539 



Miris dolabratus and Pediculoides graminum were much I'ess common 

 in 1918. The scarcity of these pests is probably due to the fact that 

 both hibernate in the stubble and, as every straw was consumed as 

 forage in 1917, were killed instead of, as in normal times, being conveyed 

 with the straw to the fields in the manure. It is probable that the 

 great extension of the cultivation of barley during the war is partly 

 responsible for this outbreak, since this involved the ploughing up 

 of much pasture land inhabited by the frit fly, which was consequently 

 forced to attack barley. The flies of the first generation appear in 

 May or June according to the climatic conditions, each female deposit- 

 ing about 60 eggs on the leaves of the young plants, preferably on 

 oats and barley, but also on timothy and quickgrass. The young 

 larvae penetrate into the axis of the plants, cutting off the stalk and 

 causing the shoots to wither. At the base of these plants new shoots 

 may appear, which, however, are very often attacked by flies of the 

 first or the second generation and also succumb. The injury caused 

 by the first generation is the more serious the more unfavourable the 

 climatic conditions have been during the spring. The time of sowing 

 therefore plays a very important part, and in Central Europe experience 

 goes to show that the earliest sown plants usually escape injury, 

 whereas the latest sown ones suffer heavily. Experience in Hedmark, 

 however, is qm'te to the contrary, the latest sown fields as a rule 

 escaping injury far better than those sown earlier. This depends on 

 the climatic conditions prevailing during the spring in so far as that 

 the latest so'wn plants appeared above the ground at exactly the time 

 when rain set in, which rendered them far more resistant to attack than 

 the earlier sown ones that had suffered from drought. During this 

 great outbreak of the frit fly, it has been found that the oviposition 

 period is comparatively long, the different stages as a consequence 

 being found together. As a rule the flies of the sgcond generation 

 appear from the end of June to the beginning of July, attacking the 

 new shoots or the spikes that have escaped the first generation. The 

 flies of the third generation appear at the end of August and the 

 beginning of September, ovipositing on autumn-sown cereals or, in the 

 absence of these, on grasses. In order to prevent the attack of the 

 third generation the sowing of autumn cereals as late as possible is 

 suggested, though this procedure does not kill the fly, but only forces 

 it to attack grasses. In order to kill a proportion of the hibernating 

 adults sowing, as traps, strips of barley or rye and barley round the 

 fields so early that the plants are ready for oviposition at the end of 

 August is suggested. At the end of September these strips are ploughed 

 and the larvae thus buried in the ground. Other cereal pests included : 

 Osci)iella pusilla, Meig., on oats ; Chlorops taeniopus, Meig., on barley; 

 Aphis avenae, L., Macros ipJium granariinn, L., Lygus pratemis, L., 

 Thrips sp., and the mites, Pediculoides graminum, E. Rent., and 

 Rhizoglyphus echinopus, F. & R. 



Grasses were attacked by Charaeas graminis, L., of which there had 

 not been any outbreak since 1911, but which was very abundant in 

 many parts of the country and did great injury ; Hepialus lupulinus, 

 L., ; Amaurosoma flavipes, Fall. ; Hydrellia griseola, Fall. ; Oscinella 

 frit, L. ; and Philaemi^ spnmarius, L. 



Peas and beans were attacked by Sitones lineatus, L., which did great 

 damage during the dry period at the beginning of the summer and a 



