Weeds in New Zealand - Teacher Resources

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Learning experiences

Note: These are general levels. Select activities or modify to suit age-group.

Weed information posters (Living World: Achievement Aim 2)

Weed Crime Files: Students (in groups of 3-4) make a poster about specific weeds "Alien Invaders". Include identification information, origin, spread/dispersal, impacts, control methods, etc. Use internet, books and people to research the information. Perhaps turn this into a 'crime busting' exercise: each student is a detective making a crime file on a weed to be captured and controlled. Poster should look like a dossier, e.g., Criminal's name, criminal's country of origin, criminal description (and idenitikit picture!), list of offences (rap sheet!), methods of control.

Weeds in my backyard (Living World: Achievement Aim 2)

Weedy visitors! Contact DOC or your local regional council and get a biosecurity or pest plant officer to visit your school or local reserve and identify the weeds. Students could take digital photos of each weed species for a display. By having a photo of each weed, students can then identify weeds at a later date (= reference collection). A world map can be put up and pins could show the origin of the weeds in your school grounds. Weed experts such as DOC staff or regional council biosecurity officers can explain why particular weed species are a problem and what can be done about it.
Mapping weeds: An additional class project has students mapping the weeds and collecting data on the number of different weed species (or exotic species), the number of individual plants of each species (for the larger weeds) and what kind of habitat the weeds were found in (e.g., shade, sun, open, under trees, etc.). ID photos can help identify weed species. Students use the photos to identify weeds in their backyard at home and add their "home" data to the pool of data collected at school. Students then discuss which weeds are the most common in their area, which habitat types are most susceptible to weed invasion, etc.

Plant diversity (Living World: Achievement Aim 1)

Bush experience: Visit a local reserve. Students take notes or make drawings on different plants, e.g., size, leaves (shape, size, colour, texture, smell), bark (patterns, texture, colour), do the leaves have galls or leaf-mining scars (insect herbivore feeding damage), etc. Discussion: are all the trees, leaves, bark, etc., the same?


gall on mist flower - caused by mist flower gall fly (Procecidochares alani)	leaf mines on old man's beard caused by the old man's beard leaf miner (Phytomyza vitalbae)

Taxonomy: Explain taxonomy as a tool. Students group together drawings or actual leaves (check with local DoC or regional council about collecting leaves), etc., of similar shape, texture, etc. Introduce the idea of a taxomonic key (for older students)
Interdependence: How does diversity of trees/leaves, etc. influence diversity of animals? Follow up with food chain discussions and activities as well as weed impacts, i.e. when weeds invade, native plants pushed out and fewer resources for animals.

happy leaf

Weed Spread (Living World: Achievement Aim 3 structure and function, but also Achievement Aim 2, diversity)

These activities can be modified to suit age group. For example, older students write up reports, make scientific posters, etc. Older students could try to identify the seeds and list weed seeds versus seeds of native plants (from books). These activities can be done without knowing whether the seeds are from weeds or native plants, and provide students with scientific skills as well as information about seed dispersal, which is an integral part of weed ecology. Students are given a sense of how seeds are dispersed, which will help them learn to avoid spreading weed seeds.

Grab it! Competition for resources: This is an activity that helps students understand competition in a practical way. The point of this activity is to demonstrate that weeds can outcompete other plants because they are often better at getting resources than native plants. First, you need a resource that is in many small pieces - it could be anything from lollies (food), to cups of water (water) to small stones (minerals). One student will act as 'a weed', another will act as 'a native plant'. The objective is to grab as much of the resource as possible in an allotted time (a stopwatch and a container to 'capture' the resource in might be useful). The weed will have a competitive ability over the native plant - in this activity it could mean that the student that is the native plant can only use one hand (or maybe no hands!) to grab bits of the resource or that the native plant student is blindfolded. There could also be more than one native plant - see how one weed can compete with many native plants. Discuss with the students what could be 'handicapping' the native plants - natural enemies? What characteristics do weeds have that might make them better at 'capturing' resources?
Weed population explosions! Discuss and list what factors keep animal and plant population numbers from exploding? List natural factors (e.g., fire, disease, predators, parasites, etc.), and human barriers (e.g., collecting, harvesting, habitat destruction, etc.). Why are we not overrun with kakapo or cabbage trees or butterflies? Why have introduced animals and plants become so numerous? Have barriers been removed?
Weed dispersal methods: List (or create a poster) all the different ways weeds can spread, both by seed dispersal and by vegetative means (stems break off and grow from broken fragment, e.g., wandering jew and crack willow).
Seeds in the soil: Take soil samples (5cm deep) from your local reserve (with permission) and sort through the soil to look for seeds. Sorting should be done on a white tray and soil dispersed with water. Pick out any seeds with tweezers. Make sure everyone has the same amount of soil in each samples (e.g., same sized container) so that data on number of seeds are comparable and scientifically robust. How many different types of seeds are present in your sample? (Collect data on number of seeds of each type). Older students could calculate mean (and standard deviation) number of seeds per gram of soil.
Seed transport by vehicles: Soil samples can also be taken from car mudflaps, gumboots or mountain bike tyres and examined. This demonstrates how humans can move seeds around.
Seed transport by humans: Get students to bring old (very old!) socks from home. Go to a grassy/scrubby area (for best results) and put socks on over shoes and walk around. Explain to students that the socks simulate the hairy feet of livestock (sheep, cattle, etc.) that transport seeds. To make this activity more scientific, take a stopwatch and everyone walk around for a specified time (e.g., 30 secs). Stop and remove socks (turn inside out to keep plant material collected inside sock) and take back to the classroom ("lab") for examination. Pull off any seeds (such as bidibids) and group by morphology (shape, size, colour, etc.) and count.
Seed transport by other animals: Collect and examine faeces (poo!!) from fruit-eating birds (e.g., kereru/wood pigeons, blackbirds, etc.) or possum poo. You may be able to do this yourself (using gloves when handling) or ask someone from DOC, local animal sanctuary, etc., to collect it for you. Disperse poo in water and search for the seeds!! Alternatively, take some fresh horse manure and add to potting mix in a potting tray (always wear gloves when working with manure). Water lightly twice a week and look for seeds germinating from the sample of horse manure. Follow this with a discussion on dispersal by animals and whether native birds help spread weeds. We should be encouraging birds to eat native fruit sources by planting native trees and removing weeds. Health and safety precautions must be taken with this exercise.
Seed structure & function: Look at seeds under the microscope or magnifying glass- are there any attachment devices or parts that might help with dispersal? Are the seeds wind-dispersed, (e.g., sycamore seeds, dandelions) or do they have attachments for sticking to animals such as sheep's wool (e.g., bidibids).
Seed Germination: Secondary-level students can attempt to germinate seeds found in the above places. Soil is potted and watered (keep moist but not soggy), etc., and numbers of seedlings recorded each week. This fits well into other plant-learning contexts. If bird poo with weed seeds is collected, these seeds could be used in a germination experiment. Equal numbers of seeds (e.g., privet) found in bird poo and seeds taken directly from fruit on privet trees can be potted for comparative germination trials, i.e. what effect does transport through a bird's digestive system have on a seed? Did more or less of the seeds from the bird poo germinate compared with those taken directly from the tree?

Animals and weeds (Living World: Achievement Aim 1 impact of weeds on NZ's special biodiversity, but also Achievement Aim 4, ecosystems and interdependence of organisms)

How are animals influenced by weeds? Do they use weeds for shelter or food? These activities include discussion of resources required by native animals and whether exotic plants provide these resources. Research to date has shown that far fewer native animals are associated with exotic plants than with native plants. Native plants generally provide better food and habitat, especially for more specialised native animals that have specific requirements. Discuss the function of animals - why do we need native animals? For example, some birds, such as tui, and some native insects are important flower pollinators, other birds such as kereru (wood pigeons) are important seed dispersers, many insects are important detritivores - without them we might be up to our necks in dead animals and plants!

Kereru

Interdependence web of life: Assign an organism to each student (e.g., cabbage tree, kowhai, tui, kereru, weta, beetle, fantail, etc.). Start with a ball of string and one of the plants - give a person/"plant" the end of the string. The ball of string is passed to other "organisms" as students see a connection. For example, cabbage tree to beetle (habitat and food), weta (habitat and food) and kereru (eats fruit) to fantail (eats beetle) to kowhai (also a source of insect food to fantail) to tui (eats kowhai nectar), etc. Add more organisms and possibly even resources such as light, water, etc. At the end, the web/string should be complex. Ask one of the "organisms" to give a gentle tug on the string. Everyone who feels the tug should also then give a tug. Within a few seconds everyone should have responded to a tug. This highlights the interdependence of organisms in the environment. What happens when one or more of the plants are replaced by weeds (which may have inferior resources or resources that native animals are not adapted to exploit).

Fantail

Bird surveys: Carry out comparative bird surveys between weedy and not-so-weedy (local native bush area, because it is impossible to find weed-free areas!) or between areas where one species of weed (e.g., privet) is quite dominant and areas of similar vegetation where this weed is absent. Groups of students can take binoculars and walk through the reserve/bush and note down any birds seen or heard. Get the students to ensure they are all using standardised methods. e.g., walk at the same pace so that the same amount of time is spent looking for birds in each treatment (weedy vs non-weedy). Which area (more or less weedy?) had more birds? More native birds versus more introduced birds (e.g., sparrows and blackbirds)? Does this matter? (More suitable for secondary level students).
Invertebrate surveys:
Beating: beat a weed plant and a similar native species (i.e. both trees or both shrubs) with a stick over a white tray, sheet of paper or material to dislodge insects. Get older students to standardise scientific methods by ensuring the same effort is put into beating each plant (e.g., 10 beats each), and the same number of samples are taken from both the native and weed species (e.g., 10 beats from each of 3 different mahoe trees AND 10 beats from each of 3 different privet trees, or manuka vs broom). Collect samples from the tray or material into an ice cream container (separate containers for separate samples). Back in the classroom carefully remove any leaves or twigs and count the invertebrates (use tweezers to separate out). One person records the data. How many invertebrates are present in each sample? (Older students calculate mean number of invertebrates and even graph the data). Does this number differ between the native and weed plant? Can you separate the spiders or any other group (e.g., beetles.)? Compare numbers of individuals in these groups between the native and weed plant. This method directly measures the invertebrates that live on the plant foliage.
Litter samples: Choose two small areas - one with lots of weeds and one with lots of native trees and shrubs. Put a hula hoop on the ground in each place and collect all the leaf litter inside the hoop and put in a container or plastic bag. Back in the classroom carefully remove any leaves or twigs and count the invertebrates (use tweezers to separate, may also need to use water in a squirty bottle to wash insects off the leaves). One person records the data. How many invertebrates are present in each sample? (Older students can calculate mean number of invertebrates and even graph the data). Does this number differ between the native and weed plant? Can you separate the spiders or any other group (e.g., beetles.)? Compare numbers of individuals in these groups between the native and weed plant. This method measures the ground-living invertebrate fauna. Are the ground-living invertebrates affected by weed invasion? Or are numbers the same under both native and exotic plant species.

Weeds & the Community (Living World: Achievement Aim 1 diversity of living organisms; Achievement Aim 4, ecosystems and food chains)

Community groups: Encourage students to get involved with a local community weeding group and take responsibility for their local "patch". Sense of responsibility and ownership will be especially strong in this project. "Empowerment" of students.
Monitoring weeding/management outcomes: Students monitor the results of weeding to give them tangible evidence of benefits. This could involve before/after photos (from exactly the same spot) over time, counts of native seedlings before and after weeding, insect and bird monitoring (as above) before and after weeding. Could become part of a larger school project or annual survey.
Science and the community: Social aspects of weed science (Nature of Science and its Relationship to Technology: Achievement Aim 1 science ideas and processes; Achievement Aim 3 implications of science). Weeds could also be integrated into the curriculum by using this section as part of social studies.
Decision-making using science: The social implications of weed control (who does the weed affect? What impact does weed control have on the community?).
Conflict interviews: Students interview community members about their attitudes to one or more plants that could be classed as weeds. For example, students could interview farmers about their attitude towards blackberry (a weed) as well as berryfruit producers who see blackberry as an important part of their livelihood. The students then write a newspaper article, give a talk to the class or create a poster.
Role play: take the 'Weedy Feelings' activity about blackberry conflicts and make them into role play cards for the students to act out. Change some of the feelings to reflect other weeds in your region.

	Love	Hate
*Blackberry (Rubus fruticosus)*	Berryfruit producers & beekeepers	Farmers & conservationists
*Gorse (Ulex europaeus)*	Beekeepers & goat farmers	Farmers & conservationists
*Pine trees (e.g., Douglas fir & Pinus contorta)*	Forest industry	Conservationists
*Japanese honeysuckle (Lonicera japonica)*	Garden nurseries & people with gardens!	Conservationists

Weed spread by humans: Create a poster of all the ways humans spread weeds, either deliberately or accidentally. Suggest ways in which we can reduce weed spread by humans. How can each of us help? Design a public awareness campaign poster to "halt the spread to weeds". Include ways in which people can help.
Maori and the impact of invasive weeds: Investigate how the replacement of native plants with weeds affects Maori. Investigate one or several native plants used by Maori for cultural purposes, e.g., harakeke (flax), pīngao (or pikao) (http://www.doc.govt.nz/templates/podcover.aspx?id=33572) and designing a poster on cultural uses of native plants. Discuss: How will Maori culture be affected by weed invasion? (use replacement of pīngao by weeds such as marram grass and lupin as an example). Are native plants useful? Could native plants be used instead of some weedy introduced plants currently used in New Zealand?
Safety for the environment: Students research and compare the safety of chemical weed control vs the biological control of weeds. Design a poster. Alternatively, for older students, this could be a debate topic.

Weed science and technology (Living World: Achievement Aim 3, how organisms reproduce grow and change. Nature of Science and its Relationship to Technology;Achievement Aim 2, science and technology)

Technology & horticultural weeds: Older students debate whether technology used in horticulture (plant breeding programs particularly with the current GE debate) produces plants that become 'super -weeds' (fast growth, disease resistance, etc).
Technology & biocontrol agents: Can technology be used to select biocontrol agents? Molecular biology can be used to determine exactly where the weed originated. This is important when a weed may have come from one of many countries. DNA analysis can be used to match up particular strains of a weed with particular strains of fungi or insects from a particular locality that may be adapted to high/low rainfall, or other climatic conditions. This may increase the effectiveness of the agent. A group of students researches and designs a poster (with a world map as the main content) about the possible origins of one weed species (could be native in that country or may be a weed there too, e.g., Australia is a good one to check). Choose cosmopolitan (found in lots of countries) weeds such as gorse. Students could make an educated guess at two or three countries that are the most likely origin of the weed (based on criteria such as native species in that country, trading partner, settlers came from here). Students research and match the climates (can be very generalised) of New Zealand and each of the countries of origin. Suggest a country similar to NZ's climate that would be a good place to look for natural enemies that would do well in NZ. Make sure students have good arguments (based on likely origins and climate similarities) - the information they provide can be used to select countries in which to obtain plant material and analyse the DNA for relatedness to the NZ weed. Use climate data to select a country to survey for natural enemies that would do well in NZ. Get it wrong and it costs the scientific research program lots of money in wasted overseas testing and surveying =FAILURE. Get it right and you have improved the likelihood of a successful biocontrol programme.

Biological control agents (Living World: Achievement Aim 3, how organisms reproduce grow and change; Achievement Aim 4, ecosystems and food chains) Bug

Multiple agents: Discuss why more than one biocontrol agent is used for one weed (i.e. most weeds have several agents). Discuss which agents eat what part of the plant for a specific weed. Create a cartoon strip (can be humorous!) of a weed before attacked by one agent (at the beginning) with more agents being added. Be sure to show damage to different parts of the weed (and its last gasp of breath!!). Control using biocontrol - A debate! Debate Topic 1: "The use of agent "x" is essential for the future control of weed "y" in New Zealand. (Consider: safety, current weed impact in NZ, effectiveness, uncertainty, cost)
Gorse Seed Weevil & Gorse Pod Moth: Gorse seed weevils are now so common adults can be found on gorse almost anywhere all year round, with peak numbers occurring from September-December. Gorse pod moths are becoming more common with each passing year and adults may also be seen all year round.


gorse seed weevil (Apion ulicis)	gorse pod moth caterpillar (Cydia succedana)

Beat some gorse with a stick over a white tray, sheet of paper or material to dislodge the small grey weevils.
Look at infestation of pods in the spring. Collect pods from bushes, open these carefully with your fingers. Look for weevil eggs, larvae, or pupae and pod moth caterpillars. Calculate the mean and standard deviation number of weevil eggs/pupae/larvae and pod moth caterpillars per pod. Compare between bushes and sites. Look again in the autumn. How many pods are infested at this time of the year?
If you do not find any pod moths in your area ask the biosecurity officer at your local Regional Council to help you source and release some.
SAFETY and host-specificity testing: In the laboratory put weevils on several plant species (in pots) that produce pods in spring-summer (e.g., peas, broom, kaka beak etc). Include gorse as a control. Do the weevils attack seeds produced by other plant species? What sorts of plants would you need to test before safely introducing a new control agent for gorse?

Gorse Spider Mites: If you cannot find gorse spider mites locally contact the biosecurity officer at your local Regional Council and ask for help.
1. Examine the colony under a microscope - look for adults, juveniles, eggs and predators (e.g., spiders, black ladybirds)
adult gorse spider mite (Tetrenychus lintearius)
1. Divide the colony using scissors or secateurs, and wedge the fragments on gorse shoots sitting in bottles of water or florist's oasis. Keep these colonies at different temperatures. What effect does temperature have on mite behaviour, life span, and the number of eggs laid?
Broom Twigminer: The self-introduced broom twigminer was first recorded in the 1950s and is now common throughout New Zealand. The small white moths may be seen flying around from December-March. Larvae damage broom twigs in spring, late summer and autumn, and spend the winter inside the stems before pupating in the spring.
1. Visit a local broom site in summer. Shake branches to see if white moths are disturbed.
2. Visit a local broom site in the autumn, winter or spring. Look for larval mining (peel back the mines and see if you can find the larvae inside) or for white pupal cases (after the moth has emerged the empty pupal cases remain for many months).
Nodding Thistle Receptacle Weevil: Receptacle weevils were released in the 1970s and are now widespread and common on nodding thistles throughout New Zealand.

nodding thistle receptacle weevil (Rhinocyllus conicus)
1. Adult weevils can be found in good numbers on nodding thistle rosettes in early spring. Visit a nodding thistle site during spring and look for the brown weevils on the thistle rosettes.
2. During the summer and autumn dried flowerheads can be examined to see if they are infested by the weevil. Infested flowerheads feel hard and lumpy. If broken open they are black inside. Collect some dried flowerheads and check to see if they are infested. Work out what percentage of thistleheads have been attacked. Compare this with other sites and time of the year (e.g., receptacle weevil destroys most seed before Christmas and is less effective in the autumn). Why is another seed feeder, the gall fly, also being released? Can you find these too? Gall fly-infested flowerheads are also hard and lumpy so you will need a knife to cut them open; they are yellow and chipboard-like inside. If you do not find any gall flies then ask the biosecurity officer at your local Regional Council to help you to source and release some.

Notes:

Please dispose of all plant material carefully (wrap carefully and put in rubbish bags) - don't spread weeds!
Invertebrates can be released on plants following surveys if treated with respect and handled carefully.
Make scientific posters to present the results of any of the above experiments or surveys. Poster content should include: Introduction, methods, results, discussion. Brief, clear sentences should be used. Graphs and/or diagrams, photos should be used.
Older students would benefit from a discussion about the methodology of these surveys and experiments and whether just measuring one or two areas lets them make global (or even local) conclusions.