A study of blackheart, soft-rot and tarnished plant bug injury on celery was made to determine their interrelationship, in addition to their individual effects on the host. The incidence of blackheart could not be correlated with a saturated condition of the soil, or with the use of various fertilizers, but under artificial conditions the disease could be induced in susceptible plants by subjecting them to temperatures ranging from 85–95° F., in a humid atmosphere. Experimental data supplemented by observations in the field indicate (i) that the disease is physiological in nature, (ii) that early plantings are more severely affected, (iii) that most extensive injury occurs when plants are nearing maturity, (iv) that vigorous plants are more subject to attack, (v) that there is a difference in varietal susceptibility, and (vi) that the appearance of the disease in the field is generally preceded by a period of high humidity or of high temperature, or of both.In addition to the soft-rot caused solely by Erwinia carotovora (L. R. Jones) Holland, necrotic blackheart tissues under favorable conditions often become infected by this pathogen, which, as a secondary decay, destroys the plant.The tarnished plant bug Lygus pratensis L. is of economic importance as a vector of soft-rot. Considerable damage, differing in appearance from either blackheart or soft-rot, may also be caused by its feeding habits.
Evaluation of glassy frits as micronutrient fertilizers. II. Manganese frits.
