[ASC-media] Grubs' passion for plastic causes water loss

joanne.finlay at dpi.nsw.gov.au joanne.finlay at dpi.nsw.gov.au
Thu Sep 27 02:28:53 CEST 2007


NSW Department of Primary Industries
FOR IMMEDIATE RELEASE

Grubs' passion for plastic causes water loss 

Research by the NSW Department of Primary Industries (DPI) has found that 
a small white grub is responsible for water leaking from sub-surface drip 
irrigation pipes used by some lucerne growers. 

The Australian Entomological Society 38th annual scientific conference 
held this week in Victoria was told there had been many suspects in the 
hunt for an explanation for small holes in the leaking pipes. 

NSW DPI entomologist, Dr Adrian Nicholas, said ants, African black beetle, 
crickets, mice and physical wearing of the plastic piping have all been 
blamed, however laboratory experiments have confirmed the culprit is the 
larvae of the Whitefringed weevil.

Dr Nicholas says experiments using glass observation chambers show that 
the Whitefringed weevil larvae, which are 13mm long and 4mm wide, bite or 
chew through the pipe using two dark brown pincers.

Sub-surface drip irrigation has been an important advance for growers 
because it improves productivity, ensures efficient use of water and 
reduces labour costs.

However when lucence is grown, the thin walled irrigation pipe or tape is 
frequently damaged, with tiny 1-2mm holes appearing which are surrounded 
by distinctive perimeter markings.

Dr Nicholas said: ?For growers, the grubs? passion for plastic is a real 
problem. There can end up being hundreds of holes?. 

Because the affected pipes are buried underground, growers have to take an 
educated guess about the location of the holes. They need to seek out the 
areas where the lucerne plants are especially lush and dig down to make 
repairs. 

The problem is that they have to track down all the holes in the 
irrigation pipe
to restore water pressure, and ensure the even distribution of water 
throughout the irrigation system.
 
To solve the chewed-pipe riddle, Dr Nicholas monitored the activity of the 
larvae in slim glass chambers containing soil, carrot and irrigation pipe 
set up in laboratories at the Tamworth Agricultural Institute.

?It was not until we identified the right environmental conditions that 
the larvae started moving freely around the chamber. 

?As soon as they did, they moved to the plastic pipe and started biting it 
and causing damage that was consistent with that seen on grower 
properties.?

The Whitefringed weevil is a well known pest of lucerne. The larvae attack 
the roots of lucerne plants causing significant yield loss and sometimes 
death of the plant.

Media inquiries: Joanne Finlay on (02) 6391 3171, 0428 491813 or 
joanne.finlay at dpi.nsw.gov.au

 
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