Sprout Suppression

Key Points

Fazor contains maleic hydrazide, a plant growth regulator for potatoes and onions
Apply to potatoes at 5.0kg/ha in 350 – 500 litres of water
Do not use on first early or seed potatoes
Do not use under drought conditions, when temperatures exceed 26°C, or when crop is under stress
Application of Fazor helps reduce the volunteer potato burden in following crops
Use of Fazor can save at least one application of CIPC to stored potatoes

Introduction

Sprout suppression in potatoes is important for two reasons: management of harvested potatoes in store and reduction of volunteer potatoes in the rotation. An integrated approach the management and reduction of volunteer potatoes is particularly important where less competitive crops, such as sugar beet, are part of the rotation. For more in-depth advice about controlling volunteer potatoes read A Practical Guide to Achieving Integrated Control of Volunteer Potatoes (1.0MB PDF).

Biology

Potato tubers growing in the field have two distinct growth patterns when bulking up. Initially, tubers begin to form and then grow by a process of cell division, up to approximately 25mm in diameter. When this size is reached cell division stops naturally. After this stage any increase in tuber size is achieved, not by further cell division, but by expansion of the existing cells through cell growth and bulking up.

Harvested potatoes, if placed in storage, will at some point begin to produce new sprouts. This obviously leads to wastage and can make a proportion of the harvested product unsaleable. Potato tubers left in the field at harvest lead to problems in following crops from volunteer potatoes. These volunteers compete with the crop for light, space and nutrients leading to reduced yields and quality. They are often also the source of potato blight infection. The problem can be particularly troublesome in crops such as sugar beet, where the crop is relatively uncompetitive during early stages of establishment and growth.

Product Choice

To reduce the burden of volunteer potatoes in following crops and to help in the management of sprout suppression in store, Fazor~ (active ingredient maleic hydrazide) can be applied to the growing potato crop. Application of Fazor should be made after natural cell division of the tubers has ceased and when translocation of nutrients from the leaves to the tubers is most active.

To maximise uptake and translocation of Fazor, applications should be made alone at 5.0kg/ha, using a water volume of 350 – 500 litres per hectare. Fazor should not be applied to any crop under stress or if daytime temperatures exceed 26°C. Rainfall or irrigation should not occur for at least 24 hours after application. It is important the crop is at the correct growth stage for optimum results.

Tubers: larger than 25mm
Flowers: some still present but most fallen
Haulm: first signs of lowest leaves senescing, majority green, actively growing and free from disease, insect attack and stress
Timing: Fazor should be applied 3 – 5 weeks prior to haulm destruction

If Fazor treated tubers are placed in storage they must be checked regularly from the end of November. The length of sprout suppression achieved varies depending on the concentration of maleic hydrazide in the tuber and the rate of breakdown. As with many biological reactions, in mild ambient stores breakdown is faster than in cold stores, thus reducing the length of sprout suppression. When used in an integrated approach to sprout suppression, independent trials have demonstrated that use of Fazor can save at least one application of CIPC.