541 



Other currant pests inoluded : RhopalosipJmm lactucae, Kalt., and 

 Myzus ribis, L. Raspberries were injured by Byturus tomentosus F., 

 Haltica rubi, Payk., and Lasioptera rubi, Heeg. ; and strawberries by 

 Jidus londinensis, Otiorrhynchus sulcalus, F„ Dolycoris baccarum,L., and 

 Tarsonemus fragariae, Zimm. 



RosTRUP (Sofie). Jordlopperna. [Flea-Beetles.] — Vort Landbrug, 

 Copenhagen, xxxviii, no. 17, 1919. 



On account of tbe serious devastation caused by flea-beetles in 

 Denmark an investigation was made by sending inquiries to farmers 

 in July 1918, and the following is a condensed report of the answers 

 received with regard to the circumstances under which the outbreaks 

 took place. The attacks occurred all over the islands and in the eastern 

 and northern part of Jylland, the middle and western part escaping. 

 The injury was most severe on the islands, especially on Sjaelland, 

 where 50% of the fields mentioned in the reports were completely 

 devastated, whereas on Jylland the corresponding nimiber was only 

 sixteen. All cruciferous plants were attacked, and resowing had to be 

 resorted to over a large area. The attack often originated in fields 

 with cruciferous weeds. In about 40% of the fields the attack started 

 during the germination period, in the rest after the plants had appeared 

 above the ground. The degree of injury decreised with the nature of 

 the soil in the following order : — clay, heavy loam, sandy loam and 

 sand. In Jylland ploughing took place to the same extent both in 

 autumn and spring ; on the islands, on the other hand, more than half 

 of the fields were ploughed in the autumn and only a few both in autumn 

 and spring. On the islands the attack was a little more serious on the 

 fields ploughed in spring, while in Jylland there was very little 

 difterence between the fields ploughed at different times, infestation 

 being less in fields ploughed both in autumn and in spring. 



The moisture in the soil on the islands was greatest in the fields 

 ploughed during winter and least in those ploughed both in autumn 

 and spring. As was expected, the attack proved least severe where 

 the moisture was greatest. On Jylland no connection between the 

 degree of injury and the time of ploughing or the amount of moisture in 

 the soil could be detected. Spring manuring on Jylland did not 

 increase the injury caused by flea-beetles, whereas on the islands 

 greater damage was done where this was carried out. The condition 

 of the soil was found greatly to influence the degree of injury, more so 

 on the islands than on Jylland. When the soil was finely pulverised 

 and contained a suitable amount of moisture, the injury was far less 

 than when it was lumpy and dry. As regards the influence of the time 

 of sowing, it was found that on the islands the attack was a little more 

 severe on those fields sown in May than on those sown in April ; on 

 Jylland the injury increased as the date of somng advanced from the 

 end of April to the 20th May but, remarkably enough, decreased when 

 the sowing took place during the last 10 days of May. Most of the 

 answers emphasise the fact that in 1918 the sowing took place too late, 

 and early sowing or, in the case of turnips, very late sowing in June, 

 is strongly recommended. 



On Jylland 59*^,', of the fields were rolled, on the islands only 33%. 

 When they were not rolled, the attack was much more serious, and 



