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THE CANADIAN HORTICULTURIST 



August, 1912 



Summer Sprays for Vegetables 



Prol. E. M. Straight, Macdonald College, Que. 



THE air is pregnant with insect life ! 

 The "hum" and the "whir" are 

 fruitful topics from the stand- 

 point of the rural poet ; but the 

 market gardener whose vegetables 

 are attacked by caterpillars on the 

 leaves, grubs in the roots, larvae 

 in the stems, besides multitudes of fun- 

 goid diseases above and below ground, 

 fails to see the poetry. One thing he is 

 obliged to see, viz.. His crops. They, 

 unless protected, will gradually go back 

 to the soil ; and the realization will be 

 forced upon him that his labor has been 

 for nought. The growers are accepting 

 the verdict, "Spray or surrender." If 

 all did so the task of protecting plants 

 would be much easier, for the gardener 

 is handicapped if forced to fight alone. 



It would seem that arsenate of lead is 

 winning a place over paris green as an 

 insecticide. It sticks better, costs more, 

 is popular and easily obtained. Paris 

 green is not to be despised by any means. 



belong to this class. Dig out the plants 

 so attacked and burn them. You can- 

 not save them and you may hinder the 

 spread of the disease to the remainder 

 of the field. 



Plant lice cannot be poisoned. They 

 do not eat, and therefore cannot be reach- 

 ed by a stomach poison. Lice suck up 

 their food. They are usually very diffi- 

 cult to control. We may hope to reach 

 them only by means of a contact poison, 

 that is, something that will kill the in- 

 sect by coming in contact with its body. 

 Hot water is a good example of a poison 

 of this kind. 



Every gardener, if he would intelli- 

 gently fight insect pests and fungoid dis- 

 eases, must know his enemies. He must 

 know something of their life history, the 

 weak point in their life cycle, or in other 

 words their most vulnerable point of 

 attack. It is not necessary for him to 

 know the scientific name or the exact 

 number of joints in their hind legs, but a 



The Relative Yiald of Potatoes with Different Sprays 



The potatoes in piles one and two show the proportion of marketable and unmarketable 

 potatoes where the lime-sulphu.r spray was used once- Piles three and four show pota- 

 toes on which Bordeaux mixture was uied once. The two piles on the right 

 were not sprayed at all. 



It will kill insects which chew if pro- 

 perly applied. The celebrated lime-sul- 

 phur, so effective as a fungicide in the 

 orchard, is not to be recommended so 

 highly as we once thought for vege- 

 tables. Our experiments would indicate 

 that the old reliable Bordeaux mixture 

 is superior to lime-sulphur for potatoes, 

 and We believe for other truck crops. 

 The grower has in bordeaux mixture and 

 arsenate of lead a combination with 

 which he may do very effective work 

 against most enemies of the garden. 



BACTERIAL DISEASES 



We have a class of diseases, however, 

 which spray mixtures cannot reach. 

 These maladies are bacterial in origin, 

 within the tissue, so that spraying the 

 plant is of no more avail than spraying 

 a man dying with tuberculosis. Melon 

 wilt and the soft rots of some root crops 



good working knowledge of his enemies 

 is essential to the best success. 



ENEMIES OF POTATOES 



The potato is attacked by Early 

 Blight, Late Blight, Flea Beetle, Blister 

 Beetles, and Colorado Potato Beetles. 

 Certain bacterial diseases also attack the 

 plant which cannot be controlled by 

 sprays. 



Early Blight of the potato is a pre- 

 mature spotting and dying of the potato 

 leaves, due to the work of a parasitic 

 fungus (Alternaria solani). The occur- 

 rence of the Early Blight, however, is 

 liable to be influenced by the general 

 vigor and other conditions of the plant ; 

 yet there is no just basis for denying the 

 parasitic nature of the disease. Early 

 Blight is the cause of the early dying 

 of potato tops, but does not cause rot- 

 ting of the tubers. 



The Late Blight and rot of the potato 

 is so generally known that frequently this 

 malady is simply called the potato dis- 

 ease. It is the oldest potato malady, and 

 was the cause of the potato famine in 

 Ireland. The spots cannot be easily con- 

 fused with other potato diseases. These 

 diseased areas frequently begin at the 

 edge or top of the leaf and spread until 

 the whole leaf is involved. They present 

 in moist weather a dark, somewhat water 

 soaked appearance with slightly purplish 

 tint. Upon the tubers this fungus de- 

 velops the well-known dry rot of the 

 field and storage pits. 



POTATO PLEA BEETLE 



The potato is often attacked by a very 

 small beetle which also attacks the to- 

 mato, cucumber and beans. This insect 

 is commonly called the potato flea beetle. 

 They often congregate in such numbers 

 that the leaves of plants appear almost 

 black with them. Potatoes and tomatoes 

 often have their leaves so badly eaten 

 that the leaves shrivel and die in the 

 case of the tomato, although the potato 

 usually pulls through. 



00T,ORADO POTATO BEETLE 



The Colorado potato beetle is a native 

 of a strip of country which lies just east 

 of the Rocky Mountain range and in- 

 cludes eastern Colorado.. In its native 

 state the beetle lives upon the wild weeds 

 of the potato family. The chief of these 

 is the buffalo bur, but the beetle is quite 

 a general feeder on plants of this group, 

 including not only potatoes, but toma- 

 toes, egg plants, tobacco, and pepper. 

 The adult passes the winter in the 

 ground. In spring the beetles emerge, 

 seek food plants on which they feed and 

 deposit eggs. These adults sometimes, 

 though not always, do much injury. 

 They die shortly after depositing their 

 eggs. The eggs hatch in from four to 

 eight davs, depending on the tempera- 

 ture. The young reach full growth 

 about three weeks later. Soon eggs are 

 laid again, and the second generation 

 hatches. Ordinarily two broods are all 

 that we may expect. 



FEMI^DTBS 



All of the.se maladies may be controll- 

 ed by bordeaux mixture and paris green 

 or arsenate of lead. Bordeaux mixture 

 of the usual formula, four-four-forty, 

 and if paris green is used, one pound to 

 forty gallons of water is quite sufficient. 

 Two pounds of arsenate of lead will kill 

 the beetles with equal certainty, and it 

 remains on the foliage longer, owing to 

 its sticking properties. The first appli- 

 cation should be made as necessary, 

 about the time the Colorado potato beetle 

 is hatching, and at intervals of ten days 

 as required. L^sually three applications 

 will be quite sufficient. 



The two principal enemies of the cab- 

 bage are the cabbage butterfly and the 



