=Sodium chlorate.=--Sodium chlorate is the standard herbicide for killing deep-rooted perennial weeds like bindweed, but when used as a spray, it is a dangerous fire hazard, and when applied dry, it sterilizes the soil for 2 to 4 years. Where sterilization of the soil is desirable or not objectionable, one application of the dry chemical, evenly at the rate of 3 to 4 pounds per square rod, is sufficient for a complete kill. If used as a foliage spray on poison-ivy, the chemical is dissolved in water at the rate of 8 to 12 ounces per gallon. The leaves are killed within a few hours, but the plants are likely to make a strong new growth and may require as many as six treatments before they cease to produce new leaves. =Sodium chlorate mixed with wood, cloth, or other organic materials is highly combustible and easily ignited. Shoes and clothing on which chlorate solution has been allowed to dry are especially dangerous, for they will ignite and burn with explosive fury. Contaminated clothing should be kept wet until thoroughly washed in a large volume of water. Chlorate should be stored only in original metal containers, as any admixture of chlorate, wet or dry, with straw, wood, dust, cloth, or leather has properties similar to those of gunpowder or matches.= =Sodium arsenite.=--Sodium arsenite is one of the most powerful plant poisons known and is widely used for sterilizing soil on railroads, roadways, and other places where no vegetation of any kind is desired. It is relatively inexpensive. In normal times sodium arsenite is obtainable in both powder and liquid form. In weak solution (4 to 6 ounces per gallon of water) the chemical can be used as a spray to destroy poison-ivy. Like sodium chlorate spray, it kills the leaves but not the roots, and five or six treatments may be required. The solution kills the leaves of all plants impartially and will also kill the young tender bark of shrubs and trees. This may be either an advantage or a disadvantage, depending upon circumstances. =All compounds containing arsenic are deadly poisons if taken internally. Arsenical sprays and chemicals should not be used where there is any possibility that materials sprayed with them will be eaten by animals or man. In some communities special permission must be obtained before arsenical weed killers may be used.= ERADICATION BY MECHANICAL MEANS