Tyler Baxby
0793160
AGR4450
April 30 2019
University of Guelph
Glyphosate resistance in wild parsnip
Experimental design presented by Tyler Baxby
For AGR4450: Research project I
To: Professor Francois Tardif
Date: April 30th 2019
Recognizing how human activity changes biodiversity is becoming increasingly important, more than ever (Potts et al. 2010). Bill 64 is a legislated provincial act banning the use of Cosmetic Pesticides across the Province of Ontario. It was created with the prospect of superseding all the municipal by-laws, into one easily understandable document. However, the creation of the policy has been found to be based off of the same misinformation which had been used in the creation of municipal by-laws across Ontario. I have witnessed many municipalities (including my own city of Kingston, Ontario) proceed through the process of banning the use of horticultural (lawn care) pesticides within their municipal regions; these processes have been based solely on the basis of public opinion where they are dangerous for both the environment and humans alike. Bill 64 was passed through legislation, there are various abundant populations of wild parsnip emerging. There are potential dangers toward humans with these developments.
The spread of invasive species within ecosystems is a primary driver of change. Many invasives reach such levels they negatively influence biodiversity. (Rejmánek et al.2005). Wild parsnip (Pastinaca sativa) is a noxious perennial weed, that is a member of the carrot (Apiaceae) family. It is an invasive and also a public health hazard. As an invasive, it has a tendency to displace natural vegetation. This occurs especially on road sides. In addition, this plant contains furanocoumarins in its sap. These molecules, when into contact with the skin, make it sensitive to UV rays, causing a condition called phytophotodermatitis. (Bowers,1999; Rietschel, et al. 1995).
This is potentially dangerous for outside workers as well as members of the public. (Zangerl and Berenbaum 1987). While road side populations of wild parsnip were historically controlled with herbicides such as 2,4-D, the introduction of the cosmetic pesticides Ban Act (Bill 64) in 2008 has caused many jurisdictions to adopt alternative measures. Some have relied only on mechanical control while others have been using glyphosate extensively. I and others in the industry have observed in the last few years that glyphosate appears to be less effective at controlling some wild parsnip populations. One hypothesis is that these populations may have developed resistance to this herbicide.
The purpose of this project is therefore to test that hypothesis. This project will involve a comprehensive review of the available existing research on known potential risks and the associated costs of wild parsnip as a preliminary study.
This will focus on the potential ramifications of glyphosate weed control usage. This literature review will outline information on the class 9 herbicide glyphosate. Class 9 pesticides are defined as a chemical that cannot be purchased for cosmetic use unless there is an exception (https://www.ontario.ca/page/classification-pesticides).
This review will also summarize published research regarding wild parsnip and what is already known about its management. Therefore, the additional part of this project outlines any potential drawbacks of excessive herbicide usage and indicate possible resistance of glyphosate and associated impacts on the environment.
The specific prediction(s) derived from the hypothesis are that there is resistance within the populations of invasives located in Eastern Ontario. The rationale to depicting this statement is simply due to the time elapsed. Bill 64 was passed in 2009 and has been held as law (for longer duration) within South-Eastern Ontario. This logic allows me to believe that wild parsnip can potentially evolve with newer traits compared to Wild Parsnip from South-western Ontario.
The plant material that is needed for this experiment are the mesocarps or seeds. These are contained in the primary, secondary and tertiary umbels of wild parsnip. (Cain et al. 2010) The Seeds of Wild parsnip that are potentially susceptible to glyphosate are classified on location as (SEWPS) south eastern wild parsnip seeds. Seeds that are located within south western Ontario will be collected as well (SWWPS). The control will be general parsnip, as they lack an entire defensive mechanism. A visual assessment of plant injury (0 to100 scale: 0.00 is equal to no injury; 100. 00 is equal total destruction) as well as the vegetative parameters fresh weight, dry weight and leaf area were recorded 7 days after herbicide treatment.
The Process to carry out while collecting the seeds from the invasive are:
To use paper bags to collect the plant material. A pruning shear to cut below the secondary umbel to allow larger sample of seeds. I need to be wearing PPE (personal protective equipment): thick neoprene gloves, eye googles, rubber boots, long shirt to cover from UVA rays to protect myself from furanocoumarins. The paper bag should be labelled with marker including the following: Name, location(county), the latitude and longitude of the plant, observational analysis of the area, the characteristics of the seed, what is in the bag, lastly date. Lastly, I would need proper storage which is an area with room temperature and ventilation, no disturbance.
The dose-response curve is a diagram that shows the effect of increasing doses of herbicide on a measured variable. The x-axis is on a logarithmic scale. This means that units on the x-axis increase by 10-fold, so that we can compare a very broad range of doses with each diagram. The y axis is the answer or the percentage of response. The dose response curve usually takes the form of a sigmoid curve, shaped like the letter “S,”. When plotting the response at various doses it corresponds as close to the individual data points as possible to a smooth curve. The vertical bar represents the diagnostic dose at which most susceptible plants show maximum response but has little impact on resistant plants.
This experiment will be carried out through the University of Guelph (OAC) in a Crop Science Growth room. The Growth room will likely have the parameters of 20-25 degrees Celsius in the daytime and 15-17 degrees Celsius at nighttime. The relative humidity will likely be 60-70% in the growth rooms.
The plant pots will be arranged on a table within one of the growth rooms following a completely randomized design with four replicates per treatment group. The treatments will be classified as, “South Eastern” and “South Western “seeds. These spherical seeds will therefore be collected, dried and analyzed. The rationale to this is to reduce overall variation within the findings. The duration of this experiment will be six weeks (two weeks for pre-germination, four weeks for replication). There were 4 treatments plus one control that were used to help determine resistance for wild parsnip. The control was classified as “normal” parsnip and it was used to see the differences within the subgenres. The reason it is a control is because it does not have the ability to develop furanocoumarins and it is susceptible to glyphosate. The treatments contained seeds collected from different locations of wild parsnip within the South-eastern and South-western regions of Ontario. These seeds were subjected to different concentration treatments of glyphosate. The treatments were watered once every day at 12 pm for the first few days and then every other day at 12 pm after that. The reasoning for this is because of potential dilution of the concentration.
If an incorrect dose or concentration of glyphosate is applied this becomes an inaccurate measurement, simply because it is influencing the results and they are not correct. These results contain variation that influence the results to favour the prediction. Uneven watering, can allow for potential cell death within a plant as well as drying of the internal organs (evapotranspiration in the warmer weather). This can cause for a negative impact on the results, as the plants need to survive to carry out the answer. Also, uneven soil distribution can lead to potential error as it can allow for non-uniform macropores and micropores within the pots, this can allow for loss of nutrient availability for the plants. Lastly during the first two weeks of pre-germination the plants want to have similarity of they are all uniform. This will allow for little variation across the entire population and allow for potentially the same results to happen to the entire population. Dose response experiment will be conducted to quantify the resistance of the wild parsnip seeds to glyphosate (applied to South-eastern and south western seeds). These seeds will be sprayed post-emergence onto plants at a rate of 210L/ha. The glyphosate herbicide is applied using a laboratory sprayer which is equipped with an 8002E even-spray flat-fan nozzle delivering 210 L ha^-1 at 40 PSI or about 276 kPa. The experiment will be conducted four times in a completely randomized design with four replications per treatment based upon location.
Ultimately, the specific use of the chemical Glyphosate and its consequences on the ongoing spread of noxious weeds in south-eastern Ontario. This research requires further investigation to better understand the impact of repeated glyphosate use on invasives. There needs to be a determination if there is actually resistance, as no recent analysis can confirm or deny the hypothesis.