Experiments in the use of DDT and other insecticides for control of the spruce budworm in Colorado in 1944


Material Information

Experiments in the use of DDT and other insecticides for control of the spruce budworm in Colorado in 1944
Physical Description:
10 p. : ; 27 cm.
Orr, L. W ( Lyman Walton ), 1915-
Wygant, N. D
United States -- Bureau of Entomology and Plant Quarantine
U.S. Dept. of Agriculture, Agricultural Research Administration, Bureau of Entomology and Plant Quarantine
Place of Publication:
Washington, D.C
Publication Date:


Subjects / Keywords:
Spruce budworm -- Control -- Colorado   ( lcsh )
DDT (Insecticide) -- Testing   ( lcsh )
Insecticides -- Testing   ( lcsh )


Additional Physical Form:
Also available in electronic format.
General Note:
Caption title.
General Note:
General Note:
"August 1945."
Statement of Responsibility:
by L.W. Orr and N.D. Wygant.

Record Information

Source Institution:
University of Florida
Rights Management:
All applicable rights reserved by the source institution and holding location.
Resource Identifier:
aleph - 030290545
oclc - 779925166
System ID:

Full Text
August 1945 1-_669

united. States Department of Agriculture
Agricultural Research Administration Bureau of Entomoloy and Plant Quarantine


By L. W. Orr and N. D). Wygant, Division of Forest Insect Investigations

The spruce budworm (Arohips fumiferana (Clem.)) is a forest insect that is very difficult to kill with insecticides, because of the
peculiar feeding habits of the larvae. Several attempts have been
made to control this pest in recreational or other high-value forest areas by the application of lead arsenate, calcium arsenate,. or cryolite spray or dust, but with only partial success. A current extensive outbreak of the budworm in Colorado offered an opportunity to
test the effectiveness of DDT insecticides for use in such areas, and
informal arrangements were made with the National Park Service and the United States Forest Service for conducting a series of experiments in the vicinity of 2stes Park in 1944.

Equipment, Mterials, and Procedure

A large power sprayer formerly used in gypsy moth control work
was made available for applying the materials. Th~e plots selected
for treatment were located along roads where it was seldom necessary to usemore than 300 feet of hose. The trees varied greatly in size,.
with the largest ones exceeding 100 feet in height. Some of the
trees were therefore too tall to be sprayed from the ground, but most
of them were less than 75 feet tall and could be thoroughly treated.
Each plot consisted of the trees which could be sprayed adequately
with 300 gallons of liquid, except for two plots where only 150 gallons were applied and two others where 600 gallons were used. In mest cases 300 gallons of spray mixture covered the trees on more
than 1/2 acre, the average application being at the rate of about 500
gallons per acre.

Spraying operations were conducted during three periods, to determine at which stage of insect development the treatment would be
most effective. The first group of plots were sprayed after some of
the overvintered larvae had left their hibernacula and moved out to the ends of the branches where they were mining the old needles, the
second group when most of the larvae were approximately half grown
and were feeding on the needles of the new growth, and the third group during the period of moth flight in an effort to kill the moths, eggs,
,or newly hatched larvae.

Technical DDTY (l-trichloro-2,2-bis(p-chlorophenyl)ethane) ,was
used in these experiments. For comparison,. and ina the hope of finding a mixture that would be more effective than those used in previous years, several plots were sprayed with lead arsenate and one plot was sprayed with a- mixture of pyrethrum. andi derris. Details as to location of the various plots, dates of application, formulas used, and results obtained are given in table 1 (see PP. 7 to 10)

Types of DDT Mixtures Used

Four types of spray mixtures containing DDT] were applied. In one the ]3IY]T powder was added to isopropyl alcohol at the rate of 1 pound to 1 gallon and dissolved by heating. The hot alcohol solution was then slowly poured into a spray tank nearly full of water. As soon as the alcohol solution came in contact with the water,. the DDT was precipitated as a very fine suspension, which sprayed out well if applied immediately. It was found, however, that some of the DDT adhered to the walls of the spray tank, piping, pump, and nozzle, with the result that a hard deposit was gradually built up until it interfered with operation of the equipment after several days of use.

The second type of mixture was prepared by dissolving 1 pound of DDT in 2 quarts of hot linseed oil (replacement grade) or light-medium. white mineral oil, and then emulsifying this solution in water. Triton X-100 (an aralky. polyether alcohol) or casein spreader was used as the emulsifying agent.

The third type of mixture contained a small amount of DDT added to the usual lead arsenate spray. The DDT was dissolved in lightmedium white mineral oil, by heating, and emulsified with casein spreader in about an equal volume of water. ThI~s emulsion was then poured into the spray tank containing the lead arsenate and water.

The fourth type was a suspension prepared by making a thin paste or slurry of the DDT, Triton X-100O, and a small quantity of water, and adding it to the water in the spray tank. Linseed oil was then
added to the dilute suspension to act as a sticker. Only one plot, No. 8 at Glen Haven, was sprayed with this mixture and, as will be noted in table 1, the results were not nearly so good as those obtained with the other mixtures.

An attempt was made to prepare concentrated stock mixtures that could be made up a day or more in advance of application and thus save time in the field. This did not prove practical with the materials being used. When the hot concentrated solution of DDT in alcohol was added to about an equal volume of water, a creamy suspension was formed, which soon thickened to a spongy mass with further cooling. When this material was poured into the spray tank containing water on the following day, a flocculated suspension was formed and relatively large masses of DDT crystals,. visible to the naked eye, were deposited on the bark and foliage of sprayed trees. Plot 2 at Moraine Park and Plot 3 at Glen Haven were sprayed with this mixture. The concentrated solution of DDT in linseed oil formed a nearly solid mass upon cooling, and therefore had to be reheated before being used.


Analysis of Results

It was found very difficult to judge the immediate effectiveness of the sprays applied early in the season. At this time most of the larvae were mining the needles or had entered the new buds, and they were therefore located only after careful examination. A number of counts of infested needles and buds were made, but such work was found very time-consuming and of doubtful value. Although the counts indicated a marked reduction In the number of larvae on the plots sprayed with DDYT) the numbers involved were too small to give anything more than a possible indication of final results. The total defoliation at the end of the feeding period was therefore used as a more significant measure of effectiveness (see table 1).

The tests that were made about the middle of June, when the l.arvae were partly grown and feeding on the new growth, save results that were much more spectacular. When heavily infested trees were sprayed with DDT, thousands of larvae dropped to the ground, usually on silken threads, within 20 or 30 minutes. Some of the larvae lived for several hours or even days after the trees were sprayed, but there was little or no additional feeding.

The derris-pyretbrum mixture applied on Plot 39 also showed very striking results. The larvae dropped in large numbers almost Immodiately and without spinning threads. The lead arsenate mixtures were not so effective, although some of them did greatly reduce the total] amount of defoliation for the season.

Only DDT mixtures were tested in July when the moths were flying. Moths that were resting in the trees at the time of spraying were affected almost Immediately, and thousands of them dropped to the ground, where they soon died. Moths moving into the sprayed plots even several days later were killed by the DDT residue on the trees.

The moths had not begun to lay eggs by the time it was necessary to terminate work in the area. This was unfortunate, because information was not obtained as to whether-DDT prevented. egg laying on sprayed trees or, if eggs were laid, whether the oung larvae were killed. All plots that were sprayed with DDT in 1944 were examined in June 1945 and found to be less heavily infested than the surrounding areas. The difference was particularly striking on the Plots that were sprayed in July, but was also noticeable on those sprayed in May and June.

As indicated above, the results of the various spray applications that were Made during the larval feeding period were evaluated largely on the basis of the grossappearance of the trees after feeding was completed. It was very evident that DDT was much ~iperior to lead arsenate in its effectiveness against the budworm. The data given in table 1 show that DDT was very effective in all the types of mixtures %ppJlied and at concentrations as low as 1/2 pound per 100 gallons of water. The two plots that received. only 1/4f pound of DDT plus 4f


pounds of lead arsenate per 100 geLI104 water showed more defoliation than did those that were sprayed with 1/2 pound of DDT., but considerably less than those that were treated with lead arsenate alone.

It was also apparent that the control was more nearly complete
on the firs and spruces than on the ponderosa pine., and somewhat better on the firs than on the spruces. This difference in effectiveness was apparently influenced by several factors., the most important of which were differences in larval feeding habits and in spray coverage obtained on the various tree species.

The first feeding by at least a considerable proportion of the overwintered larvae is done by mining the old needles. On fir and spruce each larva apparently mines several needles., and in moving from one needle to another is likely to come in contact with DDT resi(lue if the tree has been sprayed. Larvae on pine also mine the old needles but there is far less movement between needles because the needles are larger. Larvae on fir and spruce enter many of the new buds and later feed on the expanding tips or shoots, each larva often infesting several tips before reaching maturity. There are thus several opportunities for each larva to come in contact with treated surfaces., as well as several periods when it is exposed to direct contact when the spray liquids are being applied. When larvae on pines leave the old needles. they move to clusters of staminate flowers or to the new needles. Many of them feed among the staminate flowers until the flowers are dry and most of the pollen is gone. Those that infest the new needles do so by boring through the bundle sheath and eating the enclosed needle tissues. It Is only when the larvae are large and nearly mature that they spend m:uch time outside the needles., flower clusters., or needle bundle sheaths., and even then they are protected by webbing that they spin along the surface of the twig between the bases of the needles.

Spray coverage of the new foliage appeared to be best on Douglas fir and alpine fir. The fir buds open up rather quickly., and the needles spread out even before there has been much shoot elongation, particularly on alpine fir. On spruce the needles remain closely oppressed for a longer time and are not easily wetted. Larvae that have entered spruce buds continue to feed on the bases of the needles along the expanding shoot., where they are not likely to be contacted by the spray. The large "brushes" of needles at the ends of ponderosa pine branches are very difficult to wet thoroughly, as they usually droop slightly so that tae spray liquid has a tendency to run off the ends of the needles. MoreoverY the large numbers of coaxse scales at the bases of the needle bundles., around the buds, and on the expanding new shoots are.somewhat resinous and very resistant to wetting.

A discussion of the results obtained on the plots sprayed with the various mixtures of lead arsenate appears unnecessary., since DDI! Vas vastly superior even to the beat of the lead arsenate formu.1as. It vas hoped that, in case BDT did not prove to be effective., a lead arsenate formula could be developed that would give reasonably good

control. The best way to accomplish this seemed to be through the use of wetting agents that might result in better coverage of the new foliage and silken webbing, so that some of the lead arsenate would be deposited on the basal parts of the new needles where it would be eaten by the budworm larvae. A number of proprietary materials were tried. and three of them--Duponit Spreader-Sticke;r (sodium oleyl ou.1.fate and a synthetic resinous sticker), Triton B-1956 (a phthalic glyceryl alkyd), and tUltraifet (a water-soluble sodium sulfonate of petroleum hy7drocarbons)--appeared to cause a noticeable increase in effectiveness as compared with the ordinary lead arsenate spray containing linseed oil as an adhesive (see table 1, Plots 33 and 35 at Glen Haven, and plot 40 at Endovalley Camp Ground).


DDTr is very toxic to larvae and adults of the spruce budworm.
This material apparently acts primarily as a contact Insecticide a-ad continues to be effective over a long period of time. In contrast to most c ontact insecticides, it is not necessary that the spray liquid come in direct contact with the insects at the time of application, for as long as the residue remains on the trees it will kill budworm larvae or moths that may come in contact with it. This is very important, because it means that the period during which sprayIng can be done effectively is much longer than with other insecticides.

The tests conducted in 1944 indicate that the best results,
especially on pine, will be obtained by spraying Just before the overwintered larvae leave hibernation. It is believed that, where largescale operations are to be undertaken, spraying should be begun at least 2 or 3 weeks before the larvae become active. In all earlyseason spraying special attention should be given to directing the spray stream at the trunks and larger branches so as to cover the bark thoroughly. The overwintered larvae will then come in contact with the DDT when they crawl over the bark surface after leaving hibernation and before reaching the old needles or new buds. Spraying can be continued throughout the larval feeding period, at least on the firs and spruces.. although trees thus sprayed will of course be at least partially defoliated. DDT applied after the feeding period and before the moths have laid eggs,, or at least before the eggs have hatched, appears to reduce the Infestation for the next year, but further observations are needed on this point.

It is possible that sufficient residue remains on trees sprayed. early in the season to prevent oviposition or to reduce the number of eggs deposited by moths migrating into the sprayed area. If eggs are deposited on such trees, the larvae hatching from them my be killed while searching for suitable places in which to spin their hibernacula. If either of these possibilities proves to be true, it will mean that one application will protect trees for two seasons, thus greatly reducing the cost of control.


It is believed that 1 pound of DDYT per 100 galtlons of water,. or about 5 pounds per acre., will prove most satisfactory where a power sprayer is used, although 1/2 pound per 100 gallons will give almost as good control under favorable conditions and may be sufficient where it is only necessary to reduce defoliat ion enpugh to 'prevent serious injury to the trees. The lover rate may not be sufficient to allow for weathering in seasons of frequent rainfall. The cost of the insecticide isa relatively small part of the total cost of a spraying operation, and if the material is freely available it is better to use enough to insure effective results.

A derris-pyrethrum. mixture is very effective against partly grown larvae but is impractical for use in large-scale control operations because of excessive costs.


In an effort to develop an effective method of controlling the
spruce budworm. (Ach fumiferana (Clem..)) on areas of special value,.
several tests were made in the vicinity of Estes Park, Colo., in cooperation with other government agencies. A series of plots were sprayed with a large power sprayer. DDT~ (l-trichloro-2,2-bis(p-chloe rophenyl)ethane) proved to be far superior to lead arsenate. When applied at concentrations of 1/2 pound or more per 100 gallons of water, or at a dosage of about 2 1/2 pounds or more per acre, this material caused almost complete mortality of the budworm larvae on the firs and spruces. Control was not quite so complete on ponderosa pine, but it is possible that further tests with reference to prcop,-. timing of the spray application may give the desired results.

The DDr was effective when applied either as a very fine suspension produced by dissolving the DJXP in hot isopropyl alcohol and then pouring the hot solution into the spray tank containing water,. or as an emulsion produced by dissolving the DDT] in hot linseed oil and adding an emulsifier before pouring the solution into the spray tank. Best results were obtained by spraying just before the overwintered larvae left their hibernacula, although applications made later during the larval feeding period gave satisfactory control. Adult moths were also readily killed by the DDT spray.

A series of plots were sprayed with lead arsenate for comparison with D~DT, and in an attempt to improve upon results obtained when lead arsenate had been used against the budworm. in previous control work. The formulas included several proprietary wetting agents. Some of these- materials resulted in better coverage or heavier deposit, as evidenced by decreased defoliation. However, none of the lead arsenate formulas can be considered so satisfactory as those containing DDTI.

One plot was sprayed with a derris-pyrethrum, mixture, which proved very effective in killing partly grown larvae.

Table l.--Spray formulas and results obtained in spruce budworm control experiments in Colorado in 1944

Dte : Plot : Spray forI~ul& : Defoliation
Sprayed : io. : Insecticide Accessory material on July 22

Pounds Percent

Moraine Park, on ponderosa pine

May 18 1 3 Linseed oil 6 qt. plus 10
Triton X-100 8 oz.
2 3 Isopropyl alcohol 12 qts. 5
24 21 3/4 plus lead Mineral oil 6 qt. plus 25
arsenate 12 casein 16 oz.
22 3 Alcohol 12 qt. 10
23 1 1/2 Alcohol 6 qt. 15
June 23 42 3 Linseed oil 6 qt. 30
plus Triton X-100 15 oz.
43 3 Linseed oil 6 qt. 30
plus casein 8 oz.
Lead arsenate:
May 24 19 12 Linseed oil 1 1/2 qt. 75
20 12 plus nicotine Mineral oil 6 qt. 65
sulfate 1 1/2 qt. plus casein 16 oz.

Check (untreated adjacent area) 75

Glen Haven, on Douglas fir DDT:
ay 19 3 3 Alcohol 12 qt. 0
4 3 Linseed oil 6 qt. plus 0
casein 8 oz.
5 1 1/2 Linse d oil 3 qt. plus Trace
Triton X-l00 4 oz.
20 7 1 1/2 Alcohol 6 qt. Trace
8 3 Linseed oil 3/4 qt. pluq
Triton X-100 1 1/2 oz../ 40
23 17 3/4 plus lead Mineral oil 6 qt. plus 20
arsenate 12 casein 16 oz.
June 19 32 3 Alcohol 12 qt. 4h5
36 6 Linseed oil 12 qt. plus 10
Triton X-100 24 oz.
July22 2/44 6 Sam
45 3 Linseed oil 6 qt. plus
Triton X-100 12 oz.
46 3 Mineral oil 6 qt. plus
casein 8 oz.
47 1 1/2 Linseed oil 3 qt. plus
Triton X-100 6 oz.

Table 1. --(continued)

Date : Plot : Spray forwJlaq- : Defoliationg'
,prayed : No. Insecticide Accessory materials on July 22

Pounds Percent

Glen Haven on Douglas fir (continued)
Lead arsenate:
May 19 6 12 Linseed oil 1 1/2 qt. 85
23 16 12 plus nicotine Mineral oil 6 qt. plus 90
sulfate 3 oz. casein 16 oz.
18 12 Light mineral oil and 90
oleic acid (19:1) 6 qt. plus 2% ammonia 24 oz. June 19 30 16 Mineral oil 6 qt. plus 75
casein 16 oz.
31 16 plus nicotine Same 65
sulfate 1 1/2
20 33 16 Linseed oil 2 qt. plus 50
Dupont Spreader-Sticker 4 oz. 34 16 Linseed oil 2 qt. lus 75
Ultranate No. 2./18 oz. plus alcohol 1/2 oz.
35 16 Linseed oil 2 qt. plus 40
Triton B-1956 9 oz.

Check (untreated adjacent area) 90+

Endovalley Camp Ground, on Douglas fir, alpine fir, blue spruce, and Engelmann spruce DDT:
June 1 24 3 Alcohol 12 qt. 5
25 6 Alcohol 24 qt. Trace
26 3 Linseed oil 6 qt. plus
Triton X-100 12 oz. 5
23 38 3 Linseed oil 6 qt. plus
casein 8 oz. 10

39 Derris (3.9% Triton B-1956 6 oz. 15
rotenone) 3 plus
pyrethrum extract
(2% pyrethrins) 6 qts.

Lead arsenate:
40 16 Ultrawet 2 lb. 30
41 16 IN-438 6 oz. 60

Check (untreated adjacent area) 75


Table l.--(Continued)

S ,,,. ,,Spray Formlas1/
Date Plot :___Defoliatio__2
Sprayed : No. : Insecticide Accessory materials : July 22

Pounds Percent

Boy Scout Camp, on Engelmann spruce

June 19 27 3 Alcohol 12 qt. plus 10
Triton X-100 8 oz.
28 3 Linseed oil 6 qt. plus 5
Triton X-100 12 oz.

Check (untreated adjacent area) 60

North Fork Picnic Ground, on Douglas fir and Engelmann spruce

May 20 9 1 1/2 Alcohol 6 qt. 10
10 1 1/2 Linseed oil 2 qt. plus 5
Triton X-100 6 oz.

Lead arsenate:
June 19 29 16 Linseed oil 2 qt. 25

Check (untreated adjacent area) 40

Park Hill, on Douglas fir

May 22 11 3 Alcohol 12 qt. Trace
12 1 1/2 Alcohol 6 qt. 5
13 3 Linseed oil 6 qt. plus Trace
Triton X-100 6 oz.
14 1 1/2 Linseed oil 3 qt. plus Trace
Triton X-100 6 oz.
Lead arsenate:
15 12 Linseed oil 1 1/2 qt. 50

Check (untreated adjacent area) 75

Wild Basin, on Douglas fir, alpine fir, and Engelmann spruce

June 21 37 3 Linseed oil 6 qt. plus 5
Triton X-100 12 oz.

Check (untreated adjacent area) 75

3 1:2112 09238 7413
i1/ Quantities per 300 gallons of spray mixture.

2/ Percent of new foliage eaten on firs and spruces and percent of tips I oto on pine.

3/ Mixture formed a suspension.

/ ll fir and spruce plots sprayed with WYT in June showed little orno
e in defoliation after they were sprayed.

5,/ Plots 44-47 sprayed after larval feeding was completed and while moths ere i flight. Three of these plots had been sprayed with lead arsenate in My aa folioa: Plot 45 is former plot 6, 46 is former plot 16, and 47 is former plot 17.

6/ An emulsifier containing sodium sulfonate.