AgResearch scientist Colin Ferguson, of Invermay Agricultural Centre, said traditional methods of control, such as insecticide, could aggravate the problem and lead to higher costs in the long term.
''Insecticide used to be very cheap and was very effective in killing the population,'' Mr Ferguson said.
''It's not necessarily the best way to go now.''
The use of insecticides should be reserved for when a severe outbreak of grass grub occurred, he said.
Using nature's own biological controls and maintaining pasture health was the best form of protection against severe damage.
Bacteria which maintain grass grub at a sustainable level were naturally present in the soil, as long as there was a population of grass grub to sustain them, he said.
Once the grass grubs were killed, the bacteria died and the pasture would be at risk of an outbreak of grass grub in two or three years.
''We have to change farmers' thinking about how they manage the problem and create some sustainability in their practices,'' he said.
A larger problem could develop if insecticide was used incorrectly.
''The danger is if you use it at a rate lower than what is recommended,'' Mr Ferguson said.
''Over six or seven generations they become more tolerant to the insecticide.''
Mr Ferguson has carried out research, in conjunction with the Clutha Agricultural Development Board, on farms in Tapanui and Hindon.
One of the more striking findings of the research in Tapanui was the effectiveness of urea in treating the problem, he said.
While it did not kill the grass grub effectively, it did keep the pasture in good health despite the pest and the more nutritious the pasture was, the less grass grub would have to eat to fill up.
- Timothy Brown
Grass grub
- Grass grub (Costelytra zealandica) is a New Zealand native; larvae of the brown beetle, a type of chafer beetleGrass grub are soil-dwelling grey/white grubs up to 15mm long with tan coloured heads.
- Typically found lying in a c-shape.
- Feed on the roots of many pasture species and other plants.
- Damage occurs in discrete patches in pasture.
- These patches initially appear more yellow than surrounding pasture and plants are pulled easily from the ground.
- patches feel soft underfoot and are easily pugged.
Treatment and dose Grass grub per square metre on May 30 Standing dry matter on May 30 (kg per ha)
Untreated pasture 378 1270
Diazinon (insecticide) applied at 11kg per ha 22 2657
Urea (nitrogen) applied at 00kg per ha 310 1846
Two strips of pasture within a paddock were treated using different controls, a control strip was left untreated. The treatments were applied on March 15 and the strips were assessed on May 30. The starting population was 521 grass grub per square metre. Note: Natural mortality accounts for the drop in grass grub population on the untreated pasture.