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Unlike traditional nematicides, which begin to break down imme-
diately, Poncho/VOTiVO keeps deterring nematodes from attack-
ing the plant’s root system through the first two generations of
nematodes.
Do the bacteria in Poncho/VOTiVO carry
over in the soil from year to year?
While the bacteria live and grow in the soil, they are not able to
survive on dead plant tissue for very long. Therefore, a hectare of
treated seed will not result in a sustained population of bacteria
from one season to the next.
Bayer is the global leader in seed treatments, delivering the latest
seed-applied solutions to market and helping growers maximise
their seed investment and improve per-hectare profits. Seed treat-
ments provide several important benefits.
For agricultural workers, seed treatment technology can mean de-
creased worker exposure. For the environment, seed treatment
technology means a lower potential for water residue. For ‘non-
target’ species, seed treatment technology means reduced ex-
posure. For consumers, seed treatment technology means lower
food residues.
In these economic times, growers should prefer to use some-
thing that has proven itself. Poncho/VOTiVO provides that sustained
track record of success, and growers still come back to it because it
gives them what works.
The probability for stomatal penetration
is low and often happens by chance, the
fungi often grow over the stomata without
penetration. The Alternaria disease cycle is
simple due to their lack of a sexual stage.
The pathogen has the ability to overwinter
or endure as spores or mycelium on decay-
ing plant debris as dormant infections in
seeds.
Several environmental conditions including
heavy dews, frequent rains and high tem-
peratures promote the production of conid-
ia. As with any plant disease, the epidemic
depends on several factors such as the in-
oculum, environmental conditions that pro-
mote an elevated level of spore deposition
or any wounds present on the plants that
can enhance susceptibility to pathogen in-
fection. Susceptibility of the plant increases
with the maturation of the plant as Alter-
naria infection causes premature leaf senes-
cence. With favourable conditions the leaf
blight progressively spreads to the upper
leaves. The Alternaria disease proliferates
even more when the host plant is subjected
to any kind of stress, except when the stress
influences the survival of the pathogen.
Symptoms of the disease
Alternaria
spp. causes disease lesions on
leaves, petioles, stems, sepals and petals
of sunflower plants. Leaf symptoms ap-
pear as circular, dark brown to black lesions
with concentric rings ranging from 0,2 mm
to 0,5 mm in diameter.
Lesions will eventually enlarge in size
and coalesce causing blighting of leaves
(
Photo 2
). Some lesions can be identified by
distinct yellow halos, particularly on young
plants. Stem lesions start as dark flecks that
enlarge to form large elliptical to diamond-
shaped sunken lesions. Dark brown oval to
circular spots with a target board appear-
ance can form on heads. If the disease is se-
vere, plants may be defoliated prematurely
and die or frequently lodge.
Disease control
The disease can be controlled through
cultural practices such as crop rotation, de-
struction of plant debris and tillage opera-
tions that bury and rapidly promote residue
decomposition. The disease can also be
controlled by the use of resistant or tolerant
varieties and correct plant spacing.
Chemical seed treatment with fungicides
significantly reduces the incidence of
Alternaria seedling blight. Unfortunate-
ly, no fungicides in South
Africa have been registered
to be used to control Alter-
naria leaf blight.
Grain SA/Sasol photo competition
– Mari du Toit 2016
Alternaria leaf blight and seed infection