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THE CANADIAN HORTICULTURIST 



June, 1908 



The White Fly of Greenhouses 



A. McMeans, Ontario Agricultural College, Guelph. 



THE combatting of insect pests, is 

 always a serious problem 

 to the grower of green- 

 house crops. One of the hardest of these 

 pests to control, is the white fly or plant- 

 house Aleyrodes. The chief vegetable 

 crops injured by it are cucumbers, toma- 

 toes, and sometimes lettuce, in flow- 

 ers, pelargoniums, ageratum, and fuch- 

 ias, are the most susceptible to its at- 

 tack. 



Its presence can be detected by mak- 

 ing an examination of the underside of 

 the leaves of the plant. In the adult 

 stage, the insects will fly around the' 

 plant when disturbed, generally return- 

 ing to the same plant. In the egg and 

 nymph stages they are attached to the 

 under side of the leaf, and can hardly be 

 distinguished with the naked eye. 



According to observations made at the 

 New Hampshire and Connecticut stations 

 it takes about two weeks for the eggs to 

 hatch into nymphs. These nymphs move 

 about over the under surface of the leaf 

 for a few hours, and then insert their 

 tiny beak into the tissue of the leaf, tak- 

 ing on the appearance of a scale. These 

 scales remain in position two weeks or 

 more, until a T-shaped rupture appears in 

 the back skin of the pupa case, and the 

 the adult white fly emerges — a small, 

 little insect about one-twenty-fifth of an 

 inch in length, with four white wings, 

 from which it takes its name. 



This insect has sucking mouth parts 

 and canot be controlled easily by the use 

 of spray poisons. There is but one sure 

 remedy, when once these pests make 

 their appearance in a greenhouse. Pre- 

 pare to give battle to them at once, and 

 keep prepared for their return. 



FUMIGATING THE REMEDY 



Hydrocyanic acid gas is the only kind 

 of fumigation that will clean them out, 

 but on account of its dangerous charac 

 ter on human, as well as insect life, 

 it makes people rather timid about using 

 it. If ordinary precaution is observed 

 there is not the slightest danger. We use 

 it with good results in the College green 

 houses, according to the following for- 

 mula : One-fifth of an ounce of cyanide of 

 potassium ; two-fifths of an ounce (by 

 measure) of commercial sulphuric acid ; 

 four-fifths of an ounce (by measure) of 

 water, to each i ,000 cubic feet of spade. 



HOW TO DO THE WORK 



Measure the cubic feet of each house 

 carefully. See that all ventilators are 

 closed, and all doors locked, except the 

 ones through which you will make your 

 exit. Heating pipes should be set for 

 the night. The temperature of the house 

 should not be over sixty degrees Fahr. 



The foliage should be as dry as possible, 

 as the presence of moisture increases the 

 liability of injury to the foliage. Choose 

 a still, dark night, sunlight or moon- 

 light seem to have a damaging effect. 

 Use glass or stone vessels, place them 

 in the aisles as closely as needed, then 

 go along' and put the water in all your 

 jars, next add the sulphuric acid to each 

 vessel — always put in the water first, 

 never the acid. Now, we are ready for 

 the last act. Have your packages of 

 cyanide carefully wrapped in paper. Take 

 your baskets or tins^as many packages 

 in each tin or basket as you have jars in 

 each aisle, and as many tins or baskets 

 as you have aisles. Let each man take a 

 basket to the far end of each row of jars, 

 each dropping in the first package at the 

 same time. Then go quickly to the next 

 jar, and so on, until you get to the end 

 of the house, and out of the door, locking 

 it without delay. 



SOME don'ts to observe 



Do not unwrap the packages, but drop 

 them in with the paper securely wrapped 

 around them, as the acid will quickly eat 

 it off. Do not let the acid spatter on 

 your hands, either in handling it, or 

 when placing the cyanide in the jars. 

 Above all things, do not go back past 

 the jars after you have placed the cyn- 

 anidi' in them. Remember this gas is as 

 deadly to human life as it is to insects 

 Leave the gas in all night. It is per- 

 fectly safe to go into the house in tVe 

 morning. Two jars will be found sullic- 

 ient for 10,000 cubic feet of space. 



Most authorities recommend one ounce 

 of cyanide per 1,000 cubic feet of space, 

 leaving the gas in for a space of twelve 

 to twenty minutes ; if left longer at this 

 strength, it acts injuriously to the plants. 

 We have been using one-fifth of an ounce 

 per 1,000 cubic feet, and leaving it in 

 all night, with perfect success in killing 

 the fly. No injury is done, even to to- 

 matoes, which are one of the most easily 

 injured greenhouse crops. 



Onion Culture 



Herbert Hachbom, Echo Place, Ont. 



Onion seed should be sown as early 

 in the spring as possible, in drills four- 

 teen inches apart, at the rate of about 

 four pounds to the acre. When the 

 onions are about two inches high, they 

 should be weeded and thinned. If the 

 seed is not sown too thickly, they do not 

 require thinning. I generally weed 

 them about twice in a season, and 

 wheel-hoe them once every week, until 

 they commence to form bottoms, then 

 I go through them with the ordinary 

 hand-hoe. 



By the time that the tops commence 



to die off, I roll a barrel over them, two 

 rows at a time, to break down all the 

 tops. When they are fairly well dried 

 off, the onions should be pulled and 

 topped into boxes and taken to the barn 

 floor to dry. 



Should it rain before they can 1h- 

 topped and taken in, it is best to wait a 

 day or two, so as to give them a chance 

 to dry again. The rain does not hurl 

 them; in fact, two or three showers will 

 do them good. They can stand, also, 

 about three degrees of frost. 



Wilt of Cucumber 



I am sending- you a cucumber plant, and 

 should be jfrcatly obliffCd if you will give 

 me your opinion as to what disease it ha.s, 

 or the cause of its condition. I planted 

 them in the usual way, and up to a certain 

 stage they appeared healthy, and then 

 gradually went wrong. I have lost my en- 

 tire crop. I have had many year's exper- 

 ience in cucumber growing, but never met 

 with this before.— W. P. J., B. C. 



The stem and leaves of the cucumber 

 .sent with the above letter, showed that 

 the plant was infected with some form of 

 Bacterial Wilt. Microscopic examina- 

 tion from the interior of the stem and 

 leaves, showed bacteria present in large 

 numbers. Some of these were trans- 

 ferred to slices of healthy cucumbers, 

 and the slices were quickly rotted in two 

 days. The organism does not seem to 

 be identical with the one usually as.soci- 

 ated with the Wilt disease of cucumber, 

 melon and squash described by Erwin 

 F. Smith, of the United States Depart- 

 ment of .■\griculture. The wilting of the 

 plant is caused by the clogging of the 

 water tubes, through the growth of bac- 

 teria in them. Spraying is useless and 

 preventive measures suggest pulling up 

 diseased vines and burning them. This 

 disease is frequently carried by the cu- 

 cumber beetle and squash bug, hence the 

 necessity of destroying these insects. 

 Fields in which the infection has taken 

 place should be planted with some other 

 crop, and succeeding crops of cucumbers 

 should be planted on new land, which 

 has not been used for the growing of 

 cucumbers. — Prof. F. C. Harrison, 

 Macdonald College. 



Cut Worms 



Nelson Carron, Riviere do Loup, Que. 



The treatment for cut worms on cab- 

 bage, cauliflower and tomato plants, is 

 quite simple. Wrap your plants in a lit- 

 tle piece of paper, just above the fibres of 

 the root, and high enough to keep the 

 leaves upright. This prevents the cut- 

 ting of worms, and the burning of plants 

 in hot days. Some growers say that this 

 takes too long to be done profitably. 



It takes a little time, but it requires 

 still more time to replant your field four 

 or five times. Some times you come 

 short of plants, which also is prevented, 

 by adopting the method advised. 



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