SA Graan September 2018

77 / 132

75
September 2018
10 000 kl’s of liquid insecticides were pro­
duced exclusively for crop protection, of
which 43% consisted of highly toxic organo­
phosphates.
Bio-insecticides of botanical origin have
gained a great deal of interest, also being
in direct support of organic agriculture. As
pointed out in a recent review paper by Is­
man (2015), ‘…globally, bio-pesticides could
hold close to 20% of the pesticide market by
2025 and botanicals up to 7% of the mar-
ket, based on 15% to 20% annual growth in
sales’ (see Pest Management Science 2015;
71:1 587 - 1 590).
An important group of botanical insecti­
cides is the so-called pyrethrums, made
from the flowers, of mainly, the Dalmatian
chrysanthemum, Tanacetum cinerariifolium
(Asteraceae) (Photo 2). The derived insec­
ticide (pyrethrin) is a mixture of six active
components (pyrethrins I and II, cinerins I
and II, and jasmolins I and II). Pyrethrum is
the main botanical in use, capturing nearly
80% of the global botanical insecticide mar­
ket and has been used for insect control for
over 150 years.
Previously, the notion of integrating en­
tomopathogenic fungi with chemical in­
secticides was discussed by the same
authors of this article, in the September
2015 issue of SA Graan/Grain (page 42).
However, although such combinations do
show potential, expanded benefits can be
derived through the combination of an en­
tomopathogenic fungus with botanicals,
creating a purely organic alternative.
In the USA, the product BotaniGard® MAXX,
is one such product, formulated with
B. bassiana strain GHA (0,06%) combined
with pyrethrins (0,75%). However, research
with an indigenous strain of this fungus
was needed and subsequently initiated by
ARC-Small Grain as part of an MSc study by
the author, Nokulunga Mzimela.
Laboratory experiments showed compat­
ibility between B. bassiana strain R444 and
various concentrations of the pyrethrum-
based insecticide, PyrolTM, a certified or­
ganic insecticide registered under Act 36
of 1947 (L7062), with active ingredients:
Canola oil 89,5% and pyrethrins 0,5%. Inter­
estingly, at a reduced concentration of 10%,
Pyrol increased the sporulation intensity of
the fungus and the combination was then
further tested against the Russian wheat
aphid, together with a chemical (Mospilan®),
under glasshouse conditions. Mortality re­
sults are visually presented in Graph 1.
A synergistic effect was noted withB. bassi-
ana R444 + 10% Pyrol, yielding a statisti­
cally similar level of control compared with
the (full-dose) of Pyrol, alone. Likewise,
when comparing the B. bassiana R444 +
10% Pyrol treatment to the solo 10% Pyrol
treatment, efficacy was more than doubled.
These results demonstrate good compat­
ibility between the fungus and this botani­
cal insecticide, with a clear additive effect
in terms of aphid mortality.
Although so far tested only against Russian
wheat aphid, such combinations may also
prove effective against other aphid species
like the oat aphid, Rhopalosiphum padi, an
important vector of barley yellow dwarf
virus in South Africa.
The notion of combining entomopatho­
genic fungi with a chemical or botanical
insecticide as a ‘two-in-one’ tank mix, has
been successfully employed against vari­
ous insect pests to reduce the selection
pressure brought about by the insecti­
cide (some insects in a given population
inherently resistant or less susceptible)
and to avoid concurrent development of
resistance in target pests.
Other benefits relate to lower volumes of
chemical insecticides applied to the envi­
ronment, less (human) exposure to harmful
chemicals, during and after
application, and lower or no
residues on harvested com­
modities.
Graph 1: Mortality of Russian wheat aphid, Diuraphis noxia, exposed to unformulated Beauveria
bassiana strain R444, combined with a sub-lethal dose of pyrethrum and Mospilan insecticides, or
as solo products. Bars with different letters, differed significantly at the 5% test level.
Onderhoud
Sekerlik een van die maklikste en sekerste maniere om swak
spuitresultate te kry, is gesetel in iets so eenvoudig soos die korrekte
onderhoud van die spuitstelsel. Operateurshandleidings spel die
vereistes in fyn besonderhede uit en van die belangrikstes om in
gedagte te hou, is:
Spuitpunte moet weekliks getoets word om te bepaal of lewering
binne die spesifikasies is. Indien dit met meer as 10% van
leweringsnorm afwyk, moet dit vervang word.
Filters moet daagliks uitgehaal, skoongemaak en geïnspekteer
word.
Roerders moet ten minste met seisoenale onderhoud uitgehaal
en skoongemaak word.
Herkalibrasie van sensors op ‘n seisoenale basis kan groot foute
voorkom.
Skoonmaak – binne en buite – is die eenvoudigste en sekerste
manier om diensbaarheid en waarde te behou. Doen dit deeglik
en op ‘n weeklikse basis.
Volledige jaarlikse onderhoud moet direk na die spuitseisoen
gedoen word – en nie voor die volgende seisoen nie.
Voor aanvang van die nuwe spuitseisoen is dit noodsaaklik om tydig
weer die stelsels te toets en seker te maak dat alles in ‘n werkende
toestand is. Raadpleeg die volledige handleidings wat saam met die
toerusting aan jou voorsien is, ten einde die verskillende inspeksies
korrek uit te voer.
Hoe maak mens ‘n sinvolle keuse?