HAVING wrapped up seeding for the 2022 season, Western Australian graingrowers have turned their attention to other tasks, with the monitoring and controlling of pests and diseases high on the priority list.
In general, pest issues drop off the radar a bit over the cold winter period and ramp up as temperatures increase from August onwards.
However, that doesn't mean a few problem pests haven't reared their ugly heads across the agricultural region.
African black beetle
At Munglinup, African black beetle (ABB) adults and larvae were found by Farm and General agronomist Monica Field causing some damage to a wheat crop.
When crops are at the seedling stage, ABB adults and larvae can cause crop damage.
ABB adults are strong fliers but tend to colonise the same paddocks.
They are usually more common in higher rainfall areas closer to the coast and where there has been an abundance of summer perennial grasses such as kikuyu and couch.
ABB larvae are 'c' shaped, creamy-white with dark heads, have three pairs of legs on the thorax and can grow up to 25 millimetres long.
The adult beetles are 12-14mm long, cylindrical and glossy black in colour.
Department of Primary Industries and Regional Development (DPIRD) research scientist Svetlana Micic said large populations of ABB adults and larvae can chew cereals and perennial grass pasture plant parts that are below ground, resulting in bare patches.
"Adults chew plants at or just beneath ground level, leaving frayed parts and either chew right through the stem or ringbark bigger plants," Ms Micic said.
"ABB and their larvae are difficult to control as the beetles can come to the surface at night, but like their larvae, they predominantly feed underground.
"To be effective insecticide needs to penetrate the soil surface where the larvae and beetles are."
Cutworm caterpillars
Elders senior agronomist Peter Elliott-Lockhart recently found cutworm caterpillars causing damage to about 20 per cent of a wheat crop near Binnu.
At Wongan Hills, Elders senior agronomist Cameron Smith also found cutworms, but in various growth stages, causing patchy damage in a canola crop.
Cutworm caterpillars are up to 50mm long, hairless with a dark head.
DPIRD research scientist Cindy Webster said there were three main species of cutworm.
"Caterpillars with a pink tinge belong to the pink cutworm, Agrotis munda, which has caused widespread damage in agricultural areas north of Perth," Ms Webster said.
"The dark grey caterpillars of the bogong moth, Agrotis infusa, have been extremely damaging in most parts of the agricultural areas from time-to-time.
"Large numbers of patterned caterpillars belonging to different genera, Rictonis and Omphaletis, have also been found attacking cereals in agricultural areas."
The caterpillars hide in the soil during the day, often at the base of lopped plants or at the edge of the damaged patch.
They feed at or near ground level on all crop and pasture plants and are given their name because they often chew through leaves or stems giving a cut-off appearance.
"Similar to armyworm caterpillars, cutworm caterpillars are more likely to come into contact with insecticides applied in the late evening when caterpillars are actively feeding," Ms Webster said.
"Cutworm moths can fly large distances and favour bare or lightly vegetated areas for egg laying.
"Cutworm caterpillars are usually easily controlled with registered rates of synthetic pyrethroid chemicals."
European earwigs
Widespread crop damage from European earwigs in a canola crop near Wittenoom Hills was recently reported by Agronomy Focus senior agronomist Quenten Knight.
The crop was at the four-leaf stage and the European earwigs were stripping leaves and stems of entire plants.
European earwigs are an introduced species and a recurring pest on properties which can damage cereal, legume and oilseed crops.
Adult European earwigs range from 12-24mm long and have uniform brown bodies which are smooth and shiny with light brown/yellow legs, pincers (also called forceps) and shoulders.
"Crop residues on the soil surface increase European earwig survival and breeding, allowing large populations to build up during autumn and early winter and damage crops sown into the stubble," Ms Webster said.
"Earwigs have two breeding cycles per year - one breeding cycle occurs in late winter/early spring and a second in summer.
"When checking crops look for shredded leaf tips, or jagged holes in the leaves as this is typical of earwig damage."
In severe situations European earwigs can completely defoliate young seedlings leaving only stems or bare ground in patches.
This pest is hard to find during the day and it is best to look for European earwigs at night using a torch or by placing pitfall traps into the ground.
Ms Micic said insecticides, especially chlorpyrifos or alphacypermethrin applied at the highest registered rates, do have efficacy against European earwig as a contact only.
"However, European earwigs can be difficult to control as they hide under stubbles," she said.
"Sprays applied at night have worked better than sprays applied during the day as earwigs are more active at night.
"Baiting for European earwigs has provided better control for this pest than spraying, especially in paddocks with heavy stubble loads."
European earwigs should not be confused with native earwigs - native earwigs are also widespread and feed mainly on leaf litter and other organic material but are not known to damage crops.
Aphid and turnip yellow virus
Autumn and early winter is a crucial period of the growing season for early season green peach aphid (GPA) infestation and turnip yellow virus (TuYV) infection in canola.
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Aphid activity during the early part of the growing season generally increases the risk of spread of many other viruses in cereal and legume crops.
Ongoing trapping has been occurring at DPIRD focus sites in the Kwinana West, Albany and Esperance port zones.
DPIRD research scientist Benjamin Congdon said in the Albany port zone, high levels of aphid activity had been detected around Tenterden, including cabbage aphids carrying TuYV.
"Moderate levels of aphid activity have been detected around South Stirling and Amelup," Dr Congdon said.
"GPA has been detected around South Stirling, however no TuYV has been detected at these sites so far.
"Low levels of aphid activity have been detected around Cranbrook, Gnowellen, Ongerup and Monjebup, with GPA detected around Gnowellen, but TuYV has been detected at these sites so far too."
In the Esperance port zone, minimal aphid activity has been detected around Mount Howick, Beaumont and Cascade.
No GPA or TuYV had been detected at these sites so far.
Moderate levels of aphid activity had been detected in the Kwinana West port zone around Clackline, Toodyay and Muresk.
Neither GPA nor TuYV have been detected at these sites so far and the DPIRD surveillance team will continue to provide updates throughout June and July.
Dr Congdon said growers were reminded to monitor their canola crops for aphids or plants displaying TuYV symptoms.
"If you see aphids colonising canola crops, or plants that look symptomatic that you are concerned about, they can be tested for the presence of TuYV through the department's diagnostic laboratory services - Pathology Services," he said.
"To reduce the risk of resistance to any insecticide group, it is important to rotate insecticides with different modes of action, avoid the use of broad-spectrum insecticides and apply appropriate insecticides only after careful monitoring and correct identification of species."