Gauteng Smallholder March 2016 | Page 15

NEWS

Feedback on pompom weed thrips

T

he Agricultural Research
Council has announced
that, since the initial
release of the stem- and leafdeforming thrips (Liothrips
tractabilis) on pompom weed
(Campuloclinium
macrocephalum) in October
2013 at Rietvlei Nature Reserve,
an estimated 200 000 thrips
have been released in Gauteng,
North West, Limpopo and
Mpumalanga, with proportionally, the most releases in
Gauteng (56%) and
Mpumalanga (21%).
Both pompom thrips nymphs
and adults feed on the stems
and leaf tissue at the apical
shoot tips of pompom weed.
This causes deformities in plant
growth, which reduces its
height, biomass and flower
production. Although damage
to the stem tips may encourage
the plants to send out lateral
branches in response, the rapid
population increase of the
agent ensures that the new
shoot tips are also attacked, and
these display similar damage.
The thrips has greatest impact
on seedlings, or on new spring
regrowth
The ARC says it is still too early
to confirm establishment at all
sites where the thrips were
released, but preliminary data
indicate an establishment rate
of 48%. Dispersal of the thrips
after release is slow, but steady,
with the impact on infected
plants becoming more noticeable over a period of three to
five seasons following the initial
release.
Establishment on mature and
reproductive plants is less
successful. Therefore the
window period at the start of
the growing season should be
targeted.
Liamé van der Westhuizen of
the ARC-Plant Protection
Research Institute, suggests that
landowners should try to
familiarise themselves with the
very young, vegetative growth
form of the pompom weed.

To do this use a metal marker to
mark where the plants are when
you see them in full flower. Then
you will be able to find them
again in the following season
when they are at the young
stage of regrowth.
Through planned mass-rearing it
is hoped that a large number of
insects will be made available
early in the season to drastically
increase the distribution and
optimise establishment of the
biological control agent.
Pompom weed regrowth before flowering stage.

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