Effectiveness of a stem applied herbicide for the control of a woody tree
Assessment of the effectiveness of a stem applied herbicide for the control of a woody tree (Chinese elm)
Chinese elm is an invasive woody weed of creek lines and bushland on the east coast of Australia. A trial will be conducted to compare the effect of 2 previously untried herbicides (at normal and double rates) applied to drilled holes in the stem to control this species compared to the industry standard of a stem applied herbicide (Access™ in diesel) according to the following treatments:
Treatment # Treatment
1 No treatment
2 Benchmark (Access™) at recommended rate
3 Test Product 1 (recommended dose)
4 Test Product 1 (double dose)
5 Test product 2 (recommended dose)
6 Test Product 2 (double dose)
Chinese elms are tall trees which are semi-deciduous, this means that they can hold green leaves all year round, however, a good proportion of their leaves will drop during the winter months and are replaced by a heavy flush in spring. Therefore, leaf cover fluctuates during the year. Leaves go through a standard process of senescence turning colour from green to yellow to brown. Leaf cover is reduced as leaves drop from the tree.
Some symptoms of herbicide damage. When Chinese elms are affected by herbicide the following can occur:
• Leaves can rapidly undergo senescence
• Rapid leaf fall can occur
• The trunk can begin to die – this can manifest itself in various ways, a key symptom is that the green layer just below the bark can change colour from green, to brown to black
• The stem death can be identified by striking the surface with a hammer. A live stem has a dull note (tissue is moist). A dead stem has a hollow ringing note (tissue is dry).
• Trees can take between 12 and 18 months to die
Please answer these questions and give your reasoning behind these answers
1. How long should this trial run for?
2. How frequently should assessments be performed?
3. When should the first assessment be made?
4. Which symptoms would you consider to be most relevant considering the purpose of this trial?
5. What might we learn from changes in leaf colour?
6. What might we learn from the process of leaf drop?
7. Could there be other aspects we could measure, and how can we do this?
8. Design a set of assessment ratings that can be applied in this field trial and justify the logic behind them
9. Review the experimental design – can you suggest any improvements?
Sample Solution
The cornerstone of woody stem control in forests is provided by the most often employed herbicides by forest management specialists in the United States. Many of these formulae are also available to private forest owners who do not require a state applicator’s license. Herbicide spraying procedures are taken very seriously by the US Department of Agriculture. Many of these pesticides require a state pesticide handler’s license to apply or even purchase. When employed as a foliar spray on target plants, 2,4-D is a chlorinated phenoxy chemical that acts as a systemic herbicide. Many varieties of broadleaf weeds, shrubs, and trees are controlled with this chemical compound pesticide. It is very crucial in agriculture.
