Conversion possible?

[Phoenikakias]

How do we convert a dosage of a 20% active substance insecticide in solid form (i.e. 50 gr / 100 lt water) to a dosage of same insecticide 20% in liquid form (i.e. ?ml/ 100 lt water)?

[sonoranfans]

If it makes a cloudy solution you probably cannot trust the uniformity of the pesticide solution.  I would not mess with it, and I am a chemist.  Any sediment in the mix solution puts doubt on its effectiveness.  I would never add a chemical to a pesticide either(to help it dissolve).  Pesticides are reactive, you could have a poisonous gas coming off the mix if you added a chemical to help dissolve it.  I would just use it as instructed.

[Merlyn]

@Phoenikakias by law the product should have a label showing the mixing ratio.  So my solid Acephate mix is 8oz per 100 gallons of water, and my liquid Malathion is 4 tsp per gallon.  Do you not have the label for the product?  Usually you can find it online.

[Phoenikakias]

17 hours ago, sonoranfans said:

If it makes a cloudy solution you probably cannot trust the uniformity of the pesticide solution.  I would not mess with it, and I am a chemist.  Any sediment in the mix solution puts doubt on its effectiveness.  I would never add a chemical to a pesticide either(to help it dissolve).  Pesticides are reactive, you could have a poisonous gas coming off the mix if you added a chemical to help dissolve it.  I would just use it as instructed.

I fear that I did not put the question clearly enough and my apologies fot that. I do not want to transfom a pesticide from one state of matter to another.  There is in the local market same insecticide in both forms available, solid (granules) and liquid, and in both states of matter percentual content of active substance is identical (i.e. 20%). Unfortunaly it is mentioned nothing in the labels of both products about recommended dosage for the protection of palms against rpw and paysandisia archon. As a general practice local agronomists suggest that one has to double recommended dosage when applied on palms to the mentioned purpose. As for the reasons for the omission of palms, I can only imagine that it is  a political decision of EU. Systemics are considered (by majority vote in the council) harmful for the bees and a necessary evil, as long as they are still useful for the production of economically important crops. Palms here (with the exception of Spain because of the very mild climate and the many nurseries) do not have any directly economical value, only decorative and therefore are regarded inexplicitly as expendable.  So after the legal ban of imidacloprid and thiamethoxam within EU there is still available only one systemic, which is used also in the Spanish nurseries at rate of 50 gr (solid form) per 100 lt water. I have recently acquired at a better price the liquid form of this systemic (half a liter bottle) but I know nothing about the dosage for palms, except that information coming from Spain reg. the application of the solid form.  Therefore I wanted to know, whether there is a rule of thumb for converting recommended dosage reg one state of matter (in paricular here solid whereby dosage is expressed in weight unit) to equivalent dosage reg another state of matter (in particular here liquid, whereby dosage is expressed in volume unit).

[Phoenikakias]

8 hours ago, Merlyn said:

@Phoenikakias by law the product should have a label showing the mixing ratio.  So my solid Acephate mix is 8oz per 100 gallons of water, and my liquid Malathion is 4 tsp per gallon.  Do you not have the label for the product?  Usually you can find it online.

My immediately previous reply should also answer your question. Feel free to ask for more information...

[Merlyn]

@Phoenikakias ok so I did guess what you meant!    As far as I know, there's not a "rule of thumb conversion" like that.  With liquids it's fairly easy.  To find the final percentage it's just:

• Final % = (Concentration % * Volume of concentrate) / (Volume of Concentrate + Volume of Water)

So if you use 0.5L of 20% and 1L of water then you have:

• 6.67% = 20% * 0.5L / (0.5L + 1L)

If you could find the target "final" percentage for the solid (like 1% solution) then you could calculate the liquid version easily.  But figuring out the "final" concentration percentage from (for example) 5g of 20% powder in 1L of water is only slightly more complicated:

• Final % = (Concentration % * Weight of concentrate) / (Weight of Concentrate + Weight of Water)

In that case you just need to know that 1L of water = 1kg = 1000g.  So 5g of 20% powder in 1L is:

• 0.1% = (20% * 5g) / (5g + 1000g)

So while there isn't an exact "rule of thumb," you can calculate the target percentage in solid from your older product, and then use the liquid formula to figure out how much 20% to add to 1L of water.

@sonoranfans let me know if I made any mistakes in the above formulas.  It's been ~30 years since I have done even any basic chemistry.

[sonoranfans]

Looks good on the calculation of wt%.  If you have dry soil that is on a slope I would definitely use the liguid to get a more consistent application to all the roots.  Solids on slopes coulkd be problematic in that concentrated particles can be rinsed downhill.  After seeing Konstantinos Bismarckia I would use alternating wetting events of pesticide, let dry, then water and repeat a few times in the full root zone area to get best coverage of the roots.  Better coverage means more uptake.   Since I expect Konstantinos don't get florida rains I would use the liquid application approach.  If I were to treat in my yard with my high drainage sandy soil and with the rain I get, I would not use the ligiid form as rain losses would be high.  But on rocky clay soil with lots in slope, definitely use the liquid and let it soak in to dry soil, apply but don't flood it.

[Merlyn]

@sonoranfans gotcha, so using the prior example of 5g of 20% in 1L = a final percentage of 0.1%.  Usually the volume of concentrate is really small compared to the total water volume, so you can simplify the liquid formula to:

• Final % = (Concentration % * Volume of concentrate) / Volume of Water

As an example, Malathion is 4tsp per gallon at 21%.  One gallon is 768 teaspoons.  Using the full formula vs simplified it's:

• 0.1088% = (21% * 4tsp) / (4tsp + 768 tsp)
• 0.1094% = (21% * 4tsp) / 768 tsp

In most cases you can simplify both formulas without really changing the results.  So rearranging to solve for @Phoenikakias's specific problem.  He knows the original weight and concentration % of solid for xxx liters of water:

• Final % = (Concentration % * Weight of concentrate) / Weight of Water

So you can calculate that for the volume of liquid concentrate to add to water:

• Volume of Concentrate = Volume of Water * Final target % / Concentration %

In the 5g example:

• 0.1% = 5g * 20% / 1000g
• 0.005L = 1L * 0.1% / 20%

So I suppose I found a "rule of thumb" after all!    If you have the same percentage liquid and solid, and the same final volume of water, you can use 5g of solid or 5mL of liquid!