DISEASES AND PESTS OF PLANTS. 



63 



form of blisters, so prevalent in our pear-orchards. The blistering of the leaves is 

 more apparent on the upper surface of the leaves, which turn at first reddish and, 

 later, brown. In severe infestations the vigour of the tree is greatly impaired. 



This year (1915) the mites were more in evidence than usual in the Okanagan 

 Valley and attacked the young fruit to a considerable extent. This mite attacks 

 the apple, quince, hawthorn, and other trees, but serious injury has so far only been 

 observed on the pear. 



Fig. 23. Pear-leaf blister-mite, highly magnified. (After Parrot.) 



Control. Lime-sulphur, 1 part to 9 parts of water, applied just before the buds 

 open, has generally proven satisfactory in the control of this pest. It must, however, 

 be applied at the right time. If applied after the mites have deposited their eggs 

 under the epidermis of the leaves the spray cannot be effective. Experiments con- 

 ducted in the State of New York indicate that a distillate or kerosene emulsion spray 

 gives the best results. 



THE RED SPIDER (Tetranyclius bimaciilatus) . 



The red spider is present every year in large numbers and is a source of worry 

 to many growers. It is a very indiscriminate feeder, attacking a large variety of 

 plants. The plants most susceptible to serious infestation are greenhouse plants, 

 hops, bush-fruits, prunes, and plums. The adults hibernate over winter in the 

 ground. Early in the spring those that have survived the winter ascend the trees 

 or plants in their immediate vicinity. They spin fine silken webs on the under-side 

 of the leaves on which the females deposit their eggs, and feed on the under-side of 

 the leaves under their webs. They multiply very rapidly, and in favourable seasons 

 are responsible for a great deal of injury. The fruit on severely attacked trees 

 remains small and does not mature properly. 



Control. In greenhouses the frequent application of a coarse stream of water 

 applied to the plants with considerable force has so far proven the most satisfactory 

 means of control. For hops, bush-fruits, fruit and shade trees, use lime-sulphur, 

 1 part to SO gallons of water, plus flour paste 4 gallons to each 80 gallons of dilute 

 liine-sulphur spray. This spray must be applied through a fairly coarse nozzle with 

 considerable force ; a power outfit is necessary and a pressure of at least 200 Ib. ' 

 employed. Apply as soon as the red spiders are noticed on the plants or trees, 

 directing the spray principally against the under-side of the leaves and seeing that 

 they are thoroughly coated with the spray mixture. A second application should be 

 made seven to ten days after the first application, so as to catch the spiders that 

 were still in the egg stage at the time of the first application. The spray is not 

 effective on the eggs. A band of tanglefoot 3 or 4 inches wide applied round the 

 trunks of the trees in the early spring will prevent migration to the trees. This 

 would, however, require frequent renewal. 



To prepare the Flour Paste. Mix a cheap grade of wheat-flour with cold water, 

 making a thin paste without lumps. Dilute until there is 1 Ib. of flour to each 

 gallon of water ; cook until a paste is formed, stirring constantly to prevent caking 

 or burning. Add sufficient water to make up for the loss from evaporation. Use 4 

 gallons of this paste to each 80 gallons of diluted lime-sulphur spray. 



