. 
 Here again it was evident that with some mechanical adjustments, so 
 that less dust could be fed into the pipes, and with the speed of the 
 fan increased, the amount of dust used per acre could be lowered, and 
 the cost reduced accordingly. 
 
Nicotine Sulphate in a Dust Carrier. 
 
 11 
 
 While the cost per acre with this outfit is hi<2:her than with the hand 
 machines, on account of the larger amount of dust used per acre, the 
 chief advantage of the power-operated machine is the large acreage 
 covered. This would be of importance in sudden or severe outbreaks, 
 or on very large plantings. This machine, however, is subject to the 
 same objection as the horse-drawn sprayer, only to a less degree, as it 
 is smaller, much lighter, and can be drawn bj^ a pony or burro. 
 
 THE PEA APHiy. 
 
 The pea aphis {Macroslphum pisi Kalt.) is present throughout 
 California and during some years causes large losses. In fact, in 
 
 Fig. 5. — Iland-oppratert fan duster used against the pea aphis. 
 
 several localities the growing of peas commercially has been largely' 
 abandoned because of this pest. This is particularly true of sweet 
 peas grown for seed. 
 
 Experiments with the pea aphis have been less extensive than 
 with the other insects mentioned, but it has been conclusively proved 
 that this pest is much more resistant to the action of nicotine dust 
 than any other aphid upon which it has been tested. The low per- 
 centages failed absolutely to kill the aphids, but good results were 
 obtained with a 10 per cent strength when carefully applied. Sev- 
 eral large seed companies have used this strength of dust for two 
 seasons, and are much better satisfied with these results than with 
 previous control work with liquid sprays. Both hand dusters (fig. 5) 
 
12 Circular 13^, U. S. Dept. of Agriculture. 
 
 and large power-operated machines, Avliich cover eight rows at a 
 time, are used. The hitter use as high as 100 pounds of dust per acre, 
 but can cover the ground very rapidly, averaging 3 or 4 acres 
 an hour. 
 
 All of the work mentioned in this paper, except the following on 
 the pea aphis, was done with dust varying from a week to several 
 months old and which had not been kept in tight containers. As 
 will be explained later, dust which has stood for some time after 
 manufacture loses materially in toxicity, particularly if the containers 
 are not tight. It was therefore decided to test on the pea aphis some 
 freshly made material Avhich had been immediately put in tight 
 cans, applied with a bellows duster to a rather badly infested field 
 of peas about a foot high. The results are given in Table ^^ : 
 
 Table 3. — Com txt rat ire cffectireitcss of different streiif/ths of freshly made nico- 
 tine HUlphdte dust on the pea apliix at La Hahra, Calif.. Oct. 2<S, 1920. 
 
 Strength of nicotine sulpliate 40 per cent by weiglit (pei- 
 
 cent) 2 3 4 6 
 
 Percentage of aphid.s killed 60.2 70.2 90.9 98.2 
 
 The foregoing experiment showed that the '2 and 3 per cent 
 strengths were effective against the young aphids, but quite in- 
 effective against the adults, unless the latter were literally coated 
 with dust. The application was very liberal, so that, with the 
 present - cost of the 6 per cent dust at 20 cents a pound, it would be 
 impractical to use it except on sweet peas. Later experiments may 
 determine that a smaller amount of dust, or a slightly lower strength, 
 will be satisfactory ; but it seems at present that this is the one aphid 
 which requires too great a strength of nicotine sulphate to make 
 dusting as practical a remedy as spraying. 
 
 ni^Ol^MBEK BEETLES. 
 
 Two pests of considerable importance are the western 12-spotted 
 cucumber beetle {Diahi^otlca soror Lee.) and the western strii>ed cu- 
 cumber beetle {D. trivitatta Mannh.). The former injures a large 
 number of plants, while the latter feeds cliiefly on squash, cucumber, 
 and other cucurbits. Wliile Avorking with nicotine sulphate dust on 
 the melon aphis, it was observed that the dust was very toxic to the 
 occasional specimens of Diabrotica feeding on the melons, and plans 
 were made for further experiments against them. A field of young 
 cucumber was later examined and found to be badly damaged by 
 cucumber beetles. Both D. soror and D. trivitatta were present, but 
 the latter was more numerous. Some hills showed little damage, but 
 in the majority the foliage was badly eaten and sometimes all the 
 
 => (3ctol)er, 1920. 
 
Nicotine Sulphate in a Dust Carrier. 13 
 
 plants in a hill were killed outright. From two to upward of a dozen 
 beetles were found in practically every hill. Applications of dust 
 were made, using the hand-operated bellows duster. The feed was 
 fairly liberal, so that one puff of dust would be sufficient to cover a 
 hill. The effect was immediate. When struck with the dust many 
 of the beetles were unable to fly away, but crawled about on the 
 ground under the plants in very apparent distress, and in a few 
 minutes succumbed. Some which were able to fly away, on being 
 followed, were found to go only a short distance, and in a very short 
 time were overcome. Several days later the field was examined 
 again and a careful examination revealed only two living adults in 
 the entire field. New leaves had been put out by the injured plants 
 and their recovery from attack was apparent. 
 
 The material used was a 10 per cent strength of nicotine sulphate, 
 40 per cent in kaolin and lime. A 20 per cent strength was found not 
 to be superior to the weaker material. One pound of dust covered 
 from 200 to 300 hills of small plants, at the rate of nearly 1,000 hills 
 per hour. 
 
 COMBINATIONS WITH NICOTINE SULPHATE DUST. 
 
 It has long been the custom in spraying operations to combine tAvo 
 or more insecticides, or an insecticide and a fungicide, when dif- 
 ferent types of insects or a disease and an insect are infesting the 
 one plant. This practice can be continued to a large extent with 
 dusting. In fact, some combinations are more satisfactory in the 
 dust form, while others are less so. 
 
 In several sections of California the codling moth has become a 
 serious pest of walnuts. It happens that in these same localities, 
 to a large extent, the walnut aphis is present also. Therefore when 
 the nicotine sulphate dust was made, to each 100 pounds was added 
 10 pounds of arsenate of lead. At first the acid form was used, 
 but as this caused burning of the foliage the basic or neutral form 
 of lead arsenate was substituted. 
 
 At first the dusting was not as satisfactory in controlling the 
 codling moth as was desirable. The operation of dusting for the 
 aphis could be done quickly and easily, but for the codling moth 
 the dust had to be more carefully applied. Although the actual 
 percentage of worms killed was a little less with dusting than with 
 spraying, dusting is greatly preferred because of the much greater 
 speed and ease of application, as well as the lesser cost. 
 
 On cucumbers the nicotine sulphate dust not only controlled the 
 cucumber beetles but also killed any melon aphids present. Further- 
 more, with the use of a dust carrier containing from 25 to 40 per 
 cent of powdered sulphur, the development of cucumber mildew can 
 be prevented. 
 
14 Circular 15^, U. S. Dept. of Agriculture. 
 
 The use of the nicotine sulphate-sulphur dust on peas will control 
 both the pea aphis and powdery mildew, and would be equally satis- 
 factory for the rose aphis and rose mildew. 
 
 The same combination has proved successful on citrus trees against 
 the citrus aphis and the red spider. If anj'' thrips are present, they 
 AA'ill be controlled by the same dusting. 
 
 On cabbage the nicotine sulphate dust has given good success in 
 killing both the aphis and the cabbage worms, but if it is desired, 
 the combination of nicotine sulphate and arsenate of lead can be used. 
 
 Such insects as aphids, thrips, and red spidei^ and other mites re- 
 produce very rapidly. Therefore no matter what method of control 
 is used, whether it be dusting or spraying, under conditions favorable 
 to the insects, a reinfestation may take place even though a high per- 
 centage may have been killed. On account of this it is not to be ex-- 
 pected that at all times one dusting will be sufficient for an entire 
 season. It is often necessary to dust twice or even three times. In 
 fact, many growers plan on a second application, timing it to get the 
 second infestation before it begins to be serious. 
 
 All dusting and spraying should be done with the idea of pre- 
 venting a serious infestation and the resulting damage, rather than 
 waiting until the infestation is heavy before control measures are 
 undertaken. It is always easier and more satisfactory to prevent an 
 infestation than to stop it after it is well under way. 
 
 LOSS OF STRENGTH. 
 
 Since the nicotine in this dust is very volatile, some of the strength 
 is apt to be lost if the dust is held for very long in open containers. 
 The walnut aphis dust is put up in burlap sacks with paper liners; 
 but as this dust is practically all used within a short time after it is 
 made, there is little or no loss of strength. To retain the strength, 
 it is now proposed to put up the dust in air-tight drums, cans, and 
 sealed cartons. It is believed and partly borne out by experiments 
 that if these tight containers are used a 8 or 4 per cent strength will 
 do as efficient work as has been done heretofore with the 5 to 7i 
 per cent strengths put up in sacks, and a 5 or 6 per cent material 
 can be substituted for the 8 to 10 per cent strengths. This will 
 reduce the cost from 3 to 5 cents a pound. 
 
 Nicotine sulphate dust, even up to the 20 per cent strength, has 
 not been observed to cause any burning to foliage. 
 
 For walnut trees the lightest dust possible was found to be desir- 
 able; hence the carrier is mostly kaolin. For low-growing crops, 
 such as cabbage and melons, a heavier dust is more desirable ; hence 
 the carrier was composed of about half kaolin and half lime from 
 sujrar-beet factories. 
 
Nicotine Sulphate in a Dust Carrier. 15 
 
 ADVANTAGES OF DUST. 
 
 Dust can be applied much more easily and quickly than spray; 
 hence larger acreages can be covered in a given time. 
 
 Its killing efficiency is always equal to and usually more than that 
 of spraying. 
 
 It is easier of application. 
 
 Its cost of application is less than that of spraying. 
 
 Power dusters cost much less than power sprayers. 
 
 Hand dusters are much easier to operate and to carry than hand 
 sprayers. 
 
 Very much less weight of dust than of spray is required to cover 
 an acre. 
 
 Refilling the duster is much quicker and easier than refilling the 
 sprayer. 
 
 It can be combined Avith arsenate of lead or sulphur and applied 
 dry for insects and certain fungous diseases. 
 
 DISADVANTAGES OF DUST. 
 
 Its volatility causes it to lose strength unless put up in tight cans 
 or used soon after manufacture. 
 
 The dust is sometimes disagreeable to the operator, especially if 
 the latter is inexperienced. 
 
 It can not be combined with Bordeaux mixture, except Avlien the 
 latter is dry. 
 
 SUMMARY. 
 
 Ground tobacco gave good though varied results in controlling the 
 walnut aphis in California. The substitution of a certain amount of 
 40 per cent nicotine sulphate in a carrier of kaolin and lime elimi- 
 nated this variation in results. 
 
 Dusting requires much less material and may be done in a much 
 shorter time, with a less expensive machine, and at about half the 
 cost of spraying. 
 
 The action of the dust is similar to that of nicotine sulphate spray, 
 but much more rapid. 
 
 Xicotine sulphate dust has proved superior to spraying for the 
 melon and cabbage aphids, onion thrips, cucumber beetles, and some 
 other insects, giving usually a better killing at a smaller cost and 
 with a greater speed and ease of application. 
 
 Nicotine sulphate dust can be combined with arsenate of lead or 
 sulphur for different types of insects, or for insects and fungous 
 diseases. 
 
 ADDITIONAL COPIES 
 
 OF THIS PUBLICATION MAY BE PROCURED FROM 
 
 THE SUPERINTENDENT OF DOCUMENTS 
 
 GOVERNMENT PRINTrNTG OFFICE 
 
 •WASHINGTON, D. C. 
 
 AT 
 
 5 CENTS PER COPY 
 
 V 
 

 LIBRARY 
 
 |1 III HI ||1 
 
 OF CONGRESS 
 
 1 II 11 1 ||i 1 IliiH ll|| lllj 
 
 
 
 Q\ 
 
 £7lC7l£7| 
 
 ftPCTI ^7^ 
 
 R 
 
 *. 
 
^^ \^ 
 
LIBRARY OF CONGRESS 
 
 DDDDfl'^D373t. 
 
 Hollinger Corp. 
 pH8.5