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Pesticide Poison Information
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In recent years, another consideration in the application of insecticides is the pH of the water to be used for spraying. This is particularly important when organophosphate and carbamate insecticides such as Guthion, parathion, malathion, carbaryl and others are to be used. Experience in the Red River Valley area of North Dakota indicates that water with a pH of 8.0 _ 8.2 or higher will cause rather rapid degradation of these insecticides while in solution. Buffering effects occur while the insecticide is in the spray solution, from mixing, through storage in the tank and continues until the water has evaporated from the spray droplet lying on the leaf.
Half-Life* of Some Insecticides At Different Water pH
| Insecticide Product |
Buffering Advised | Optimum pH | Half-Life for given pH | |||||
| 9.0 | 8.0 | 7.0 | 6.0 | 5.0 | 4.0 | |||
| Actara | 7.0 | Susceptible to alkaline hydrolysis in pH<9.0 | ||||||
| Actellic | 7.0 | 12 days | 35 days | 7 days | ||||
| Admire | 6.0 | 355 days | Fully stable at a pH of 5 and 7 | |||||
| Ambush (permethrin) |
7.0 | Stable at pH 6.0 - 8.0 | ||||||
| Asana XL | 7.0 | Stable over a pH 5.0 - 9.0 range | ||||||
| Di-Syston | X | 5.0 | 7.2 hours | 32 hours | 60 hours | |||
| Diazinon | 7.0 | 29 days | 70 days | 14 days | ||||
| Dibrom | X | 5.0 | Hydrolized in 48 hours In pH > 7 | |||||
| Dimethoate / Digon | X | 5.0 | 48 min. | 12 hours | 20 hours | |||
| Dipel (Bac.) | 6.0 | Unstable in pH>8.0 | ||||||
| Furadan | X | 5.0 | 78 hours | 8 days | ||||
| Guthion | X | 5.5 | 12 hours | 10 days | 17 days | |||
| Imidan | X | 5.0 | 4 hours | 12 hours | 13 days | |||
| Lannate | 6.5 | stable in slightly acidic water | ||||||
| Lindane | 11 days | 27 weeks | ||||||
| Lorsban | 7.0 | 1.5 days | 35 days | 63 days | ||||
| Malathion | X | 5.0 | 5 hours | 19 hours | 3 days | 8 days | ||
| Monitor | X | 5.5 | Decomposes rapidly at pH > 7 | |||||
| Orthene (acephate) | 7.0 | 16 days | 46 days | 40 days | ||||
| Pounce (permethrin) | 7.0 | Stable at pH 6.0 - 8.0 | ||||||
| Provado | 7.0 | Stable over wide range of pH | ||||||
| Reldan | 7.0 | 3 days | 38 days | 10 days | ||||
| Sevin (carbaryl) | X | 7.0 | 24 hours | 2.5 days | 12 days | |||
| Spintor | 7.0 | Stable in pH from 6.0 to 11.0 | 12 hours | |||||
| Thiodan | 6.5 | some alkaline hydrolosis | ||||||
| Vydate | X | 5.0 | 3 hours | 8 days | stable at 4.7 pH | |||
| Warrior | 6.0 | stable in pH 4.5 - 7.5 | ||||||
* Half-life is the time it takes for 50% of the chemical to decompose
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