Pecan Diseases, and Spraying Outfits 195 



Winter-injury is much more troublesome than tip-burn, 

 and under certain conditions causes heavy losses in young 

 orchards. The trouble is caused by sudden and great changes 

 or fluctuations in the temperature in late autumn and win- 

 ter. Vigorous young trees making a late fall growth are 

 most likely to be injured. The tender cambium cells do not 

 seem to be able to adjust themselves to sudden freezing fol- 

 lowing a warm period of weather. More especially, however, 

 does the injury result when the sun shines out warm sud- 

 denly foUoA^dng a freeze. Winter-injury usually occurs on 

 the trunks of the trees just above the ground. On examina- 

 tion, the injured portion shows a dark watery condition just 

 under the bark and has a sour odor. The injury is thus 

 sometimes called ^^sour sap." 



Winter-injury rarely affects pecan trees after they are 

 eight or nine years of age, or after they begin to bear com- 

 mercial crops of nuts. It can be largely prevented, however, 

 by wrapping the younger trees with fertilizer bags or some 

 similar material in the late fall just before the weather turns 

 cold. The trunk is ^vi^apped ^^dth four to six thicknesses of 

 the sacking material for a distance of about three feet above 

 the ground, and is allowed to remain until the following 

 spring. 



If the orchard is sown to cover-crops in June or July and 

 no fertilizer applied after that date, the trees will cease 

 growing earlier in the fall and will be more resistant to cold 

 injury. 



SPRAY OUTFITS AND METHODS OF SPRAYING PECAN ORCHARDS 



For most satisfactory results it is necessary to have an outfit 

 with sufficient capacity and power to spray satisfactorily a 



