| The dust is just beginning to settle from the chaos growers refer to as the spring season, and you find yourself wondering if there isn't a way to make your life a little easier next year. You are willing to plow some of your hard earned dollars back into the business, but only if the return on investment is sure. |
| Over the past decade the amount of low volume pesticide equipment being utilized in greenhouses has increased significantly. There must be good reasons for this, so let's do a brief review of the technology and see if it makes sense for you to consider low volume pesticide equipment for your operation. |
What is low volume pesticide technology? |
| Low volume pesticide equipment comes in many shapes and sizes, capable of treating the smallest Quonset huts to one acre and larger gutter connected ranges. Some use gasoline or batteries, but most are powered by electricity. At the heart of this technology is the ability of these machines to produce billions of micro-particles containing pesticides and deliver them to all surfaces within the greenhouse. These machines are designed to deliver the same amount of active ingredient in substantially less water than traditional hydraulic spraying equipment. Thermal foggers use a chemical carrier, or a combination of water and a chemical carrier. Cold foggers and automated whole house foggers simply use water as the carrier. (Aerosol pesticide cans and smoke generators also provide low volume applications, so much of the information in this article applies to them as well). |
Advantages of low volume pesticide technology |
- Application time - growers find cold fogger and thermal foggers to be about ten times faster than hydraulic spraying. Auto-foggers are unattended and operated by timers.
- Reduced runoff - greatly reduced water volumes lead to less runoff of pesticides.
- Coverage - all surfaces in the greenhouse are treated, including the weeds under the benches. (Of course, there are none of those in your greenhouse...)
- Pesticide usage - most growers feel they make fewer pesticide applications over the course of a year due to improved effectiveness.
- Phytotoxicity - in some cases growers have reported that pesticides that caused plant damage when sprayed with high volume equipment did not when applied through low volume equipment. Caution: Heed all label precautions concerning possible phytotoxicites, don't assume that low volume applications will not cause damage!
- Dry foliage - foliage remains dry during treatments, reducing the risk of foliar disease.
- Reduced pesticide exposure - (auto-foggers only) the applicator is not in the greenhouse at any time during the time of application.
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| Limitations of low volume pesticide technology |
- Chemical selection - some pesticides have labels that forbid the use of low volume applicators. Horticultural oils and microencapsulated pesticides are not recommended through certain machines.
- Plant growth regulators - foliar PGR treatments are still being applied by high volume spray equipment.
- Spot spraying - it is not possible to treat individual benches or groups of plants with low volume equipment. Greenhouses with vegetable and herbs have to be treated with products approved for those crops, greatly reducing pesticide choices.
- Equipment costs - on average low volume equipment is more expensive to purchase than hydraulic spraying equipment.
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| Additional WPS considerations |
| If the pesticide application in the greenhouse is made as a smoke, mist, fog, or aerosol, one of the following ventilation criteria must be met in addition to the expiration of the restricted-entry interval before workers are allowed into treated areas, whichever is later: (Note: The restricted-entry interval (REI) does not begin until the end of the pesticide application. In the case of an automated fogger, if it takes two hours to complete the fog application, that is when the REI begins.) |
| A. |
The concentration of the pesticide in the air is measured to be less than or equal to any inhalation exposure level required on the labeling. |
| B. |
If no inhalation exposure level is listed on the labeling, keep workers out until after:
| 1) 10 air exchanges, or |
| 2) 2 hours of ventilation using fans or other mechanical ventilation systems, or |
| 3) 4 hours of ventilation using vents, windows or other passive ventilation, or |
| 4) 11 hours with no ventilation followed by 1 hour of mechanical ventilation, or |
| 5) 11 hours with no ventilation followed by 2 hours of passive ventilation, or |
| 6) 24 hours with no ventilation. |
| The REI and the ventilation criteria can run concurrently, but both must be satisfied before workers can re-enter treated areas. |
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| Calculating rates of approved pesticides for low volume applications |
Check your owners' manual for rate calculation as it may vary from this example.
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The multiplier of .35 is arrived at by estimating that a typical high volume application would require 40 gallons of water to treat 10,000 sq ft. The manufacturer assumed 5 gallons of that total to be lost to runoff. Multiplying the per 100 gallon label rate by .35 (40 gal - 5 gal runoff= 35 gal) approximates how much active ingredient would be applied to 10,000 sq ft by a high volume application. |
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| *** Read and heed all of the information on pesticide labels! *** |
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