THE COLEOPTERA 119 



often destroying plants, this adds to the importance of the insect as a 

 pest. 



On the Pacific Coast is a slightly larger species known as the Western 

 Striped Cucumber beetle (Diabrotica trivittata Mannerh.) which has much 

 the same habits as the eastern form. In the more southerly portion of 

 this region the adults are more or less active during the cold months. 

 There appear to be at least two generations a year, and the methods given 

 below for the control of the eastern species also apply for this one. 



Control. This is a difficult insect to control, particularly where large 

 areas are planted to any of the cucurbits and small garden methods will 

 not pay. Protective methods, practicable in gardens, enable the plants 

 to get well started, after which they are able to grow and produce the crop 

 to quite an extent, despite the insect. Screening the plants before they 

 come up, using fine-mesh wire or thin cheese-cloth stretched over a 

 frame, works well for this purpose, provided the edge of the frame fits 

 tightly into the earth everywhere, so that the beetles cannot burrow un- 

 der it. Sometimes an excess of seed is planted with the idea of giving 

 the insects enough food so that few or none of the plants will be too thickly 

 infested to be able to live, and the poorest ones can be thinned out later. 

 Gathering all but a few of the plants as soon as the crop has been har- 

 vested, and burning them will leave the others for the beetles to gather 

 on. These can then be sprayed with a strong stomach poison or a strong 

 contact insecticide. Early cucurbits such as gourds, can be planted near 

 later cucumbers and will act as trap plants, attracting the beetles. 



Spraying with a stomach poison, either alone or with Bordeaux 

 mixture, is a good treatment if both sides of the leaves and the stems are 

 well covered. Arsenate of lead 6 Ib. of paste in 50 gal. of water seems 

 generally to give the best results. The addition of 3 Ib. of soap to each 50 

 gal. of spray makes the latter adhere better to the plant. Arsenate of 

 lime gives fair results. Dusting the plants with the dry poison mixed 

 with air-slaked lime or plaster, at the rate of 1 Ib. of the poison to any- 

 where from 25 to 50 Ib. of the inert material, sometimes works well. 

 Its weakness as a treatment is mainly that it is difficult to get it onto the 

 under side of the leaves and have it stay there. 



Whatever spray material is used, give the first treatment as soon as 

 the plants show above ground and repeat two or three times at about 

 weekly intervals, or oftener if rain makes it necessary. 



Several other minor remedies such as dusting the plants while the 

 ground is moist, with tobacco dust, lime, or a mixture of the two; and 

 hastening the growth and increasing the vigor of the plants by fertilizers 

 and frequent cultivation, have some merit. If any or all the above-sug- 

 gested treatments have been used, however, some of the insects will 

 generally be present, none of these methods giving absolute freedom from 

 the pest. 



