5 Effective Ways to Easily Eliminate Pasture Rust in Ryegrass
RUST
Otherwise known as Crown rust (Puccinia coronata) or Stem rust (Puccinia graminis).
Crown rust is found throughout New Zealand and is the most common type of rust that occurs.
Crown rust is usually found in Hybrid, perennial ryegrass, and tall fescue. If you happen to notice orange powdery spots on the leaves, chances are, your grass has contracted crown rust. The first signs are small and round, orange-yellow pustules that appear on both sides of the leaves. Afterwards, the pustules join together to form evenly affected areas. Small and black pustules form later in the season.
The pustules produce orange spores that are carried by wind and rain to the other leaves. These pustules germinate to produce new pustules.
20 degrees Celsius with high humidity is the ideal climate for this to thrive!
Stem rust tends to be more of a South Island issue, most often seen in the autumn.
As a fungus, a surge in warm, moist weather sets off the right conditions for rust to grow, especially in long overgrown pastures that is Nitrogen-deficient.
Some ryegrass cultivars will be more susceptible to this fungal disease than others, for example, Old varieties such as Nui have a much lower rating for rust resistance.
Rusty pastures don’t look good, they don’t grow as well and palatability is much lower, and can often affect bailage, silage, and hay.
The best way to manage rust if it is already present is to hard graze affected pastures, or cut for bailage then apply some N fertilizer to stimulate healthy re-growth. New growth should show little to no rust.
To prevent rust in the first place, graze pastures at the correct time and don’t let them get too long.
As far as animal health issues go, there are no specific animal health issues to worry about if stock graze rusty pasture, as far as consuming the Puccinia fungi, dry matter intake and pasture utilisation can be reduced, also note facial eczema (Pithomyces chartarum) spores can increase in warmer regions of New Zealand when rusty, dead or dying pasture material builds up in the base of the pasture sward.
A longer-term solution is when selecting ryegrasses, ensure you select a variety with a higher level of rust resistance, monitor N levels regularly, and don’t let pasture get too long.
There are some fungicide chemical options available like Prothioconazole to help treat rust issues in ryegrass and seed crops this isn't a very economical option for grazing pastures.
CONCLUSION
Hard graze affected pastures
Cut for bailage
Apply N fertilizer to stimulate healthy re-growth
Graze pastures at the correct time and don’t let them get too long.
Select a seed variety with a higher level of rust resistance