36 



THE CANADIAN HORTICULTHRIST 



Feb 



ruary, 1912 



Wingless Aphis, Greatly Enlarged. Thrips 



you look with great care. Only as adults 

 are they red. While young they are 

 green or yellow. The leaves attacked 

 first turn a light green and later yellow 

 and eventually fall from the plant. If 

 houses are properly ventilated and the 

 correct moisture content maintained, red 

 spider will give little trouble, as it 

 thrives in a hot, dry atmosphere. 



The thrips have long slender bodies 

 and four wings. The wings are fringed. 



Red Spider 



Mealy Bug 



The thrips, becau.se of the peculiar for- 

 mation of their mouth parts, have the 

 power of biting and sucking. It is very 

 difficult to decide from the nature of 

 the injury whether a sucking or chew- 

 ing insect has been at work. 



The mealy bug is one of the scale in- 

 sects. It is so called because of the white 

 cottony substat^ce with which they cover 

 themselves. When about to lay eggs, a 

 mass of long, cottony particles of wax 

 is secreted, under which the eggs are 

 deposited. The male is somewhat differ- 

 ent from the female. It is darker. The 

 wings are long and gray. 



In every damp, untidy house slugs, 

 snails and sow bugs are much in evi- 

 dence. They delight in damp, decaying, 

 unwholesome quarters. Slugs are es- 

 pecially fond of seedling plants, and 

 sometimes give much trouble, but are 

 easily got rid of. 



Eel worms have given as much 

 trouble at Macdonald College as any 

 other greenhouse pest. These nematodes 

 work on the roots, and gall-like swell- 

 ings are produced, which interfere seri- 

 ously with the normal development of 



the plant. When they once gel into a 

 Ijed they are got rid of with much dilK- 

 culty. 



FUNQDS D18KA8E8 



The most common diseases caused by 

 fungi in the greenhouse are the follow- 

 ing: 



Carnation Rust was first noticed in this 

 country about 1890. The plants were 

 attacked some time before any pus- 

 tules were formed. These are noticed 

 just beneath the surface. Soon the epi- 

 dermis bursts showing large numbers 

 of brown spores. 



The chrysanthemum is subject to a 

 number of forms of fungi, which are 

 commonly called "leaf-spot." Picking 

 off every affected leaf will sometimes 

 hold the disease in check, but the spray 

 pump is essential in many cases. 



Lettuce growers are fortunate if they 

 have not seen more or less of the rot, 

 usually more if Boston Head Lettuce is 

 grown. Particular attention must be 

 given to the soil. The disease revels in 

 a wet, heavy soil. Decaying vegetable 

 matter forms an excellent medium for 

 its development, hence manure should 

 be well worked into the soil. 



Young seedlings are very subject to 

 "damping off." This fungus is not a 

 refined species, for it attacks the stem 

 close to the ground and almost at once 

 causes the death of the plant, thus de- 

 priving itself of further food supply. 

 However, it is not dependent on any 

 one plant. A host of seedlings are 

 subject to its attack. Too much water 

 and sudden change in temperature pro- 

 duce conditions favorable to the growth 

 arid rapid development of the fungus. 

 If the "flats" have a large amount of 

 sand in the surface soil, and some care 

 exercised in the watering this disease 

 will give little trouble. 



The control of all these difficulties 

 group themselves under three head- 

 ings, viz., .spraying, fumigation and 

 sterilizing. Spraying may be with some 

 ar.senicai for insects which chew ; or 

 some contact poison for insects which 

 suck ; or for the various forms of fungi. 

 Fumigation may be used for the con- 

 trol of insect life which cannot be readi- 

 ly controlled by the ordinary .spray mix- 

 tures, in fact, it is coming into general 

 use, and constantly crowding out the 

 sprays. Sterilizing is u.sed for such 

 forms as occur below ground. It may 

 not be perfect sterilizing in the strict 

 sense of the term, for bacteria are still 

 alive, unless the proce.ss is much pro- 

 longed. Such a condition would not be 

 desirable, and for all practical purposes 

 is never sought. 



Of all the arsenicals, paris green still 

 holds a prominent place. Arsenate t.f 

 lead probably sticks better than the 

 green, but we think that the old poi.son 

 is still more extensively used in the 

 greenhouse. One teaspoonful to two or 

 three gallons of water will usually clear 

 out many leaf eaters.- A small amount 

 of water-.slaked lime will prevent any 

 burning which mightt^ occur from the 

 presence of any soluble arsenic. This is 

 effective for thrips ; and if added to 

 sweetened bran will clear out slugs, and 

 similar pests. Hellebore is used for a 

 similar purpose, and may be used in any 

 required strength. It seldom or never 

 injures plants. 



CONTACT POISONS 



Contact poisons are not used to the 

 same extent as they once were. The old 

 reliable kerosene emulsion is still some- 

 times used and most excellent results have 

 been secured, but few growers have 

 used it long without having some in- 

 jury to the foliage. Plants will not 



Fumigating with TobaccQ Stems, All Re«dy_to_ Start. The Fir^ 



