I
n general, the occurrence of insect pests
in the 2016/17 growing season was ad-
dressed by the corn farmers. “Except
for the maize leafhopper (Dalbulus
maidis), which could turn into a focus
of more than one disease”, says research-
er Simone Martins Mendes, from the Ento-
mology department at Embrapa Corn and
Sorghum, in Sete Lagoas (MG).
According to Simone, the armyworm
(Spodoptera frugiperda), keeps its sta-
tus as leading corn pest, for its vast occur-
rence in fields from the North of the Coun-
try to the South, causing problems in the
first and second stages of the cereal. “None-
theless, this pest is no novelty for the farm-
ers, who, in general, had no difficulty man-
aging the pest in the 2016/17 season”, she
observes. During the season, according to
Simone, theuseof cornwith theBt technol-
ogy was the main Integrated Pest Manage-
ment (IPM) strategy the farmers reliedon, in
spite of reports on the receding efficiency of
the technology in some fields.
For this reason, different results were
achieved for different regions and situa-
tions. Within this context, she recalls the im-
portance of planting refuge areas, which,
combined with the effect of high dosages,
play a fundamental role in keeping the du-
rability of the technology, delaying the evo-
lution of pest resistance in the field. “Farm-
ers have already understood that there is
no IPM strategy which, in itself, is capable of
solving the entire problem”, she stresses. In
many cases, it is necessary to associate the
management techniques with chemical or
biological controls formaximumresults.
Another serious pest, especially for sec-
ondcropcorn, is knownas stinkbug (Diche-
lops melacanthus). This insect is particular-
ly common after soybean harvest, when its
population develops. There were various
outbreaks, always after summer crop soy-
bean harvest. The bug feeds on plantlets,
jeopardizing their development, giving ori-
gin to a symptomknown as hollowkernel.
DIAGNOSIS
Many diseases that
infest the corn crops in Brazil were pres-
ent in the 2016/17 growing season, say
Phytopathology researchers Dagma Di-
onísia da Silva and Luciano Viana Cota,
from Embrapa Corn and Sorghum. The
main diseases were as follows: white
spot, cercosporiosis, helminthosperiosis,
foliar anthracnosis, diplodia foliar spot
and bipolaris, mildew, polysora rust,
tropical rust, white rust, maize bushy
stunt and corn stunt spiroplasm, stalk rot
Armywormpests andwhite
spotdiseasescausedconsiderabledamageto
thecornfieldsinthe2016/17growingseason
56
Persistent
enemies
Bt technology has been suggestedagainst corn pests anddiseases
Inor Ag. Assmann
