For a number of decades it has been understood that weighted drop hoses are one of the better ways to deliver liquid aquatic herbicides within the water column. The key to a successful treatment is to understand the concentration exposure time relationship for the herbicide selected and the target plant, and then to deliver it in a fashion that enhances uniform delivery and exposure within the weed beds. The University of Florida and applicators in that region developed the concept of weighted hoses about 30 years ago.
One of the issues with weighted hose delivery systems has always been that the deeper the treatment site, the harder it is to keep the hoses down there. Treating water depths up to 15 feet with conventional weighted hose technology is no problem. The problem occurs when the target weed beds are in 15-25 feet of water.
One solution to this problem was the development of the Littline approximately one decade ago. This technology uses a very long hose dragged behind the application boat, this additional length of hose and the weight of the hose overcame the issues with treating weed plots in excess of 15 foot water depths. It does however present some challenges to uniform delivery of herbicides within the water column.
The Littline system relies on 2 long hoses with a small spray tip on the end of the line. If you view the Two Hose System diagram shown here, you will see that the entire herbicide load for the entire horizontal and vertical cross section of water are placed in two lines near the bottom of the lake about the size of a dime. This means that at the point of delivery, the herbicide rate in the water is very high and the dynamic of dilution is required to spread the herbicide both vertically and horizontally in the water column to obtain a uniform exposure.
This doesn’t always happen and is variable at best in terms of uniformity of herbicide concentration in the target weed beds. There can be zones in the treatment area with very high rates of herbicide and zones with low rates of herbicide causing an uneven concentration and exposure rate throughout the target zone. This can impact the efficacy of the application.
The T.R.U.E. System
The Target Rate Uniform Exposure or TRUE Aquatic Herbicide Application System improves upon this concept of delivering and maintaining a concentration and exposure time of an aquatic herbicide within the weed bed.
The TRUE system consists of two large herbicide storage tanks, a GPS controlled herbicide flow system for precision application and from six to eight drop hoses with variable depth herbicide discharge points.
This diagram shows the concept of using micro tips. Instead of discharging the entire herbicide load for the entire cross section of water through two dime sized tips near the lake bottom, the TRUE system has from 24 to 36 (depending on configuration) discharge points uniformly placed within the treatment cross section profile. This allows for uniform placement of the targeted application rate throughout the horizontal and vertical profile. The herbicide only has to dilute from 1 to 2 feet before it overlaps with the adjacent injection point as opposed to up to 20 feet with the two hose system.
This technology is the next logical step in the evolution of aquatic herbicide application technology. It insures that the applicator can comply with NPDES requirement of delivery the herbicide with the Best Available Technology (BET). It insures better control with the herbicide applied because of the improved delivery. It also results in being able to deliver control with less herbicide, there can be savings of up to $200.00 per treated acre vs. a two hose system.