Library

eCommons

 

CCE Commercial Vegetable Production

Permanent URI for this collection

https://hdl.handle.net/1813/115484
The CCE Commercial Vegetable sub-community contains resources including factsheets, books, PowerPoint presentations and other materials that were produced by experts associated with the CCE Vegetable Program Work team. These experts are faculty associated with Departments of Horticulture, Plant Pathology and Entomology, as well as regional and county-based Cornell Cooperative Extension Educators. The sub-community contains content appropriate for connection and outreach to commercial vegetable growers in New York and elsewhere, as well as extension educators and other professionals who support the grower community.

Browse

Recent Submissions

Now showing 1 - 1 of 1
  • Thumbnail Image
    Item
    Shades of Black: Storage disorders of cabbage
    Björkman, Thomas (2009)
    There are a variety of storage disorders that afflict cabbage. They can be hard to distinguish because all of them turn black. All the black color means is that cells have died, so the color has no diagnostic value. Unfortunately, even a little black color stands out sharply against the pale cabbage leaf. It takes very little to make coleslaw look unappetizing. Whether a cabbage variety has the ability to store a long time or only a couple months, that storage capacity can only be realized if the cabbage is physiologically ready for storage when it is harvested. Obviously, an overmature cabbage has less life left than an optimally mature cabbage. On the other hand, a cabbage that has not had time to acclimate for winter dormancy will also store poorly. All these disorders are more common when cabbage is growing rapidly late in the season. Unfortunately, that means that there is a tradeoff between yield and disorder susceptibility. There are three main types of injury that are seen in New York. They each have a characteristic appearance. An extension fact sheet with some of these is available at Vegetable MD http://vegetablemdonline.ppath.cornell.edu/factsheets/Crucifers_Nonpathogenic.htm Tipburn. There are two forms of this disorder. When it is on the outer leaves, it looks the same as tip burn in many other leagy crops. The leaves half an inch to an inch under the top of the head dry out. There is less black color than with the other disorders. In the second form, it occurs close to the center of the head. This disorder usually appears in storage and progresses quickly. Dark areas first appear an inch or two above the tip of the core when a head is split. Often the black areas are found when the head is trimmed, and the black gets worse with additional trimming. The cells just under the epidermis die. The lesions take on a pearly appearance because the epidermis remains intact. This form of the disorder is also called internal blackening or zwart. An intermediate form is called tobacco leaf because it is dark brown and partly dried. Tipburn is caused by water movement going from the roots to the outside of the head, without carrying enough calcium to the center while the cells are forming. An uneven water supply is probably the most common situation to trigger the disorder. However, moist soils combined with high transpiration are especially bad. Tipburn can also be caused if a sudden flush of ammonium cations is taken up in place of calcium. Therefore, side-dressing with ammonium fertilizer should be avoided. Black Midrib (or black petiole). This disorder also has two forms. The classic form is when the outer leaves are affected, turning dark on the outside of the midrib, starting near the attachment point. The distributed form has black lines following the major veins of internal leaves. The diagnostic feature is that in cross-section there is a pair of black layers in the leaf, or a pair black spots, one on each side of a vein. While the cause is unknown, it appears to be associated with mineral nutrition. Dr. Nathan Peck of Geneva studied this disorder in the 1970's and attributed it to a deficiency of K in soils that have abundant P. Additional K fertilizer has been effective at reducing the incidence. Uneven water supply has also been implicated. There is substantial varietal difference in susceptibility, and seed companies are now testing new releases. Galaxy, Bingo and National have shown susceptibility. Bartolo has been resistant. This disorder gets worse more quickly in controlled-atmosphere storage than in a regular atmosphere. Pepperspot (also black speck or grey speck). There is also a viral disorder with the same name. This disorder starts with a blackening of the cells surrounding stomata. The lesions grow with time. Pepperspot is the result of salts or toxic metals that accumulate at the stomata after high transpiration. Either a salty soil, or a low pH soil that has high Ni and Cu available will predispose plants to pepperspot when weather is dry and warm. Too much nitrogen applied after head formation will aggravate the disorder. Overmaturity will also favor development of the disorder.