Risks and opportunities for Australian watermelon pollination

18 September 2018

Helping farmers get full pollination of hybrid watermelon crops is the goal of a study co-funded by Plant & Food Research and Hort Innovation. Honey bees are known to be good pollinators of watermelon, but their vulnerability to the varroa honey bee mite means that growers need to be ready for changes in the future. The study, now beginning its second year, aims to further understand just how important honey bees are and also investigate the function of other insects like flies and native bees, which also visit watermelon flowers.

In 2017, Plant & Food Research Australia scientists surveyed eight watermelon farms across three growing regions (Chinchilla, Gumlu, Lakeland) in Queensland to see which insects were visiting flowers and how efficient they were at transferring pollen. They identified 79 types of insects on water melon flowers. The common ones include: honey bees (Apis mellifera), sweat bees (several species of Halictidae), stingless bees (Tetragonula hockingsi) and hoverflies (several species of Syrphidae). 

Honey bees, stingless bees, sweat bees, and other native bees (between 5 mm and 10 mm in length) are all capable of pollination. However, honey bees deposited the most pollen grains per visit (an average of 40) and more frequently crossed between male and female flowers. Honey bees also represented between 79% and 90% of the flower visiting insects recorded in each region. 

While watermelon pollination appears to be heavily dependent on honey bees, unmanaged pollinators are likely to be contributing to pollination on some farms. The contribution of native bees is consequential for watermelon production in other countries such as the United States. 

“Heavy dependence on honey bees is both an opportunity and a risk for watermelon growers,” said Dr Lisa Evans, Scientist at Plant & Food Research. “These pollination services could be vulnerable to local or regional environmental change. In particular, the potential for the honey bee destroyer mite Varroa destructor to become established in Australia remains a concern.”

As part of an ongoing research programme, scientists will develop new ways of managing honey bees on farms to help growers to respond to such a change without interruption to crop pollination outcomes.

Contact:
Nickkita Lau
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Plant & Food Research Mt Albert,
120 Mt Albert Road, Sandringham
Auckland, 1025, New Zealand
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