| Sumario: | The fall armyworm (FAW) is the most
important threat to corn crops in Argentina, and
there exists very little up-to-date information
on its actual pest status because the available
literature was published more than 20 years
ago. Therefore, field surveys were carried
out in the northeast of Argentina, in order to
establish the attack rates and injury levels of
the pest in relation to the crop phenology. The
study was carried out at two localities: Colonia
Benítez, an agricultural region, and Tapenagá,
a cattle-raising area. At each site two 1-ha plots
were sown either with a Bt-corn expressing
Cry 1F protein or with an untransformed corn
germplasm. Optimal and late sowing was
assayed and FAW larval abundance, relative age
composition, attack rates and level of damage to
corn were recorded. At the moment of the field
experiments, Bt-corn was not affected by FAW
larvae. However, untransformed germplasms
were severely affected by FAW larvae, with an
average of attacked plants of 18% or more. In contrast to data obtained 30 years ago, higher values of FAW density were registered. Levels
of damage to corn plants were higher after the
V4 stage. It was found that the sowing date
affected the infestation levels and early seeding
avoided high armyworm densities that develop
later in the season; in northern Argentina, this
was only relevant in agricultural areas.
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