Part 2

Poison sumac grows as a coarse woody shrub or small tree (fig. 19) and never in the vinelike form of its poison-ivy relatives. This plant is known also as swamp sumac, poison elder, poison ash, poison dogwood, and thunderwood. It does not have variable forms, such as occur in poison-oak or poison-ivy, and botanists agree to call it _Rhus vernix_. The area in the Eastern States where it is likely to be found is chiefly eastward from eastern Minnesota, northeastern Illinois, Indiana, central Kentucky and Tennessee, and southeastern Texas, as shown on the shaded area of the map, figure 20. This shrub is usually associated with swamps and bogs, and the most typical growth occurs along the margin of an area of wet acid soil.

_Figure 21._--Small branch of poison sumac with six compound leaves.

_Figure 22._--Fruit of poison sumac, one-third natural size. These fruits somewhat resemble those of poison-ivy. They are always on drooping slender stems attached at the side of the small branches and are never terminal as in the species of sumac that are not poisonous.

The plants range in height from 5 or 6 feet to small trees that may attain a height of 25 feet. The poison sumac shrub shown in figure 19 is growing on the edge of a swamp and is quite typical of the general appearance of the larger shrubs, which approach a treelike form. As a rule the shrubs do not have a symmetrical upright treelike appearance. They are more or less inclined to lean and have branched stems with about the same diameter from the ground level to the middle height of the shrub.

Occasional isolated plants are found outside of swampy regions. Apparently these plants are started from seed distributed by birds. The plants in dry soil usually do not become more than a few feet tall. They are likely to cause poisoning to unsuspecting individuals, as single isolated plants are not readily recognized, especially out of their usual region.

The leaves of the poison sumac are divided into 7 to 13 leaflets, arranged in pairs with a single leaflet at the end of the midrib (fig. 21).

_Figure 23._--_A_, Smooth sumac and dwarf sumac growing in a mixed stand. These plants are not poisonous. _B_, Terminal fruiting spike of smooth sumac, about one-seventh natural size. This form of terminal fruiting spike is typical of all the species of sumac that are not poisonous.

The leaflets are an elongated oval shape without teeth or serrations on the margins. They are 3 to 4 inches long and 1 to 2 inches wide, with a smooth velvetlike texture and bright orange color when they first appear in spring. Later they become dark green and glossy on the upper surface and pale green on the lower and have scarlet midribs. Early in fall they turn to a brilliant red-orange or russet shade.

The small yellowish-green flowers are borne in clusters in slender stems arising from the axis of leaves along the smaller branches. The slender clusters of flowers have much the general appearance of the poison-ivy flower, but hang in much longer clusters. The flowers mature into ivory-white or green-colored fruits resembling those of poison-oak or poison-ivy, except that they are usually less compact and hang in loose clusters that may be 10 to 12 inches in length (fig. 22).

CONFUSION OF POISONOUS AND HARMLESS SUMACS

Because of the same general appearance of several common species of sumac and the poison sumac, considerable confusion has occurred as to which one is poisonous. Throughout most of the range where poison sumac grows, three other species are the only ones that are likely to be confused. These are the smooth sumac (_Rhus glabra_), staghorn sumac (_R. typhina_), and dwarf sumac (_R. copallina_). All the nonpoisonous species have red fruits that together form a distinctive terminal seed head, as shown in figure 23. These are easily distinguished from the slender hanging clusters of white fruit of the poison sumac, as shown in figure 22. Sometimes more than one species of the harmless sumac grow together, as shown in figure 23, _A_.

When seed heads or flower heads occur on the plants it is easy to distinguish the poisonous from the harmless plants; however, in many clumps of either kind, flowers or fruit may not develop. Fortunately, the leaves have some rather distinct characteristics, which can be easily observed. Figure 24 shows leaves of the three harmless species as compared with poison sumac.

The leaves of the smooth sumac (fig. 24, _A_) and of the staghorn sumac (fig. 24, _B_) have many leaflets, which are slender lance-shaped with a toothed margin. In these species there are usually more than 13 leaflets. The leaves of the dwarf sumac (fig. 24, _C_) and the poison sumac (fig. 24, _D_) have fewer leaflets, and these are more oval-shaped, with smooth or even margins.

The dwarf sumac, however, may be readily distinguished from the poisonous sumac by the winged midrib of the leaf (fig. 24, _E_). There is considerable variation in the size of the wing margin along the midrib, which in some cases may be reduced almost to a line between the leaflets. The winged midrib is more prominent near the terminal leaflet and can always be detected. The midrib of the poison sumac is never winged. A little study of the fruit and the leaf characteristics of the poisonous and harmless species will make it possible to avoid the poisonous one and utilize the other, which has considerable value as an ornamental plant, as a source of commercial tannin, and for controlling erosion on waste hillsides.

_Figure 24._--Leaves of species of sumac that are often confused: _A_, Smooth sumac; _B_, staghorn sumac; _C_, dwarf sumac; _D_, poison sumac; _E_, enlarged portion of dwarf sumac leaf from _C_, showing the wing margin of the midrib. Poison sumac does not have the winged midrib.

INTRODUCED POISONOUS SUMAC AND RELATED SPECIES

The small Japanese lacquer-tree, although uncommon in the United States, is an introduced species of sumac (_Rhus verniciflua_) that is quite similar to the native poison sumac. It is native to Japan and China and is the source of Japanese black lacquer. Cases of poisoning hare been traced to contact with lacquered articles. Because of its poisonous properties, this tree should never be planted.

A native shrub or small tree called poison-wood, doctor gum, or coral sumac is commonly found in the pinelands and hummocks of extreme southern Florida, the Keys, and the West Indies. It is much like the poison sumac and closely related to it. Most botanists name it _Metopium toxiferum_, although previously it was named _Rhus metopium_, and sometimes metopium is used as its common name. The small tree, or shrub, has the same general appearance as poison sumac. The leaves have the same general appearance, except that there are usually only three to seven leaflets, which are more rounded. The fruits are borne in clusters in the same manner as those of poison sumac (fig. 22), but individual fruits are two or three times as large and orange-colored. All parts of the plant are exceedingly poisonous to the touch and cause the same kind of skin irritation as poison-ivy or poison sumac.

POISONING

Through experience, many people know that they are susceptible to poisoning by poison-ivy, poison-oak, or poison sumac, while some others either have escaped contamination or have a certain degree of immunity. The extent of immunity appears only relative, and absolute immunity to the toxic principle apparently does not exist. Persons who have shown a degree of immunity upon repeated contact with the plants may develop poisoning on subsequent exposure.

The skin irritant of poison-ivy, poison-oak, and poison sumac is the same toxic agent. It is a nonvolatile phenolic substance called urushiol and is found in all parts of the plant, including roots and fruit. It occurs in great abundance in the plant sap. The danger of poisoning is greatest in spring and summer, when the sap is abundant, and least late in fall or in winter.

Poisoning is usually caused by contact with some part of the plant. A very small quantity of the poisonous substance is capable of producing severe inflammation of the skin and can easily be transferred from one object to another. Clothing may become contaminated and is often a source of such prolonged infection that it is likely to be judged as a case of poisoning difficult to cure. Dogs and cats frequently touch the plants and transmit the poison to unsuspecting persons. The poison may remain on the fur of animals for a considerable period after they have walked or run through poison-ivy plants. Smoke from burning plants will carry the toxin and has been reported to cause severe cases of poisoning. Cases of poisoning of children from eating the fruit have been reported. A local belief that eating a few leaves of these plants will develop immunity in the individual is unfounded. It never should be attempted. No part of the plant should ever be taken internally, as it is a violent irritant and poisonous to man.

Cattle, horses, sheep, hogs, and other livestock apparently do not suffer from skin irritation caused by these plants, although they have been observed to graze upon the foliage occasionally. Bees collect honey from the flowers, though no reports are on record of any ill effects from the use of the honey.

The time between contamination of the skin and the first symptoms varies greatly with individuals and probably with conditions. The first symptoms of itching or burning sensation may develop in a few hours or after 5 days or even more. The delay in development of symptoms is often confusing in attempting to determine the time or location when contamination occurred. The itching sensation and subsequent inflammation, which usually develops into water blisters under the skin, may continue for several days from a single contamination. Persistence of symptoms over a long period is likely to be due to new contacts with plants or with previously contaminated clothing or animals. Severe infection may produce more serious symptoms, which result in much pain through abscesses, enlarged glands, fever, or complicated constitutional malfunction. Secondary infections are always a possibility in any break in the skin, such as is produced by breaking vesicles that have formed as large water blisters.

PRECAUTIONS AGAINST POISONING

The most effective way to prevent poisoning from the plants is to avoid contact with them. If it is necessary to work among them, some measure of prevention can be gained by wearing protective clothing, but it is necessary to remember that the active poisonous principle can easily be transferred. Some protection also may be obtained in advance by the use of protective creams or lotions. They prevent the poison from touching the skin, or make the active principle easily removed, or neutralize it to a certain degree.

Various formulas containing ferric chloride and glycerin have been used more or less effectively as a preventive measure, although there may be some danger of pigmentation of the skin from the ferric chloride. A common formula is ferric chloride, 5 parts; glycerin, 25 parts; alcohol, 25 parts; water. 50 parts.

A lotion of this formula applied to the exposed skin prior to contact with poisonous plants gives effective protection for many people. It is especially effective if followed by thorough washing with soap and water. Such washing, even if no protective lotion has been used, is often effective in preventing poisoning. Proper precaution should be taken by repeated lathering with a strong alkali soap, followed by thorough rinsing and repeating the process several times. The water should be frequently changed, and a shower or flowing water bath is preferable. The soap probably only emulsifies the active principle, and thorough rinsing is necessary to avoid spreading the poison to other parts of the body.

The United States Public Health Service reports successful chemical protection against ivy poisoning by use of an oxidizing agent--sodium perborate prepared and used fresh as an ointment. Following is a formula given for the ointment: Cetyl alcohol, 35.1 percent; stearyl alcohol, 5.3; ceresin, 3.5; castor oil. 20.8; mineral oil, 21.9; Duponol WA pure, 1.7; sodium perborate. 10.0; and boric acid, 1.7 percent.

A more recent less oily formula recommended for both mechanical and chemical protection is given as follows: Shellac, 13 parts; isopropanol, 31; linseed oil, 4; titanium oxide, 12; sodium perborate, 13; talcum, 20; and carbitol, 3 parts.

Sometimes cottonseed oil, olive oil, or petrolatum is applied as a protective ointment when contamination is anticipated. Later the oil must be completely removed by repeated washing.

Clothing, wearing apparel, and tools that have been contaminated are often difficult to handle without further danger of poisoning. Some who are more or less immune to poisoning often contaminate others by carelessness. Contamination on automobile door handles or on a steering wheel after a trip to the woods often causes prolonged cases of poisoning of persons who have not been near the plants. One of the most effective ways for decontaminating articles is by thorough washing through several changes of strong soap and water. Contaminated clothing should not be worn again until thoroughly washed. It should not be washed with other clothes, and care should be taken to rinse thoroughly any implements used in washing.

Dogs and cats can be decontaminated in the same manner; precaution should be taken, however, to avoid being poisoned in doing the washing. It is likely that most "dry cleaning" processes will remove any contaminant; but there is always danger that clothing sent to commercial cleaners may cause poisoning to unsuspecting employees.

Certain prophylactic inoculations for the prevention of ivy poisoning have been developed and used with limited success; such treatment, however, should be administered by a physician only. The theory that eating a few leaves of these poisonous plants will confer immunity is without foundation; it should not be attempted even as an experiment, because very serious poisoning is likely to result.

TREATMENT FOR POISONING[1]

[1] For a fuller description of treatments for poisoning see: United States Public Health Service, ivy and sumac poisoning. Pub. Health Rpts. Sup. 161 (rev.), 8 pp., 1943. For sale by the Superintendent of Documents, Government Printing Office, Washington 25, D. C. Price, 10 cents.

There seems to be no absolute quick cure for ivy poisoning for all individuals, even though many studies have been made to devise effective remedies. Remedies may be helpful in removing the poisonous principle or rendering it inactive and for giving some relief from the irritation. Mild poisoning usually subsides within a few days, but if the inflammation is severe or extensive a physician should be consulted. Self-treatment also has other dangers, as the symptoms of ivy poisoning may be confused with those of other conditions and harm may be done by improper treatment. In all cases the safest procedure is to consult a physician.

Some tried remedies are effective on certain individuals and ineffective on others. Sometimes a person will find one remedy effective and later, to his surprise, get very little relief from it. A large number of patent medicine remedies of doubtful value are commonly offered for sale. The following are more or less standard measures that have been advocated by different individuals and found helpful in certain cases.

The United States Public Health Service recommends a 10 percent alcoholic solution of tannic acid applied as a lotion. It is stated that in using it the tops of the blisters should be rubbed off with sterile gauze saturated with the solution and that any large blisters should be opened with a sterile instrument. The treatment should be repeated three or four times at 6-hour intervals. A modified form of this treatment recommends vigorous rubbing of the lesions with alcohol-soaked gauze to remove the tops of blisters, followed by application of a 10 percent aqueous solution of tannic acid as a lotion. Any treatment involving opening of blisters and the application of alcohol is severe, and many cases requiring such treatment should be handled by physicians.

One of the oldest well-established remedies is a fresh solution of one 5-grain tablet of potassium permanganate dissolved in 1 quart of water; concentrations as much as 5 percent, however, have been used. The potassium permanganate is apparently active in neutralizing any poison that may remain on the surface of the skin and it has some therapeutic properties. This solution may be applied freely to the irritated or contaminated skin, but the skin should be rinsed with water a few minutes after the stronger solutions are used. Applications should be repeated every hour or two. The brown stain it causes on the skin will in time wear off, or it may be removed with lemon juice. It more or less permanently stains clothing.

Ferric chloride in combination with several other substances has been used effectively by many people. One of the most common formulas is that given under the discussion of precautions against poisoning (p. 22). To this formula 1 to 3 percent of phenol is frequently added to reduce the itching; however, not more than 1 percent of phenol should ever be used without the advice of a physician, on account of the danger of systemic absorption and poisoning. The solution should be freely applied to the irritated or contaminated skin every hour or two. Some instances of persistence of the brown discoloration of the skin have been reported. For this reason its use is limited, but for most individuals the discoloration completely disappears after a few days. Stain on clothing is usually permanent.

Photographer's hypo solution has been used with good results in many cases. This is a 10-percent solution of sodium thiosulfate in water. The irritated or contaminated skin should be bathed in it every hour or two. It does not stain skin or clothing.

A calamine lotion with the addition of about 2 percent of phenol is often used and in many cases is effective. Frequent applications are necessary. For some people it is effective in relieving the itching. The pink stain is not permanent.

It is better to leave inflamed areas exposed to the air rather than cover them with dressings. If poisoning is so severe that dressings appear necessary, a physician should be consulted before any home remedies are applied.

ERADICATION OF PLANTS

Poison-ivy[2] can be killed either by mechanical means, such as digging, or by applying chemical herbicides. The best modern herbicides are so deadly to plants that a single treatment kills all the leaves and 90 percent or more of the roots. This is the easiest and least dangerous way to destroy these poisonous pests. There are places, however, where chemicals cannot be used, as in hedges and shrubbery where the poison-ivy is closely mixed with the valuable plants. In such situations, hand-pulling is the only satisfactory method. At times also chemicals and spraying equipment are not available, and then the mattock, scythe, or plow must be resorted to. Even with these simple tools some timing and handling methods are better than others.

[2] For brevity, the single designation poison-ivy is used under this heading to apply equally to all poison-ivies and to poison sumac.

CHEMICAL WEED KILLERS

By using care poison-ivy can be destroyed with chemicals without danger of poisoning to the operator. Except in very heavy growth, one may stand at a distance from the plants and apply the herbicide without touching the leaves. Most chemicals are applied as a spray solution, and many sprayers can be equipped with extension nozzles 2 feet or more in length. The greatest danger of ivy poisoning occurs from careless handling of gloves, shoes, and clothing after finishing the work. Garments should be worn that can either be destroyed after use or washed thoroughly in hot soda solution and soapsuds.

The chemicals thus far found most satisfactory on poison-ivy are, in approximate order of effectiveness, ammonium sulfamate, 2,4-D (2,4-dichlorophenoxyacetic acid), ammonium thiocyanate, borax, carbon disulfide, coal-tar creosote oil, fuel oil and similar petroleum distillates, sodium chlorate, and sodium arsenite. Less effective chemicals include common salt, kerosene, gasoline, calcium cyanamide, ammonium sulfate, and iron sulfate.

Chemicals other than borax are best applied as a spray to the foliage. Borax is scattered dry on the soil around the plants. Any field or garden spray machine or even a sprinkling can is useful for applying the liquids, but a common knapsack sprayer holding about 2 gallons is convenient and does not waste the solution, application should be as a fine spray under moderate pressure rather than a driving mist, since the object is to wet the leaves of the poison-ivy and avoid wetting the leaves of desirable plants.

Most chemicals used on poison-ivy are injurious to the foliage of all kinds of plants and must be applied with caution if the surrounding vegetation is valuable. During the early part of the growing season the leaves of the poisonous plants usually tend to stand conspicuously apart from those of adjacent plants and can be treated separately if sprayed with care. Later the leaves become intermingled and injury to adjacent species is unavoidable. Chemicals other than oil are not injurious to the thick bark of an old tree, and poison-ivy clinging to the trunk can be safely sprayed with them.

Chemical sprays can be used at any time when poison-ivy is in full leaf, June and July being perhaps the best months. Ordinarily treatments should begin not later than August 15, as poison-ivy then begins to go dormant and sprays are ineffective.

Best results are obtained both with sprays and with dry chemicals when the soil is moist but not wet at time of treatment. Borax can well be applied just before a rain, but sprayed chemicals are likely to be washed off if rain falls within 24 hours. One gallon of spray solution is sufficient to cover all the leaves on 1 square rod (272 square feet) of dense poison-ivy, or 2 to 4 square rods of a scattered stand.

Sprays give best results when applied in early morning or late afternoon when the air is cool and moist. Spraying in the middle of a dry, hot day is likely to be disappointing unless the plants are in deep shade.

No method of chemical eradication can be depended upon to kill all the plants in a stand of poison-ivy with one application. Three to four light retreatments made as soon as the new leaves are fully expanded are always necessary (1) to destroy plants missed the first time, (2) to treat new growth from the old roots, and (3) to destroy seedlings. At least three and sometimes four treatments at intervals of 2 to 8 weeks are necessary before all plants are dead. These followup treatments do not require much time or material, but neglect of them may easily lead to serious reinfestation.

Poison-ivy has an annoying habit of "playing possum." Plants believed dead sometimes revive after many months. Thus an area under treatment must be watched closely for at least a year if complete eradication is to be assured.

Dead foliage and steins remaining after the plants have been killed with chemicals are only slightly poisonous, but to avoid difficulty the dead stems should be cut off and burned.