Dear List members,
I would be grateful for any comments on the management of ryegrass pastures
that are infested with grass grubs. Here is my situation.
We have been using NZ ryegrass seed for more than 20 years now and
constantly improving soil fertility. Soil tests for P are around 30-35,
great organic matter content, but we still have a bit of S and Mg to add. We
are located at 3000 m above sea level. In the past 5 years we have seen the
ryegrasses being pulled by the cows as they graze to the point that pasture
persistence is diminished to 3 years. Since kikuyu is present it readily
takes over. Examination of the root structure reveals poor root penetration
to deeper parts of the soil, although examination of the soil profile
indicates no level of compaction ( and water drains freely). Grass grubs are
present at rates of 2 to 10 per area of 20 square cm. which I have been told
is a level of action in NZ.
If treatment is needed for the pasture the question is with what. I have
thought of using systemic insecticides that are sprayed on the grass and its
transported to the roots where it will kill the grub. I do have access to a
sprayer. Application of insecticide granules on to the soil is a bit harder
as I will need a seed drill with discs.
I think the grubs are a problem but that maybe grazing management would help
control them. At this point I HAVE to do something drastic to save some of
the better paddocks. What would be the insecticide to use (generic name for
ingredient, please), rate, when to apply, when to graze again.
Thanks so much for any comment.
Liliana Sotomayor, DVM
Casilla 17-12-245
Quito, Ecuador
