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Sick of Cicadas

Page history last edited by Jacob Martin 10 years, 3 months ago

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Melissa Thomson, 18 “Sick of Cicadas”


My name is Melissa Thomson and in 2008 I was in year 13 at Katikati

College. As part of a biology internal, I had to do a science fair project

investigating the ecological niche of an organism. I wanted to make my

project useful in some way, rather than just to fulfil the requirements of

the achievement standard, and my home was actually the perfect place

to conduct this research.


I live on a 400 acre kiwifruit and avocado orchard at Waihi Beach, which

provides a home to millions of cicadas which are becoming an increasing

pest to orchardists. The kiwifruit canes provide the female with a suitable place to lay her eggs, and this significantly weakens the cane and makes it more susceptible to breakage. This causes a huge problem in the orchards. The adult cicadas do not actually cause a lot of damage due to their feeding habits; there is only minimal harm to the kiwifruit where they suck the sap. A spot of juice then leaks from the fruit, allowing sooty mould to leave a black blemish which causes the kiwifruit to be classed as a reject. Most of the damage from the species is caused by the nymphs feeding on the roots. The nymphs damage the kiwifruit roots by sucking the sap from them while they live underground. They also effectively reduce the nutrition that the vine receives from the roots. Therefore the orchard offers an appropriate habitat in which the chorus cicada can live, and the high population of cicadas means that there is a lot of damage caused by these insects.


Therefore, the aim of my project was to investigate the depth under the soil surface in kiwifruit orchards where nymphs of the cicada mostly inhabit. Furthermore, I investigated the distribution of the cicada nymphs in relation to size.


I carried this out by digging holes under the kiwifruit vines and recording the number and size of the nymphs found at certain depths. From my data, it could be seen that there is a relationship between the number of cicada nymphs and the depth they are found under the soil surface, with cicada nymphs mostly found at depths of 11 to 30cm. Furthermore, it was determined that there is also a relationship between nymph size and depth they are found below the surface. The small nymphs were found at shallower depths and bigger nymphs were found deeper. It was also established that there are an astounding number of nymphs living underground in the kiwifruit block; approximately 150 per metre² ! This suggests that there are about 3870 nymphs per bay, which means a lot of damage to both the kiwifruit roots and the canes.


My findings can be applied to the situation of cicada eradication. Based on the results, most cicada nymphs are found below the top 10cm region, which provides some difficulty in access to eradicate them. I decided to contact an entomologist at Hort Research so I could talk through my findings with him and find out what this meant for cicada eradication. We concluded that there may be a long-term solution by developing a biological insecticide based on fungi. By applying the fungus to the soil surface, eradication may only occur to the nymphs inhabiting the shallower regions. However, the fungus is likely to persist in the soil and could therefore provide several years of control which would have a more significant effect on the cicada numbers.


After carrying out all this research, I decided I might as well enter it into the Bay of Plenty Regional Science Fair. There I managed to come second in the senior science section and win the Statistics NZ award; at the end of that day walking away with over $700. But that’s not where it ended; I was also awarded a nomination to compete at Realise the Dream.


After making a DVD of the summary of my project and sending it away as part of my nomination, I found out that I had been accepted. So in December 2008 I headed off to Wellington to spend a really fun week at Realise the Dream! I was not at all expecting to receive any more awards there; I thought this was the end of the road for my project. However, at the barbeque at the end of the week, I won a trip to the Beijing Youth Science Creation Competition along with 3 other students. This involved a 2 week trip to China in March 2009. It was such an amazing experience being able to meet Chinese students and look at their projects, visit places like the Great Wall of China, Forbidden City, Olympic Stadium and Summer Palace and to experience the diverse Chinese culture.


My project started as just a school internal and grew into the opportunity of a lifetime. I began the project not knowing where it would take me, or even that it could take me that far. While carrying out this project, I spent a lot of time not only talking to the entomologist, but also to my teachers at school. They were really helpful as they were able to guide me through the steps of the project, as well as help me with the statistics behind the project. I would definitely recommend talking to your teachers at school because a lot of them are more than happy to help out in any way they can. So my advice to all students is to get involved and put in the time and effort, because you’re likely to get a lot more out of it than just a few school credits.

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