Bioinsecticides derived from garlic could play a role in combating vine weevil, a troublesome pest to soft fruit and ornamental plant growers.
Garlic extracts have proven effectiveness against pests of stored products such as mealworm to some effect, as well as against mosquitoes, but have yet to be widely applied in growing environments.
Eugenia Fezza and a team at Harper Adams University set out to explore whether Pitcher GR, a garlic-based insecticide, could do the trick against vine weevil (Otiorynchus sulcatus) eggs and larvae.
Efficacy explored
They set up a series of laboratory experiments which looked at the effects of the product through direct contact with eggs and early-stage larvae in petri dishes, as well as fumigation, which was achieved by mixing the product in solution in a separate petri dish, with a hole leading into the dish where the eggs or larvae were present. They also observed the outcome when both contact and fumigation were used.
From the tests, they saw that egg hatch rate was significantly reduced when the garlic product was used as a fumigant but not as a contact pesticide alone, although a combined effect of the two approaches also appeared to be present. Both contact and fumigation reduced the survival of larvae compared to controls.
Rigorous field testing next
“Natural products such as phytochemicals derived from plants offer a potential solution to address this need and it is widely believed that they can play an important role in sustainable agriculture,” wrote Fezza in Journal of Economic Entomology.
“Such products have been shown to be effective against several economically important weevil pests.”
Though the lab results using Pitcher GR are promising, the real test will come in the field, explained Fezza. It remains to be seen how well the product performs under commercial growing conditions, while the timing of applications also needs to be assessed, so that the most vulnerable life stages of the weevil can be effectively tackled. Further experiments are also needed to see if the product works as well against late-stage larvae, pupae and adult insects.
Bioinsecticides are widely seen as a particularly useful option when applied alongside other sustainable options such as biological controls, as part of integrated pest management strategies. As such, the compatibility of the product will need to be tested with existing measures used against vine weevil, such as nematodes which kill the larvae of the species in soil.
“The product’s multiple toxic effects are particularly promising for effective control. While field trials are essential to validate efficacy in outdoor settings, these results establish a strong foundation for developing garlic-based bioinsecticides as a sustainable vine weevil management tool,” added Fezza.
