Vegetable Plant Lice 21 



Summary of Measures of Control 



1. The weather, affecting the lice directly through freezing and 

 indirectly through limiting the work' of natural enemies, determines 

 largely whether there shall or shall not be a vegetable plant louse 

 outbreak. 



2. Because of the fact that the plant lice winter upon plants oth- 

 er than vegetables or upon the useless remains of vegetable crops, 

 clean culture — keeping down weeds and destroying the useless rem- 

 nants of vegetable crops — is an important measure of control, pro- 

 vided that its general adoption can be secured. 



3. Because of the inconspicuous nature of the work of vegeta- 

 ble plant lice — the effects of their work not appearing until the dam 

 age has largely been completed — it is highly important that the be- 

 ginning of the infestation be detected by the growers. 



4. Under garden or field conditions promptly apply a mixture of 

 40 per cent, nicotine (1 part), water (500 parts), and soap (2 lbs. if 

 water is soft or 4 to 5 lbs. if water is hard, to 50 gallons) as soon as 

 infestation appears. 



5. For garden crops use a knapsack or compressed-air sprayer 

 equipped with extension rod specified on page 18 and illustrated in fig- 

 ure 14. For field crops use a modified engine-driven potato sprayer, 

 maintaining a pressure of 250 pounds to the square inch and deliver- 

 ing at least 100 gallons per acre. When plants stand upright the modi- 

 fication is merely a matter of adjusting the nozzles in such a way that 

 the plant is completely covered and the lice well wetted. When plants 

 have a pronounced drooping leaf habit, as in turnips, attach a lifting 

 device to the sprayer. 



6. For cold-frame or greenhouse vegetable crops the lice may be 

 destroyed by use of tobacco smoke of strength corresponding to the 

 tightness or looseness of the enclosure. In a few of the vegetable 

 crops grown in greenhouses, such as cucumbers and tomatoes, hy- 

 drocyanic gas is successfully employed. 



7. In cantaloupes, when the infestation appears suddenly after 

 the vines are well grown, apply the nicotine, soap and water mixture 

 with a good orchard sprayer after the vines have been turned over in 

 such a way as to expose the plants. Use a good orchard sprayer 

 when the infestation appears early. 



