Disease Update August 2019
So far this year, we have seen crop diseases popping up all over the place. The recent misty rain we had over a prolonged period created perfect conditions for most diseases to take hold and spread throughout crops. Below is a list of what you should be looking out for in your crops.
We are starting to see Septoria Tritici Blotch show up in later wheat crops around the Mid North. On the York Peninsula, we are finding it constantly in low levels across most wheat varieties. Make sure you are keeping an eye out for Septoria and be ready to apply a preventative fungicide. A preventative spray will be a better option than a curative spray.
These cold drizzly conditions have also brought on some powdery mildew in some wheat varieties. As we get warmer conditions and the crops will begin to canopy over and create their own microclimate. Then the humidity and moisture in the canopy will speed up the disease. If you miss applying a protective spray before canopy closure, it will be very difficult to get good coverage of fungicides onto the crop.
Side note: Are you seeing yellow?
It is important to remember that not all yellowing of wheat or durum is due to disease, or nutrient deficiencies, or toxicities. AGT varieties such as Kord CL, Mace, Scepter & Hyperno for example, may get the ‘AGT Yellows.’ This seems to be caused by a nutritional aspect and the genes that play a role in boron tolerance. However, this is not the whole story. Adding nitrogen can help lessen the visual appearance of the yellows but will not address the cause. Research at this stage has shown that it appears there is no significant yield effect associated with the yellows.
Symptoms of both Spot Form Net Blotch (SRNB) and some Net Form Net Blotch (NFNB) have appeared in barley paddocks both on the Mid North and the Yorke Peninsula. Crops sown into infected barley stubbles are at the highest risk. As the GRDC have noted, Spartacus barley crops treated with Systiva on the Lower YP haven’t been getting the expected benefit of control for NFNB, especially those sown into barley stubbles. However, all paddocks will be at risk as the season progresses and airborne spores increase. We advise all barley growers to monitor their crops closely.
Barley Leaf Rust:
Barley leaf rust has also been starting to show up in earlier sown crops. Look to apply dual active fungicides to treat both leaf rust and blotches.
Red Leather Leaf:
Some early signs of red leather leaf in oats have been found across the state. This disease can reduce the visual quality of the resulting hay, which then can cause price reductions, as well as yield losses in milling oats.
Aschochyta in Beans:
In beans so far there have been low levels of Ascochyta Blight and Cercospora leaf spot in the Mid North. This is good news as it usually is a hot spot. However, it is still crucial to stay on top of your preventative fungicide program and prevent both these diseases from entering your paddock.
Note to growers: Most crops in this area would be due for their first fungicide if it hasn’t already been done.
Ascochyta in Peas (blackspot):
Ascochyta has been found in peas on both the YP and Mid North, confirming the warnings earlier this season. If found, it is essential to spray between the 4-8 node growth stage if there is a potential yield of more than 1.5t/ha. This will prevent the movement of the disease up the plant and may require another spray if the season is conducive.
Downy mildew has also been spotted in pea crops. However, this would have to be severe to warrant a spray, as there are limited fungicide options available in crop to control the disease. As days get longer and warmer this disease will slow down, and we will likely see Powdery Mildew incidences increase. Apron XL as a seed dressing is the best product available. But unfortunately this won’t help now if crops didn’t receive it prior to seeding.
Ascochyta Blight in Chickpeas and Lentils:
Ascochyta blight was seen early in volunteer plants of lentils and chickpeas and is now present in crops. Severe leaf and stem lesions have been observed on seedlings of Hurricane lentils, meaning that the resistance in this cultivar is eroding even further. With damp conditions and longer/warmer days ahead ensure crop have protective fungicides applied particularly prior to canopy closure. Getting coverage to the base of stem where grey mould begins is impossible once the crop has closed over.
If you need help identifying what may be in your paddock, give us a call.