New Insecticides Control Soft Scale, Vol.3, Issue 3
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OREGON K. G. Swenson August 1959 AND Entomology Department ORNAMENTAL Vol. 3, Issue 3 Oregon State College NURSERY DIGEST Page 1,2 Corvallis, OR NEW INSECTICIDES CONTROL SOFT SCALE Several newly developed insecticides now provide a high degree of control for soft scales on many broadleaved evergreens. Holly and camellia in Oregon are commonly and consistently infected by these scales. The two most common soft scale insects on holly and camellia in Oregon are the brown soft scale (Coccus hesperidum) and the cottony camellia scale (Pulvinaria floceifera ). Brown soft scales infestations are characterized by considerable variation in scale size (Figure 1). Infestations of cottony camellia scale are made up of scales of uniform size and are also distinguished by the presence of white, elongated egg masses (Figure 2). Mold increases injury Injury from these scale insects is greatly Figure 1. Brown soft scale, Coccus increased by the sooty mold which hesperidum, on holly. Infestations of this grows in the excretion of the scales. The scale are characterized by variation in the sooty mold develops to a point where size of the scale. the vigor of the plant is impaired if the scales are not controlled. Losses also occur because holly cannot be cut on many infested trees. Virtually 100% control of the cottony camellia scale can be obtained by spraying thoroughly with malathion in August after eggs have hatched. Control of the brown soft scale has been more difficult. Results of 1954- 1955 tests with malathion applied at the rate of 2 ½ pints of 57% emulsifiable concentrate in 100 gallons of water gave Figure 2.Cottony camellia scale, Pulvinaria floceifera, on holly. Black areas are sooty mold. The upper surface of the leaf is completely black. from 85 to 95% control. The 5-15% survivors were primarily adult scales. Two or three applications were needed to obtain adequate control. Evaluated in 1958 Further insecticide evaluations were made in 1958. The first test was for control of a mixed infestation of brown soft scale and cottony camellia scale on holly. Insecticides used and rates and times of application are given in Table 1. Cottony camellia scales were in the adult stage on May 14 but had not yet begun egg laying. Complete control was obtained with Diazinon and Sevin. About 85% control was obtained with light-medium summer oil and malathion-Glyodin combination. Malathion applied May 14, Demeton ( Systox) and Phosphamidon gave about 60% control. Somewhat less control was obtained with malathion applied March 18 and with Thimet. Scale infestations in the Dibrom plots were almost as severe as in unsprayed plots. Table 1. Insecticides evaluated for control of soft scales on holly. 1 2 Insecticide Rate Formulation Applied Diazinon ------------------6.0 pts. 25% e. c. May14 Sevin ----------------------2.0 lbs. 50%w. p. May 14 Light-medium summer oil----------------24.0 pts. March I8 Malathion + ----------- 3.0 pts. 57% e.c. Glyodin ------------ 2.0 pts. 34% e.c. May 14 Malathion------------------_' -- 3.0 pts 57% e.c. May 14 Demeton ---------------------1.0 pt. 23% e. c. May 14 Phosphamidon --------- 0.5 pt. 48% e. c. May 14 Malathion --------------- 3.0 pts. 57% e.c. March 18 Thimet -------------- 0.5 pt. 47.5% e.c May 14 Dibrom ........................ 1.5 pt. 64.5% e.c. May 14 1One-fourth pint Triton 1956-13 to 100 gallons of water was added to all sprays except light-medium summer oil and Malathion-Glyodin combination. 2e.c. = Emulsifiable Concentrate: w.p. = wettable powder. Holly scale tested Another 1958 test was made with brown soft scale on holly trees. This infestation consisted primarily of adult scales, which are difficult to control. Most of the same insecticides were used and sprays were applied on July 2. Results are presented in Table 2 and are essentially the same as those obtained in the first 1958 test. The only inconsistent results were with the malathion- Glyodin combination. This combination was tested because of reports of increased insecticidal efficiency when Glyodin was used with insecticides in sprays to control orchard insect pests. This capacity to increase insecticidal efficiency is apparently due to its properties as a wetting agent. In view of the degree of scale control obtained with Diazinon and Sevin, it is no longer necessary to increase the efficiency of malathion. The control obtained with malathion in this test was lower than usual and is attributed to the fact that the scale population consisted primarily of adult scales. Table 2. Control of brown soft scale on holly. 1 2 Insecticide Rate Formulation Control Pints Percent e.c. Percent Sevin ------------- 8.0 12 100 Diazinon -------- 6.0 25 99 Malathion ---- 3.0 57 74 Demeton .. --- 1.0 23 54 Phosphamidon 0.5 48 43 Malathion --- 3.0 57 +Glyodin 2.0 34 36 Thimet ---------- 0.5 47.5 32 1One-fourth pint Triton 1956-13 to 100 gallons of water was added to all sprays except the Malathion-Glyodin combination. 2e.c. = emulsifiable concentrate. Another series of insecticide evaluations was made in 1959. results of which are presented in Table 3. In addition to Seyin and Diazinon, Dimethoate and Guthion proved highly effective. Tests lasted 5 years This information summarizes results of five years' experimentation and observation in control of soft scales. Sevin, Diazinon, Dimethoate, and Guthion were more effective for brown soft scale control than malathion which is currently used. These four insecticides applied as summer sprays also are more effective than oil sprays applied in spring before buds open. Table 3. Control of brown soft scale in holly. Formu- Insecticide1 Rate2 lation Applied Control Percent Sevin -------------2lbs. 50% w.p. June 3 100 Dimethoate ----- 1 pt. 46% e. c. June 3 100 Guthion -------- 5 pts. 17.5 %e.c. June 3 100 Diazinon ----------6 pts. 25% e. c. June 3 98 Seyin --------- 2 lbs. 50% w.p. April 24 93 Light-medium summer oil 24 pts. April 10 92 Volck 16 pts. April 10 91 Supreme Oil Malathion ---- 3 pts 57 % e.c. June 3 89 Diazinon ………6 pts. 25% e.c April 24 84 1One-fourth pint Triton 1956-B to 100 gallons of water was added to all sprays except the oil sprays. 2e.c. = emulsifable concentrate ; w.p. wettable powder. No phytotoxic effects have been observed on holly as a result of applications of Sevin, Diazinon, Dimethoate, or Guthion. Sevin and Diazinon have been applied to holly extensively enough so that there appears to be little likelihood of plant injury. So far Guthion and Dimethoate have been applied to only a limited number of trees. A spreader-sticker should be included at the maximum dosage recommended on the label when applying insecticides to holly and camellia. Thorough coverage is also essential. Oregon Ornamental and Nursery Digest was published from 1957 to 1975 by the Agricultural Experiment Station, Oregon State University, Corvallis. Pesticide Use - Due to constantly changing laws and regulations, no liability for the suggested use of chemicals in this reprint is assumed. Pesticides should be applied according to label directions on the pesticide container. Permission to Reprint material appearing in the Oregon Ornamental and Nursery Digest is granted with the request that you credit the source: Oregon Ornamental and Nursery Digest, date, volume, issue, page numbers. Do not excerpt or reprint in such a manner as to imply the author's endorsement or criticism of a product or concept. Nondiscrimination - The information in the Oregon Ornamental and Nursery Digest is provided with the understanding that no discrimination is intended and that listing of commercial products implies no endorsement by the authors. Criticism of products or equipment is neither intended nor implied. .