How do I control brown beetles on my feijoa tree?

Q.

Hi, what is this bug and how to stop it eating leaves on my feijoa tree? Already using regularly neem oil, neem granules, moth traps....with no success.

Maja Heiniger

A.

Hi Maja, that looks like grass grub beetle which emerge in spring from the ground after overwintering as grubs. They are nocturnal and so come out at night to feed, mate,  drop their eggs into the soil and the lifecycle starts again. Alternatively, there is a smaller bronze beetle that also feeds on new foliage striping leaves, they move in almost overnight, feed for about 10 days and then move on. Either way, both are difficult to control at the adult beetle stage due to their hard shell. The best stage to control them is when they are in the ground, some people suggest using neem granules as you have done, or try Diatomaceous Earth which is a silica based product, to get them as they emerge from the soil. Your local garden centre will be able to recommend a suitable soil insect control product. Other suggestions are washing the beetles off using a hose, going out at night with a torch and bucket of water, shaking the tree as they will drop to the ground, then feed them to the chooks, if you have them. The beetles are attracted to light, if you have solar lights or an outside light near the garden, turn them off at night in early spring. From a social media post, a person posted a solution using a pane of glass smeared with Vaseline and a light behind it, the beetles flew towards the light and got stuck to the Vaseline. In late winter, early spring treat your lawn for grass grub with Scotts Grub and Insect Control – it contains bifenthrin which is a synthetic pyrethroid and helps control grass grub in lawns. I hope these are helpful solutions. Lianne.

 

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