Lucerne crown borer on the move in soybean in 2015

Lucerne crown borer (Zygrita diva) (LCB) is caus­ing severe dam­age in a num­ber of soy­bean crops in the Bund­aberg region of SE Qld, and on the North Coast region of NSW. In some cases up to 75% of plants are infested and early plant death is evident.

Dam­age seems to be worse in the early (November-planted) crops which were sown in or adja­cent to pad­docks planted to soy­beans last year.

Lucerne crown borer in early planted soybean at Bundaberg. Image by Simon Andreolli

Lucerne crown borer in early planted soy­bean at Bund­aberg.
Image by Simon Andreolli

In some early crops, lar­vae are already pupat­ing, with stem girdling and plant death occur­ring in crops that are only at the pod set stage. In these crops, it is likely that, after pupa­tion, emerg­ing bee­tles will re-infest the crop. The sec­ond round of pupa­tion will most likely not occur until pods are fully filled, but this could be ear­lier if heat wave con­di­tions return.

Once only a spo­radic pest in some sea­sons, LCB num­bers seem to be increas­ing in coastal soy­bean grow­ing regions. How­ever, because of its biol­ogy and feed­ing behav­iour, con­trol is difficult.

Biol­ogy and Dam­age
LCB over­win­ter as pupae in soy­bean stem stub­ble. Bee­tles emerge in the spring/early sum­mer. They are not strong fliers, and hence soy­bean planted in pad­docks that had soy­bean the pre­vi­ous sea­son (or adja­cent to such pad­docks) are at greater risk.
The prox­im­ity to other LCB hosts such as lucerne and phasey bean is also a risk factor.

Adult crown bor­ers lay eggs in a slit in the stems of young plants. The hatch­ing lar­vae then tun­nel imme­di­ately into the stems where they feed on the stem pith, i.e. not the vas­cu­lar tis­sue. Lar­val feed­ing in the pith does not affect yield, but the dam­age is caused when lar­vae com­mence pupa­tion. Lar­vae gir­dle (inter­nally ring­bark) the lower stem to plug the pith tun­nel and pupate in the tap root.

Stem girdling at pupation

Stem girdling at pupation

LCB dam­aged pith turns a red brown to orange colour, but be aware that tun­nelling by other pests can cause a sim­i­lar discolouration.

Pupa­tion can be trig­gered as crops dry down or through heat stress, espe­cially in early planted crops. In crops where pupa­tion occurs when pods are not yet set or filled, yield losses can be severe. Yield losses are far lower if pupa­tion occurs when pods are nearly or fully filled, pro­vided that the dam­aged plants do not lodge before harvest.

Chem­i­cal con­trol
Crown borer lar­vae can­not be con­trolled with insec­ti­cides. Because they feed on the pith inside stems, they can­not be reached even by sys­temic insec­ti­cides or those with ‘upward xylem mobil­ity’ such as Altacor.

Lucerne crown borer adult, three barred type

Lucerne crown borer adult, three barred type

Although the adult crown borer may be sus­cep­ti­ble to a num­ber of insec­ti­cides, they invade crops over an extended period of time which would require mul­ti­ple sprays to give sat­is­fac­tory pro­tec­tion. Please note that NO insec­ti­cides are reg­is­tered against LCB lar­vae or adults.

Cul­tural control

On a long-term area-wide basis, cul­tural con­trol offers the best means of man­ag­ing this pest effec­tively and sus­tain­ably, with­out cre­at­ing other pest prob­lems. Spe­cific strate­gies include:

Crop rota­tion: Do not plant soy­beans in the same ground as last year. Where pos­si­ble, plant crops as far as pos­si­ble from last year’s plant­i­ngs. Avoid plant­i­ngs into or close to lucerne. Crop rota­tion is also a key strat­egy to reduce the build-up of inocu­lum of soil borne dis­eases such as char­coal rot and pho­mop­sis.
Weed con­trol: Elim­i­nate weed hosts such as phasey bean, ses­ba­nia and budda pea.
Time of plant­ing: Avoid early plant­ing as these crops have a greater risk of early dam­age.
Post-harvest cul­ti­va­tion: Aim to split stems and roots and bury stub­ble to a depth of at least 10 cm. Split­ting the tap roots destroys LCB’s over­win­ter­ing refuge, and bury­ing stub­ble reduces the emer­gence of bee­tles in the fol­low­ing spring. This is a key strat­egy to attack the pest at its most vul­ner­a­ble stage. Although cul­ti­va­tion opposes the zero till phi­los­o­phy, strate­gic cul­ti­va­tions may be needed to not only man­age this pest but also reduce the inocu­lum build-up of soil borne dis­eases such as char­coal rot and pho­mop­sis.
Min­i­mize lodg­ing: Higher sow­ing rates will lead to denser plant stands that can sup­port gir­dled plants and reduce lodg­ing.
Min­imise water stress: In irri­gated crops, do not allow crops to become stressed. Stress can trig­ger early plant girdling. In dry-land crops, poten­tial crop stress is a major rea­son to avoid those early plant­i­ngs in which plants grow much larger, and hence need more water.
Har­vester set up: Ensure har­vester set-up allows for pick­ing up any side branches that have drooped or plants that have lodged due to LCB damage.

Other stem tun­nelling pests
Other pests can also be found tun­nelling in soy­bean stems. In recent sum­mers, sig­nif­i­cant etiella out­breaks were reported in veg­e­ta­tive soy­beans in the Bur­nett and Dar­ling Downs in Qld, and in NW NSW. Major soy­bean stem fly out­breaks were reported the North­ern Rivers of NSW in 2013 and lesser num­bers in 2014. Stem fly were detected in rel­a­tively low num­bers in the South Bur­nett in 2014, and have recently been reported in the Bur­dekin. A sig­nif­i­cant stem fly out­break was reported near Mackay in 2009. Both etiella and stem fly cause sim­i­lar dis­coloura­tion of the pith, but their lar­vae are very dif­fer­ent. Etiella lar­vae are pale green/cream with pink stripes, while soy­bean stem fly lar­vae are small mag­gots with­out a dis­tinct head capsule.

Use the search func­tion on the Beat­sheet to find more infor­ma­tion about Etiella and Soy­bean stem fly.

Arti­cle by Hugh Brier and Kate Charleston

Posted in grains, pulses, soybeans | Leave a comment

Overview of the green peach aphid and beet western yellows virus outbreak in southern Australia (2014)

In the autumn and early win­ter of 2014, large areas of canola in South Aus­tralia, Vic­to­ria and south­ern NSW were heav­ily infested with green peach aphid (GPA), and many of the infested crops tested pos­i­tive for beet west­ern yel­lows virus (BWYV). GRDC TV  has com­piled a series of three videos that dis­cuss what fac­tors con­tributed to the GPA out­break, and key man­age­ment issues that have been highlighted.

Whilst GPA has not been a major pest in canola crops in the north­ern region, it is often present in low den­si­ties in veg­e­ta­tive — flow­er­ing crops. Con­se­quently the lessons that are being learned from the south­ern region out­break in 2014 may be crit­i­cal to the man­age­ment of GPA and BWYV in the north­ern region in sea­sons that favour GPA outbreaks.

Posted in aphids, canola | Leave a comment

Grass blue butterfly damage to navy bean pods

Grass blue butterflies

Grass blue butterflies

The lar­vae of the grass blue but­ter­fly (Ziz­ina labradus) are nor­mally minor leaf feed­ing pests, although they can be dam­ag­ing in seedling crops where they attack ter­mi­nals and axil­lary buds.

Soy­beans are their favoured sum­mer pulse host, but they can also attack other pulses includ­ing navy beans.

Recently, grass blue but­ter­fly lar­vae have been observed caus­ing major pod dam­age in a crop of navy beans. Small lar­vae fed ini­tially on the leaves, where they caused only very minor dam­age. How­ever, larger lar­vae sud­denly switched to attack­ing pods in the early pod­fill stage. This behav­iour is highly unusual and has resulted in major pod damage.

Typical leaf damage caused by grass blue butterfly larvae

Typ­i­cal leaf dam­age caused by grass blue but­ter­fly larvae

Pod dam­age was char­ac­ter­ized by mul­ti­ple holes per pod, made by indi­vid­ual larva. Some holes were fairly shal­low, but oth­ers were deeper and reached the seeds. Many of the holes secreted sap and the edge of the holes turned black. These holes are likely to result in the weath­er­ing of those seeds not yet dam­aged directly.

The ‘mul­ti­ple holes per pod’ dam­age looks very much like that caused by heli­cov­erpa in Faba beans. A pos­si­ble expla­na­tion is that lar­vae bor­ing inwards are ‘suf­fo­cated’ by sap ooz­ing into the holes, forc­ing them to retreat and to try again, to the detri­ment of the pods appear­ance and its capac­ity to pro­tect the seeds from weathering.

Damaged navy bean pods

Dam­aged navy bean pods

Close-up of navy bean pod damage caused by grass blue butterfly larvae

Close-up of navy bean pod dam­age caused by grass blue but­ter­fly larvae

Man­ag­ing Grass Blue
No pes­ti­cides are reg­is­tered specif­i­cally against grass blue but­ter­fly in sum­mer pulses. Grass blue lar­vae will be con­trolled by insec­ti­cides tar­get­ing other cater­pil­lars such as heli­cov­erpa. Dipel or Bt  (Bacil­lus thuringien­sis) is also effec­tive against grass blue and although lar­vae do not die imme­di­ately, they stop feed­ing. Thor­ough cov­er­age is essen­tial with Bt (at least 100L water/ha) and should tar­get small lar­vae feed­ing on leaves, before they move to the pods. Look for the early warn­ing signs, in this case, the adult but­ter­flies flut­ter­ing over the crop in ques­tion, fol­lowed by numer­ous small leaf win­dows made by small larvae.

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Etiella alert for mungbean on the Darling Downs, Goondiwindi and Northern NSW growing regions

A sig­nif­i­cant etiella out­break was recently reported in pod-filling mung­bean in the Moree region of North West­ern NSW. In this par­tic­u­lar crop, it is esti­mated that etiella lar­vae have infested pods on 50% of plants. Etiella eggs, at low den­si­ties, were also recently observed in an early flow­er­ing crop near Bun­gunya (west of Goondi­windi, Qld).

Etiella (Etiella behrii) is also known as the Lucerne seed web moth. Ellip­ti­cal shaped eggs are laid on pods and flow­ers or under bracts and are very hard to detect. Newly-hatched lar­vae bore straight into pods leav­ing a near-invisible entry hole. The lar­vae are pale cream/orange when small while larger lar­vae are cream or green with pink stripes. Lar­vae near­ing pupa­tion often have a pink tinge all over. Etiella can be dif­fer­en­ti­ated from bean pod­borer which has dis­tinc­tive black spots.

Etiella moth - 12 mm long

Etiella moth — 12 mm long

Etiella eggs (0.6 mm) on rattle pod

Etiella eggs (0.6 mm) on rat­tle pod

Medium etiella larva (5 mm), with typical pale green colour and pink stripes.

Medium etiella larva (5 mm), with typ­i­cal pale green colour and pink stripes.

Dam­age at bud­ding and flow­er­ing
Etiella lar­vae feed on buds and flow­ers, dam­ag­ing these struc­tures. Larger larva may also tun­nel into plant stems. Major infes­ta­tions in crops at the budding/flowering stage will likely reduce yield how­ever there are no val­i­dated thresh­olds for etiella at this crop stage. For this rea­son, researchers in GRDC’s North­ern Grains IPM project would wel­come any reports of, and sam­ples from cur­rently infested crops and again at harvest.

Etiella damage to mungbean buds.  Look for dead buds, fine webbing and frass

Etiella dam­age to mung­bean buds. Look for dead buds, fine web­bing and frass

Etiella damage to mungbean stem

Etiella dam­age to mung­bean stem

Crops with ade­quate mois­ture will most likely com­pen­sate for low to mod­er­ate lev­els of early dam­age but major dam­age would most likely reduce crop yield.
Pre­lim­i­nary data in soy­bean sug­gests this crop can com­pen­sate for early stem dam­age by set­ting addi­tional side branches. How­ever, it is unknown how well, or if mung­bean can com­pen­sate for this type of damage.

Dam­age at late pod-fill
Late dam­age at the pod-fill stage will reduce yield because of the direct con­sump­tion of seeds. Data from soy­bean shows each etiella lar­vae con­sumes only 0.2 gram which is equiv­a­lent to one soy­bean seed. Because mung­bean seeds are smaller, it is likely that each etiella will con­sume more seeds, pos­si­bly as many as 4 to 5. How­ever, the yield loss in mung­bean is likely to be sim­i­lar to that in soy­bean, which is 2kg/ha for every larva per square metre. This equates to a the­o­ret­i­cal thresh­old of 30 to 40 larvae/m2. This is a very high thresh­old but keep in mind that etiella lar­vae are much smaller than heli­cov­erpa lar­vae and there­fore con­sume pro­por­tion­ally less. Also remem­ber that this is a the­o­ret­i­cal thresh­old as tri­als last year sug­gest that once lar­vae are inside pods, they are very dif­fi­cult if not impos­si­ble to control.

Large etiella larva (13 mm) in soybean pod.  Note pinkish colour typical of large larvae approaching pupation

Large etiella larva (13 mm) in soy­bean pod. Note pink­ish colour typ­i­cal of large lar­vae approach­ing pupation

Qual­ity issues
Qual­ity may be an issue if a sig­nif­i­cant num­ber of seeds only have par­tial dam­age, and they are not lost out the back of the header at har­vest. The risk of par­tial seed dam­age could increase in black pods where, as the seeds dry down, larva feed­ing could con­ceiv­ably slow down and lar­vae fail to reach full size by harvest.

Assess­ments of dam­aged sam­ples from infested mung­bean crops will enable researchers to mea­sure the impact of etiella dam­age on mung­bean seed qual­ity, and estab­lish thresh­old guide­lines. Researchers are also keen to eval­u­ate insec­ti­cides reg­is­tered in the crop against other pod-boring cater­pil­lars (heli­cov­erpa and bean podborer).

Etiella damaged mungbean pod with frass inside

Etiella dam­aged mung­bean pod with frass inside

Etiella damaged mungbean seeds

Etiella dam­aged mung­bean seeds

Any­one with sus­pected etiella dam­age,  please con­tact Hugh Brier, DAFF Kingaroy on 0428 188 069.


Posted in Etiella, mungbeans, pulses | Leave a comment

Bruchids infesting pulse crops in the field

There have been two reports recently of cow­pea bruchid activ­ity, with these pests infest­ing pulse crops in the field prior to har­vest. The first report con­cerned the cow­pea bruchid (wee­vil) Cal­loso­bruchus mac­u­la­tus in field peas from Goondi­windi. The bruchids were noticed at intake and con­tin­ued to breed in an untreated grain sam­ple post-harvest. This clearly indi­cated they were not pea wee­vils (bruchids) Bruchus piso­rum, which do not breed in stored grain.

Cowpea bruchid (weevil) adults (3mm) in field peas, harvested 16/10 Goondiwindi and noticed at intake on 17/10. They continued to breed in the seed sample.

Cow­pea bruchid (wee­vil) adults (3mm) in field peas, har­vested 16/10 Goondi­windi and noticed at intake on 17/10. They con­tin­ued to breed in the seed sample.

The sec­ond report was of the closely related Cal­loso­bruchus phase­oli, also known as cow­pea bruchids, in chick­peas at Moura. This is the first time this par­tic­u­lar species has been found in chick­peas in Queens­land although C. mac­u­la­tus has been fre­quently reported in this crop. The bruchids in chick­peas were dead at intake, most likely because the crop was frosted prior to har­vest in Sept 2014.

Bruchid damage in chickpeas from Moura, Central Qld.

Bruchid dam­age in chick­peas from Moura, Cen­tral Qld.

In view of these reports, it is rec­om­mended that grow­ers check their pulse crops in the field for seed dam­age and dur­ing har­vest by siev­ing grain. A sub sam­ple of grain at har­vest time should be kept in a con­tainer as a ref­er­ence sam­ple. Keep this in a warm ‘place’ to check for post-harvest breed­ing from unde­tected bruchid eggs or other life cycle stages. If the sam­ple is kept at around 30 °C and is still bruchid free after 30 days, it is almost cer­tainly clear of insects. This sam­ple serves as an early post-harvest warn­ing of bruchids present, but not detectable at harvest/intake. In all cases, always ensure insects are cor­rectly identified.

If a bruchid prob­lem is evi­dent, store grain in an aer­ated, seal­able silo. For spring and sum­mer pulse har­vest times, when bruchid detec­tions indi­cate a low level infes­ta­tion, under­take stan­dard aer­a­tion cool­ing pro­ce­dures for the first two weeks of stor­age to cre­ate uni­form mois­ture con­di­tions in the freshly har­vest grain. This puts the grain in a safe con­di­tion prior to seal­ing up the silo for fumigation.

Grain tem­per­a­tures should come down from 30 to 35°C at har­vest, to 20 to 23°C fol­low­ing aer­a­tion. Hav­ing used a pres­sure test to check the silo is gas tight, now con­duct a 10 day phos­phine fumi­ga­tion to kill all life stages of the bruchid infestation.

For more information:

Arti­cle by Hugh Brier and Philip Bur­rill
Images by Joe Wessels

Posted in Crops, mungbeans, pulses | Leave a comment

Watch for Rutherglen bugs moving from canola into neighbouring crops.

Ruther­glen bug (RGB) num­bers in canola stub­ble are again high in some fields. These infes­ta­tions pose a risk to neigh­bour­ing crops, either through dam­age to estab­lish­ing sum­mer crops or con­t­a­m­i­na­tion of unhar­vested win­ter crops. Both the canola and adja­cent crops war­rant mon­i­tor­ing for RGB infes­ta­tion and move­ment out of the canola field. If large num­ber of nymphs move into adja­cent fields with seedling sum­mer crops (cot­ton, mung­bean, soy­bean, sorghum, maize) they can cause the seedlings to dehy­drate and die from sheer feed­ing pres­sure (see video of RGB impact on a cot­ton seedling over a 4 day period).

In the event of high RGB num­bers, seed treat­ments will not pro­tect the seedlings from feed­ing dam­age, and plants on the field mar­gins may be killed. Before RGB will die from feed­ing on a seed treated seedling they have to feed, and the cumu­la­tive feed­ing dam­age of dozens of RGB can kill the seedlings.

Ruther­glen bug nymphs con­gre­gat­ing in bar­ley heads in a crop adja­cent to recently har­vested canola.

RGB may also pose a con­t­a­m­i­na­tion risk to neigh­bour­ing win­ter cereal crop at har­vest. RGB have been observed con­gre­gat­ing in the heads of a bar­ley crop adja­cent to canola. The first 50m of the bar­ley was infested with RGB num­bers drop­ping off fur­ther into the crop. Where crops are infested with RGB at har­vest, seg­re­ga­tion of the grain from the infested area may be war­ranted to avoid high lev­els of live insects in the load.

RGB may start mov­ing out of canola crops prior to har­vest, so mon­i­tor­ing sus­cep­ti­ble sum­mer crops adja­cent to both har­vested and stand­ing or windrowed canola is suggested.

Move­ment of RGB into bud­ding sun­flow­ers can also increase the risk of dam­age along the field edge clos­est to the canola.

If infes­ta­tions have a clear edge effect, there is an oppor­tu­nity to con­trol the RGB in the affected por­tion of the field only, rather than the whole field. RGB move­ment out of canola can occur over sev­eral weeks, so ongo­ing mon­i­tor­ing and repeated treat­ment of prob­lem areas may be required.


Watch a short video that shows the den­sity of RGB nymphs mov­ing out of the canola stubble.


RGB adults and nymphs on canola stubble.

RGB adults and nymphs on canola stubble.

Ruther­glen bug biology

Ruther­glen adults move into canola dur­ing flow­er­ing — pod­ding. Females lay eggs up to 400 eggs each into the soil, trash and around the base of the plant. The eggs are elon­gate, about 2mm in length. Eggs are white when laid, red­den­ing as the nymph devel­ops inside. First instar nymphs hatch in 5–10 days (shorter when warmer tem­per­a­tures). Over 3–4 weeks, the nymph moults 3–4 times before moult­ing to adult. Nymphs are dis­tin­guished from adults by the absence of wings. Later instar nymphs have vis­i­ble wingbuds.

Rutherglen adults (left) and nymphs (right)

Ruther­glen adults (left) and nymphs (right)

Posted in canola, cotton, Rutherglen bug | Leave a comment

Seedling thrips in spring mungbean crops

There have been sev­eral reports of seedling thrips in spring mung­bean crops in the Goondi­windi region. Seedling thrips (Thrips tabaci) are also known as win­ter cereal thrips or cot­ton seedling thrips. The thrips move out of win­ter cere­als when these start to dry off into new green spring growth such as mung­bean, navy beans or cot­ton. Spring planted crops, espe­cially those in close prox­im­ity to matur­ing cereal crops are at great­est risk. In most cases, early thrips dam­age does not trans­late to yield loss. How­ever if you fear an extended thrips inva­sion and you do spray, please leave some unsprayed strips to deter­mine if the spray was worthwhile.

Adult thrips are 2 mm long and are dark, cigar shaped and have nar­row feath­ery wings folded along their back. Lar­vae are smaller, lack wings and are pale.

Adult seedling thrips. Image by Lewis Wilson

Adult seedling thrips.
Image by Lewis Wilson

Dam­age symp­toms
Adult thrips can infest a seedling’s grow­ing point as soon as it emerges from the ground. In crack­ing soils, seedlings may even be infested before they emerge. Lar­vae feed inside veg­e­ta­tive ter­mi­nals. Pop­u­la­tions typ­i­cally peak within 4 weeks of plant emer­gence.
Thrips attack the seedlings grow­ing point and dam­age the embry­onic leaves. How­ever, in mung­bean, the dam­age is usu­ally not man­i­fested until the first tri­fo­li­ate leaves open. How­ever in some of the Goondi­windi crops, there also appears to be dam­age to the uni-foliate leaves. Dam­aged leaves can be severely dis­torted and dis­coloured and may resem­ble her­bi­cide (2,4-D) damage.

In most cases thrips dam­age is largely cos­metic and will not com­pro­mise yield or matu­rity. In a DAFF trial on the Downs, seedling thrips pop­u­la­tions peaked at over 6 per plant ter­mi­nal at 9 days after emer­gence (DAE), but crashed to less than 0.5 per plant by 37 DAE. Dam­age symp­toms on newly expanded tri­fo­li­ate leaves in untreated con­trol plots peaked at severe lev­els at 16 DAE but crashed to zero in new tri­fo­li­ate leaves by 37DAE as the crop ‘grew away’ from the early dam­age. In this trial and a similarly-infested crop at Kingaroy, thrips had no effect on yield or plant matu­rity (i.e. on time to flow­er­ing or har­vest), despite seedlings dis­play­ing severe leaf distortion.

Seedling thrips damage on the first true leaves in spring mungbeans at Goondiwindi. Image by Andrew Walker

Seedling thrips dam­age on the first true leaves in spring mung­beans at Goondi­windi.
Image by Andrew Walker

Seedling thrips damage to tri-foliate leaves in  spring mungbean

Seedling thrips dam­age to tri-foliate leaves in spring mung­bean. Image by Hugh Brier

How­ever if thrips from sur­round­ing cereal crops keep invad­ing mung­bean over an extended period of time, they could pos­si­bly impact on plant growth and ulti­mately yield.

Man­ag­ing thrips
In cold springs, where the mean tem­per­a­ture is below 18°C, slow plant growth and stunt­ing is often wrongly attrib­uted to thrips. Cool weather can how­ever exac­er­bate thrips dam­age while warm weather will help plants grow away from the dam­age hence the risks are higher in the cooler regions.

Mon­i­tor for thrips by check­ing the plant’s grow­ing points. A good hand lens should be used as the pest is very small. Grow­ing points can be sub­merged in alco­hol to dis­lodge the thrips.

There are no thresh­olds for seedling thrips in mung­bean. Thresh­olds in seedling cot­ton of 10 thrips (adult and lar­vae) and 80% dam­age to leaves may pro­vide a guide. Remem­ber that thrips dam­age to new leaves is inflicted in the ter­mi­nal before they emerge and expand. So spray­ing spray now won’t undo cur­rent dam­age but would pre­vent future dam­age. How­ever the pesticide’s impact may not be obvi­ous imme­di­ately, as leaves yet to emerge may have already been damaged.

Before imple­ment­ing any chem­i­cal con­trol, con­sider that thrips are also impor­tant preda­tors of spi­der mites, other thrips and small eggs.

Thrips can be con­trolled with dimethoate at a rate of 800mL/ha, under per­mit PER13155. Apply a nar­row band spray over the seedlings to reduce the impact on preda­tors such as spi­ders in the inter-row. In crops where there is an edge effect (more dam­age clos­est to the cere­als), con­sider only spray­ing the severely dam­aged pro­por­tion of the crop.

Seedling thrips leaf dam­age can be greatly reduced if dimethoate is applied within 3 days after plant emer­gence. Spray­ing after dam­age symp­toms are man­i­fested is usu­ally too late to reduce dam­age symp­toms, unless thrips keep invad­ing from sur­round­ing cere­als over an extended period of time.

No seed dress­ings are cur­rently reg­is­tered for thrips con­trol in mung­bean. If pos­si­ble, do not plant mung­bean crops adja­cent to win­ter cere­als. Avoid spring mung­bean plant­i­ngs in regions where cool spring weather is likely, as low tem­per­a­tures have a far greater impact on mung­bean growth than seedling thrips.

Mon­i­tor the out­come and com­pare with unsprayed strips
Where pos­si­ble, leave some unsprayed strips to see whether pes­ti­cide appli­ca­tion was really needed and how crops recover from thrips dam­age. It would also be use­ful to pho­to­graph tagged plants over time in sprayed and unsprayed parts of the crop to ascer­tain whether there is a vari­a­tion in time of flow­er­ing and matu­rity, and yield.

Please report any out­breaks to Hugh Brier on 0741 600 740 or 0428 188 069 or email:

For infor­ma­tion about thrips in seedling cot­ton visit the beat sheet arti­cle on seedling thrips in cotton

Arti­cle by Kate Charleston and Hugh Brier

Posted in Crops, mungbeans, pulses | Leave a comment

Leaf mining fly (Agromyzid) infestations in wheat in NW NSW and southern Qld

Agromyzid mine in wheat. Photo: Chris Teague. Landmark, Goondiwindi.

Agromyzid mine in wheat. Photo: Chris Teague. Land­mark, Goondiwindi.

Leaf min­ing caused by Agromyzid flies has recently been reported in wheat crops in the Goondiwindi/ Toobeah (late August) and Quirindi (late Sep­tem­ber) regions. Con­sul­tants reported their ini­tial impres­sion was that the dam­age symp­toms, pale stripes on the leaves, resem­bled old stripe rust infec­tions. How­ever on closer inspec­tion, the leaves were actu­ally a win­dowed with frass vis­i­ble inside the translu­cent dam­aged leaf tis­sue. When cut open, many of the ‘mines’ had small (1 to 1.5 mm) fly lar­vae chew­ing away. Small fly pupae (2 mm) were also found inside the dam­aged leaves.

Cereal leaf miner. Cerodontha sp (3 mm). Copyright: Jim Moore

Cereal leaf miner. Cerodon­tha sp (3 mm). Copy­right: Jim Moore

Agromyzid larva. Hugh Brier. QDAFF.

Agromyzid larva

Agromyzid_pupa. Hugh Brier. QDAFF

Agromyzid pupa










The leaf min­ing flies detected are in the Agromyzid group, which includes other pest species such as bean fly and soy­bean stem­fly (which don’t attack cere­als). At this stage, the species respon­si­ble has not been deter­mined. DAFF ento­mol­o­gists are cur­rently try­ing to rear adult flies from lar­vae in dam­age sam­ples as adults are much eas­ier to spe­ci­ate than lar­vae. How­ever it is most likely a native Agromyzid species, quite pos­si­bly Cerodon­tha aus­tralis. This is a com­mon species which also feeds on pas­ture, and which is usu­ally kept in check by native wasp par­a­sites in pad­docks not sprayed with dis­rup­tive insec­ti­cides. Note that Agromyzid par­a­sites were detected in the Quirindi samples.

There are no thresh­olds for Agromyzids in cere­als, but major out­breaks are uncom­mon, and the pest is most dam­ag­ing in seedling crops. Reports from Goondi­windi and Quirindi sug­gest the affected crops have grown out of the dam­age (no mines on new leaves) and that pes­ti­cide con­trol was not necessary.

DAFF ento­mol­o­gists, work­ing on a GRDC-funded project, are keen to doc­u­ment the extent of the cur­rent out­break and to con­firm the species. Accord­ingly if you have a sus­pected out­break, please con­tact Hugh Brier (0428 188 069),

Posted in winter cereals | Leave a comment

Recognising caterpillar pests of canola.

Canola showing signs of leaf-feeding caterpillar activity.

Canola show­ing signs of leaf-feeding cater­pil­lar activity.

As canola sets and matures pods, and spring tem­per­a­tures rise, there are a num­ber of cater­pil­lar pests that are active in this crop. Along with heli­cov­erpa there are dia­mond­back moth lar­vae (Plutella xylostella) and cab­bage white but­ter­fly lar­vae (Pieris rapae) in crops. It is crit­i­cal that you can dis­tin­guish the species, and be famil­iar with their respec­tive thresh­olds, in order to make sound deci­sions about whether con­trol is warranted.

Dia­mond­back moth (DBM), also com­monly called cab­bage moth, is a spo­radic pest in the north­ern region, and is prob­a­bly the species with which we are least famil­iar. This year, DBM num­bers are higher than have been seen for some years. DBM cater­pil­lars are typ­i­cally light green and grow up to 12mm in length. They are tapered at each end and wrig­gle vio­lently when poked. The uni­form colour, taper­ing and vio­lent wrig­gling are key dis­tin­guish­ing char­ac­ter­is­tics that you can use to sep­a­rate DBM from Heli­cov­erpa lar­vae. DBM moths are often vis­i­ble in a flow­er­ing crop, par­tic­u­larly in the evening.

Cabbage white butterfly larvae

Cab­bage white but­ter­fly larvae

Cab­bage white but­ter­fly lar­vae are eas­ily iden­ti­fied. They are round bod­ied, uni­formly green, and char­ac­ter­is­ti­cally look soft and downy. The adult but­ter­flies are pale yellow-white with a black spot on the forewing.

Watch a short video that shows how to dis­tin­guish DBM and heli­cov­erpa lar­vae.


DBM thresh­olds vary depend­ing on the stage of crop devel­op­ment and the risk to crop growth and yield, and are pre­sented in table 1 below. DBM lar­vae will feed on foliage, and on flow­ers and devel­op­ing pods. Once pods are mature, lar­vae will graze on the sur­face of pods caus­ing ‘win­dow­ing’, but rarely pen­e­trate pods and affect­ing yield.

Source: GRDC factsheet

Source: GRDC factsheet

No work has been done to com­pare the rel­a­tive effi­cacy of sweep­net and beat­sheet sam­pling. How­ever, I esti­mate that beat­sheet­ing 1 m of row (not a square metre), is approx­i­mately equiv­a­lent to 3 sweeps. There­fore, use the above thresh­olds for a 3m of row beat­sheet sam­ple (or divide by 3 if using a 1m row aver­age). If you want to work on a square metre basis, then there is approx­i­mately 3m of crop row (on 30cm row spac­ing), so use the same thresh­old value as for the 10 sweeps.

The Heli­cov­erpa thresh­old has not been val­i­dated for the north­ern region, so we are work­ing with the thresh­old estab­lished some years ago in the south/west of 5–10 lar­vae per 10 sweeps. Again, con­vert­ing sweeps to beat­sheet esti­mates described for DBM above.

There is no estab­lished thresh­old for cab­bage white but­ter­fly. This species is not known to be eco­nom­i­cally dam­ag­ing to canola.


DBM pop­u­la­tions can change quickly, and a deci­sion to treat should not be made on a sin­gle sam­pling occa­sion, unless num­bers are well above thresh­old and sig­nifi­ant dam­age to pods is evi­dent. Wind, rain and dis­ease can result in rapid decline in DBM pop­u­la­tions, and cool con­di­tions will slow activ­ity. Con­versely, warm con­di­tions can accel­er­ate pop­u­la­tion growth and lar­val feed­ing activ­ity. If DBM num­bers are approach­ing thresh­old, recheck the crop in 3–4 days to deter­mine what the pop­u­la­tion is doing.

Con­trol­ling DBM can be chal­leng­ing with some pop­u­la­tions in the south hav­ing resis­tance to syn­thetic pyrethroids. We don’t know what the resis­tance sta­tus of DBM is in the north­ern region canola crops, but it would be pru­dent to expect there to be some level of resis­tance. Other reg­is­tered options are Affirm®, Suc­cess Neo® and Bt.

 For more infor­ma­tion on DBM and man­age­ment options, read the GRDC fact­sheet.

Heli­cov­erpa lar­vae will graze on devel­op­ing and matur­ing pods, with medium and large lar­vae able to pen­e­trate pods and con­sume grain. In con­junc­tion with esti­mat­ing lar­val den­si­ties, esti­mat­ing the pro­por­tion of dam­aged pods will help in deter­min­ing if the pop­u­la­tion war­rants con­trol. As the crop dries down and pods harden, it is less likely that smaller lar­vae will be able to pen­e­trate pods. In the north­ern region, the pro­por­tion of H. armigera can be expected to increase from late Sep­tem­ber through to mid Octo­ber when emer­gence from win­ter dia­pause typ­i­cally occurs.

DBM activ­ity is also high in south­ern Aus­tralia this year, as dis­cussed in this GRDC media release.




Posted in canola, diamondback moth, helicoverpa | Tagged , , | Leave a comment

Spring pest activity — Pulses and winter cereals.

As tem­per­a­tures start to warm up there are a num­ber of insect pests becom­ing active and caus­ing crop dam­age. This post pro­vides an overview of cur­rent and poten­tial issues for field crops.
Read More »

Posted in armyworm, faba beans, helicoverpa | Leave a comment
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