Formulation of Chemicals for Seed Treatment


Seed treatment fungicides, both systemic and non-systemic, are formulated in several ways for application to seeds. Five main groups are recognized in the United Kingdom. The abbreviations are standard codes derived from the catalogue of pesticide formulation (GIFAP, 1989).
1.      Powders for dry seed treatment, i.e. they contain the active ingredient plus additives to prevent the cohesion of particles and/or stickers to improve the adhesion to seeds.
2.      Wettable powders, i.e. they contain the active ingredient, filters and a wetting agent for use in slurry (water and fungicide applied together or one after other) to seeds.
3.      Water dispersable powders, i.e. fine powders (particles up to 90 ┬Ám) to be dispersed  at high concentration in water for application as slurries to seeds.
4.      Solution for seed treatment, i.e. fungicide solutions (non-aqueous) for application directly for seeds.
5.      Flowable concentrates, i.e. stable fluid dispersions (solids in liquid) for application directly or after dilution to seeds.
The advantages and disadvantages of the type of formulation for seed treatment, you can look at table this below:
formulation
advantage
disadvantage
DS (powder for dry seed treatment)
WS(water dispersable powder for slurry treatment)
FS (flowable concentrate)




LS (solution)



formulated products applied in polymer film coats (FC)
‘on farm’ application possible

‘on farm’ application possible
Accurate loading
Good adhesion
Excellent efficacy
Application machinery
Can be washed out
No organic solvents used
Accurate loading
Excellent adhesion
Efficacy maximized

Accurate loading
Excellent adhesion
Efficacy maximized
No phytotoxicity
No hazards to health or environment
Reduced adhesion
Reduced efficacy
Efficacy not maximized

Specialist machinery needed for application



Organic solvents present can be phytotoxic
Specialist machinery needed for application




Specialist machinery needed for application

From table which indicate that flowable concentrates have superior overall qualities by comparison with the other types. Fifty three percent of pesticide products listed for seed treatment use in the United Kingdom, excluding those for potatoes, are formulated as flowable concentrates with 18% formulated as dry powders, 13% as solutions and 11% as wettable/dispersable powders; other minor formulations make up the remainder. Some formulations containing single active ingredients are available but to broaden their range of action, and possibly to reduce the likehood of selection for resistant forms of fungi, systematic fungicides have been formulated with other systematic protectant fungicides. In addition, the change in formulation technology to liquid pesticides noted by Jeffs and Tuppen (1986) has continued (Elsworth, 1988).