[Dane Keriboi Hawker]

Yesterday I had a scare. I thought my new buddleia had a massive invasion of Buddleia Weevil larvae.
After investigating it turns out it was not BV. Phew

I spent all night researching the weevil and trying to come up with a plan to save my plants. I could not find any way to stop BV other than spraying. Some people have had success spraying a contact insectide like Mavrik from Yates. It needs to hit the weevil to kill it. No good if they are hiding under the leaf.

So moving forward I feel the best way to beat the weevil is to get a systemic into the buddleia plant just as the larvae is starting to feed. If the larvae are controlled, then there will be fewer adults in the future to lay further larvae. Lessening the cycle is the best chance we have if we wish to keep the buddleia. It was sad to read in the latest magazine that Jacqui is thinking of pulling out her plants.

I started looking into systemic insecticide sprays but the best I could find is imidacloprid but that is the worst for the bees and butterflies. What else is out there?

So I came across a product that looks interesting. It is a granule so there is no worries about spray drift. It is sprinkled in the dripline of the plant and taken up by the roots and kills bugs eating the foliage. Perfect!!…. But…. “We advise not to apply to plants in flower as it may affect foraging bees.”

No doubt that means butterflies too.

I have about 20 plants and It wouldn’t take long to go around and take off all the flower heads and apply the granule kill the weevil and move on happily. But how long will the chemical stay in the plants? It is all a guessing game. I am expecting the weevils anytime soon. I have seen plants in the area with the damage. I am going to fight the battle and will get back to you all with my findings. Please put up anything I could try.

If you are interested in the granule it is here.

http://www.kiwicare.co.nz/help/product/?sid=plant-health-insect-hit-granules

[Dane Keriboi Hawker]

I can confirm the granules work. I noticed some severe damage on my plants this week and covered in larvae. Applied the granules and three days later all the larvae is gone. There are no flowers on the plants so no problems about hurting butterflies.

[Dane Keriboi Hawker]

Update – I am pretty sure the granule has worked. My sungold yellow was covered in weevil larvae. I applied the granule on Sunday and watered it in. Looking today I could only find one larvae!!!!! I pulled off all the flowers but saved my plant.

I have a cutting in a pot that is riddled with larvae and have tried again with the granule. It should be easier to monitor.

[Jacqui]

There’s an article in the latest magazine about it…

[Dane Keriboi Hawker]

Will look into it. Thanks Jacqui

On another note I read “Buddleia leaf weevil: 7 years in New Zealand”

To date forestry companies have NOT been able to reduce pre and post-plant herbicide treatments Mainly due to other weeds still need to be controlled

SO in other words. It hasnt worked for them how they liked

[Jacqui]

We definitely don’t want to do anything to harm the bees, Dane. I would steer away from chemicals as (eg tobacco/humans, CocaCola/humans, and DDT) they may be touted as safe one year and a few years later we know what effect they’re having. I try and reduce as many chemicals as I can into my home/lifestyle.

However, I did find out something about the buddleia weevil that you might like to explore. This time last year I had been looking for natural controls for the weevil, and found the document below.

http://www.caes.uga.edu/content/dam/caes-website/departments/entomology/documents/publications/braman-publications/Gradients%20in%20Susceptibility%20and%20ResistanceMechanisms%20of%20Buddleia%20L.%20Taxa%20to%20the%20Two-spottedSpider%20Mite%20(Tetranychus%20urticae%20Koch).pdf

A second mechanism that may affect arthropod herbivory in Buddleia taxa is the presence of highly branched, nonglandular trichomes (Rogers, 1986). Although the ability of these trichomes to prevent herbivory is not well characterized, there is evidence that they are defensive structures that limit arthropod feeding. Cleopus japonicus Wingelmuller, a weevil that is host specific to Buddleia, avoids the trichomitous undersurface of B. davidii leaves (Zhang et al., 1993) and feeds on the upper surface. This feeding behavior indicates that mechanisms present on the underside of Buddleia leaves, most probably trichomes, are affecting the weevil’s ability to feed successfully on this portion of the leaf.

A trichome is ‘a small hair or other outgrowth from the epidermis of a plant, typically unicellular and glandular’. So I’m wondering if we could perhaps spray our buddleias with a substance that would have small fine hairs in it (and something to stick it to the leaves) and that would deter the weevil? Something like little bits of fluff? Maybe silk from the milkweed? I’ve got enough of that!!!

This is possibly why my spring Buddleja is not affected by the weevil, as the leaves on that one are hairy. But it’s also possible that it’s come from a different region of the world to the B. davidii cultivars that the weevil attacks.

MAYBE you’ll be able to create a product that would work, something that wouldn’t hurt the bees and butterflies, and will address the weevil issue in our domestic gardens. I’d buy it if it worked.

[kay2]

Good luck with that. Had to take two out here in waipukurau, one of them was huge

[Author]

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