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Weevil of all evils

The Sigastus weevil has recently become a major pest of macadamia farms in Queensland and New South Wales, Australia. This pest threatens the industry as it currently has no biological control agent to combat it. Previous pests like the lace bug and fruit spotting bug have come under control with the use of the biological control agents of lacewings and Anastatus wasps respectively. While volunteering for BioResources Queensland with Richard Llewellyn, I had the opportunity to explore macadamia farms for their insect diversity and interview farmers on their growing techniques and increasing weary of this weevil pest. 

This weevil is terribly cute, resembling a woody dinosaur crossed with a tiny elephant. 


But it uses that trunk-like rostrum to chew its way through the husk of a macadamia nut. Once a hole is created, it lays a single egg then seals off the entrance with the chewed up remains. 



Many of these can be found in the trees or on the ground depending on how successfully the weevils chew the base of the nut off from the branch where it formed. On the ground or in the tree, that larvae develops inside the nut until it consumes the entirety of the nut inside. 



Eventually this chubby baby pupates from a larvae into the golden nugget seen below. This pupae remains inside the nut until it can burst out as an adult. 


Once emerged, the weevils start the process all over again, sometimes mating in the process of depositing their eggs in the Macadamia husks. More research has to be done to determine what the adults eat, if anything, and how many eggs each adult can lay. 


In the meantime, I and other biological control scientists continue to investigate options for controlling this weevil without the use of pesticides. Options currently include a type of fungus or Braconid wasp parasitoid, but several challenges remain in developing these options commercially and determining their efficicacy for farmers. 

In my short time volunteering with Richard Llewellyn I have already met several farmers and learned about several issues that come into play with biological control. These fascinating reltionships and what people are doing to control pests are rarely shared with the general public. I find it wonderful to know so many people are invested in finding alternatives from using pesticides. There's a lot of work to be done, but each chllenge is a fun puzzle. 


It's been a pleasure to invest my interest in entomology where it can be used by farmers. Across ages and cultures, I have connected with several people over my interest in entomology and genuinely hope to contribute to resolving this weevil issue and others!

Just yesterday I was dissecting some macadamia husks in the search for parasitized weevil larvae. This is part of the search for natural predators of the weevil which we may use to control the pest in the future. When the youngest daughter of Ross Arnett, the macadamia farmer I was staying with, saw me looking through the nuts, she asked to help out. Once I shared my hand lens, she was fascinated to see all the different sizes of the larvae and what they did to the macadamia nuts. She loved how cute the weevils were and that initial interest sparked a curiosity that I was honored to assist.

Interactions like these are incredibly important for encouraging an interest in entomology and ecology in children. Based on my own past, I also think it's great to expose young girls to female scientists. It wasn't until I was in high school that I first considered women as being scientists too. Even then I struggled until college to be confident in my own abilities as as scientist. When we're exposed to a limited image of people in certain careers, it's difficult to envision ourselves in those positions. Now, I have been given the opportunity through the Watson Fellowship to share my interest in entomology with farmers and children, increase my knowledge of insects in agriculture, and hopefully inspire others to pursue their own passions, as quirky as they may be! 

Furthermore it was an honour to experience all of this on what would have been my Granny's 90th birthday. She passed away in 2011, but everything she taught me about gardening and being kind to others has resonated into my success on this Watson Fellowship. She was the first person to teach me about how plants develop and what they need to survive. This gave me the perspective as a young girl to notice development in nature and how we might grow things ourselves. She also taught me to be kind and patient with others through her own example. Though I can only dream of being as kind as my granny, her lessons have allowed me to communicate with farmers on a more personal level as I consider their perspective first. Assuming I know more about their farming system based on my status as scientist is a foolish approach, as their life-long experience can provide novel ideas for improving the ways we grow food. This communication has taken me through farms and homes, while supplying me with ideas that will shape what I study in graduate school and what I do with the rest of my life. 

I never could have predicted what I would learn or where this year might take me. It's wonderful to be given the gift of time to explore these interests around the world. Extraordinary things continue to bombard me on this Watson, but I hope these tid-bits of facts and reflections are helpful to others as they pursue their own interests or if they simply are curious about this little Sigastus weevil!


For more frequent updates, bug posts can be found on my Instagram: justanothernakedape

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