ae Insects and insecticides. New Dork State College of Agriculture At Cornell Cniversitp 3 STATE HORTICULTURAL COMMISSION ELLWOOD COOPER, Commissioner INSECTS AND INSECTICIDES oe" SACRAMENTO W. W. SHANNON,’ BS LE~O CALIFORNIA STATE COMMISSION OF HORTICULTURE. ELLWOOD COOPER .-.-..------ Commissioner -------------- Santa Barbara. JOHN ISAAG coscecss cocewssses Secretaryecccecesusercsenend San Francisco. ED. M. EHRHORN -_.--_--.---.- Deputy co ss205 so ecae tec nces Mountain View. RB; Ki, CARNES) 2 2.2g22c2ee rene Assistant Deputy -.-.----.------- Riverside. oO. E. BREMNER...-...--.------ Second Assistant ---.---------- Santa Rosa. GERTRUDE BIRD ..------. --- Stenographer -._--.---.---.---- Sacramento. OFFICE: Room 41, State Caritot, SACRAMENTO. Brancu Orrice, Room 11, Ferry Burtpine, San FRANCISCO. INSECTS AND INSECTICIDES. In order to intelligently apply insecticides, and to be able to judge whether one remedy or another will be more effective, it is necessary to understand something of the habits of the different insects attacking plants. Many insects, like cater- pillars, grasshoppers, and beetles, devour the foliage, while others, such as scale insects, plant lice, squash bugs, etc., injure the plant by inserting their sharp beaks into its tissue and sucking the sap from beneath the surface. Insects of the first class can nearly always be destroyed by means of poisons, such as paris green and various forms of arsenates. Those of the second class, or sucking insects, are unaffected by these poisons and must be killed by contact sprays, such as kerosene emulsion, whale-oil soap, crude-oil mixtures, or the lime-sul- phur-salt' remedy. Another class of insects, and which none of the above remedies will reach, are those which burrow into the bark and trunks of trees. These must -be treated mechan- ically—dug out, and barriers or repellants provided to prevent - them from regaining entrance into the trees. In the following pages the most successful remedies are given, but, under cer- tain climatic conditions or in abnormal seasons, other steps may become necessary and advice from the State Commission of Horticulture should always be obtained in cases where any doubt exists. It should be remembered that the successful application of remedies is dependent upon the exercise of proper judgment. It is essential to first positively identify the insect to be destroyed, then to know the most effective remedy to use, and finally to apply it at the proper season. -Promptness, thor- oughness, and persistency, combined with good judgment, are the essential factors necessary for the successful application of insecticides. ' This office is at all times glad to render any assistance pos- sible in determining the identity of insects and in advising as to the remedy to be used for their control. Insects should not 4 STATE HORTICULTURAL COMMISSION. & be sent by mail in envelopes or pasteboard boxes, as they are almost invariably crushed beyond recognition; strong wooden or tin boxes should be used. Openings to admit air are not necessary. Plant specimens, showing the injury done, are desirable. The name and address of the sender should be on every package. It will help greatly if correspondents, when writing about insect pests, will give as full a description of the habits, food plants, injury and abundance as possible. Specimens of twigs, living plants with foliage, etc., should be wrapped in damp (not wet) cotton cloths so that they will reach us in fresh condition. Correspondents can materially aid the work of this depart- ment by informing it of their success or failure in using the methods recommended for controlling injurious insects, at the same time giving a detailed account of the method used and the results obtained. Such information will prove of value to all. SCALE INSECTS. These insects are among the most dreaded pests on fruit trees in the State, owing to their prolificacy and easy mode of transportation. They are generally firmly attached to the foliage or bark of trees, and when present in great numbers soon kill the plant on which they are feeding. All the species in our orchards have been intro- duced. Although many now have their natural enemies, it hav- (A ing been the pol- RWS many years to . control these pests by their" *~ Fic. 2, Pear, showing effects of San José scale. Fic. 1. San José scale on twig. natural para- sites,” yet it is necessary, in abnormal seasons, to use artificial means to combat them. The grower very often overlooks the few small INSECTS AND INSECTICIDES. 5 specks on the leaves, fruit, or bark of his trees until it is too late. The proper time for effective work is when the insects first appear, and not after the trees are half killed by their attack. Nearly all species of scale insects can be killed by the reme- ‘dies recommended in this bulletin, but some species have to be treated by fumigation with hydrocyanic acid gas; especially is this true on evergreen trees, it being difficult, owing to the . dense foliage, to reach every individual by sprays, and a suffi- cient number always escape to reinfest the trees. Our report for 1903-04 gives a list of scale insects and also illustrates many species of parasites which attack . them, colonies of which will be supplied to growers on applica- tion to this department. Following are the sprays rec- ommended for the various scale insect pests: Winter Wash for San Jose Scale, Pear Diaspis, and Greedy Scale.— Following is the lime-sulphur- salt solution: Unslaked lime------ 40 pounds. SULPHUP s2seseeeses 20 pounds. Stock salt. _,-.--.--- 15 pounds. Water, to make ---__. 60 gallons. Place 10 pounds of lime and 20 pounds of sulphur in a boiler Q with 20 gallons of water, and Fic. 3. Brown ae scale (Huteca- boil over a brisk fire for not less " nium armeniacum, Craw). than one hour and a half, or until the sulphur is thoroughly dissolved. When this takes place, the mixture will be of an amber color. Next place in a cask 30 pounds of unslaked lime, pouring over it enough hot water to thoroughly slake it; and while it is boiling, add the 15 pounds of salt. When this is dissolved, add to the lime and sulphur in the boiler, and cook for half an hour longer, when the necessary amount of water to make the 60 gallons should be added. 6 STATE HORTICULTURAL COMMISSION. Rosin Wash for all Species of Scale Insects on Deciduous Trees.— The following are the proportions of materials for the winter wash: MOS accacceeonds sacesee ee CRAs oat aie un os eee 30 pounds. CaUSticsOda (O87) occ ccccescawccecewsscv twos eee ceeds 8 pounds. ishsOFl oe nade eh etn ese Soe Sees 44 pints. Waterrtoimake ooo saccricsatisas eeccesece eescstueeene oes 100 gallons. Place the rosin, caustic soda, and fish oil in a large boiler, pour over them about 20 gallons of water, and cook thoroughly over a brisk fire for at least three hours; then add hot water, a little occasionally, and stir well, until you have not less than 50 gallons of hot solution. Place this in the spray tank, and add cold water to make the necessary amount. Never add cold water when cooking. Distillate Spray for Young Black Scale on Orange Trees.—To be used with power machine, fitted with an agitator, speeded at 65 or 70 revolutions per minute: Distillate: 28?) os.c2ccee waseee Sees easels 2 gallons. Water n nie sce eciate wets pen teuneneesieeueceeceaee 100 gallons. Use only the best 28° distillate and see that a perfect mixture is attained at nozzle before applying to trees. This can be determined by agitating for a sufficient time to thoroughly mix the contents of tank; the time will vary somewhat according to speed and construction of agitator. Examine the mixture at nozzle by holding hand in front of same; when the mixture is at its whitest it is ready to apply. When engine stops from any cause, immediately discontinue application of spray. When starting up again, empty hose into tank until the mixture is again at its whitest. Apply spray at a pressure of 160 pounds. Do not spray an orchard in need of irrigation. Trees that are not in a thrifty condition should be sprayed with a weaker solution. . Avoid spraying during the prevalence of high winds, cold weather, or when trees are wet with rain or fog. For Red Scale increase the solution to 24 per cent on orange and to 24 per cent on lemon trees, and add one quart of pure turpentine to the 100-gallon tank. INSECTS AND INSECTICIDES. 7 Distillate Emulsion for Black Scale on Citrus Trees.—The follow- ing are the proportions for the stock solution: Distillate 28° (untreated)..----.----.-.-. ..----------- 5 gallons. Hot waters x ccsecinseeue seeetes oer nec enece een ceeweets 5 gallons. Wihtale-ouli sa prec ace eerie oe teens See ees 14 pounds. The whale-oil soap must first be dissolved in the water. Then add the dissolved soap to the distillate. It is important that the distillate be placed in the mixing vessel first, then place the dissolved soap on top. Then attach the spray pump to the bottom of the vessel in which the compound is being mixed, and keep pumping it out of the vessel through the spray pump and back into the vessel, until the whole becomes of a rich creamy substance. Keep pumping or churning it through the pump until it becomes a complete emulsion, without a speck of free oil in sight, which will take from ten to fifteen minutes. When properly emulsified, it should increase in volume about one third, because it becomes aérified. After the stock solution has been thoroughly prepared, it will readily mix with cold water. To each gallon of the above stock solution add 14 gallons of cold water: Always place the emulsion in the spray tank first, then add the water, as by this means a more uniform mixture can be made. This emulsion can be applied with an ordinary hand spray pump. Summer Wash for San Jose Scale and Other Armored Scales on Deciduous Trees —Following are the proportions of materials to be used: Wehale-oil s0api.sess cccecewese setiiec see eeseatee aes 20 pounds. NUIPAUR co sssococ nets odacemes Gkadcececsemcencce. 8 DOUNGE: CaUStiC S008 98 Hors heer gaa eee sees sete dee nee eae 2 pounds. Waters cece eno eee cereetene Siem etaa tees 100 gallons. Place sulphur and caustic soda in about two gallons of water and boil for at least one hour. Dissolve the soap by boiling in water. Mix the two solutions, and reboil all for a short time. Apply the spray warm. This wash also makes a good combination spray for scale and fungus. , For Individual Trees and Shrubs on a Small Scale use the fol- lowing: W Rale-otl s0ap ices c< cmedusesee ene reeteoweeneceeeseces 1 pound. EL Ot WALGER ace cee oc eee eee lee 5 gallons. Dissolve the soap by boiling, and apply warm. 8 STATE HORTICULTURAL COMMISSION. Hydrocyanic Acid Gas Treatment, for Destroying Scale Insects on Citrus Trees.—This treatment should be used in the night so as to avoid light, heat, and sea breeze, which neutralize the effect of the gas. The chemicals used for producing the gas are: Sulphuric acid (commercial), cyanide of potassium (98% to 99%), and water. The following instructions must be carefully observed: First, the tent, which must be air-tight, is placed over the tree; second, the tent is made air-tight around the bottom by throwing some loose soil over the bottom of the canvas; third, the necessary amount of sulphuric acid, together with the required amount of water, is put in a glazed earthenware ves- sel, and placed under the canvas, and the cyanide of potassium is added. A piece of sacking or burlap is thrown over the top of the vessel, to spread the gas and prevent it from burning _ the leaves immediately above the generator. The tree is left covered forty minutes. The Riverside County Board of Horticultural Commis- sioners recommends the following proportions of chemicals: Height of Diameter of Cyanide C. P., 93 | Sulphuric Aci Wee. Tree. Water. Mi per cent. . per So a Feet. Feet. Ounces. Ounces. Ounces. 2 1 8 6 3 1 14 10 8 5 at 25 12 14 11 5 5s 16 16 17 8 Q° 20 16-20 22 10 12 20-24 18-22 30 14 16 24-380 20-28 34 16 : 18 30-36 25-30 52 24 28 The cyanide should be used about the size of walnuts, so that the chemical action will be less violent. The gas is also generated more evenly, and there is not so much danger of the chemicals boiling over or spattering the tent. As soon as the tent is removed ;the vessel is rinsed with clean water and prepared for another charge. APHIDS,ZOR PLANT LICE. Next to the scale insects are the aphids, or plant lice, as they are generally called; these also belong to the sucking insects. Plant lice are small, usually green, but varying to brown or black insects, and are generally found on the under side of INSECTS AND INSECTICIDES. 9 leaves or on growing shoots. These insects multiply very rapidly, but fortunately for the grower the hot summer climate of California prevents long duration of their attack and there also exist in California hordes of natural enemies which attack them shortly after their appearance and soon reduce their numbers. In favorable seasons, however, plant lice become a very seri- ous pest and artificial means for fighting them have to be resorted to. Near y all varieties of fruit trees are attacked by them and a great many of our early fruits are rendered unsal- able by the abundance of honey-dew exuded by these insects. The principal known species are: Woolly Aphis (Schizonewra lanigera).—This little insect secretes a white cottony mass about its body and infests both the roots and _ the branches of apple trees. Its presence can be readily de- ’ tected by this white cottony mass, and upon close examina- tion the brownish- pink lice are found under the cotton. The Fig. 4. Woolly Aphis of the apple (Schizoneura lanigera, Hausm.) root form causes great damage to the tissues of the roots by forming swellings or galls, giving an unhealthy growth, which soon kills the small roots. As the root-infesting form is by far the most destruc- tive, it is important that remedial measures should be directed against it. By eradicating the root form in winter a great reduction in the branch or aérial form follows, but it can be readily understood that this underground form is extremely difficult to combat. Early in the fall dig a trench around the tree, uncovering the crown roots as much as possible; in this trench place one or two shovelfuls of unslaked lime, according to the age and size of the tree; add enough water to slake the lime, and cover up with earth. The rain will keep carrying the lime to the roots and reduce the pest. As a substitute for the unslaked lime, gas lime is very often used, but great caution must be 10 STATE HORTICULTURAL COMMISSION. exercised, for if applied in too great quantity there is danger of killing the tree. One or two shovelfuls can be used on an old tree, but a young tree should not be treated with this substance. The use of tobacco dust has given good results, particularly on young trees and nursery stock. The application should be made in the fall of the year, so that the rains can leach out the tobacco juice and bring it in contact with the aphids. For the branch, or aérial, form a good kerosene emulsion or whale-oil soap wash (summer formula) will soon reduce the pest. KEROSENE EMULSION. Coal:oil 60? teSt osc cso cos ecedec acest saci cece 4 gallons. Laundry sOa pio. scsce secede see eet eecc eteeenes vekexs 1 pound. Wratel 2.0 sceeccectusscecseiceviscnscussceassdenedeensee 2 gallons. Dissolve the soap by boiling in the water, and when dissolved and while boiling pour with a dash into the kerosene. Churn the mixture for ten or fifteen minutes, either by pouring back and forth from one vessel to another, or by pumping the liquid back upon itself. The emulsion should have the consistency of cream. For a winter wash when trees are dormant, use one gallon of emulsion to six gallons of hot water. For a summer wash use one gallon of emulsion to ten gallons of hot water. Prune Aphis (Aphis prunifoliz)—These insects are readily recognized by their bluish-green color and by the abundance of honey-dew generally found on the ground under the infested trees. In abnormal! sea- sons only does this pest become inju- rious to the prune trees. Our native lady-birds and syrphus flies generally keep this species under control, but in the absence of these friends use the summer formula of the kerosene Fig. 5. Prune Aphis (Aphis emulsion or the whale-oil soap ‘solu- pruntfolizx). ti ion. Black Peach Aphis (Aphis persice-niger).—This insect is one of the most dangerous foes of the peach tree, and the grower should, at the very start, wherever he notices its INSECTS AND INSECTICIDES. 11 appearance, thoroughly eradicate it. It is a small brownish- black insect and exists in the wingless as well as in the winged form. It attacks the roots as well as the foliage, and this makes it all the more diffi- y cultto combat. The branch >, form is readily controlled by the use of kerosene emulsion or the whale-oil soap wash, using the sum- mer formula; but, so far, no wash or remedy has been found to give perfect Fic. 6. Black Peach Aphis (Aphis results on thé root form, persic#-niger). only partial relief having been obtained by the use of a diluted kerosene emulsion, used around the base of the tree and applied during or just before arain. This allows the water to carry the emulsion to the infested parts. Tobacco dust, as recommended for the root form of woolly aphis, will also give partial relief. Hop Louse (Phorodon humuli).—The following is recom- mended, to be applied as a spray: Whale-oil soapiussscseissesscateseccie: Geese ets 7 pounds. QUaSsSIaCHIPS:.