Questions for Aquatic Herbicides in Lakes and Ponds:

Blue represents responses by Michael S. Blankinship, Blankinship & Associates, Davis, CA

8/20/09.

Identification of Problem

1. If pesticide applicators are required to identify problem weed areas and application areas,

what methods (including equipment) do you think they would use to perform this

activity?

Yes, pesticide applicators are absolutely required to correctly identify weed type. This is critical

in making correct decisions on pesticide selection. Then, pesticide applicators are in most cases

required to obtain a written recommendation for a California Department of Pesticide

Regulation-licensed Pest Control Advisor (PCA). See the attached form. Prior to determining if

a pesticide application is needed, correct target pest identification is critical.

Various methods are used and often more than one method is used in an integrated pest

management (IPM) approach. Scouting is the general term and involves correct weed

identification, location, density evaluation. This is done, by walking, ATV, boat, windshield

survey, and aerial survey using either helicopter or plane. We’ve also worked preliminarily with

interpretation of IR aerial photography in certain weed types in commercial crops such as

tomatoes. As of now, this has not been adopted to aquatic weed management. Locations and

densities are commonly plotted using commercially available GIS software. In cases where

submersed aquatic weeds are present, bathymetric surveys are commonly employed in lakes,

ponds, and reservoirs.

Ultimately a variety of control measures are considered. These methods are generally broken

down into main categories that include: mechanical (cutting, excavating, dredging, aeration,

circulation, etc), biological (carp, tilapia, nutrient sequestration agents, competing algal

additives, etc), cultural (best management practices including exclusion, placement of native

species, nutrient control, UV exclusion, buffer strip placement, damage threshold evaluation, etc)

and chemical ( pesticide application, growth regulator use).

a. How much time do you think they would spend to identify these areas (i.e.

number of hours per waterbody)?

The amount of time required to do proper and adequate scouting is highly variable and depends

on many factors, including but not limited to: water body size and depth, access restrictions,

different weed type(s), time of year, frequency of re-infestation, etc.

b. OR how much do you think this weed identification would typically cost (per city,

county or state)?

This is again dependent on the same variables as listed above. Some counties in CA are larger

than entire states on the east coast. Further, some irrigation districts were aquatic weed control is

done have > 500 miles of canal and/or creek.
2. If pesticide applicators are required to identify weed species and conditions that

necessitate weed control measures, what methods (including equipment) do you think

they would use to perform this activity?

See answer to #1 above.

a. How much time do you think they would spend to identify the species and

conditions (i.e. number of hours per waterbody)?

b. OR how much do you think this identification would typically cost (per city,

county or state)?

3. If pesticide applicators are required to identify sources of the problem (i.e. nutrients,

invasive species, etc.), what methods (including equipment) do you think they would use

to perform this activity?

Same as #1 above.

a. How much time do you think they would spend to identify these sources (i.e.

number of hours per waterbody)?

b. OR how much do you think this identification would typically cost (per city,

county or state)?

Mechanical Control, Biological Control, and Habitat Modification

4. If pesticide applicators are required to implement mechanical control techniques:

As mentioned above, it is unusual that control is necessarily mandated to take a particular

approach. Instead, a combination of approaches is used.

a. Please use table provided to answer the following questions:

1. How much time do you think they would spend on mechanical control?

This is impossible to answer because it is highly site-specific. Below are some costs that are unit

costs consistent with research we have done and experience in the field.

2. How much do you think mechanical control would typically cost?
Activity

Number of Hours

(Please specify; per

waterbody, etc.)

Cost

(Please specify; per city,

county or state, etc.)

Weed removal by hand or

machine

Highly Variable Man: $20K -$60K/Ac

Goat: $500- $2000/Ac

Machine: $1500-$3000/Ac.

Note (1): The use of

mechanical removal in

some cases is not advised

due to the risk of plant

fragmentation and

subsequent downstream

reestablishment

Sediment tilling Highly Variable Machine: $1500-$3000/Ac

See note (1) above.

Soil and vegetation

compression through “weed

rolling”

Highly Variable I am unfamiliar with this

approach and have never

seen it done. It is not

applicable for aquatic

weeds.

Other (please specify): Lots of alternatives. See

description above.
5. If pesticide applicators are required to utilize habitat modification practices:

a. Please use table provided to answer the following questions:

1. How much time do you think they would spend on habitat modification?

2. How much do you think habitat modification would typically cost?

Activity

Number of Hours

(Please specify; per

waterbody, etc.)

Cost

(Please specify; per city,

county or state, etc.)

Light attenuation Highly Variable This is typically

accomplished with dyes put

into water. Costs are

variable depending on water

use, holding time, depth,

etc. Costs may range from

$50/surface ac to

$500/surface ac.

Other (please specify):

Pesticide Use

6. If pesticide applicators are required to conduct maintenance activities to minimize

potential leaks, spills, and accidental releases of pesticides or to maintain equipment to

ensure effective application and control, how much time do you think they would spend

on these activities? (i.e. number of hours per establishment or per applicator)?

They are indeed required to do this work. I would say approximately 5-15% of an applicator’s

daily effort is related to this type of activity. Quantitation on a per establishment or per acre

basis is difficult due to large # of variables involved.

a. OR how much do you think these maintenance activities would typically cost (per

establishment, city, county, or state?)

Again, highly variable depending on the equipment, terrain, weed type, etc. But for the sake of

discussion, here is an example: Lets say the burdened cost of a pesticide applicator or weed

technician is $25/hr and he works 7 out of 12 months at a FT rate of 2,000 hrs/yr on weed

control. This is perhaps a fairly typical # as in CA we do most of our week control work from

March to September. There maybe from 1-10 of these individual weed technicians per public

works department or irrigation district.

Lets assume a smaller irrigation district that covers approximately 10K acres and has 2

applicators. The total cost for both individuals is then estimated at $60K. His maintenance

activity is on the low end (5%) is then $3000 and highend is $9000. Note to in CA that a

licensed pesticide applicator needs to take no less than 20 hours of continuing education every 2

years to maintain his/her license. The PCA needs 40 hours/year.
Education

7. If pesticide applicators are required to post information to users (to address weed

identification, the role of nutrient availability in weed occurrence and abundance,

accidental weed introduction avoidance, and the pesticide product being used for aquatic

weed control), how much time do you think they would spend to post this information

(i.e. number of hours per waterbody)?

This would add between 3-10% to there total time spent. These signs have to be prepared,

maintained, replaced, and taken down. So, lowend is 7/12 x4000 x0.03= 70 hours or highend is

240 hours.

a. OR how much do you think education by posting would typically cost (per

waterbody, city, county or state)?

There are too many variables to estimate this cost on a waterbody, city, etc basis.

Using the above example, ~$2K to $6K per year per 10K ac irrigation district.