DISEASES AND PESTS OF PLANTS. 51 



THE ROUND-HEADED APPLE-TREE BORER (Saperda Candida). 



This insect takes two years to complete its life-cycle. The adult beetles com- 

 mence to emerge from the middle of May to about the end of July. The female eats 

 out a small slit in the bark in which it deposits an egg, which is often pushed under 

 the bark and then covered with a gummy substance. The eggs hatch in two or three 

 weeks. The young larva? tunnel just under the bark on the sap-wood, usually work- 

 ing down towards the base of the tree. At the beginning of the second season the 

 larvae are about % inch long. They continue in the sap-wood during the second 

 season, and it is at this time the most serious damage is done, for where several 

 occur in a tree they may girdle it. 



The next season they penetrate into the heart-wood, and several of them will 

 fairly riddle a small tree-trunk with their cylindrical burrows. The full-grown 

 larvre continue these burrows out into the bark, often cutting clear across a tree. 

 When the fully grown larva has completed its tunnel nearly through the bark it 

 pupates, and emerges as an adult beetle about three weeks later. 



Control. (See "Flat-headed Apple-tree Borer.") 



THE FLAT-HEADED APPLE-TREE BORER (Chrysobothris femorata). 



The larvre of this beetle live just beneath the bark, where they hollow out broad 

 channels which extend slightly into the sap-wood. Infestation may be detected by 

 the discoloration of the bark. Where abundant they will often completely girdle 

 young trees, thus causing their death. They are frequently found under the loosen- 

 ing bark of dying limbs of large apple-trees. 



The adult beetles emerge from about the middle of May until about midsummer. 

 The eggs are deposited in crevices in the bark. The larva becomes full-grown in one 

 year, remaining in the pupal stage about three weeks before emerging as an adult 

 beetle through an elliptical exit-hole in the bark. 



t'nnirol. Mechanical barriers to prevent the females from depositing their eggs 

 on the tree-trunks are sometimes used. These barriers are usually composed of fine- 

 mesh wire netting or building-paper wrapped round the trunks. The base of such 

 a barrier must be placed an inch or two below the surface of the ground and 

 extended up to the lower branches of the tree. When wire netting is used as a 

 harrier it must be kept from contact with the trunk by packing the top with cotton 

 batting or other suitable material. This is to prevent the beetles from depositing 

 their eggs on the bark through the meshes of the wire. These protectors should be 

 placed in position early in May and kept in place until late summer. 



Other deterrents which have been recommended are heavy washes of soap to 

 which a small quantity of carbolic acid is added, and then painted in a thick coat 

 on the trunk and lower limbs. Heavy limewashes have also been advised. 



THE FRUIT-TREE LEAF-ROLLER (Archips argyrospila) . 



This insect is responsible for a large amount of low-grade and deformed fruit 

 every year, the greatest injury being done to the fruit during the early stages of its 

 growth. The larva; eat holes into the fruit which, though healing over during growth, 

 leave a corky scar, and in the more serious cases cause a malformed growth. One 

 larva may attack a considerable number of fruit, so that not many need be present 

 to cause extensive injury. 



< ni/trol. This is a difficult insect to control during its active state owing to its 

 habits. The most effective spray is a 10-per-cent. solution of crude-oil emulsion 

 applied before the eggs hatch ; i.e., about the time the buds are beginning to open. 



THE TENT-CATERPILLARS (Malacosoma spp.). 



These caterpillars are usually kept well in check by parasites or other natural 

 agencies. "In favourable seasons, however, their unsightly tents are very conspicuous 

 on the wild cherry and are frequently found in considerable numbers in our orchards, 

 where, if allowed to develop unchecked, they soon defoliate whole limbs or even 



