What else to look out for?

Crops approaching swathing and harvest remain prone to pests as grain contaminants. These can be controlled culturally. There are also some summer strategies to manage these pests next season

 

Bronzed field beetle adult emergence

Bronzed field beetles (Adelium brevicorne) were particularly abundant and damaging this year in some areas of southern NSW and northern Victoria during autumn and early winter. Adult beetles from these infestations started to emerge from mid October and will begin to accumulate under, and in, windrows. The flightless beetles, which grow to about 11 mm with a shiny black to bronzed appearance, can become grain contaminants. We advise that, in pest prone areas, windrows are harvested as soon as possible, preferably through the hottest part of the day, which will reduce beetle loads. Click here for images and information on bronzed field beetles.

When growers are planning for the following cropping season, it is also worth noting that the next generation of the pest can be controlled in summer. Trials in WA have shown that removal of much of the surface plant material in February (where it is considered to be a suitable practice) will reduce or eliminate bronzed field beetle by preventing egg-laying. This may be achieved through cutting and baling, grazing or burning.

 

Rutherglen bugs coming in from weeds

Rutherglen bugs (Nysius vinitor) are native insects that attack a wide range of weeds and crops in the warmer months. They can arise from weeds beneath a crop, or migrate into the crop on warm northerly winds. They are well adapted to dry warm weather and are often most damaging to moisture-stressed plants. They can invade windrows in vast numbers, searching out the last remnants of green plant material. Consequently, adults and nymphs can become a grain contaminant when in high numbers. Highest numbers of Rutherglen bugs are often observed along crop perimeters. Populations will increase with the warmer weather conditions and can reach damaging levels very quickly.

Check crops over the coming weeks, particularly canola, linseed and sunflowers. Contamination can be minimised by attaching screens to headers or by harvesting at night. As the Rutherglen bugs can readily re-invade a sprayed area, insecticide application will not guarantee a clean sample. Click here for images of Rutherglen bugs and here for an overview of Rutherglen bug management in canola.

 

Summer ‘green bridges’ and aphids

Many summer weeds are hosts of crop pests and the viruses they sometimes carry. For example brassica plants (such as the turnip weeds, wild radish, mustards and Lincoln weed) are not only persistent in the ‘green bridge’ but are preferred hosts for green peach aphid (Myzus persicae - GPA) and Beet Western Yellows Virus (BWYV). BWYV has an extraordinarily wide host range of summer weeds and pasture species.

Controlling these host plants in the vicinity of next years canola and legume crops is an important tactic that should lesson the likelihood of GPA and BWYV next season, especially if late summer rains re-occur, and early sowing is undertaken. The same principle applies to the summer grass hosts of cereal aphids and Barley Yellow Dwarf Virus (BYDV). Applying herbicides to weeds and volunteer plants at sowing or after may be too late to prevent the movement of pests and diseases into the emerging crop. For more information see GRDC GreenBridge.

 

Acknowledgements

We thank the SARDI team, particularly Bill Kimber, for contributions to this article.