280 



The problem is to produce varieties that will flower so early that the 

 beetle, when it appears, will find no opening for attack. To do this 

 it is necessary to ascertain the temperature requirements of both plant 

 and beetle, but it is very doubtful whether it is possible to produce 

 plants requiring the little warmth that s'.iffices to cause Meligeihes 

 aeneus to begin feeding preliminary to mating. 



It may be possible to advance flowering by 10-14 days, but this is 

 of no value at all, early flowering being a character of quite secondary 

 importance. Rapidity of blossoming is the important point ; the 

 time between the appearance of the bud and the opening of the 

 blossom must be shortened. Even so, success is doubtful because 

 the beetle neglects the open blossom for the bud as long as possible. 

 This habit is chiefly due to weather conditions. 



The flowering dates of the common German rape crops are examined, 

 and it is concluded that there appears to be little hope of shortening 

 the bud period. It was found that by ante-dating sowing by 14 days 

 the injury was less marked at first, but that at the end of the vegetative 

 period no advantage at all was gained. 



Weather is the most important factor in infestation. Warmth 

 and sunshine promote the growth of the plant and discourage attack, 

 the beetle appearing less ready to seek the shelter of the bud. 

 A high ground temperature also favours the plant. Examination 

 of the losses in 1920 shows that April is the danger month, and 

 plant-breeding experiments must take this into account. 



Remedial measures hitherto employed are mostly of a mechanical 

 nature, and have given no result. They may be of some use in small 

 fields, but are not so in cultivation on a large scale, such as is generally 

 practised in Germany. If the average annual loss exceeds 50 per cent, 

 it is necessary to stop growing crops of winter rape. Such areas can 

 only be determined by experiments over a number of years. A change 

 in crop rotation is the only radical measure, or perhaps a summer rape 

 crop may be grown. If the loss does not exceed 25 per cent., 

 combative measures may be taken provided that their cost is found 

 not to be excessive. 



P.\LM (B. T.) & MjoBERG (E.). Bestrijding van Rupsenvraat in 

 Deli-Tabak. III. Wenken voor Bespuiting met Loodarsenaat- 

 Zeepemulsie. [Measures against Caterpillar Injury to Tobacco 

 in Deli. III. Advice on Spraying with an Emulsion of Lead 

 Arsenate and Soap.] — Deli Procfstation, Medan, Vlugschrift no. 7, 

 February 1921, 3 pp. 



The emulsion of lead arsenate and soap applied as advised by the 

 Deli Experiment Station, Sumatra [R.A.E., A, ix, 225], has given 

 good results except in a few cases when scorching occurred, .partly 

 owing to lack of uniformity in the quality of the lead arsenate. 



It is well to delay spraying as long as possible. Under normal 

 conditions the seedlings should be 25-28 days old. If Phytophthora 

 appears, this fungus should be treated with Bordeaux mixture alone, 

 the lead arsenate not being applied until the first signs of caterpillar 

 injury are seen, when the emulsion must be used, either alternately 

 or mixed with Bordeaux. Spra^'ing with lead arsenate must not be 

 repeated at shorter intervals than five days. If screens are used 

 on the beds, they must be entirely removed during spraying and 

 replaced immediately afterwards, as the newly-sprayed plants must 

 not be exposed to full sunshine. The lead arsenate must be dissolved 



