Oedema of Cabbage
Oedema is a physiological response of the plant to excessive soil moisture during periods of cool nights and warm, humid days. Many small scabby lesions form on the underside of the cabbage leaves. Avoid irrigation during times when day-night temperature variations are great. Oedema may be confused with thrips damage.
Head Rot and Brown Beading (Broccoli)
Both problems are caused by several factors. Problems with calcium uptake combined with rapid growth can result in either condition, even when soil calcium levels are high. Head rot results from bacteria breaking down the tissues under wet conditions, and brown beading results from individual flower buds aborting under dry conditions. Extended periods of wet or dry conditions during warm temperatures give rise to rapid plant growth while calcium uptake is diminished due to poor transpiration rates in the plants. Mixing varieties based on rate of maturity offers growers the only practical defense against either head rot or brown beading. Selecting a later-maturing cultivar to be harvested along with your typical cultivar during those parts of the growing season when problems have typically occurred can reduce the risk of whole-crop losses during challenging weather conditions.
Cauliflower and Broccoli Premature Heading and Lack of Heads
Buttoning is most common when transplants are too old and past the juvenile growth stage when transplanted. Other stress factors such as low fertility, low moisture micronutrient deficiencies or disease and insects can also be causes. Strong healthy plants lacking heads can occur due to periods of extremely warm weather (days over 86º F and nights over 77º F).
Bracts (leaves) in Cauliflower or Broccoli Heads
High temperatures or low soil moisture can result in the formation of bracts, small leaves, between segments in the heads of cauliflower and broccoli.
Yellow or Brown Beads in Broccoli Heads
Yellowing of florets may be due to an over mature head, high storage temperatures after harvest, or exposure to ethylene. Brown beads in broccoli are areas where florets do not properly develop and die. Possible causes include nutritional imbalances, or feeding damage by insects such as harlequin bugs or tarnished plant bugs.