PestFacts Issue 9, 2018
The Etiella () degree-day model predicts the timing of the onset of peak flight activity when the cumulative number reaches the target value of 351. The model predictions for degree-day accumulations based on current and 7-day forecast temperatures indicate that Etiella flights have commenced near Cleve (376) and Roseworthy (366), and indicate that peak flights are expected to commence in the next week around Cummins (327), Kadina (318), Lameroo (322), and Keith (310), and in the next 2-3 weeks around Horsham (270).
Large numbers of diamondback moth (), Plutella xylostella, larvae have been detected in mid-late flowering canola in patchy areas around Mount Hope on the west coast of Eyre Peninsula (> 100 grubs per 10 sweeps; but Mount Hope overall average is < 100). Low-moderate numbers were also found around Elliston (30-50 grubs per 10 sweeps) and Calca (1-8 per grubs per 10 sweeps). The numbers observed fall below treatment threshold guidelines for mid-late flowering canola (> 100 larvae per 10 sweeps), however populations in all districts are expected to increase during coming weeks as warmer conditions increase development rates.
This week (19th September to 27th September), the moth trapping network detected large flights (>200 individuals) of the native budworm (), Helicoverpa punctigera, at Mannanarie and Streaky Bay. Moderate flights (30-200 individuals) were observed at Cummins and Port Broughton, and light activity detected at Naracoorte, Yeelanna and Cleve (Figure 1). Numbers of the cotton bollworm (), H. armigera, were generally low, except in Cummins, where moderate flights were observed.
Based on these flight dates, and long term average temperatures, the target size of larvae for treatment (2-3rd instars, 10-15mm in length) should be present during the following dates: Mannanarie – 16th to 30th Oct; Streaky Bay – 12th to 24th Oct; Cummins and Yeelanna – 17th to 4th Nov; Port Broughton – 14th to 27th Oct; Cleve – 14th to 29th Oct; Keith and Naracoorte – 20th to 8th Nov.
Low numbers of larvae were observed in canola crops around Jamestown (<5 mm in size), near Kadina (<5 mm in size), and western Eyre Peninsula (5-10 mm in size)
Large numbers of cabbage aphid (), Brevicoryne brassicae, colonies have been detected on late flowering canola around the Tumby Bay area, where 40% of plants were affected in some fields. Canola is particularly susceptible to aphid damage during bud formation to early flowering, and the impact on yield declines substantially after late flowering.
Low numbers of cowpea aphid (), Aphis craccivora, have been observed in vetch in the mid-upper North, upper Yorke Peninsula, lower Eyre Peninsula and South-East. Cowpea and bluegreen (), Acyrthosiphon kondoi, aphids were observed in lentils on the upper Yorke Peninsula and the South-East, and green peach aphid (), Myzus persicae, was observed in canola around Loxton.
Blue oat mites (), Penthaleus spp., have been observed on the lower leaves of cereals crops on the Eyre Peninsula near Cummins. Lucerne flea (), Sminthurus viridis, and redlegged earth mite (), Halotydeus destructor, activity has been observed in low numbers on lentils near Kadina.
The pea weevil model predicts that the invasion of pea crops by pea weevil (), Bruchus pisorum, ended around September 21 in most districts. Hence any pea crops that were sprayed on or after about September 10 will have been protected from any late pea weevil colonization.
Sources of all reports: SARDI, Andy Bates (Bates Ag Consulting), Steve Richmond (Landmark), Nigel Myers (Cummins Ag), Chris Davey (YP Ag), Bryan Lynch (Elders), Adam Hancock (Elders), Lou Flohr (Byrne Ag Landmark), Chris Pearce (Landmark).