102 MISC. PUBLICATION 62 6, U. S. DEPT. OF AGRICULTURE 



Wettable Sulfur 



Wettable sulfurs, consisting of finely 

 ground sulfur mixed with a suitable 

 wetting agent, are available on the 

 market. These materials mix readily 

 with water and should be used as 

 directed by the manufacturer. Sulfur 

 may also be prepared as a spray by 

 mixing 1% level tablespoonfuls of sulfm 

 dust in 1 quart of water, or, for larger 

 quantities, 1 ounce to 1 gallon. Since 

 sulfur does not mix easily with water, 

 it is best to stir the water slowly and 

 thoroughly into the dry sulfur. 



Lime-Sulfur Concentrates 



Commercial lime-sulfur concentrates 

 (liquid) are very effective against some 

 of the armored scale insects, such as the 

 San Jose scale and the pine needle scale, 

 and mites, when applied as dormant 

 sprays. The concentrates should have 

 a density of about 33° on the Baume 

 scale. For dormant or winter sprays 

 use 1 pint of the concentrate to 1 gallon 

 of water. For summer spraying liquid 

 lime-sulfur is usally diluted at the rate of 

 2Y-1 ounces (5 tablespoonfuls) to 1 gallon 

 of water. Since the concentrate may 

 vary, it is advisable to follow the manu- 

 facturer's directions. 



Concentrated liquid lime-sulfur (32° 

 Baume) with a spreader added may be 

 used to control the red spider mite on 

 various plants, and also against exposed 

 cyclamen mites on chrysanthemum and 

 snapdragon. The following proportions 

 are used: 



Small Large 



quantities quantities 



Lime-sulfur (1-100) _-. 2 teaspoonfuls 1 quart. 



or 9.5 ml. 



Wetter and spreader 54 teaspoonful 0.8 pint or 

 (1-1,000). or 4 ml. \\h. cupfuls. 



Water 1 gallon. 100 gallons. 



Do not apply this spray during the heat of the day 

 or in strong sunlight as injury may result from the 

 hot sun rays. This spray does not stain the foliage 

 as does lime-sulfur solution without a spreader. 



Caution. — Lime-sulfur will dis- 

 color paint, brick, or cement work; 

 therefore, either avoid using it on 

 shrubbery against buildings or protect 

 the walls with canvas or other material 

 while spraying. Do not use oil sprays 

 on plants which have recently been 

 treated with sulfur-containing insecti- 

 cides. In extremely hot weather sulfur 

 should be used with care, since it may 

 burn tender growth. 



When using sulfur, especially as a 

 dust, care should be taken to avoid 

 getting it into the eyes. If the eyes are 

 affected, do not rub them. It is well to 

 wear goggles and a respirator. 



Mercuric Chloride 



Mercuric chloride, or bichloride of 

 mercury, is known commercially as cor- 

 rosive sublimate. It acts as a contact 

 insecticide against such soil-inhabiting 

 pests as the larvae of fungus gnats, cer- 

 tain root maggots, earthworms, slugs, 

 and snails. This material is used by 

 drenching the infested soil with a solu- 

 tion containing 1 part to 1,000 parts of 

 water. Where only a few plants or 

 small areas are to be treated, dissolve 1 

 level teaspoonful in 10 quarts of water, 

 or 2 tablets (each containing 7.5 grains) 

 in 1 quart of water. These tablets are 

 obtainable at drug stores. For larger 

 quantities use 1 ounce of the powder to 

 7 l A gallons of water. Since mercuric 

 chloride dissolves slowly, it is advis- 

 able first to dissolve it in a small quan- 

 tity of hot water and then dilute it to 

 the correct quantity with cold water. 

 When it is used as a soil drench, care 

 should be taken that none of the solu- 

 tion gets on the foliage. A solution 

 of the same strength is used to control 

 the gladiolus thrips on the dormant corms 

 (p. 45). 



Caution. — Since mercuric chloride is 

 a deadly poison, great care must be 

 taken to keep it, or any seed, corms, or 

 tubers treated in it, out of reach of 

 children and domestic animals. It 

 must be handled carefully, since it will 

 seriously burn the skin when undiluted. 

 Persons who are susceptible to mer- 

 cury poisoning should wear rubber 

 gloves when handling this poison. 

 Mercuric chloride attacks metals; there- 

 fore only wooden, glass, or earthenware 

 vessels should be employed in preparing 

 and handling the solution. These ves- 

 sels should be thoroughly cleaned im- 

 mediately after use. 



Orsanic Mercurials 



In the last few years several organic 

 mercurial compounds have become 

 available under various proprietary 

 names. Their chief use is for disin- 

 fecting seeds and soil, but some of them 

 are also used to control certain insects. 

 Semesan, for example, may be used to 

 control the gladiolus thrips on the corms. 

 The recommendations of the manufac- 

 turer should be followed. 



Caution. — See Caution under "Mer- 

 curic Chloride." 



Thiocyanate Sprays 



Certain synthetic organic compounds 

 known as thiocyanates have recently 

 been developed for use as horticultural 



