408 CRAFTS 



at Wells, Nevada, in 1935, and for several years its harmful effects were not 

 known. However, it spread rapidly over the desert ranges of Nevada, Utah, 

 Idaho, and neighboring states, and as soon as it became dominant over large 

 areas, trouble started. Halogeton has the property of accumulating large con- 

 centrations of oxalates, attaining values as high as 22 per cent of the dry 

 weight in extreme cases. 



Oxalates precipitate calcium from the blood, causing tetany. Sheep may die 

 from eating 5 ounces of the dry plant; cows succumb from 3 to 5 pounds. 

 Poisoning was first recognized in 1942, and new cases have been reported 

 each succeeding year. In one instance Halogeton is known to have killed 1,620 

 sheep in three days, and many smaller losses occur annually. Lije magazine 

 featured Halogeton poisoning in Volume 30, January 15, 1951, and the U.S. 

 Department of Agriculture started investigating means of control late in 1952. 



Although considerable progress has been made in finding ways for control- 

 ling Halogeton, none found so far, and probably none to be found in the 

 future, will take care of the entire problem, for in the two decades since its 

 first discovery this weed has spread over some three million acres of desert 

 range that is not productive enough to pay for any type of control. Biological 

 control by insects is the only method that can possibly handle the situation, 

 and the chances of finding a suitable predator for a plant so closely related 

 to the sugar beet seems unlikely. 



Weed losses. One principle of plant control is to allow a disturbed flora 

 to return to its original status so that competition may re-establish a favorable 

 balance or condition. Another is to eliminate the pest plant by frequent and 

 effective tillage. A third is to introduce selective predators that will suppress 

 the pest without harming crops. And a fourth is to treat the pest chemically 

 whenever necessary to keep it at a low competitive level. Of the four examples 

 of weeds cited, St. Johnswort seems to be submitting to biological control. 

 The other three by their very nature cannot be controlled by competition, for 

 each represents a new element in the vegetative complex that has superior 

 competitive ability. The flora cannot return to a previous favorable status 

 because a new factor of great competitive vigor has been introduced, and 

 once established any new balance attained will be less favorable. 



Tillage cannot be effective because these weeds have literally ''taken to 

 the hills," and gradually they have occupied millions of acres that cannot 

 be treated economically. Biological control is always a possibility, but the 

 chances of finding insects or diseases selective enough are pretty small. And 

 chemicals offer little hope, for they too are costly to produce and apply. 

 Although a few weeds like common mustard, pigweeds, lamb's quarters, 

 annual bindweed, sagebrush, and some of the ragweeds are being economically 

 controlled on millions of acres by chemical means, there is still a host of 

 these pests that resist all control methods. 



A good many people, and even some botanists, regard weeds as a personal 



