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Why chitosan is the most flexible fungicide

Updated: May 18, 2022

Flexibility before harvest

Every fungicide is designated a ‘pre-harvest interval’ (PHI) when it is first released for sale. The PHI is the is the minimum amount of time between the last application of the fungicide and when the crop can be harvested.

For fungicide that are particularly toxic, this PHI can be exceedingly long. This is especially the case if the fungicide is sprayed onto the part of the crop that is eaten (eg. lettuce leaves, or tomato fruits). For other fungicides, containing more benign chemicals, the PHI can be much shorter.

Pre-harvest intervals are determined by scientific studies during the registration process and are in place to protect us from consuming high residues of toxic compounds. As such, the PHI provides time for the compound to be broken down or washed off the plant.

Unfortunately for some farmers growing crops particularly prone to certain fungal diseases, a very long PHI can be a real challenge. What if the weather turns wet/humid and your crop starts to develop fungal growth that could seriously impact your final yield and crop quality?

Well, this is where chitosan comes into its own. Chitosan as a biofungicide (under Basic Substance regulations) has a stated PHI of zero days!

Chitosan has been designated a PHI of zero days because of its innate safety. Unlike other pesticides, chitosan controls plant pathogens by activating the plant’s own defence mechanisms, not directly killing the fungicide. As such, it is not classed as a biocide. It is also natural in origin, and has a long history of use as a food additive and in medical applications.

Despite its safety to humans, chitosan is an effective fungicide with its effectiveness shown again and again in multiple independent scientific studies.

So if your crop is starting to develop the sure signs of fungal attack and it is too late to apply your usual go-to fungicide, consider chitosan! Why not have a polycan or two in the cabinet ready to apply, just in case?

Easily purchase a polycan of chitosan using the link below to our shop:

For a comparison of the range of PHI for the most popular fungicides in the UK see the tables below. The first table is for horticultural/field crops, and the second is for cereal crops. As you can see, some fungicides have very long PHI. This even includes many products that would be classified as bio-pesticides.

Other flexible features of chitosan are the facts that farmers can make up to eight applications for many crops, and there is a wide range of dosages allowed for each crop.

So chitosan certainly is a very flexible fungicide that helps farmers respond to rapidly changing and challenging situations; especially when it comes close to harvest time.

Please let us know your thoughts on this subject in the comments section.

Dr Russell G. Sharp

Eutrema Ltd

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