University of Manitoba - Faculty of Agricultural & Food Sciences - Blossom-end Rot
Blossom-end Rot

Problem type: Disease

Name of problem: Blossom-end rot

Plant name(s): Tomato, pepper, eggplant, squash, watermelon and apple

Symptoms / Characteristics:
Brown rotted patches develop at the blossom end (the end opposite to stem attachment) of the fruit and sometimes on the sides. These depressed lesions darken and expand, eventually covering a significant portion of the fruit. The interior of the fruit may also turn black and rot, a condition known as blackheart. In apple, blossom-end rot can be caused by two fungal species and symptoms vary accordingly. Rotted lesions may be soft and leathery (resembling that of the tomato) or dry and cork-like with a reddish border.

Blossom-end rot is caused by calcium deficiency during fruit formation. Disease development is facilitated by dramatic fluctuations in temperature and moisture, excess nitrogen and magnesium in the soil, high soil salinity and root damage. These conditions inhibit calcium uptake by the plant and subsequent transport to developing fruit. Drought conditions render plants especially vulnerable to blossom-end rot.

Control / Preventions:

The most effective control is to avoid conditions that lead to calcium deficiency and the subsequent development of blossom-end rot. This involves effective water management and a balanced fertilizer program. The goal is to promote steady plant growth and ensure that an adequate amount of calcium is readily available to the developing fruit. Avoid applying excessive amounts of nitrogen fertilizer as this results in rapid vegetative growth. If the rapidly growing plant cannot absorb calcium fast enough, symptoms may develop.

Avoid damaging the roots during cultivation. A layer of mulch can help eradicate weeds and reduce the need for cultivation. In drier regions, mulches may also be used to retain soil moisture. Ensure that plants are hardened off prior to transplanting in the field and avoid planting into cold soils. Other preventative measures include the addition of lime to the soil before planting and a foliar application of calcium chloride or calcium nitrate during the growing season. If symptoms are detected early and the calcium deficiency is addressed, later developing fruit will not be symptomatic. However, once symptoms appear on a fruit, they are irreversible.