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Crown MH

Growth Regulants
Crown MH

Growth Regulants

19495 (PCS 06217)

Crown MH

A soluble concentrate formulation containing 270 g/L maleic hydrazide used to inhibit sprouting in onions and potatoes during storage and to control the growth of volunteer potatoes in succeeding crops.

Liquid non-foaming Maleic Hydrazide. 

Start you sprout supression programme in the field.

Control secondary growth and sprouting tubers in the field.

Reduce volunteers in following crops.

For top tips on application, check out the brochure, FAQ's and videos below. 

  • Onions
  • Potatoes (Ware)

Product Label

Extension of Authorisation for Minor Use (EAMU)

Authorisation No.





Outdoor garlic, Outdoor shallot



Outdoor carrot, Outdoor parsnip

New Fastran 850 Closed Transfer Sytsem for 600L IBC's


Guidance on Best Use - Questions from the field

Not all varieties flower so only a guide and length of flowering can vary. It’s more important to know how far off desiccation or flailing the field is. Ideal timing is applying CrownMH ~5 weeks before desiccation or flailing.

Numerous trials conducted by Certis show that there is a real risk of a yield decrease if applied too early - so if applied 7-9 weeks before desiccation, this can lead to a ~10% yield drop – which could equate to ~£750/Ha (based on 50t crop @£150/t). 

If the next 3-day weather forecast looks “catchy” and then fine afterwards, it is much better to wait until more settled weather. Whether it's 5.5 weeks or 4.5 weeks before desiccation won’t change things drastically.

We recommend no rain for 24 hours to give maximum chance of uptake, 10 hours would be the shortest effective period. People have become used to applying fungicides with a short drying time (30 mins - 1 hour). This is most definitely not the case with MH. In a Certis Netherlands trial, 2mm rain 4hrs after application resulted in 4ppm v 28ppm with no rain.

No, it should not. The dew actually “sits” on the leaf surface and does not roll off like water from a heavy rain shower or irrigation. This is a good time to apply CrownMH as it will stay on the leaf for as long as possible.

Mancozeb can form a layer on the leaf which can inhibit the uptake of MH. Ideally leave as long as possible after the last mancozeb spray before going on with CrownMH. As for the following mancozeb spray, this can be straight after the MH as the water volume in the fungicide (~200 L/Ha) will not be sufficient to “wash off” the MH.

The priority is an even canopy coverage at the high water volume. Although drift is always of concern, it isn’t so critical in this situation. You are spraying a PGR not a broad spec herbicide. A Flat Fan would work well, so long as it met the desired L/Ha and the pressure was obtainable.

06 (Grey) Flat Fan at 4 Bar would give 400 L/Ha just over 8kph – giving a Fine spray quality.

08 (White) would do the same giving a Medium spray quality.

An 08 (White) Hi-Flow nozzle would meet the flow rate demands, however the very course spray quality would not be quite as ideal, a greater tendency of the product running or bouncing of the leaf. Please ask your agronomist or local sprayer dealer stating aspects of your required situation; 400 L/Ha water, 8 kph, PGR, mature potato crop canopy.

  1. CrownMH will dry too quickly on the leaf, restricting uptake. 
  2. A potato plant will start to flag and moves into survival mode, again restricting uptake.

For best practice, do not mix CrownMH with anything! The fundamentals of applying a fungicide and maleic hydrazide are different, to apply them together would compromise the efficacy of both. Differences in mode of action, uptake speed, water volume, forward speed, drying time and the use of adjuvants.

An adjuvant (spreader) is not required as CrownMH is systemic and not contact. The  wetters within some fungicides can speed up the uptake and surface drying time, this is not ideal for CrownMH. Aim is to keep CrownMH on the leaf surface for as long as possible, giving it the maximum amount of time to be absorbed into the healthy growing plant.

Avoid using a fungicide containing mancozeb with or before an application of CrownMH. Mancozeb can form a layer on the leaf which can significantly restrict CrownMH uptake.

Always go first with CrownMH, ideally leave 24 hours. When spraying a fungicide after a CrownMH application, the water volume of the fungicide spray solution (~200 L/Ha) should not be enough to cause the MH to run off the leaf.

When CrownMH is applied to the small and immature plants, the MH will not allow the tubers (if there are any) to grow since MH inhibits cell division - therefore the tubers will not continue to grow.

However, MH does not supress cell growth and elongation – hence, mature tubers will continue to bulk after an application.

No. There is no benefit. With a water volume of ideally 400 L/Ha when applying CrownMH, the droplet size is generally medium, which will not be prone to drifting.

It’s all about keeping the CrownMH on the leaf for as long as possible. CrownMH is a systemic product, so anything that can be done to extend the drying time - maximizing the uptake period.

If the crop is healthy and actively growing, it’s fine to apply CrownMH. You’ll know this from rainfall record and how the crop canopy is looking. If we are in the middle of a dry period, with no rain forecast for the next 2-3 weeks, the best time to apply CrownMH is late in the evening. Taking advantage of the longest period of the low air temperatures, giving ~12 hours of uptake time, before temperatures increase again.

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