Here's a good example of how grass grub damage in pastures can be avoided without chemicals.
Grass grub is a severe pasture pest in many regions. It has devastating affects by devouring the roots of plants in large patches, which are usually then replaced by low producing weed grasses. It catches farmers out as the presence of the insect is often not noticed until winter grazing, and it reduces feed availability at the most crucial time of the year.
Some chemicals are still allowed to be used to control grass grub, but they expensive and difficult to use as they require irrigation or immediate heavy rainfall.
Thankfully farmers can almost eliminate future damage to pastures from grass grub by using species that are tolerant. It has been known that lucerne, phalaris and tall fescue have tolerance to grass grub.
An excellent example of how these tolerant pastures can work well for farmers was seen in a paddock where DLF Seeds have had an endophyte evaluation trial for four years near Roxburgh, in Central Otago (see photo).
Photo: Tower was planted to the left of the red line and ryegrass to the right, and no fence has separated them for four years.
The farmer tested Tower tall fescue by drilling it in one half of the paddock and compared it with perennial ryegrass in the other (2013).
By the third year more than half the ryegrass pasture was severely damaged by grass grub, when the Tower tall fescue had no damage visible.
In the fourth year (2017/18), most of the ryegrass pasture has been overrun by Yorkshire fog and browntop which have established in the absence of ryegrass plants. This part of the paddock browned off early in summer and has grown very little feed (see photo).
In stark contrast, the Tower tall fescue was green and healthy and growing plenty of high quality feed (see photo). As a result, animals in the paddock have spent most of their time on the Tower side. In the fourth year there were some patches of grass grub, but the tall fescue plants seemed to be surviving the feeding by the grubs.
The farmer has also discovered how easy Tower is to graze and manage. It remains mostly leafy through spring and summer, with just short and soft stems lightly scattered across the paddock, even though it has been set stocked. It has also supported a strong clover base, important for animal performance and nitrogen supply.
It's probably no surprise to have found that in the trial site within the paddock, Tower has persisted better than 14 of the 17 ryegrass cultivars tested. In fact Tower has 100% survival and some ryegrasses only 60%.
So the solution if you want a grass pasture that will not be wiped out with grass grub, is Tower tall fescue.
Photo: Cattle enjoying the constant supply of Tower pasture and growing well in the Roxburgh paddock.