152 MISC. PUBLICATION 4 3 4, U. S. DEPARTMENT OF AGRICULTURE 



A condition generally referred to as "chlorosis" has been observed on 

 some sites, where several broadleaf species have shown a characteristic 

 yellowing or mottling of the leaves accompanied by a stunted growth. 

 A rosettelike growth and a streaking of the leaves are also sometimes 

 observed. This condition is commonly attributed to the lack or non- 

 availability of iron, but it may be associated with a deficiency or an 

 excess of any one of a number of elements such as nitrogen, phosphorus, 

 manganese, zinc, or magnesium. 



Hardy catalpa (Catalpa speciosa) and black locust appear to be 

 especially susceptible to chlorosis, particularly on sandy soils. Several 

 iron compounds have been used in periodic sprayings in an attempt to 

 correct the chlorotic condition of these two species in an Oklahoma 

 nursery. Ferric citrate, ferric tartrate, and ferrous sulfate were used 

 as spray solutions and were applied at the strengths of 1, 3, 5, 7, and 10 

 percent. No noticeable changes were effected by the 1 and 3 percent 

 sprays, while the 5 percent solution caused some slight improvement. 

 The 7 and 10 percent sprays burned the catalpa leaves but did not 

 appear to have either a detrimental or beneficial effect on the foliage 

 of black locust. A soap spreader was used in these spray tests. 

 Ferrous sulfate is ordinarily not as safe as ferric citrate or ferric 

 tartrate, and even at 1 -percent strength has been known to burn the 

 leaves of some tree species. 



In a northern nursery a chlorotic yellowing of American elm leaves 

 was corrected by deep cultivation. This occurred on a heavy soil 

 where apparently aeration was insufficient for normal growth. 



The most satisfactory solution to the problem is to locate the species 

 susceptible to chlorosis on areas where this condition is found to be 

 uncommon. Soil acidification is also said to eliminate chlorosis but is 

 generally not practical for large areas in the Great Plains region. 



Storage Problems 



One of the most difficult seedlings to handle under inside storage 

 conditions is the Siberian elm. This is due to the fact that the 

 Siberian elm roots are commonly affected by a black rot. The occur- 

 rence of this root rot in the Great Plains region was first reported in 

 1935 (18). The causal organism is Chalaropsis thielavioides Peyron. 

 Original infections appear to take place in the seedbeds and spreads 

 rapidly under improper storage conditions or during transit. A gray- 

 ish white, moldlike growth is characteristically found at injuries or 

 broken places on the roots. The outer root tissues become dark 

 brown to black and are broken down to a slimy mass as the rot ad- 

 vances. The roots of the infected plants in the nursery row usually 

 show only blackened, decayed areas. 



A large number of chemical dips have been experimented with in an 

 attempt to control the spread of this rot during inside storage. So far 

 no completely satisfactory chemical control has been found, although 

 sodium perborate at a concentration of 1-35 gave the best control of 

 any of the dips used. 



The most satisfactory means of controlling the root rot is to heel-in 

 the seedlings in sand or sandy soil out of doors over winter, protecting 

 the tops with a straw mulch when necessary. Heeling-in the seedlings 

 in heavier soil has not proved satisfactory even when the roots have 

 been previously dipped in chemical solutions. The advantage of sand 



