Lawn rust disease in NZ: orange powder on grass blades
Hey team, noticed this morning there’s this orange powdery stuff all over my lawn blades, and my shoes were completely orange after walking through it. Looks like rust on steel almost. Is that what this is and what do I do about it?
This is rust. Early on it can look like the lawn is just hungry and short on nitrogen. Pull a blade and have a look at it and you'll see small yellow spots forming along the surface. As it progresses those spots develop into reddish-brown pustules on the leaf surface like the close up you've posted.
That's when you get the orange powder on your shoes. What you're walking through are spores sitting on those pustules, breaking off when disturbed. It's important to catch your clippings as those spores will spread through the lawn if they're left.
It behaves a lot like red thread in that it's mostly a slowed growth and lacking nutrients causing it. You'll start seeing a few of these posts popping up soon, it happens every year about this time. It comes through in autumn as growth slows and dew periods get longer. One thing you need to make sure you're not doing is watering in the afternoon or at night. The canopy needs time to dry during the day.
When nitrogen goes in and the grass starts moving again, it outgrows the infection. An application of NZLA All Seasons would normally be enough to push it out. If it's earlier in the season N+ is fine, but heading into late autumn the standard All Seasons is the better call so you're not pushing excessive growth late. Our application guide on the website has granular fertiliser timings if you're unsure when to apply these.
NZLA Azoxy will definitely clear it up if you want to go the fungicide route, but it's not the best first option. Feed first and see what happens over a couple of weeks.
All Seasons: https://www.newzealandlawnaddicts.com/product-category/granular-fertiliser/nzla-all-seasons/
Azoxy: https://www.newzealandlawnaddicts.com/products/nzla-azoxy-lawn-fungicide/