GREENHOUSE RED SPIDER. 173 



portant when plants are started very early in the season, while the second 

 is of importance only after the warm days of spring have started these 

 outside weeds. 



Fumigation of Greenhouses and Equipynent with Sulfur Fumes. 



Immediate!}^ before setting the cucumber plants in a house, and before 

 fumigation is begun, all boards which are to be used either between the 

 cucumber rows or to make "A" trellises should be taken inside the green- 

 house. Do not lay the boards on the ground, but stand them against the 

 steam pipes or in some similar manner to allow the poisonous gas free 

 access to all parts. Other equipment which has been in any way con- 

 nected with a previous infestation and is to be used during the cucumber 

 season should also be placed in the house for fumigation. Do not intro- 

 duce living plants until after a thorough fumigation and a subsequent 

 airing of the houses, as sulfur fumes are deadly to plant life. 



In fumigating, each house should be tightly closed and sulfur used at 

 the rate of one-third of a pound to every 1,000 cubic feet of space. (In- 

 crease to one-half pound in case of houses that are not fairly tight.) 



Directions for Fumigation. — "Weigh the required amount of sulfur and 

 di\ade it into four equal parts upon pieces of paper. This is about the 

 right number for a 150-foot house. Metal pans with plenty of breadth 

 are perhaps the best containers for the fumigating operation. First 

 cover the bottom of each pan with chips that have been soaked in kerosene, 

 and distribute these containers at various points through the house, 

 placing beside each the sulfur to be used. When all is in readiness set 

 fire to the chips, and when these are burning well drop in the sulfur. Be 

 certain that the sulfur has ignited and then withdraw from the house. 

 Allow the sulfur fumes to act for at least twelve hours before opening the 

 house. This fumigation may be done during the day or at night, accord- 

 ing to the convenience of the grower, and if the method is followed out 

 careful!)^ the red spiders wall be completely exterminated within the 

 house. 



Special attention should be paid to the house in which potted cucumbers 

 are to be grown, and fumigation should be very thorough, for in many 

 cases the seat of infestation occurs here. At the conclusion of the cu- 

 cumber crop in the late summer the whole house should be fumigated with 

 sulfur before the plants have died, thus preventing the borders from 

 becoming infested from throw^n-out cucumber plants, and reducing the 

 number of red spiders which would otherwise winter over and attack the 

 next cucumber crop. 



Destroying Outside Sources of Infestation. 

 The next problem which confronts the grower is to eliminate the possi- 

 bility of infesting the houses from outside sources. Investigation has 

 shown that many weeds and grasses, often found around greenhouses, 

 serve as breeding places for these pests, and undoubtedly are the source 



