Welcome to our July update for 2022. June and July have been drier than we would all have liked, however crops are hanging on well thanks to all that summer moisture and its a credit to all the time and money spent in the sprayer over that period.
With the limited winter rain comes we still have weeds, disease, pest and nutritional decisions so we must remain vigilant with paddock inspections and make the most of the moisture profile we are given.
Have a read below of the happenings in the district and key things to think about and keep an eye out for moving forward.
Please put Tuesday 13th of September in your diary for our Spring Field Day Trial Site Walk!
Top Priorities For The Coming Month's |
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Barley Foliar Disease
There are two types of "blotch" that occur on barley, Spot Form of Net Blotch (SFNB) and Net Form of Net Blotch (NFNB). Early sowing of barley increases the risk of infection and hence we see this as an increasing problem with modern farming practices. Yield losses of 20-30% as well as reductions in grain quality, particularly increased screenings, can occur if not managed properly throughout the season.
Historically we have seen mostly Spot Form of Net Blotch (SFNB) on our barley and we have controlled this successfully with Propiconazole at various rates.
The varieties we are currently growing are very susceptible to both SFNB and NFNB most notably Spartacus CL.
Spot form of net blotch (SFNB)
Symptoms develop as small circular or elliptical dark brown spots becoming surrounded by a yellow margin. These spots do not elongate to the net-like pattern seen with the net form. The spots may grow to 3-6 mm in diameter.
Net form of net blotch (NFNB)
The net form of net blotch starts as brown lesions, which elongate and produce fine, dark brown streaks along leaf, creating a distinctive net-like pattern. Older lesions continue to elongate along leaf veins, and often are surrounded by a yellow margin.
NFNB is stubble borne with infected stubbles the main cause of infection and occasionally, barley grass residues hosting infection.(Have a look at any Barley Grass at the moment you will see NFNB all over it)
Spores can survive on infected stubble for up to three years.
This season we have seen Net Form of Net Blotch (NFNB) spread across barley paddocks around the district. It has become quite clear that our district practice of Propiconazole as a stand alone product has not been doing a adequate job of controlling NFNB in many local paddocks.
I have attached some photo's of Commodus CL Barley that had two different fungicide treatments applied.
The first treatment was 300ml/ha of a 250g/l active Propiconazole.
Large amounts of NFNB infection could be seen on the lower and now moving to the upper canopy. With favorable conditions this will continue to move and spread up the canopy to more yield defining leaves. Multiple lower leaves have been dropped off.
The second treatment in the same paddock, treated at the same time with 400ml/ha of TopNotch (Azoxystrobin 200 g/L + Propiconazole 200 g/L)
This one application has significantly reduced the NFNB in the canopy and therefore allowed the Commodus CL to retain its green leaf resulting in a much healthier and competitive plant.
It is quite noticeable standing in the paddock looking at the two treatments side by side.
As the season progresses the barley treated with TopNotch is given a greater chance of reaching its yield potential.
It will be interesting to see the difference in grain yield and quality when this paddock is harvested.
Septoria Tritici Blotch in Wheat
Septoria Tritici is again showing up more and more in early sown wheat and wheat on wheat paddocks. With Scepter being susceptible to Septoria Tritici there is a large area of the district that is vulnerable to the spread if suitable conditions occur.
The Septoria Tritici fungus causes pale grey to dark brown blotches on the leaves with yellow boarding margins. It can look very similar to yellow leaf spot, or Zinc deficiency however the diagnostic feature of Septoria tritici is the presence of black fruiting bodies within the blotches.
Late season infection if left untreated can accelerate crop maturity leading to poor grain quality.
Whilst over the last month it has been seen on lower leaves, it has occasionally being found in mid canopy and will cause its most damage on the more yield defining leaves such as flag leaf and flaf -1 and -2.
Septoria spread is favoured by cool, wet conditions with temperatures ranging from 15°c to 20°c and a wet crop canopy.
So whilst the warmer weather can slow the spread we will only need wet cooler conditions again and it can spread fast.
Our advice is early sow wheat crops with 3t+ potential need monitoring and may need fungicide applications if hopefully the conditions come in wet again.
Powdery Mildew
We have now been observing Powdery Mildew showing up in thicker canopy crops.
This will need to be kept a close eye on especially if wet weather recommences and where high Nitrogen rates have been applied.
Powdery Mildew will move very quickly up the canopy and into the head if conditions suit and left untreated.
Scepter and Vixen are both S-VS and are high risk varieties when conditions suit.
Yield loss of 10-25% are common
Foliar Diseases in Legumes
Moving forward we need to be keeping an eye out for Black Spot in Field Pea's and manage accordingly.
We have sighted Downy Mildew in multiple Field Pea paddocks.
Downy Mildew is most severe early in the growing season when the crop canopy remains wet for long periods following rain or heavy dews. Warm, dry conditions prevent the spread of the disease.
There is no foliar fungicides that control Downy Mildew, seed treatments containing metalaxyl can be effective but have been to shown to negatively effect rhizobium inoculant. Best management is to have a break of at lease 3 years between Field Pea crops and avoid sowing close to last seasons pea crop stubble.
For Lentil and vetch growers we are at or very close to our canopy closure fungicide application for protection against Botrytis Grey Mould.
Factors to consider to get your best results with foliar fungicides
All foliar fungicides we use work better as a preventative application rather than a curative application so we are much better being on the front foot with disease. Letting disease get out of hand and spreading throughout the canopy before controlling will decrease fungicide efficacy and increase the rate required as well as the your input cost. Pays to proactive!
Fungicides do not generally increase yield, but they protect the yield potential of a given crop by maintaining the green vegetative area including leaves and stems.
Foliar diseases reduce the green area of the plant and its ability to produce energy (via photosynthesis), particularly during key growth stages such as grain fill.
Timing of application of foliar fungicides is important consideration for effective disease control.
Key points to consider with fungicide timing are:
. Application at critical growth stages - protect the plant leaves that contribute to yield
. Multiple applications may be required as fungicides cannot protect leaves that haven’t emerged at the time of spraying
. High disease pressure/susceptible variety = earlier spraying + multiple sprays
. Applying fungicides to prevent the disease from becoming established. Do not rely on curative ability.
Nitrogen top dress decision's
With stored soil moisture obtained through good summer rainfall events and low district average on Deep N soil tests top amounts of Nitrogen would be required to reach yield potential.
However for many since taking delivery of your urea on farm the rainfall events have dried up and hence made decisions regarding top dress urea difficult.
If you spread urea and come back the next day or two and the granule is gone, this does not always mean it has been washed in. Urea will rapidly dissolve on the soil surface within 48 hours even without a rainfall event.
So where does it go? In our environment we can expect losses from Volatilisation.
Volatilisation is when urea changes from Urea to Ammonium and then to Ammonia (NH3). The Ammonia gas is then lost into the atmosphere.
Factors favouring Nitrogen volatilisation losses from top dressed urea
· light rain/dews post application, enough to dissolve the urea granule but not enough to wash the dissolved granule into the soil
· temperatures above 18°C
· alkaline soils
· wind
· low soil cation exchange capacity (Sandy soil types)
· application to a moist soil that dries after application
. Open crop canopies - Thin/Poor crop canopies allow more wind at the soil surface (the crop can absorb some NH3 through the leaves)
Green Urea
Green Urea NV is a urea-based product that is treated with N-(n-Butyl)-thiophosphoric triamide (NBPT).
When NBPT is added to urea it inhibits the activity of the urease enzyme for a period of up to 14 days. During that period the losses of N as Ammonia (NH3) from top dress applied urea are significantly reduced (Green Urea shown to reduce losses by 89%) and N is still present for the next rainfall event.
When to consider using Green Urea
. You cannot rely on a upcoming rainfall event within four days
. your are top dressing an alkaline soil type
. The soil surface you are applying to is drying out
. Strong wind conditions are forecasted
. The crop canopy you are applying to is still open (thin)
. The paddock has a high level of stubble
Herbicide Resistance
Pre harvest last season we collected seed samples of 13 Annual Ryegrass and 4 Barley Grass populations.
These samples were sent away to Plant Science Consulting where Dr Peter Boutsalis and his team sampled a range of herbicides for us to gain a better understanding of our current herbicide resistance status.
The results raised some concerning issues with products such as Trifluralin, Glyphosate and Clethodim.
Out of 13 Ryegrass population's that were tested, 9 of those showed a level of survival up too 3lt/ha to Trifluralin. (see figure below)
Two populations showed 90% survival at that 3lt/ha rate.....
The take home message from these results... when Trifluralin was tank mixed with another herbicide group which in this case was Avadex (Triallate) and Dual Gold(S-Metolachlor) we seen no survival with the same Ryegrass populations.
So, what does this mean for Trifluralin? It shows that we cannot keep increasing the rate with the aim to increase our level of Ryegrass control. What can be seen is the 3lt/ha rate did offer more "suppression" than the lower rates.
We need to be adding a mix partner with Trifluralin if we aim to see effective long term results with this product. Avadex, Dual Gold, Prosulfocarb, Sakura are all options in mixing our herbicide groups.
This will be a requirement if we wish to keep this cost effective herbicide in your rotation.
The second concern was the growing level of resistance to Glyphosate.
At 1lt/ha of a 540g/l formulation (equivalent to 1.20lt/ha of 450g/l) we saw 6 of the 13 populations showed a survival of 10% - 55%. Once again a product we cannot afford to lose, so look to double-knock where possible, keep rates robust enough to target size weeds you are treating. Look to add products that offer a "spike" on Ryegrass such as Terrador.
The quickest way to get a resistant population of any weed species is to "under dose" using low rates for the target weed being treated! Which has been very evident in all resistance testing over the years.
The final point i want to make and that is with Clethodim, four out of ten samples at the 350ml/ha rate and one at the 500ml rate either developing resistance or is resistant. This needs to be monitored closely over the coming years, keep rates robust, avoid spraying in poor or stressed conditions and look at using mix partners such as butroxydim or your Fop's if they still are working. Crop top paddocks where possible to control survivor's.
Ep Ag n Fert's seed sample results from plants collected pre-harvest 2021.
We will be collecting seed samples to be sent away and tested, so before harvest make sure samples have been collected. So please get in contact with us if you think you have potential issues in paddocks to assess the level resistance or rates that are most effective in your rotation. This information is invaluable moving forward with herbicide decision making.
Be on the look out for aphid's in crop as weather warms up. Cabbage Aphid on canola and Cow Pea Aphid on vetch already becoming a commons site in paddocks.
Please talk to myself and Troy and make sure your paddocks are being closely monitored.
As always, please feel free to ring us to discuss any of your specific issues, questions or you are looking for more detail.
Kevin Dart - 0474 272 577
Troy Maitland - 0499 272 544
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