56 MISC. PUBLICATION 4 4 0, U. S. DEPARTMENT OF AGRICULTURE 



and to avoid the use of seedlings from seedbeds where the disease 

 is in evidence. Field sanitation and crop rotation are also 

 recommended. 



Celery from fields in which phoma root rot has appeared should 

 not be stored longer than is commercially necessary, and when stored 

 it should be examined periodically for evidences of decay. Heavy 

 losses may occur in crated celery during storage if it shows any evi- 

 dence of this decay prior to storage. 



(See 162, 176, 195.) 



PITHINESS (HOLLOW STEM) 



Pithiness is a condition of celery characterized by the central tis- 

 sues of the leafstalks being soft and spongy. Frequently the affected 

 tissues are pulled apart so that the leafstalks are hollow. 



There appear to be two types of pithiness. One type is a heredi- 

 tary condition and is therefore associated with certain strains and 

 varieties. It regularly affects all leafstalks of the plant throughout 

 the season. The second type is not hereditary but is apparently the 

 result of unfavorable growing conditions. It may, therefore, be found 

 in varying amounts in different seasons and localities regardless of 

 the variety grown. This type of pithiness, identical in appearance 

 with the first type, is usually confined to the outer leafstalks and 

 frequently is more important late in the season as the crop approaches 

 maturity. It is this type of pithiness that is frequently found on the 

 market associated at times with brown stem. 



(See 171, 173.) 



TARNISHED PLANT BUG INJURY 



During certain seasons considerable loss occurs in the northern 

 celery-growing sections of the country through attacks by the tar- 

 nished plant bug (Lygus pratensis (L.) ). The injury is produced by 

 the insect during the feeding process, which involves the puncturing 

 of the leafstalk and the sucking of the plant juices. Feeding usually 

 occurs near the upper leaf joint, as the result of which the tissues in 

 the center of the stalk at and near the joint become brownish black. 

 Because of this the injury is commonly known as "black joint." The 

 leaflets above the point of injury become chlorotic and wilt. Tar- 

 nished plant bug injury is occasionally found on the market on celery 

 from the Northeastern and North Central States. 



(See 166, 167, 206, ®13.) 



WATERY SOFT ROT 

 {Sclerotinia sclerotiorum (Lib.) DBy. and other Sclerotinia spp.) 



OCCURRENCE, SYMPTOMS, AND EFFKCTS 



Watery soft rot, known also as pink rot and as sclerotinia rot, is the 

 most important decay of celery in transit, in storage', and on the 

 market. It also occurs on beans, peas, carrots, finoechio, parsley, 

 parsnip, and in fact on practically all vegetables, with the notable 

 exception of potato and onion. In the field it is frequently serious 



