Horticulture, a constant learning curve
I know spring is well underway when I see little visitors scuttling around my office despite my best efforts to discourage this activity. I was not surprised when reading research by Johnalyn Gordon and others, published in the Journal of Economic Entomology, describing cockroach resistance to pyrethrum-based surface sprays.
Pyrethrum is a natural insecticide derived from Chrysanthemum cinerariifolium and Chrysanthemum coccineum. It is not the first plant extract used as an insecticide; nicotine, the tobacco alkaloid, has been used as an insecticide since the middle of the 18th century.
More recent research by a group at the College of Food, Agriculture and Environmental Sciences, Ohio State University, investigated the effectiveness of hemp leaf extract for controlling pyrethroid-resistant strains of Aedes aegypti mosquitos. The mosquitos can carry diseases such as malaria, yellow fever and more. As hemp is an emerging crop, E. J. Rodriguez, one member of the research group, is optimistic that materials will be readily available and is keen to explore the insecticidal effects further. Using hemp byproducts could increase the profitability of industrial hemp production.
According to NSW DPI, hemp (Cannabis sativa) is one of the oldest crops known to man and is generally thought to have originated in China. Also of Chinese origin is the camellia. Camellia sinensis gave us the tea break, and a relative, Camellia oleifera, could provide a more eco-friendly vegetable oil.
Researchers Thomas Wanger and Siyan Zeng at Westlake University, Hangzhou, compared the greenhouse gas emissions, water use, land use, and pesticides of the six main vegetable oil crops: oil palm, soybean, rapeseed, groundnut, sunflower, and olive. It is documented that more than 30% of total agricultural land is used for vegetable oil production. They were interested in quantifying the benefits of replacing established vegetable oil crops with Camellia oleifera, a hardy shrub little known outside China.
The oil yield from Camellia oleifera is only second to palm oil. Wanger and Zeng conservatively estimated that replacing about 11% of current oil crops with camellia would reduce greenhouse gas emissions by 14% and almost 5% water use, depending on which oil crop it replaced.
In addition to environmental benefits, camellia oil has health benefits similar to those attributed to olive oil and is high in oleic acid. When consumed instead of other oils and fats, oils high in oleic acid appear to reduce the risk of heart disease.
There is always something new to learn; I often feel that I could live ten lifetimes in horticulture and would only be scratching the surface with learning. Education and professional development are featured in many of our articles this month. Reading these articles and perhaps doing more self-research on the topics will carry you a long way with your knowledge and career. I am always amazed at the research that is carried out. With constant improvements in using sustainable products, we have come a long way, particularly in the use of pesticides.
As we move into summer, some advice from the Cancer Council: Slip on your protective clothing, Slop on your sunscreen, Slap on your hat, Seek some shade and Slide on your sunglasses.
Enjoy the read
Karen Smith and your Hort Journal team