The Ups and Downs of Tansy Beetle Numbers at Rawcliffe Meadows (Revised August 2019)

TB Pond South 6 (1024x949)

The Pond at Rawcliffe Meadows was excavated in May 1991, and the mounds and funnel that surround it were created from the spoil. Although Tansy Beetles had been seen along the Ings Dyke, that runs between Rawcliffe Meadows and Clifton Ings, and Blue Beck, that runs across the top of the site into the Ings Dyke,  previously and one copulating pair was found by Pond in 1993. These beetles had disappeared in 1994 but instead some were found that year in the New Meadow, just north of Blue Beck.  In 1994 some Tansy Beetles were found in the Blue Beck Copse ( a rough patch planted with saplings in 1993 between Blue Beck and the New Meadow) and alongside the hedge at southern end of Rawcliffe Meadows. The populations appeared to remain small from then onward.

There were sightings by the Pond in early 2000 but beetles were not seen later that year probably due to the severe flooding of the River Ouse that summer, although beetles were noted by the Blue Beck and Ings Dyke in 2000.

Beetles were sighted by the Pond again in June 2001 and in 2002 they were noted again by Blue Beck (on 8 April), plus at the Pond and by the New Meadow. The  2004 record was 100 by the Pond, a further 36 on the Ings Dyke bank (at the north by theold oak tree) and 101 on the Blue Beck bank with an additional 3 seen on the New Meadow and  4 near cattle grid leading the Copse.

In 2006 121 were counted at the Pond, with several on the New Meadow. Unfortunately in the previous year the Blue Beck verge was massacred by the Internal Drainage Board and that expanding population of plants and beetles were wiped out. Beetles continued to be sighted at the Pond and New Meadow during 2007.

By 2010 the Pond mounds were noted as a major habitat, and planting of tansy was extended further over  them. Unfortunately there were none recorded that year in the New Meadow

In 2012 the western edge of the New Meadow was fenced off to protect tansy and beetles from grazing and eight beetles were introduced from the Pond in June of that year and the count in late August had a total of 175. By that year we had recognized the significant effect that shading had on tansy plants, and hence beetles so that with the assistance of funding from Yorkshire Water which we received in 2013 we began cutting back and coppicing trees shading the Pond mounds, along with pollarding the trees overlooking the western edge of New Meadow (winter 2013/spring 2014). We also introduced cutting around  the tansy patches at the Pond, New Meadow and plants that started to reappear alongside Blue Beck. The count for 2013 was 208, which jumped to 368 in 2014 with all the care and attention to surroundings (with 60 on western edge of New Meadow and a single one to the south).

Following discussion with Geoff and Roma Oxford of the Tansy Beetle Action Group (TBAG) we decided in 2013 to manage the area to the south of New Meadow for tansy, along with the area near the cattle grid, and those adjacent to Blue Beck and the Ings Dyke where there were existing records of beetles. This has been started by regular cuts of the competing vegetation, and then fencing where practical. Other actions will be considered as we learn more about tansy, the beetles and their habitat needs.

With Rawcliffe Meadows being home to between 10% and 20% of the UK population of Tansy Beetles we feel it is important to try and increase our own stock of beetles in a manner that will leave many protected in the event of the unseasonable floods or other environmental issues that might wipe out an isolated population. The graph below should demonstrate the variations to the populations, whilst the Blue Beck, Ings Dyke and Cattle Grid are areas that once supported plants and beetles but being reinstated. During 2014 we put additional plants in the New Meadow, further around the Pond, by the cattle grid at the north, in the Reservoir Basin, and by Blue Beck. Whilst some of the areas were better prepared than others and may take years to establish properly, some are fenced off from grazing/public access, others are not. Only time will tell where the beetles  and plants best prosper, and perhaps answer some questions as to why. In 2019 we have a volunteer regularly observing the Tansy Beetle population at New Meadow – we hope that might give shed some light on the variations.

It must be noted that the numbers are a snapshot from the day of the survey. Additional Tansy Beetles may be discovered at the other locations on sunnier days later in August or early September. As in the case of September 2015 when Tansy Beetles were found in large numbers at the south of the Pond (where there had been none a few weeks before), along with being on plants by Blue Beck and over the Barrier Bank along the Cricket Field fence. The 2018 figures on 21st August are disappointing in that the 35 counted on New Meadow is well down on the 206 on 4th May 2018, whilst the 147 counted in August by the Pond is less than half the 363 quickly counted in May.Perhaps the exceedingly hot, dry summer had an effect. The leaves of the plants were noticeably well eaten, and for the first time we sighted galls on the tansy flowers, whilst the browning off (blight) was reduced from 2017.

A further 720 tansy plants were nurtured from seed provided by us into 9 cm pots by Brunswick Organic Nursery during 2015. These were being used to extend tansy coverage through the existing areas as well as on the banks of the Reservoir Basin. These plants were funded jointly by the Yorkshire Wildlife Trust and Yorkshire Water . The increasing number of tansy clumps can be seen on the graph below. The existing clumps are also spreading, seeding and in some cases disappearing. The dip in 2018 is a mixture of the cattle eating and trampling the tansy due to the reduced herb growth from the dry summer, along with the developing clumps merging together into bigger ones. The cattle had a similar effect in 2019 many of the cattle-accessible clumps flourishing only at ground level.

However, the count team when they went out on 29th August 2016, a relatively sunny day, we disappointed to see numbers had dramatically fallen from the previous year, and even a fortnight before when the clumps at the Pond had been managed – might this be as a result of the flooding and standing water on their habitat for almost all of the winter? The numbers at New Meadow had slightly increased, although it had been more days earlier, as were the new population along the Ings Dyke. In 2017, despite seeing large numbers of Tansy Beetles over an extended period in the Spring and Summer, and the tansy foliage being voraciously attacked by beetles and larvae, the numbers have still only gently risen at the time of counting.

The count team in 2018 (c) Ian Smith

The count team in 2018 (c) Ian Smith

We now have an established population of tansy plants and the challenge is to get the newer clumps inhabited by Tansy Beetles and expanding in the new locations to ensure that areas like the Pond, which was under water for a lengthy period of the winter of 2015/2016 are not the only expanding populations. However, whilst cattle trampling the plants may be beneficial for their spread, it doesn’t do a lot for counting them in late summer! The August heatwave of 2019 also appears to have had a disastrous on count numbers as there were many more in earlier weeks, despite many of the enclosed plants appearing to be in excellent condition!

We also need to understand why some tansy clumps ‘brown off’ before flowering as can be seen in the picture below, which is a drastic occurrence in this instance but then seemingly recover in subsequent years

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A 'blue' Tansy Beetle

A ‘blue’ Tansy Beetl

Tansy clump in 2019

Tansy clump in 2019

About greatemancipator

Researcher and practioner in matters relating to egovernment, government ICT and their approach to the citizen.
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