Cabbage and swede: Reducing wastage in stored winter crops

Project summary:

Significant losses in winter cabbage and Swedes occur after harvest with up to 30-40% wastage during storage, due to fungal decay and physiological breakdown leading to water soaked lesions. Strategies that control physiological breakdown and the incidence of post-harvest disease require further investigation.

A number of post-harvest strategies that; combine treatments to improve crop health and lower fungal load will help reduce wastage

Calcium is an important regulator of plant cell health, strengthening cell walls, preventing localised tissue death and slowing the ingress of disease. Increasing the uptake and translocation of calcium into the head of cabbage and swede will increase the storage life of the crop. Newer formulations of calcium nitrate/ammonium nitrate and zinc nitrate (Inca^TM,) and a calcium/boron formulation (Headland Carnival) tested recently on apple have shown improved uptake of calcium into tissue and may provide a valuable method to strengthen tissue.  Boron deficiency in swedes has been linked to brown heart and low boron is often associated with increased tissue browning    

Additional treatments during storage such as humidification, ethylene removal and ozone treatments are also beneficial in reducing water loss, and thereby improving the financial return on the saleable crop coming out of store whilst reduced dehydration reduces disease development. Ethylene removal using catalytic scrubbers from the storage environment has proved a successful method of extending the storage life of broccoli (FV395) by reducing the rate of senescence and water loss. This technology is currently being trialled commercially in cabbage with some success. To date, the threshold of ethylene removal required for effective reduction in water loss and senescence/decay in cabbage and swede has yet to be determined and requires further investigation. Recent trials with ozone trials (NRI) on cucurbits led to reduced water loss via increased stomatal closure on the skin surface, and lowered disease development. Earlier trials with cabbage with higher concentrations of ozone  led to surface pitting/browning. Identifying an effective dose of ozone that both lowers disease and water loss of both crops without discolouring cut surfaces has yet to be determined

Moreover, advances in the formulation of bio-control agents (Serenade and Nexy) against Botrytis may provide longer-term protection during storage diseases in cabbage. Often the efficacy of biocontrol agents is enhanced with pre-harvest treatment with calcium.

Aims and objectives:

1. Project aim(s): Reducing wastage in stored winter cabbage and swede.
2. Project objective(s):

1. Evaluate pre-harvest spray application of new formulated calcium products to improve the quality of cabbage and swede in storage and reduce the incidence of disease.
2. Evaluate the use of Biological Control Agents for the control of Botrytis rots on cabbage.
3. Evaluate control methods (ozone, ethylene removal) for maintaining crop health and reducing the incidence of Botrytis, Phytophthora and Phoma rots and wastage in stored produce.
4. Develop a strategy for reducing the incidence of storage rots based on a combination of treatments.