Page 40 



BETTER FRUIT 



March 



THE COMPOUNDING OF SPRAYS AND THEIR USES 



BY A. B. CORDLEY, OREGON AGRICULTURAL COLLEGE, CORVALLIS, OREGON 



THIS article is open to the criticism 

 that so many formulas may be 

 confusing to the orchardist who is 

 just beginning to spray. I believe, how- 

 ever, that no formula has been included 

 which is not of value for some special 

 purpose, although many of them are used 

 but little, if at all, in orchard practice. 

 Orchardists who understand the range 

 of usefulness of the lime-sulphur spray, 

 arsenate of lead and Black Leaf, who are 

 equipped with a good spray pump and 

 have the determination to do thorough 

 work are as well fortified as may be 

 against most orchard pests. 



None of the crops of orchard, garden 

 or field; none of our domestic animals; 

 practically none of our food products, 

 household effects or wearing apparel but 

 are subject to the ravages of insects or 

 fungi, or both. Even man himself is 

 subject to great personal annoyance, 

 and even disease, by these ever-present 

 agencies. 



To understand the general principle 

 which underlies the selection of the 

 proper remedy to be used for any par- 

 ticular insect one has only to know that 

 practically all insects may be divided 

 into two great groups: 



Group one includes all insects that 

 have biting mouth parts — mandibulate 

 insects — and which actually chew and 

 swallow the tissues of the plant or other 

 substance upon which they feed. Grass- 

 hoppers, caterpillars, flea-beetles, striped 

 cucumber-beetles, codling moth larvae, 

 etc., are good examples of this group. 



Group two includes all insects with 

 beak-like suqking mouth parts — haustel- 

 late insects — which pierce the plant or 

 animal upon which they feed and suck 

 up its juices or blood, but neither chew 

 nor swallow any of the structural tissues. 

 The apple tingis, woolly-aphis, hop louse, 

 green apple-aphis, black cherry-aphis, 



San Jose Scale, etc., are good examples 

 of this group. 



In general, insects which belong to 

 group one may be poisoned by sprinkling 

 or dusting the surface of the plant upon 

 which they feed with some poisonous 

 substance, but insects which belong to 

 group two cannot be so poisoned, since 

 they secure their food from beneath the 

 surface, and cannot be made to eat 

 poison. They must be destroyed by 

 gases, washes or other substances which 

 act externally upon their bodies. 



All insecticide substances may, there- 

 fore, be arranged into two general 

 groups : 



Group one includes principally the 

 various arsenicals, such as paris green, 

 London purple, Scheele's green, arsenate 

 of soda, arsenate of lead, etc. These 

 poisons are all valuable against insects 

 which belong to group one, and feed 

 upon the surface of plants, but are prac- 

 tically valueless against those of group 

 two. 



Group two includes a great variety of 

 substances which act externally upon the 

 bodies of insects, either as mechanical 

 irritants or caustics, or to smother them, 

 by closing their breathing pores, or to 

 fill the air about them with poisonous 

 gases, or simply as repellants. Soap, sul- 

 phur, tobacco, insect powder, kerosene 

 emulsion, crude petroleum, the lime-sul- 

 phur wash, resin washes, hydrocyanic 

 acid gas and carbon bisulphide are some 

 of the most -^aluable insecticides of this 

 group. These are used successfully not 

 only against sucking insects but many 

 of them are also used against biting 

 insects when for any reason it is unde- 

 sirable to use poisons, or when it is 

 impossible to apply poisons directly to 

 the food supply, as in the case of insects 

 which work beneath the surface of the 

 soil, or as borers or miners in wood, leaf 



Figure 4— LAWTON BLACKBERRIES BADLY INFESTED WITH ANTHRACNOSE 

 The healthy drupels are plump and smooth, while the diseased ones 

 are dry and shriveled. 

 Read article by W. H. Lawrence, page 73 of this issue 



or fruit, or in stored products, or as ani- 

 mal parasites or household pests. 



Likewise it should be understood that 

 a fungus is a plant as truly as is the apple 

 tree, the prune tree, the wheat plant or 

 any other plant upon which it may be 

 growing. It dififers from the common 

 plants essentially in being much more 

 simple in structure and in being devoid 

 of chlorophyll — the green coloring mat- 

 ter of plants. Its seeds, which are called 

 spores, are more simple and very much 

 smaller than the smallest seeds of our 

 common plants, and are produced in 

 almost inconceivably great numbers. 

 The vegetative portion of the fungus, 

 the part which, in a sense, corresponds 

 to the roots, stems and leaves of ordinary 

 plants, the part which absorbs the food 

 materials and eventually produces the 

 spores, consists of a mass of more or 

 less branched, white or colorless, and 

 very minute threads, and is called the 

 mycelium. 



Being so small and light, the spores 

 are readily carried long distances by the 

 wind, are washed about by the rains, and 

 are also carried by birds and insects, 

 and probably by other agencies. These 

 agencies are thus largely responsible for 

 the spread of fungus diseases from leaf 

 to leaf, plant to plant or orchard to 

 orchard. Over greater distances the 

 spores may be carried on shipments of 

 infested nursery stock, fresh fruits, vege- 

 tables, seeds, etc. 



Should a spore fall upon suitable soil, 

 such as the surface of leaf or fruit and 

 the conditions of heat and moisture be 

 favorable, it will germinate — push out a 

 delicate, slender germ-tube. In the case 

 of most parasitic fungi this germ-tube 

 soon penetrates the epidermis of the leaf 

 or fruit and the mycelium develops in 

 the underlying tissues entirely beyond 

 the reach of fungicides. In some cases, 

 however, the mycelium spreads over the 

 surface of the plant. In other words, 

 fungi, like insects, may be divided into 

 two groups, as follows: 



Group one, internal fungi, includes 

 those fungi in which the germ-tube pene- 

 trates the skin of leaf, fruit, branch or 

 root, and the mycelium develops entirely 

 within the tissues of the host plant. 

 Apple-tree anthracnose, brown-rot, the 

 grain-smuts and rusts, the downy-mil- 

 dews, for all practical purposes apple- 

 scab, and many others may be included 

 in this group. The philosophy of spray- 

 ing for this group of fungus diseases is 

 based upon the fact that they cannot be 

 cured, but can be prevented. This 

 germ-tube must be destroyed before it 

 penetrates the epidermis, and to do this 

 the surface of the host must be thor- 

 oughly protected by the fungicide during 

 the entire time the spores are ger- 

 minating. 



Group two, external fungi, includes 

 those fungi in which the mycelium 

 spreads over the surface of the host. 

 This group includes but comparatively 

 few serious pests. Perhaps the one that 

 has attracted most attention in this state 

 is the powdery-mildew of gooseberries. 



