HOW TO CONTROL GRASSHOPPERS

Transcription

1 STATE AGRCULTl CCLL[tjf~: FORT COLLNS, COLO. Circular 59 March, 1934 HOW TO CONTROL GRASSHOPPERS OFFCE OF STATE ENTOMOLOGST COLORADO AGRCULTURAL COLLEGE GEO. M. LST, State Entomologist FORT COLLNS, COLORADO

2 8UMMARY 1. Grasshoppers are important pests to crops in Colorado. Records of the last 30 years show a major outbreak about once every 10 years. The last general outbreak which started in 1930 and reached its peak in 1931, cost the farmers approximately $70,000 in money actually expended in control. A survey of crop losses would bring this total much higher. 2. There are five major species of grasshoppers in Colorado. These are important for the reason that all have a large potential egg-laying capacity and are therefore capable of reproducing rapidly in favorable seasons. 3. Dry hot seasons, especially during the egg-laying period, are favorable for grasshopper increase. Severe outbreaks. occur fouowing and during drouth periods. 4. Poisoned-bran mash is recommended as the best means of control. This may be supplemented with fall or spring plowing of egg-beds and the use of the hopper dozer. Several items of importance should be stressed in the preparation and use of bran mash. a. nsist on good bran, free from shorts. b. Mix well with proper ingredients. c. Be sure to spread at proper Um.e of day with reference to temperature. d. Scatter in the approved manner and avoid losses in livestock. e. Do not look for results too quickly. Give the poison time to work.

3 HOW TO CONTROL GRASSHOPPERS By FRANK T. COWANt Colorado has always been, and probably always will be, a "grasshopper state." General outbreaks have occurred on the average of about once in 10 years since 1900.* Hardly a year passes without it being necessary to do control work in some part of the state. During the last 3 years the farmers of Colorado have spent over $70,000 :fighting these pests in an effort to save their crops. Even so, the crop loss in 1931 amounted to thousands of dollars, but was confined, for the most part, to areas where little or no control work was undertaken. n 1932 this loss dropped off considerably, and in 1933 it was practically negligible. There is no way of estimating what the damage would have been had no control work been done. At the present time (1934) this state is as free of grasshopper troubles as can reasonably be expected. However, with another series of dry years such as have just been experienced, the grasshopper populations will again build up and another general outbreak will be in store. The purpose of this bulletin is to familiarize the farmer with grasshoppers, their life histories, habits and control. t is felt that if each farmer will make it his business to know as much as possible about grasshoppers, such outbreaks as have been experienced may be successfully prevented in the future. This information should be gathered from actual experience with the help of such publications as are available. Now is the tim,e to learn while the grasshopper populations are low. Do not wait until they are doing damage to crops to do your experimenting. FVE DESTRUCTVE SPECES OF GRASSHOPPERS N COLORADO There are many species of grasshoppers in Colorado, but only five may be considered of economic importance. Their life histories, habits and control are alike in so many respects that they may be treated in one discussion. The essential differences in appearance and ha;bits are pointed out in the following paragraphs. :j: Formerly Deputy State Entomologist. Earlier authentic records are not available.

4 4 STATE ENTOMOLOGST Circular 59 TWO- STRPED GRASSHOPPER (Melanoplus bivitattus Say). - This grasshopper (Fig. 1) is a compact species, yellowish on the underside and dark gray above, with two yellow strips running from the forehead down each side of the back. The female is from 1 to 11;2 inches long, while the male is considerably smaller. t is without a doubt the most destructive species found in this state. t has a large potential egglaying capacity and, given the proper weather conditions during the late summer and fall, is capable of showing a remarkable increase at hatching time the following spring. For the most part its eggs are laid in the native sod of headlands and roadsides but may be deposited freely in alfalfa fields and along d 1 itch banks. Oftentimes the eggs are laid in the crowns of the alfalf'a plants. t seldom deposits eggs in cultivated fields. Fortunately the two-striped grasshopper does not migrate Figure 1. Two-striped grasshopper. any great distance. The nymphs, (M. bivitattus). Adult female. Twice natural size..(owa Ex- Or young hoppers, will Of COUrse tension Service Bul. No. 182 ) move into CUltivated fields from the hatching grounds and the adults will often move from one field to another. For the most part, however, outbreaks of this species are restricted to certain areas. For this reason it is possible for the individual farmer to protect his crops from hoppers moving in from neighboring fields. THE DFFERENTAL GRASSHOPPER (M elanoplus dijjerentialis Uhl.).-This grasshopper (Fig. 2) is usually yellow in color but occasional individuals are found that are black with only a few yellow markings. The adult averages 1112 inches in length and has distinct yellow and black chevron-like markings on the large part of the hind leg. The egg-laying and m'igrating habits are quite similar to

5 March, 1934 HOW TO CONTROL GRASSHOPPERS 5 those of the two-striped grasshopper except that the differential grasshopper lays its eggs almost entirely in native sod. Like the two-striped grasshopper it does not migrate any great distance. Figure 2. Differential grasshopper (M. differentialis). Adult male. Twice natural size. (U. S. D. A. Farmers' Bulletin No. 1691). THE LESSER M 1 GRATORY GRASSHOPPER (Melanoplus mexicanus Sauss). - This species (Fig. 3) is a sm~a-11 yellowish - gray grasshopper averaging about 1 inch in length. t has a distinct patch of black on its neck. A.l t h o comparatively small in size it is a Figure 3. Lesser migratory grasshopper (M. strong flier and capamexicanus). Adult male. Twice natural ble of mi"gr oti"ng for size. (U. S. D. A. Farmers' Bulletin No.!Q > some distance. ts capacity for egg-laying during favorable seasons exceeds that of the two-striped grasshopper. t is widely distributed over the state but is usually more of a pest in the dry1and sections than in the irrigated ones. The eggs are laid in a light, sandy soil along fence rows, in weed patches and stubble fields. The nymphs start migrating from the egg-bed's as soon as they are hatched. THE RED-LEGGED GRASSHOPPER (M elarwplus femur-rubrum De Geer).-This species (Fig 4) resembles the lesser migratory grasshopper quite closely. t is slightly smaller in size and has a distinct sulfur-yellow color on the underside of the body. The small part of the hind leg is red. ts egg-laying habits are similar to the lesser migratory

6 6 STATE ENTOMOLOGST Figure 4. Red-legged grasshopper (M. femttrrubrwn). Adult male. Twice natural size. (U. S. D. A. Farmers' Bulletin No ) than in native pastures or uplands. Circular 59 grasshopper and the two are often found intermingled. n its other habits it differs in that it seldom migrates and is commonly more abundant in cultivated fie ds THE LONG-VVNGED GRASSHOPPER OF THE PLANS (Dissost e i r a longipennis Thos). - This is a gray and brown mottled grasshopper oft e n attaining a length of 2 inches. t has long, stout wings and is capable Of migrating long Figure 5. Long-winged grasshopper of the distances. (Fig. 5). plains. (D. longipennis). Adult female. About one-third enlarged. (U. S. D. Bulletin 747.) A. Farmers' Fortunately it is found in outbreak numbers but seldom and is confined to the dryland areas of Eastern Colorado. ts eggs are laid in native pastures. LFE HSTORY THE EGGS are laid by the mature females during the late summer and fall, beginning about the last of July and continuing until the heavy frosts. They are laid in pods (Fig. 6) 1 to 2 inches long. Each pod contains from 10 to 100 individual eggs according to the species that laid it. These eggs are held together within the pod by a mucilaginous substance supplied by the female hopper. Various locations are chosen by the different species, but for the most part egg-beds are confined to roadsides, native sod pastures, headlands, ditch banks, weed patches and alfalfa fields. Ordinarily a sunny, slightly raised location is chosen. Cultivated fields are seldom selected for egg-laying. Each female hopper may in favorable seasons, lay as many as 4 to 8 pods, or from 100 to 400 individual eggs.

7 1\lanh, 1934 HOW TO CONTROL GRASSHOPPERS 7 These eggs lie in the ground a winter and unless disturbed are not affected by extreme temperatures. THE NYMPHS or young h o p p e r s start hatching in May and continue until the last of June. At hatching time t h e y are about one-fourth inch long and resemble the parent hopper in every respect except that they have no Egg pods of the two-striped grasshopper. wings. During the Figure 6. The pod on the right has the outer surface re- h. moved. Enlarged two times. (Colo. Exp. Sta. Bul. hate ng Season 287). much confusion arises among farmers because of the tiny leaf hoppers that are so abundant. These insects resemble the young grasshoppers to some extent when they are observed hopping about on the ground. Closer examination, however, will show that they are full-grown insects and possess wings, while the young hoppers have no wings in this stage. HOW THE YOUNG GRASSHOPPERS DEVELOP.-Since the skeleton of a gr.asshopper, like all other insects, is on the outerside of the body the only way they can grow is b~ shedding this and growing a new one. This process is called "molting" and takes place every week or 10 days until the grasshopper is full grown. The space of time between molts is called an "instar." Each hopper goes thru from 5 to 7 instars in attaining full growth. Often during severe epidemics these cast-off "skins" or skeletons are mistaken for dead grasshoppers and the report goes around that they are "dying by the thousands." This is a natural mistake for the casual observer. Closer examination will show the difference between a cast-off "skin" and a dead hopper. THE ADULT.-The first adults appear early in July or the l ast of June.and continue to increase in numbers until about the last of July. Egg-laying is started shortly after maturity is reached and continues until the hopper dies.

8 8 STATE ENTOMOLOGST Circular 59 HABTS MGRATONS.-During the first two nymphal instars the young hoppers do not move far from the hatching grounds. Later, when the native vegetation starts to dry up, there is a concentrated movement toward the crops. There are also distinct movements from one field to another when harvest is started. These migrations take place first from alfalfa fields to small grains and later from grain fields to corn. The farmer must be on guard at all times in order to anticipate and stop these migrations. n the dryland wheat-growing sections there is usually a distinct migration during the fall from the native pastures to winter wheat. Oftentimes severe d am(age is done on the edge of the fields before the farmer realizes what is happening. FEEDNG AND THE EFFECT OF TEMPERATURE ON THS ACTV TY.-Grasshoppers like all insects, are "cold-blooded." That is, their body temperature is regulated' by the temperature of the surrounding medium. For this reason temperature plays an important part in their daily activities. Experiments have shown that they normally begin moving from their roosting places at from 60 to 65 degrees F. Feeding begins at from 65 to 68 degrees F. At 85 to 90 degrees F. there is a marked decrease in their feeding.activities on or near the ground, altho they may continue to feed in localities where the temperature is still near their optimum. Ordinarily there is a second feeding period during the afternoon, altho usually of short duration. At times, if the temper ature is high enough, grasshoppers will feed at night. This is probably of little consequence in Colorado, where the nights are usually too cool. Little or no feeding takes place during dark, cloudy weather. NATURAL CONTROL WEATHER CONDTONS AS THEY AFFECT GRASSHOPPERS. For the reasons given in the preceding paragraph, weather conditions from year to year pl.ay an important part in the fluctuations of grasshopper populations. Normally the period of greatest numbers is during or following a period of drouth. Also, the greatest amount of damage occurs in dry years. Thus "grasshopper years" are closely correlated with drouth. This may be explained in part by the fact that high temperatures during the egg-laying season give the females opportunity of laying a maximum amount of eggs. Parker* has demonstrated that the number of egg pods deposited by a single Montana Agr. Exp. Sta. Bul. No. 223.

9 March, 1934 HOW TO CONTROL GRASSHOPPERS 9 female may be more than doubled by increasing the temperature. Likewise, the amount of food consumed over a definite period of time is greater during dry, hot weather. DSEASE AS T S AFFECTED BY WEATHER.-During every outbreak numerous inquiries come in as to the possibilities of spreading disease among the grasshoppers. This practice was investigated many years ago and found impractical for the reason that the disease thrives only during wet, cloudy weather. Ordinarily if such weather is encountered the disease will develop of its own accord and aid materially in bringing the insects under control. This is especially true if it occurs shortly after the young hoppers hatch. Likewise, cool, cloudy weather in August and September will not only favor the development of the disease, but will decrease the number of eggs deposited. l<...,igure 7. A sarcophagid or flesh fly, parasitic on grasshoppers. Adult. Enlarged about four times. (U. S. D. A. Farmers' Bul- BRDS.-Little need be said as to the value of birds in grasshopper control. Many of the wild birds in Colorado help a great deal each year by destroying these insects. Gulls are extremely valuable, especially in the irrigated sections where they are attracted to the reservoirs by the thousands. Poultry of all kinds, especially turkeys, are a valuable aid in destroying the pests in the proximity of farm dwellings. NSECT ENEMES.-V ery often during grasshopper ou~ breaks individuals may be found with from 1 to 10 maggots ins'ide their bodies. These maggots are the larvae of a fly, (Fig. 7) closely resembling the house fly. They are called Sarcophagid or "flesh flies" and lay a living maggot on the hopper at the base of the wing while it is in flight. This tiny maggot burrows into the body of the grasshopper where it lives on the fatty tissue and juices and eventually causes death. letin 7 4 7). On reaching maturity the n1aggot leaves the body of the grasshopper, bores into the ground and emerges some time later as an.adult fly. There are probably several generations each year. At times they may become so numerous as practically to wipe out an infestation. There are several kinds of flies that kill grasshoppers in

10 10 STATE ENTOMOLOGST Circular 59 much the same way as do the flesh flies. Also robber flies are known to catch and kill many young hoppers. Digger wasps use both nymphs and adults to provision their nests while the larvae of ground beetles and bee flies consume large quantities of grasshopper eggs. The small red mites often seen on adult grasshoppers are of little benefit to control. ARTFCAL CONTROL CULTVATON.-Plowing and disking of egg-beds where it does not interfere with good farm practices will do much toward destroying the eggs. n plowing the eggs should be turned under at least 6 inches and the plowed soil firmly packed. This should be done either in the fall after the eggs have been 1aid, or early in the spring before they hatch. Disking should be done in the fall in order that the egg pods may be broken up and exposed to the weather. Extreme temperatures during the winter will destroy many of them. WHERE AND HOW TO LOOK FOR GRASSHOPPER EGGS.-The general locations of egg-beds have already been discussed in the paragraph on "eggs" and will not be repeated here. Much time can be saved by observing where the female hoppers congregate for egg-laying during the summer and fall. The eggs,are found within the upper 3 inches of the soil. A small hand trowel or other similar instrument, serves very well as a digging tool. Search should be made in several likely places, since it is very easy to overlook the eggs on just casual observation. THE HOPPER DOZER.-This instrument is well known in grasshopper control, since it has been in use in various forms for years. Figure 8 shows the details of one type that has proved quite successful. The hopper dozer is restricted to small level areas such as pastures and meadows where it can be used without injury to the crop. AtJJest it is seldom more than 60 percent efficient. For this reason it should be used only as a supplement to poisonedbran mash and should not be depended upon to give complete control. n this capacity it has had a wide usage and has proved quite practical. POSONED BAT.-t is agreed by all authorities that poisoned bran when properly mixed and applied, is the most practical and economical method of controlling grasshoppers. The proper bait to use will vary in different states and also within this state according to the existing supply of certain ingredients in the bait. t was determined from tests conducted at Fort Collins, that there are several combinations of attrahents in common use in grasshopper baits that might he expected to give equal con-

11 16ft 2ft ) J J -~ ~ ) 1 1 entra..nee to trap inverted y front ~... ""'" ) ( covered wi-th \\ ~ ~,., ( } Top f.leva"tion \ -1~. l&~r---{ covent~ wota ) lc~ sejr e.n \ _j~ v :~- \ l '- - ~ ;r~ Rear Elevation Figure 8. A detailed diagram of a grasshopper-catching machine. (Colo. Exp. Sta. Bul. No. 233.) N ;to

12 12 STATE ENTOMOLOGST Circular 59 trol under similar conditions. Of all the baits tested the one containing beet molasses and amyl acetate (banana oil) ranked at or near the top. There exists in Colorado a large supply of beet molasses which can be bought from the sugar companies very cheaply while cane molasses is very expensive in comparison. For this reason the following formula is given to the farm.ers of Colorado as the cheapest and most efficient bait under existing conditions in this state. FORMULA FOR POSONED-BRAN MASH VVheat bran pounds Sodium arsenite (Liquid 8 pound material)... 1 quart Beet molasses... 2 gallons Amyl acetate (Banana oil)... 3 liquid ounces VVater to 12 gallons EMERGENCY FORMULA TO BE USED ONLY ON DRYLAND Bran pounds Sodium arsenite... 1 quart Banana oil... 3 ounces VVater to 12 gallons FORMULA FOR SMALL AMOUNTS OF BAT Bran pounds Paris green or crude white arsenic... Y2 pound Molasses (any cheap grade) Y2 pints Lemon or orange (run thru food chopper)... 1 fruit VV ater... 1 gallon THE BRAN should be coarse and free from shorts and middlings. Shorts and middlings cause the bait to lump and instead of "flaking out" when broadcast it f<alls in small balls and pellets. A mixture of this type is very dangerous to livestock and birds. SODUM ARSENTE.-This material is a liquid containing 8 pounds of arsenic to the gallon. t has the advantage of being soluble in water, thus when a flake of bran is wet, it is certain to be poisoned. With such insoluble materials as white arsenic and paris green this is not the case. Sodium arsenite may be dbtained at cost from your county extension agent or by writing to the State Entomologist or the Colorado Experiment Station at Fort Collins. t is packed in 2-quart cans which also contain the necessary amount of banana oil. BEET MOLASSES may be obtained from any beet-sugar factory and should be added to all bait that is to be used on irrig.at-

13 March, 1934 HOW TO CONTROL GRASSHOPPERS 13 ed lands. t is felt that when possible it should be used in bait intended for dryland, but may in an emergency be omitted. AMYL AcETATE (Banana oil).-this material should be What is commonly called a "technical" grade. Bronzing fluids containing only a relatively small percentage of amyl acetate will not do. t is contained in the grasshopper poison sold by the Colorado Experiment Station. THE WATER will vary somewhat with the coarseness of the bran. A coarse bran, free from shorts, will absorb more water than other types. Enough should be added to the mixture to make a moist crumbly mass, but not so much that a part of it will drain off after the bait is sacked. MXNG THE BAT During large campaigns it is often advantageous to establish central mixing stations for a community. There, it is possible to use power mixers which insure a uniform "mix" on each batch of bait. For this purpose a motor-driven cement mixer serves admirably. t is usually possible to find such a machine close by that may be borrowed for the duration of the campaign. Another advantage in the central mixing stations is that the bait can always be made available when needed. All liquid ingredients-the water, molasses, amyl acetate and sodium arsenite-should be mixed together in a barrel or tub. This mixture should be agitated thoroly for at least 5 minutes to insure a thoro mix. n case the bait is to be mixed in a cement mixer, a part of the bran should be placed into the drum with about an equal share of the liquid mixture. The mixer should then be set in motion and the remainder of the bran and poison mixture added. Usually 10 to 15 minutes are required to miix thoroly the two. A good "mix" is obtained when all flakes of bran are wet, and all wet, soggy lumps have been worked out. When the bait is to be mixed by hand the bran should be spread about 4 inches thick on a concrete or tight, board floor. The wet mixture is then gradually slopped on and worked into the bran. n starting the mixing a scoop shovel is used to turn the mass over two or three times or until the poison is all added. t is then worked back and forth with garden rakes until all wet, lumpy masses have been broken up and every flake of bran is wet. t is better to mix all bait in the evening so that it will be ready to scatter early in the morning. Do not wait until morning to mix poisoned bait. When it is impossible to scatter the bait on the following

14 14 STATE ENTOMOLOGST Circular 59 morning it should be placed in sacks and covered with a canvas or sacks to prevent evaporation. Bait protected in this manner will keep for at least 48 hours. SCATTERNG THE BAT TME OF DAY.-Since temperature has such a decided effect on the feeding activities of grasshoppers it is essential to watch the thermometer when scattering poisoned bait. Operations should begin at about 60 degrees F. and should be completed by the time the temperature reaches 80 degrees. The time of day these temperatures occur varies with the season. Early in June it may not reach 60 degrees F. until 7 or 8 a. m. Later in the season the time will be advanced until it may be necessary to start poisoning as early as 4:30 or 5 :00 a. m. Do not scatter the bait after the temperature goes above 80 degrees F. and do not scatter it during the afternoon or evening. t is true that occasionally good results are obtained by spreading the b.ait in the evening, but more often it will be a waste of time and money. METHODS.-The bait is preferably spread by hand from the back end of a truck or wagon, altho certain mechanical spreaders have been developed that do a very thoro job. n spreading by hand use a full arm swing with plenty of force and snap as in broadcasting seed. Do not try to throw an entire handful at once. Break it up into two or three casts. Above all, do not pitch the bait out as one would pitch wheat to chickens. The finest bait that it is possible to obtain may be thrown in lumps by this method. (Figs. 9 and 10.) WHERE TO SCATTER THE BATS FOR TilE BEST RESULTS. Since many of the most destructive hoppers in Colorado lay their eggs around the edge of cultivated fields, much good can be done by poisoning these places as soon as the hoppers hatch. Keep watch of these egg-beds and start poisoning before the small hoppers leave them. Much damage to grain fields can be prevented in this manner. n alfalfa fields the conditions are a little different because the eggs are usually scattered over the entire field. t is doubtful in this case whether it pays to poison until after the first cutting is removed. As the first crop is cut it is always advisable to leave the back swaths along d itch banks and fence rows and an occasional strip of 1 or 2 swaths thru the center of the field. As soon as the first crop is off the grasshoppers start moving into these strips where they can be readily killed with poisoned... bran mlash. As a supplement to the poisoned bait the hopper dozer may be run over these strips to good advantage. Where the hoppers are scattered over an entire field and it

15 March, 1934 HOW TO CONTROL GRASSHOPPERS 15 Figure 9. The wrong way to spread poisoned bran. Showing the results of scattering poisoned-bran mash by merely pitching it ovt on the ground. The large lumps in this photograph are dangerous to livestock. Natural size. Original. Figure 10. The correct way to spread poisoned bran. The bran in this picture was scattered in the approved manner with a good full arm swing and plenty of force. When spread in this manner it is not dangerous to livestock. Natural size. Original.

16 16 STATE ENTOMOLOGST Circular 59 becorr1es necessary to poison, the strip method may be used. By this method strips 1 2 to 2 rods wide and 1 to 2 rods apart, are spread across the field. t is better to lay out these strips across the wind. WHEN AND HOW TO LOOK FOR RESULTS.-Sodium arsenite is a slow poison and does not kill within the first 24 hours. Ordinarily from 2 to 5 days are required to obtain the maximum kill. Soon after eating the bait the hoppers become sick and seek some secluded spot to die. Look for the dead ones around the base of plants and under debris. DANGER TO LVESTOCK.-The question always arises: "Will poisoned-bran mash kih livestock and poultry?" The answer is: "NO" PROVDNG the directions for mixing and scattering the bait as described here are followed to the letter. However, it must be borne in mind that arsenite is a DEADLY POSON. Every precaution must be taken to see that the bait is properly scattered and that all containers are thoroly cleaned and kept away from children, livestock and poultry. All excess bait should be spread thinly in the field or buried. Burning does not destroy the poison. AMOUNT TO APPLY.-Poisoned-bran ba'it should be applied at the rate of 10 pounds dry weight or 20 pounds wet weight per acre. n other words 100 pounds of bran, when mixed, should be applied to 10 acres. On this basis 100 pounds of bran will scatter a strip 2 2 rods wide around a 160-acre field. Two hundred pounds will spread a strip equally as wide around a section. How OFTEN TO APPLY THE BAT.-n trying to protect a field from incoming hoppers it is necessary to apply the bait at least every 5 days while the migration threatens. n some extreme cases it may become necessary to poison every other day. This point must be determined by the farmer from his own observations. COLORADO PEST LAW One question that is always asked during a grasshopper outbreak is: "f do poison my hoppers what about my neighbor?'' This is usually a timely question. n most any community there ar-3 those who stand back and "let the other fellow do it," and tracts of land held by people at a distance, who may not be interested or are not familiar with the situation, are a menace to ~control. f these cannot be taken care of thru volunteer community cooperation, the Colorado Pest Law* provides a means of organizing definite districts in which uniform control work can be required. Furthermore, it provides a method of financing the campaign thru cooperation with the county in case the burden of the expense is too great for some to carry. * A copy of this law may be obtained by writing to the State Entomologist, at 1<-.ort Collins.