CIPC Sprout Inhibition

Sprout inhibition is essential to maintain tuber quality for the table and processing markets. Sprouting causes tuber dehydration, physiological aging and affects the appearance of the tuber for the table market. Sprout inhibition is achieved through a combination of proper storage management and the use of a sprout inhibitor. There are two sprout inhibitors registered for use in Canada. MH60, which is applied to the crop approximately 2-3 weeks before harvest or vine kill (Sprout Inhibition in the Field) and Chloropropham (CIPC), which is applied to potatoes after harvest.

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CIPC is available either as an aerosol or an emulsifiable concentrate. CIPC aerosol may only be applied to stored potatoes by trained applicators using specialized equipment. The grower applies the emulsifiable concentrate as a direct spray onto fresh market potatoes during the grading and packaging process. The balance of this section deals with the application of CIPC aerosol.

CIPC aerosol, which prevents cell division, must be applied after wound healing (suberization) and curing and before dormancy breaks. Historically, CIPC aerosol was applied with equipment originally designed for insecticide fogging. The by-products of combustion used to generate the CIPC aerosol have negative effects on potato quality. These by-products include heat, carbon dioxide and ethylene. This problem was resolved by designing an applicator specifically for CIPC aerosol application. The new applicator technology eliminates the deleterious effects of combustion by-products and improves the effectiveness of the treatment. Both the old and new style applicators are used in Western Canada.

Storage managers should contact the custom applicator for specific recommendations before preparing the storage for CIPC application. CIPC has an affinity for water, so the humidifier should be turned off at least two days prior to application to ensure the plenum and air ducts are dry. Before applying CIPC into the potato storage, the custom applicator checks and adjusts the air system, protects the refrigeration coils and reports any factors (disease, dirt, frost damage, etc) that may affect sprout inhibition. If storage conditions are suitable, the storage is sealed and the treatment is applied. After the treatment is complete and the fog has cleared from the storage, the applicator enters the building to perform post treatment cleaning of fans, fan guards, plenum, and other surfaces in contact with the chemical. Sealing materials are removed and the storage controls are reset to pre-treatment conditions, allowing the grower to resume normal operations.

WARNING: Only trained personnel wearing protective clothing should enter the storage during treatment.


Internal sprouting

Occasionally, CIPC treated potatoes sprout prematurely. Poor performance of the sprout inhibitor could be caused by:

• Temperature fluctuations and “hot spots”. These increase the rate of tuber respiration resulting in poor sprout inhibition. Temperature fluctuations and “hot spots” are caused by an improperly designed or malfunctioning ventilation system or excessive dirt and tuber rot in the bulk pile.
• Physiological stress. Field-stressed potatoes may respond differently to CIPC application than potatoes grown under normal conditions. Studies have shown that potatoes grown with deficient nitrogen will sprout earlier than adequately fertilized potatoes. Other field stresses (disease, drought, excessive moisture, and extreme temperatures) may also reduce the effectiveness of the sprout inhibitor.
• A low CIPC concentration on the sprout can cause internal sprouting where the sprout grows inward into the tuber or outward into an adjacent tuber. This defect occurs mainly in long-term storage. Late application, pile settling or the presence of excessive dirt and debris may interfere with the application, resulting in a low concentration of CIPC on selected tubers.
• Improper application.
• Poor storage management including fluctuating temperatures, high levels of respiration gases, low humidity, etc. shorten the dormancy period and reduce the effectiveness of sprout inhibition.