BACTERIAL WILT OF CUCURBITS. 43 



effect on the rate of wilting. The principal essentials to maximum 

 damage in cucumbers from wilt disease in the Northern and Middle 

 States consist in maximum numbers of wilt-carrying cucumber beetles 

 together with succulent, rapidly growing vines. Given these condi- 

 tions, the injury will be severe with either wet or dry weather and 

 within a considerable range of temperature. 



Where the disease is likely to be severe, spraying with strong Bor- 

 deaux mixture and lead arsenate powder (4-5-50-2) is recommended. 

 Treatments should begin as soon as the cucumber plants develop their 

 first true leaves and should continue at intervals of about a week 

 until the cucumber beetles practically disappear from the field. In 

 localities where downy mildew is also prevalent the treatments 

 should be continued later as a partial insurance against this disease. 

 The beetles prefer unsprayed plants as food, and undoubtedly the 

 efficiency of wilt control would be enhanced if a slightly earlier trap 

 crop, such as squash, were planted along the edges of the cucumber 

 field. The beetles could be poisoned there with a strong insecticide. 1 



The pulling of wilted vines during the first part of the season, or as 

 long as it can be done without mechanically injuring the healthy 

 plants, will greatly assist in controlling bacterial wilt if consistently 

 done in all neighboring fields. The diseased vines should be buried 

 or otherwise removed from access by the beetles. 



Where a few plants only are grown in garden plats, screening the 

 hills with fine mosquito netting will prevent the appearance of the 

 disease. On a large scale this method of control obviously would be 

 impractical. 



For control in greenhouses the beetles should be kept out in the 

 first place if possible. Do not grow cucurbits nor pile cucurbit refuse 

 in the immediate vicinity of greenhouses, as this attracts the beetles 

 and many will later find their way into the houses. If the beetles 

 once gain entrance to a house filled with growing plants hand picking 

 is the only remedy to be recommended until some fumigant is found 

 that will kill the beetles without injuring the cucumber plants. 

 Besides destroying the cucumber beetles, great care must be exer- 

 cised in disinfecting all instruments used in pruning wilted vines 

 before using them again on healthy plants. This may easily be 

 done with a bottle of 1 to 1,000 mercuric chlorid and a sponge. In 

 some cases it may be advantageous to keep the beetles out by 

 screening doors, ventilators, and other openings into the greenhouse. 

 For this purpose a netting with 18 meshes to the inch will be necessary. 



1 Directions for the control of the striped cucumber beetle are given in Farmers' Bulletin 1038. (Chit- 

 tenden, F. H. The striped cucumber beetle and its control. U. S. Dept. Agr. Farmers' Bui. 103S, 20 p., 

 15 figs. 1919.) This publication may be obtained free on application to the Secretary of Agriculture, 

 Washington, D. C. The most approved methods as given include covering young plants, planting an 

 excess of seed, clean culture, the use of trap plants, spraying with arsenate of lead and other arsenicals 

 with or without Bordeaux mixture or the dry dusts, stimulation of growth, keeping the plants in good 

 condition, and cooperation with neighboring grgwerS of cucurbits in the use of control methods. 



