Using Maleic Hydrazide as a sprout suppressant

Monday, 3 February 2020

With the withdrawal of CIPC now a certainty, the race is on to plug the sizeable gap left in a potato store manager’s toolkit. Maleic Hydrazide (MH) may already be familiar to growers as a foliar spray used to control volunteers but research has shown in many cases that it should be an integral part of a sprout suppression strategy.

The most important thing to bear in mind is that MH is not a like-for-like replacement. In a post-CIPC world, a combination of alternatives will be most effective when controlling sprouting. Store managers should consider using MH alongside other actives such as ethylene and spearmint oil.

Unlike CIPC, MH is applied in field to the growing crop rather than in store. This means there are a number of considerations to bear in mind when using it as a sprout suppressant:

  • Timing: the timing of MH application is a crucial consideration. Applying too early reduces yield, while applying too late reduces sprout control. Treatment is recommended around late July or early August (around 3 to 5 weeks before defoliation) for best results. The crop should be green and actively growing, and only lower leaves may show senescence. Earlier applications results in better sprout control.
  • Weather: As MH is a foliar spray, the weather at the time of application can have a significant impact if it hampers uptake through the leaves of the crop. There are temperature restrictions on when it can be applied
  • Stress: The crop’s level of hydration at the time of treatment and disease status can affect uptake and impacts on the crop’s reaction to MH treatment. Recent drought conditions in 2018 meant MH had a considerable effect on crops following application. Crop must be actively growing.

Another consideration is dormancy period. In this case dormancy refers to the period during which a crop doesn’t grow even when conditions favour growth. Because dormancy varies widely with each variety, a store manager can turn a knowledge of dormancy to their advantage because sprouting doesn’t occur during this period. AHDB is currently undertaking research in this area in trials at Strategic Potato (SPot) Farms.

Maleic Hydrazide: current practice

In late 2018 and early 2019, AHDB surveyed a number of contacts within the industry on the current use of MH:

A summary of key points from the survey are provided below:

  • 40% of users apply MH to potato every year
  • 78% of users apply MH for sprout suppression
  • 66% of users apply MH for volunteer control


  • Respondents applied the product on average 5.1 weeks before defoliation but there was a lot of variation around this figure from 2 weeks to 8 weeks
  • 88% of users timed application relative to defoliation rather than harvest

A study of overseas store management yielded that Dutch and German growers storing without CIPC considered it a ‘must- have’ component of a store manager’s arsenal. The study involved AHDB staff visiting a number of commercial businesses early in 2019, all of which used MH in combination with other actives, such as spearmint oil and dimethylnaphthalene, to control sprouting.

If you’d like further advice on storage please call the storage advice line on 0800 02 82 111.