Crop rotation a useful tool to manage crop pests

Date:03-11-2011

Crop rotation has proved to be an effective means to help minimise the impact of mite pests on certain crops.

The findings from a two year trial at the Department of Agriculture and Food’s Esperance Downs Research Station was profiled in a paper at the Agribusiness Crop Updates, supported by the Grains Research and Development Corporation (GRDC).

The results from the trial, also funded by GRDC, showed the pest pressure of mites was influenced by changing the sequence in which the crops were sown.

Department entomologist Svetlana Micic said the information would help farmers to reduce their reliance on chemical controls and avoid the risk of pesticide resistance.

"There have already been reports of redlegged earth mite resistance to commonly used synthetic pyrethroids, which are proving difficult to control in bare ground prior to seedling emergence,” Ms Micic said.

"While Balaustium mites are not resistant, they are more tolerant of SPs than blue oat mites or non-resistant redlegged earth mites and can be difficult to control.”

The trial examined the effect of rotations of canola, wheat, barley, lupins and pastures on pests and beneficial invertebrates.

The results showed that canola could be planted as a break crop after a pasture paddock to set up a cereal rotation – so long as the mites were effectively controlled in the original pasture crop.

"Canola is the crop most sensitive to mite damage in the seedling stage,” Ms Micic said.

"Pasture has the highest mite pest pressures but it is possible to use canola as a break crop after pasture, if mites have been controlled in the pasture phase and insecticidal seed dressings are used.”

Ms Micic warned growers to stay on top of weeds in the crop phase to make sure the mite risk remained low.

"Many of the weeds that occur in crops are considered to be part of the plant compositions of pastures,” she said.

"So if there is a good germination of weeds prior to crop germination then there is potential for high numbers of Balaustium mite and earth mites to occur and cause damage to emerging crops.”

The trial also showed that canola could be planted after cereals but there was an increased risk of Balaustium mite numbers.

"Crops planted post cereals will have decreased pest pressures from earth mites but may have higher pest densities of Balaustium mite,” Ms Micic said.

"Balaustium prefer grasses and cereals but plant death is rare and cereals can outgrow the damage. As a result, the mites that survive into the following year may pose a risk for canola or lupin crops.”

Source: seed quest