NBHTA Environment Committee Draft

By Neil Pond
November 20, 2004

Introduction:

The purpose of this discussion paper is to provide background information and recommendations on the development of operational guidelines to IPM practices for weed control in home lawns in the Maritime Region. Technical input was provided by Neil Pond, from Urban Landscaping Ltd., an IPM service provider using monitoring thresholds for weed control in New Brunswick.

The goal for the NBHTA Environment Committee is to develop practical, operational guidelines that can be adopted by the lawn care service industry in the Maritime Region and be easily trained to lawn care technicians working in the field.

Weed Thresholds are “Customer Driven”:

Typically, a pest threshold is reached when there becomes a point of visible damage to a lawn (ex. chinch bugs). Thresholds vary from site to site based on the specific tolerance level of a given site to stress from pests. With people, tolerance levels vary as well. Typically in the lawn care industry, we have experienced a zero tolerance towards the presence of visible weeds. Through public awareness based on environmental concerns, and educational efforts, some people have moderated their views allowing for a minimal amount of weeds with the understanding that they are not as much of a threat as they are a nuisance and, are worth tolerating if they can reduce pesticide usage. With this in mind, the lawn care industry is still driven by the customer’s tolerance level toward weeds in their lawn.

Urban Landscaping Ltd. Weed Counting Methodology:

Urban Landscaping Ltd. has developed a weed counting methodology that is in correlation to its’ customers tolerances and has incorporated this into its’ IPM practices. It is based on what is acceptable for its’ customers and what is achievable to deliver as a service provider. Treatment thresholds were established based on the point in which the average customer would become concerned about weeds in their lawn. Urban Landscaping Ltd. has also successfully convinced its’ customers over a period of time that zero tolerance to weeds is “not an option” and therefore “minimal weeds” are tolerated. Counting is achieved while walking the property for inspection and like with insect pests (chinch bugs), the more problematic or probable areas where thresholds might be reached are the areas where counting occurs. A quadrat or grid method is used based on a 10 ft x 10 ft area (100ft²). The larger area in comparison to other methods allows for fewer counts to be performed and to still get a reasonable indication of the overall weed population. Another reason is that 100ft² is a more proportionate scale for a person standing to count as a reasonably sized area. Thirdly, weeds are not always uniformly dispersed and a larger area captures a more random representation of weed populations than that of a smaller area that could be more “hit and miss”. Finally, 100ft² quadrats are more productive to use in the field because they are quicker to perform and easier to train technicians to use (100ft2 = 3 large paces X 3 large paces to form a square).

What is Minimal Weeds?

A weed was only counted based on a visual “glimpse” without bending over and looking carefully at every weed that could possibly exist. In other words, the more obvious weeds are the weeds that matter to the customer and therefore the counting methodology was developed to reflect this. Most weeds that are counted are broadleaf such as plantain and dandelion (also the more obvious) and are of a significant size (4” in diameter based on 2/3 mature size). Sometimes a prostrate spreading weed (ex. knotweed) might be counted as 2 or 3 weeds depending on its’ size. Provided the weed counts are well below the threshold level, weed control treatment is not required due to minimal weeds present.

The Magic Number:

Urban Landscaping Ltd. realized that a weed count of 5 weeds per 100ft² was the tolerance limit to the amount of weeds the average customer would bear. This average represents a huge majority of its’ customer base. For the sake of simplicity, this was considered to be 5%. At this percentage, customers would not be happy and therefore treatment thresholds were driven by not allowing weed counts to reach or exceed 5%. Spot treatment and sometimes blanket treatments were required. Urban Landscaping Ltd. has been successful at keeping most, if not all of its’ customers below 5% (5 weeds/100ft²) using IPM practices. Typically, hand weeding is performed in the summer months around less than ideal treatment windows, as well as on “pesticide free” lawns.

Field Terminology:

Spot Treatment (spray):

Spot treatment is achieved by pressing the spray trigger to deliver brief “bursts” (up to 3 seconds) of control material to within an area that does not require step movement (within reach without taking a step).

Blanket Treatment (spray)*:

Blanket treatment is a continuous spraying method achieved by pressing and holding open the spray trigger (for more than 3 seconds) to deliver a constant stream of control material to a grid area in a fashion that requires step movement.

It should be noted that blanket treatment can be achieved while practicing IPM when it is limited to the threshold areas only. The term “blanket treatment” does not necessarily apply to the entire lawn area and can represent a small percentage of overall areas treated on a given property.

Urban Lawn Classifications for IPM Weed Thresholds:

Class “A”:
Little or no weeds at a glance; Well under 5 weeds per 100ft²; hand and spot treatment required typically. Little or no blanket treatment required.

Class “B”:
Weed counts frequently exceed class “A” threshold levels, (Typically 5 weeds /100ft² up to 75 weeds/100ft²); Hand weeding not feasible; Frequent spot treatment required and blanket treatment necessary to bring down populations to Class “A” threshold level.

Class “C”:
Weed counts in excess of Class “B” levels (in excess of 75 weeds/100ft²); Typically, lawn condition is irreversible without renovation measures (such as rototilling, adding topsoil & reseeding; or core aerating, topdressing with compost & overseeding using slice seeding method).

Hand Weeding as a Method of Non – Chemical Control:

Hand weeding can be considered as an alternative to spot treatment when the weed counts are low enough that the productivity rate of each method is comparable. There becomes a point (threshold) when it becomes too laborious and time consuming to hand weed an entire property based on the total weed count. At that point, a spot treatment method is the more practical alternative.

At Urban Landscaping Ltd., the average lawn size is approximately 8,000ft² and the average time to spot treat that area is 10 – 15 minutes based on a weed count at or below 5% (5 weeds per 100ft²). A hand weeding strategy should therefore show comparable productivity or better in order to be viable.

Hand Weeding Productivity:
Urban Landscaping Ltd. typically can spend up to 10 minutes per visit hand weeding and can manage to remove most of the noticeable “obvious” weeds on a property with a relatively low weed count (1 weed /200ft²). Typically, approximately 30 – 35 weeds would be pulled in a ten minute period with an average productivity rate of 3 weeds/minute. The weed count in this situation is approximately 0.4 weeds /100 ft² or just under 1 weed /200ft². It is important to note that the lower weed count per 100ft² does not result in a lower productivity rate for hand weeding. This is due to having more time spent searching for weeds in a lower weed count between the time spent pulling weeds because the weeds are farther apart.

Hand Weeding Productivity Rates:

The above chart indicates that based on a feasible productivity rate for lawn care service providers, a reasonable threshold for weed pulling would be up to 1 weed /100ft² (0.1% weed coverage) which is well below 1%! Beyond 1 weed/100ft², the spot treatment method becomes more feasible because you can cover more area with less effort than with hand weeding.

Weed Pulling Logistics:
Most lawn care services visit the property on 5 – 6 week intervals (rounds). At 10 minutes per visit, this would equal 60 minutes per season. Over a 5 – 6 week interval, it is more probable that there will be 1 weed/100ft² as opposed to 0.5 weeds/100ft². If you were to visit every 3 weeks, for example, the results would more likely be 1 weed/200ft² or 0.5 weeds/100ft². At 1 visit every three weeks assuming 10 minutes per visit, the total weeding time for the season is 120 minutes (2 hours).

When adding a hand weeding service to an IPM program, it is recommended to start with a higher allowance for hand weeding time until there is a more predictable weed count confirmation and productivity rate established. It is not probable that all weeds are going to get pulled at any one time. Weeds are perpetually germinating and growing so the more frequent visiting interval will result in less fluctuation of weed counts. Moreover, some weeds get missed which is why this method will not satisfy zero tolerance customers.

Weed Counts VS. Actual % Levels:

Previous studies (ex. B.C. IPM Manual) suggesting that Class “A” fine home lawns can have between 5% – 10% weed cover and that it is considered weed free will not be accepted in the Maritimes either by the lawn care industry or the general public based on the methodology used in this paper. There would simply be far too many noticeable weeds without the proper means to control them. It would appear that the methodology, particularly, the counting methods differ enough that the results appear to be dramatically different. Previous studies must have meticulously counted every weed in a given area regardless of its noticeability. This discussion paper, as previously stated, is driven by the customer based on the perception of what is noticeable and obvious and must therefore not capture the same number of weeds in a given area.

Actual % Vs. Feels like:
There appears to be a significant difference between actual percentages and the perception of what those percentages look like as in the case when you look at the chart showing 5% in graphic form (see attached illustration). In this case the perception of what 5% weed cover looks like is a lot less than what the actual illustration shows. That is the real danger in using and talking percentages because it is more difficult to relate to the numbers as opposed to more objective weed counts. It is easier to visualize 5 weeds /100ft² than 0.5% weed coverage. An analogy for comparison would be like in the weather forecasting industry when they use a “feels like” temperature rating in comparison to the actual temperature. It enables people to more easily relate to what is happening. For similar reasons, Urban Landscaping Ltd. adopted a rating scale that interpreted 1 weed/100ft² to be 1%, 2 weeds/100ft² to be 2% and so on. When you actually look at the lawns using this method, 1 weed/100ft² actually looks like it is approximately 1% and so on. In other words, Urban Landscaping Ltd. uses a “feels like method’ vs. the actual percentage.

Recommendations:

• The large 10’ x10’ quadrat counting system is efficient and easy to use. It could be readily adapted by industry and converted into metric as well.
• Thresholds and operating guidelines should be verified by count as opposed to percentages for more relevance and objectivity. Percentages can be used to communicate to public (outside industry) in order to facilitate their perceptions and understanding of the interpretation of weed counts.
• A hand weeding only policy could be developed, however, the weed counts must be very low and be in keeping with the economics of what the lawn care service industry can realistically deliver.
• A minimum weed count threshold level for spot treatment can be developed based on the level at which hand weeding is no longer feasible. The count and percentage will have to be lower than what has been previously published if it is to be based on criteria as indicated in this paper.
• A minimum weed count threshold level for blanket treatment can be developed based on levels at which it becomes more productive to blanket treat than to use spot treatment methods. Productivity information based on time-motion studies would suggest that blanket treatment would be more feasible at or above 5 weeds/100ft² (0.5%).
• A “feels like” percentage conversion policy (similar to what Urban Landscaping Ltd. uses) could be developed for the purpose of using percentages in a more meaningful objective fashion when used by industry. Such percentages might be more relevant and easier to communicate to the public.

Recommended Thresholds for Weeds: