Apr. 1, 1918 Stone flies Injurious to Vegetation 39 



and the stonefly was observed feeding to some extent on the leaves of the 

 wild rose, on the leaves and catkins of the willows iSalix spp.), and on 

 the leaves of the wild cherry (Prumcs emarginata and P. demissa) and 

 alder (Alnus temdfolia), and also on the cultivated elm {Ulmus ameri- 

 cana). The insect seems to prefer the rosaceous plants, although it 

 does not confine its feeding to them. 



The injury caused by this stonefly was quite noticeable, especially in 

 the lower part of the Wenatchee Valley, known as the Rock Island 

 district, where there are extensive orchards near the Columbia River. 

 Many growers here said that it was very seriously damaging their apri- 

 cots and peaches, necessitating the discarding of much of the fruit. 



CONTROL 



Owing to other work, it was not possible to carry out any extensive 

 experiments in the control of the stonefly. It was noted in 191 5, however, 

 that plum trees which had been sprayed with crude-oil emulsion and 

 nicotine sulphate for aphids were not as badly injured as those not 

 sprayed. Several growers reported spraying their trees with nicotine 

 sulphate and soap, with varying success. On April 3, 1916, an apricot 

 orchard was examined, part of which had been sprayed about April i 

 with lead arsenate at the strength ordinarily used for the codling moth 

 on apples (2 pounds of lead arsenate to 50 gallons of water). At this 

 time the buds were beginning to show green. A number of buds were 

 examined and counted on both sprayed and unsprayed trees. On the 

 latter trees 60 per cent of the buds were injured, while on the former only 

 24 per cent were injured, and it is probable that much of this latter 

 injury was done before the trees were sprayed, as the flies had been 

 numerous for over a week. It seems probable that in order to protect 

 the trees completely two applications of spray would be necessary, as 

 the buds are developing rapidly at this time. The first application would 

 naturally be put on as soon as the flies appear, and the second either 

 just before blossoming or just as the petals are falling. 



LIFE HISTORY 



At the time the stoneflies were abundant several of the smaller streams 

 flowing into the Columbia River near Wenatchee were examined, but no 

 emerging flies were found. The shores of the Columbia River, which 

 at Wenatchee is a large, swiftly flowing stream about one-fourth of a 

 mile wide, were then examined, and the flies were found emerging in large 

 numbers. Thousands of cast nymphal skins (PI. 3, C) were strewn along 

 the shore from the water's edge to 10 or 15 feet above it. Hundreds of 

 crippled flies were scrambling about over the rocks, but few perfect ones 

 were seen, as these evidently fly away as soon as their wings are sufficiently 

 dried. In the shallow water under the larger stones the nymphs were 

 found, most of them just ready to emerge. 



