There are a select handful of garden pests that really crank my handle. These are pests that cause lots of damage, are hard to control and affect a wide variety of crops. One of the worst I think is a relatively new pest on the scene – guava moth, a native Australian that probably blew over the ditch and which, since 1997, has been spreading from Northland down the country. This tiny moth creates havoc in the orchard, infesting a very wide range of fruit, including citrus, guava, feijoa, stonefruit, some pipfruit and even macadamias.
The reason it is hard to control is that soon after the eggs are laid on the fruit, the larvae drill into it and are therefore impervious to most sprays. Often the fruit will become infected with secondary diseases, making them completely inedible. Fruit will often fall off before it is ready and once it hits the ground the larvae move to the next stage, which is pupation in the soil or leaf litter under the tree. As yet, there don’t seem to be many natural predators for this pest, so unlike in Australia where it is a minor issue, over here it causes significant fruit loss.
Limited control is achieved by picking up, or raking out and destroying (a mower works well) any fruit that have fallen under the tree. It’s important to do this regularly, weekly if not daily, if you want to reduce the numbers. Unfortunately, the moth seems to be active pretty much year-round, moving from crop to crop as each crop comes to ripening stage, so this type of control will need to occur year round also to have any effect.
Particularly precious fruit can be covered in curtain netting or similar while still green, although obviously this will be impractical for large trees with multiple small fruit. There are pheromone traps available to trap male moths, although in my experience these are nowhere near as effective as the ones used against codling moth.
A helpful neighbour recently sent me a link to an article that has a very clever and cheap invention using solar-powered garden lights which may prove to be the best control yet.
A commercial trap produced by ecotrap.co.nz has a similar mode of operation and might be useful for people that are less handy or have less time to make traps. Again, these should work pretty well and as someone who fits both of these categories, this is probably the option I’ll take this year.
Hopefully a combination of these traps and picking up fallen fruit will have some impact on the numbers. It’s an unpleasant surprise to be faced with one of these grubs when you’re halfway through a fruit!