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White Fringe Weevil Trial

The white fringed weevil trial commenced in 2007-08.

The pre-seeding treatments we sampled with no weevils being found in the control bays or in the treated bays. These areas were sampled again when the pre-irrigation treatments were sampled.

The pre-irrigation chemical application was completed. This was followed by digging and sifting several small soil pits to determine how effective each of the treatments were. With the assistance of 10–12 growers, the soil samples were dug and sifted to determine how many weevils survived the treatments. A second dig was scheduled to assess if there was a longer term population control achieved with the different treatments. Results as follows:

14/12/07 (sample taken after first irrigation): Paddock E – established lucerne

No weevils (adults or larva) located in following treatments:
Chlorpyrifos 1.0 l/ha, 2.0 l/ha, Regent 200 ml/ha, Regent 100 ml/ha
No larvae and average of 0.1 adult/sample in Chlorpyrifos 500  ml/ha
No adult and average of 0.7 larva/sample in Regent 50 ml/ha
Average 1 larva/sample and 0.5 adult/sample in Chlorpyrifos 250 ml/ha
Average 0.5 adult/sample and 0.7 larva/sample in control

This data suggests higher rates controlled early presence of the beetle adult and larva

20/3/08 (sample taken after final irrigation in ripening crop): Paddock E

All treatments and controls had basically nil adults.
Control, Chlorpyrifos 2.0 l/ha and 1.0 l/ha had over 1 larva/sample.
All other treatments had between 0.3-0.8 larva/sample.

The data suggests that the pre irrigation control did not control the beetle through the season. However it does warrant more investigation as the Regent 200 ml/ha did have considerably less beetle presence at the end of the irrigation season. This finding is to be compared to similar populations being found in the Chlorpyrifos 500 ml/ha whereas significantly more larvae were found in the Chlorpyrifos 1 and 2 l/ha treatments. Consequently it suggests Chlorpyrifos does not provide long term control of this pest and nor does it suggest Regent is a better alternative.

Lucerne Australia would like to acknowledge the support given to the project by Nufarm, Tim and Joan Oldfield for allowing the trial to be carried out on their farm, and Ian and Scott Manser for fabricating the sieves.