Lucerne use in NZ
Lucerne is used extensively for making hay and feeding stock animals in dry parts of New Zealand. As climate change warms and dries New Zealand, lucerne will become a more important feed source.
About alfalfa weevils
The native range of this weevil is parts of Africa, Europe, and Asia. It's now spread to North America, Japan, Australia, and some Pacific islands. The alfalfa weevil could establish in warm and dry places across New Zealand.
There are other pests commonly called alfalfa (or lucerne) weevil present in New Zealand. But this species, Hypera postica, is not here. In America, it is called the alfalfa weevil because alfalfa is another name for lucerne.
Global distribution of alfalfa weevil
Why this weevil is a problem for NZ
This weevil is the biggest insect threat to lucerne pasture. The weevil and its larvae eat the leaves and growing tips of the lucerne plant. This stunts its growth and reduces crop yield.
The weevils are good fliers and can fly 15km to 25km. They could spread easily if they got to New Zealand.
How could it get here
The weevil spends most – if not all – of its life in lucerne pasture. However, it has been found on many other hosts, including clover, potatoes, beans, and lettuce.
MPI has strict measures in place to limit the chances of alfalfa weevil coming to New Zealand. While it's unlikely this weevil could get here, it could cause major damage to our lucerne pasture if it did arrive.
How to identify alfalfa weevil
There are native species of weevils that eat lucerne. Unusual damage to your lucerne crop will be the most obvious sign. Larval feeding can look like frost damage.
Adults
Adult weevils:
- are about 3mm to 6.5mm long
- are coloured brown to black
- can fly (unlike some other weevils).
An adult alfalfa weevil.
Image: Creative Commons license, Stanislav Snäll, The Naturalist
Eggs
The eggs of alfalfa weevils are:
- oblong
- yellow, changing to brown when they're about to hatch
- 0.5mm long and 0.3mm to 0.5mm wide
- laid singly or in groups of up to 40 eggs
- found inside hollow stems of lucerne or clover, or on leaves or buds of lucerne.
Larvae
The alfalfa weevil has 4 instars (growth stages). In the 4th and last stage the larvae are:
- 7mm to 10mm long
- slightly curved
- mostly green.
Alfalfa weevil larva on a plant.
Image: Creative Commons license, Clemson University – USDA Cooperative Extension Slide Series
Pupae (stage between larva and adult)
- Olive green.
- 4mm to 6mm long.
If you think you've found alfalfa weevil
- photograph it and its damage
- capture it (if you can)
- call 0800 80 99 66
Note: This information is a summary of this pest's global distribution and potential impacts on New Zealand.
