72 THE REPORT OP THE No. 36 



potatoes, mangels, oats ; hence, they are better adapted to follow sod. Clover can be 

 sown with barley and rye and plowed down after a cutting has been taken. This 

 may be followed by corn or roots. Such a rotation will gradually exterminate the 

 Wireworms, and furnish crops that give a good yield. 



Short crop rotations will never allow Wireworms or White Grubs to make 

 headway and develop, for there is too much disturbance of the soil and change of 

 food plant. The best method of breeding these insects is to allow pastures to 

 go unbroken for a series of years, for then conditions are particvilarly favourable 

 for their development. 



Sometimes it is possible to force the crops through an attack of Wireworms, 

 by the application of mineral fertilizers to stimulate the plants. 



White Grubs. White Grubs, as already stated, are the larvte of June beetles, 

 and are large, soft, whitish or yellowish grubs, with brown heads and three pairs 

 of legs. The bodies are larger towards the hind end, and usually appear half- 

 coiled. Like the Wireworms they require about three years to complete their 

 development from egg to beetle. The adults appear in May and June, often in 

 large numbers, to feed on the foliage of certain trees, such as plums, willows, etc.,. 

 and to deposit eggs below the surface of the ground, usually on the roots of grasses 

 and many other kinds of plants. The grubs on hatching begin to feed on the 

 roots, and often do considerable damage. Dr. Forbes, of Illinois, who has given a 

 great deal of study to White Grubs, is of the opinion that the grubs do not change 

 to pupae until June or July of the third season; that they change to beetles 

 a few weeks later, but that these do not emerge from the pupal cells until the 

 following spring. He is also able to identify several distinct species of Lach- 

 nosterna, of which fusca is the most common. 



As with Wireworms, remedial measures are difficult. Special rotations are 

 advisable. Fletcher says: "A short rotation in which clover follows grass or is 

 grown at short intervals, will prevent the increase of these insects. In this special 

 rotation the small grains should follow clover before corn or potatoes.^' When 

 a field becomes infested with White Grubs a portion of the clover field, for example, 

 might be broken and planted to com instead of planting corn after timothy or 

 grass. To make up for the deficiency of clover, that portion of the sod field which 

 would have been devoted to corn could be sown with oats, vetches, etc., for green 

 feed and hay. It is perfectly safe to put mangels, turnips and rape after old 

 sod, although one will have to be on the guard against cutworms nipping off the 

 young plants. 



Cutworms and Flea-heetles. Considerable damage was done in June by cut- 

 worms on turnips, carrots and mangels, before they were detected, but the appli- 

 cation of poisoned bait prevented further action. 



In the Experimental Plots at Macdonald College the Wheat Aphis and the 

 Wheat-Stem Maggot again made their appearance, but not in such numbers as in 

 1908. Flea-beetles were observed on some plots but they did no serious damage. 



Root Maggots. These were numerous on many kinds of plants, viz., radish, 

 cow-peas, soy beans, cabbage, onions and turnips, and caused considerable loss. 



Cucumber Beetles. These appeared about June 10th at Macdonald College, 

 and did more harm to squash than to cucumber, pumpkin or melon. Mr. Swaine 

 reports that Bordeaux Mixture seemed effective, but they return to the new leaves 

 and flowers. 



Leaf Miners. Beets and spinach at Macdonald College were injured by leaf- 

 miners. They attacked small leaves, and had practically disappeared by July 4th. 



