| dc.description.abstract | It was evaluated the possible interactions among the following
agents of natural control of Spodoptera frugiperda (Lepidoptera: Noctuidae):
Campoletis flavicincta (Hymenoptera: Ichneumonidae), the Nuclear
Polyhedrosis Virus (NPV - Sf) and different maize genotypes with different levels
of genetic resistance [Resistant exotic parental Zapalote Chico (ZC) (Zea
mays), the adapted parental BR 105, and four semi-exotic populations, with
different percentages of gene introgression: 50% of ZC + 50% of BR 105 (or
simply F1), 25% of ZC + 75% of BR 105 (backcross 1 or simply BC1), 12,5% of
ZC + 87,5% of BR 105 (or BC2) and 6,25% of ZC + 93,75% of BR 105 (or
BC3)]. The incubation period of the eggs of C. flavicincta was approximately
48 hours. Most of the caterpillars of S. frugiperda contained more than one
eggs of the parasitoid. However, 24h after eggs eclosion, it was observed the
presence of only one developed larvae in the same caterpillar. Probably there
is a competition among newly hatched larvae and through physical attack
only one survives. Females of the parasitoid laid more eggs in healthy
caterpillar than in infected one, when they did not have choice option. When
in contact with healthy caterpillars and infected by NPV - Sf at the same time,
there was not difference in the number of deposited eggs, probably because
the female could not discriminate between of healthy or NPV infected host. In
olfactometer test, healthy S. frugiperda larva and corn leaf attracted 50% of
the C. flavicincta females. In the treatment with infected caterpillars and your
leaf, they were attracted 32,1% of the females. Where just had leaves, that
value was of 14,3% and the witness, without any scent source, it attracted
only 3,5% of the females. To discriminate healthy hosts of having infected can
minimize the negative impact of NPV - Sf on the parasitoids. Increase of the
size of the caterpillar implicates in a reduction in the efficiency of the virus.
The united use of virus and parasitoid in laboratory increased the mortality of
caterpillars of S. frugiperda in laboratory, when compared with the treatment
where was just used the virus. As larger the interval of time between
parasitism and infection, larger the survival of C. flavicincta. The previous
infection with NPV - Sf reduced the emergency of the parasitóide, mainly in
caterpillars infected in the 2nd and 3rd days of life. Not only originated
females of caterpillars infected by the virus they were capable to transmit the
pathogen for healthy caterpillars, but also those females initially exempt of the
virus, but that were coupled with males originating from of infected
caterpillars. In laboratory, the genetic materials didn't indicate significant
differences in the biological parameters (efficiency of parasitism, weight of
healthy caterpillars and sponged, weigh of the pupas, duration of the phase
pupal and sexual reason of the host and of the parasitoid). In the field
smallest number was collected of caterpillars of size 3 and any caterpillar of
size 4 in ZC, besides smallest number of caterpillars of S. frugiperda, of
pupae of the parasitoid and where the damage level was smaller, indicating
that there was effect of that material. | |
