The 2013/14 soybean growing season has been challenging for many growers with very low rainfall and high temperatures until late March. Crop stress was sometimes wrongly attributed to insect pests although a number of crops were infested with more unusual pests such as etiella. The high temperatures also increased the impact of lucerne crown borer in infested crops.
Background: Significant etiella outbreaks have recently been reported in soybeans and mungbeans on the Darling Downs, in the South Burnett (SE Qld) and in the Moree and NorthernRivers regions of NSW. In some soybean crops on the Downs, 100% of plants were infested and 72% of axilliary buds damaged to varying degrees. These outbreaks are similar but more widespread than… Read more »
An estimated 4,000 ha of soybeans near Casino in Northern NSW have been affected to varying degrees by soybean stem fly (Melanagromyza sojae) , a pest rarely seen in damaging numbers in Australia. Damage in many Casino crops is confounded by the presence of charcoal rot, a disease which blocks the plant’s vascular (xylem and phloem) tissue and causes similar… Read more »
Etiella (Etiella behrii) larvae have been observed in significant numbers (up to 10 larvae per square metre) in vegetative soybean crops in the Cecil Plains/ Pampas regions of the Darling Downs, and in low numbers (<1/sqm) in a DAFF soybean trial at Kingaroy. These infestations are likely due to the current hot and dry seasonal conditions which historically favour increased… Read more »
High soybean looper (Thysanoplusia orichalcea) populations (20-40/m2) have been reported in many regions in flowering and podding soybeans. While soybeans can tolerate 33% defoliation with no yield loss during the vegetative stages, their defoliation tolerance slips to 16% during podset/early podfill. Consequently, consider taking action if high looper populations are threatening your crop. Large soybean looper (38 mm). Note the tapered… Read more »
Noticeable numbers of grass blue butterfly larvae (Zizina labradus) have been observed in young soybean crops in the Wide Bay Burnett. While the small green larvae (maximum length 10 mm) may be difficult to see in the crops, the damage they cause is very obvious. Grass blue butterfly larvae feeding results in windowing of the leaves (this is mostly cosmetic)… Read more »
While soybeans are more likely to be attacked by helicoverpa from flowering onwards, severe infestations can occur as early as the seedling stage. In recent years, severe early infestations have been reported on the Downs and in the coastal Burnett with the affected crops experiencing significant yield losses. The latest published thresholds for helicoverpa in vegetative soybeans (Rogers and Brier,… Read more »
Field crickets High numbers of field crickets have been reported across the Darling Downs in the last couple of weeks, with some large aggregations of adults attracted to lights at night. Are these crickets doing damage to crops? The answer may well be yes. .
Soybean moth Aproaerema simplexella is a very common pest of soybeans but is usually only present in very low numbers. This season high numbers of moths and caterpillars were found especially in the Wide Bay Burnett region with some fields sustaining extensive damage. Similar leaf miners attack many horticultural crops, but are species other than A. simplexella. Weed hosts of… Read more »
The new economic threshold for Helicoverpa in vegetative soybeans is 8 larvae per sqare metre and replaces the old 33% defoliation threshold. The new threshold is based on field trials conducted by John Rogers (formerly with DPI&F at Kingaroy). These field trials show that approximately 7.5 larvae per square metre can be tolerated with no yield loss, but that severe… Read more »
