SA Releases Exotic Bug to Control Invasive Plant

[Westley Price]

I dont know...I am never fond of the idea of using one alien species to control another. The idea seems great at the time until things go awry. Especially insects that reproduce so fast can go through multiple generations in a single year. How long before their native foodplants are wiped out and the adapt to feed on indigenous plants? I hope I am wrong, but I see an EPIC fail on the horizon.



http://www.news24.com/Green/News/SA-pins-hopes-on-small-Brazilian-bug-20141011

Cape Town - Researchers on Friday released several small Brazilian bugs into the wild, marking the start of a campaign to halt the spread of an alien invasive plant infesting large areas of South Africa's north-east coast.

Known to entomologists as Catorhintha schaffneri, the yellowish-brown insect, about half the size of a human thumb, feeds on Pereskia aculeata, a type of primitive cactus indigenous to South and Central America.

A century and a half ago, pereskia was brought into South Africa as a botanical curiosity. The fast-growing invasive weed took a great liking to the warm sub-tropical coastal region between Port St Johns and the Mozambican border, where it now infests large areas.

Which is why Rhodes University lead researcher Dr Iain Paterson has been studying the Brazilian bugs for the past seven years - and rearing them in large numbers since 2012 - after receiving permission to do so from the agriculture, forestry and fisheries department.

On Friday afternoon, Paterson released some of them for the first time, with official approval, on the campus.

In a statement, he said the small creatures - which he has dubbed stem-wilters - feed exclusively on the growing tips of pereskia plants, stunting their growth and reducing their ability to compete with other plants.

He described the bugs as the "perfect biological control agent" because they have no interest in any indigenous plant or crop.

"After many years of research, it is now clear that the pereskia stem-wilter can only survive on pereskia, and will die if it is forced to feed on any other plant... it will feed on pereskia only, and will not harm any indigenous plants or crops," he said.

Pereskia is a spiny vine with slender branches and pretty cream-coloured flowers, but it kills indigenous plants, including large forest trees, by climbing up and smothering them, to the extent that they collapse under the weight of the invader.

It grows in ecologically sensitive and difficult to access areas, making it difficult to control through herbicides and physical removal.

The plant can also reproduce from small fragments, so after clearing operations the tiny fragments of the plant that are left behind will grow into new plants.

Paterson said efforts were now under way to "mass rear" the stem-wilter bugs.

He said on Friday that the next step would be to release stem-wilter eggs -- about 500 at each site -- at "as many sites as possible" across the pereskia-infested region.

[vuduman]

It reminds me of the Canetoads in Australia

[Ruan Stander]

Certainly not ideal.
However, let's hope that the seven years were well spent in terms of research.

[Westley Price]

There are so many examples of failed biological controls!

- Cats introduced in Australia to control the alien rabbit population
- European Carp introduced to many rivers/lakes world-wide to control plant growth
- Cane Toad introduced into a few countries to control alien and indigenous beetle populations (who damage sugar crops)
- Asian ladybugs introduced to the US to control aphid populations

I am sure all the historic introductions also had prior studies, but it is difficult to anticipate how a species will adapt/react when exposed to a new environment and new, alternative food types. They might totally ignore their natural food and go for something indigenous.

[Chopper 1]

Not a good idea at all - history will repeat itself.

[Ruan Stander]

True, but hopefully by now things have changed and improved to allow more accurate predictions.
However, like Westley mentioned, there is no way of knowing how a species will adapt to a new environment until it is introduced there.

[dgh]

Main thing that gets considered when researching potential biological control agents, is the agents host specificity. The agents may not eat any indigenous plants, else that one gets scrapped. Its not merely a case of releasing an insect and hoping for the best. From finding a potential bug, to obtaining release permits takes around ten years of constant research. Also due to predator prey relationship, the biocontol agent will (almost) never completely destroy the population of the plant it attacks
SA is amongst the top three in the world in this field. Heres an excellent summary of whats been done: http://www.sajs.co.za/sites/default/fil ... 0Views.pdf

[Scavenger]

I feel compelled to comment on this as I deal directly with alien plant control. To me this is great news as already mentioned in the previous comment South Africa has one of the best track records for introducing biological control agents. This is definitely not the first and not the last, with there already been multiple introductions in the past as far back as back as 1933 for Opuntia ficus-Prickly pear been one of the firsts refer to the link of successful bio-control agents http://www.arc.agric.za/arc-ppri/Documents/WebAgentsreleased.pdf. When introducing a species especially in terms of plant control the introduced species will never exterminate the plants entirely as they've adapted to one another for millenia BUT RATHER CONTROL IT a parasite will as per definition harm its host and provide no mutual benefits for the hosts survival, although the majority of hosts have adapted to this. The examples given by Westley were unsuccessful because of the lack of research and the lack of understanding of the potential dangers and as one can notice most if not all the species given as examples were used to control other introduced VERTEBRATES. I for one believe if the correct procedures are followed biological control can be very successful and in most circumstances is a cost effective method and ensures our biological diversity in South Africa. I hope I've made a valid argument/statement as there is a lot more that goes into this for example one of the worst species to arrive in South Africa is Pom-pom weed which is threatening our entire grassland biome and one species I deal with intensively, we are looking at the new biological control agent to release to assist our fight against this species so that our grasslands and savanna don't drown in pink.

[Westley Price]

I totally understand the last two comments about the amount of work and consideration that went into selection of the control species/agent, but don't you think the other failed bio-control examples were also confident in their success?

I am very sure they also conducted years of studies, but some outcomes are just not predictable, no matter how hard people try.

I make no mistake, I am not saying this will fail, nor am I wishing it to fail, I just feel introducing an exotic species to control an exotic species is a bit "one step forward, two steps back."

So what happens if the introduced species doesn't have a effect on the Pereskia that one would like? Does another species get introduced? In the link Scavenger gave, some of the invasive plants have had up to 5 exotic invertebrates introduced into RSA to control the problem. How can one justify controlling one invasive species by introducing a potential 5 invasive species?

I guess the issue is that I am a layman on the topic so I am becoming defensive too quick, but to me it just doesn't make sense.

[Scavenger]

Westley the sad reality is by us bringing these alien plants into the country we have created a problem already and yes I agree biological control has it's faults as has been proven if not done correctly. But by us creating the problem we are obligated to find solutions to it to protect our heritage.

Certain alien plants threaten our biodiversity at a unprecedented scale and when you look at a monetary value to control it with chemical and mechanical means, it starts becoming a really negative picture. As already mentioned most of the biological control will never exterminate but rather control the target species therefore you still need to follow a multi-pronged approach using: Chemical, Mechanical and Biological control together.

Just another example in Australia another form of control was introduced for the rabbits after the cats, were introduced that proved very successful, but was considered quite extreme http://www.csiro.au/Outcomes/Safeguarding-Australia/Myxomatosis.aspx.

[Bushviper]

The research done on these control agents is extensive and of extreme diligence. Just like certain animals will never become invasive to point out a few mistakes made in Australia does not mean we should not try this. South Africa exported dung beetles to Australia to help with the fly problem. That you dont read about because it never became a problem. Imagine koala bears becoming an invasive species in South Africa. All they will eat are blue gum trees. I dont see the problem.