This is a photograph of one of our more aggressive pest insects here at Arendell Hill Nursery, commonly known as a Glassy Winged Sharpshooter, (Homalodisca vitripennis).
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| Glassy Winged Sharpshooter on the stem of one of our hemp plants |
When we first began growing hemp I would sometimes mistake the whitewashed appearance of hemp leaves as white mold. However what we learned was that the leaves' white coating was actually defecation material from the glassy winged sharpshooters.
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| Glassy Winged Sharpshooter 'Whitewash' on one of our hemp plant leaflet |
Glassy winged sharpshooters require copious amounts of liquid to grow and reproduce. Much of this liquid is excreted out in the form of a white paste, hence the whitewash effect across our hemp leaves.
Across Florida and throughout much of North America, the glassy-winged sharpshooter is a serious agricultural pest known for its potential to spread bacterial diseases to a variety of plants, including agricultural hemp. It feeds on a wide range of host plants and can spread the bacterium Xylella fastidiosa, the causal agent of diseases such as Pierce's disease in grapes and leaf scorch in a variety of other plants.
The glassy-winged sharpshooter, like other members of the leafhopper family, has specialized mouthparts adapted for piercing plant tissues and sucking out fluids. These mouthparts, known as stylets, function much like a straw. However, unlike a typical straw, the process involves more than just applying suction.
When feeding, the sharpshooter pushes its stylets into the plant tissues, navigating past cells until it reaches the plant's xylem - the system of tiny tubes that transport water and dissolved nutrients from the roots to the rest of the plant. Xylem fluid is under negative pressure, or tension, due to the process of transpiration (water evaporation) at the plant's leaves.
Once the sharpshooter's stylets are in the xylem vessels, the tension within these vessels causes the fluid to move into and up the insect's food canal (formed by its stylets), similar to how water will rise in a thin tube or straw. Thus, the sharpshooter doesn't need to actively suck up the fluid. In fact, the sharpshooter has to work to prevent the xylem fluid from flooding its alimentary canal and has a special filter chamber to help manage the volume and pressure of the ingested fluid.
It's worth noting that feeding on xylem fluid presents nutritional challenges, as this fluid is low in nutrients compared to the sugary sap in the plant's phloem (which many other sucking insects, like aphids, prefer). Sharpshooters have adapted to this diet in part through symbiotic relationships with bacteria that help them metabolize and extract nutrients from their food.
When it feeds, it can also introduce the Xylella fastidiosa bacterium into the plant, leading to blockages that can cause leaf scorch, wilting, and even death of the plant. Glassy winged sharpshooters also may be a host for Xylella fastidiosa, another significant plant pathogen.
As for the Integrated Pest Management (IPM) of the glassy-winged sharpshooter, here are some strategies that could be used:
Monitoring: Regular inspections of the hemp fields to catch any sharpshooter infestations early before they become a significant problem.
Biological control: There are several natural predators and parasites of the glassy-winged sharpshooter that could potentially be used for control. For instance, egg parasitoid wasps, such as Gonatocerus spp., lay their eggs inside the eggs of the sharpshooter, preventing them from hatching.
Cultural control: Changing farming practices to make the environment less conducive to the sharpshooter. This could include altering irrigation practices (since sharpshooters are attracted to water), removing potential host plants around the hemp field, or adjusting the timing of planting and harvesting to avoid peak sharpshooter activity.
Chemical control: If necessary, organic-approved insecticides could be used to control sharpshooter populations. These should be used judiciously to avoid killing beneficial insects and to prevent the development of resistance in the sharpshooter population.
As always, the specific IPM strategies used would need to be tailored to the individual farm and its unique conditions. Always consider local laws and regulations when implementing pest management strategies.
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