Banca de DEFESA: EDUARDO ALVES DE SOUZA

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
STUDENT : EDUARDO ALVES DE SOUZA
DATE: 23/06/2025
TIME: 14:00
LOCAL: online
TITLE:

Entomopathogenic potential of Bacillus strains against Spodoptera frugiperda (Lepidoptera: Noctuidae) and effects of interaction with diazotrophic bacteria and nitrogen on corn (Zea mays L.) development in the field.

KEY WORDS:

Biological control; Insect pests; Nitrogen; Productivity.

PAGES: 108
BIG AREA: Ciências Agrárias
AREA: Agronomia
SUBÁREA: Fitossanidade
SPECIALTY: Entomologia Agrícola
SUMMARY:

Spodoptera frugiperda is a major pest in Brazilian agriculture, with increasing resistance to chemical pesticides leading to the need for sustainable alternatives. One promising solution is using Bacillus bacteria, particularly B. thuringiensis, which produce species-specific toxins. This study aimed to evaluate and select Bacillus strains with entomopathogenic potential against S. frugiperda in corn crops. Forty strains from the B. cereus group, sourced from Embrapa Agrobiology’s Genetics and Biochemistry Laboratory, were tested in laboratory bioassays to assess first-instar caterpillar mortality. The strain Btk S76 proved most effective, causing over 90% larval mortality within seven days, compared to less than 33% in other strains. Given this promising outcome, Btk S76 was tested in greenhouse trials, where spraying with B. thuringiensis spores significantly affected pest control. The average attack score of S. frugiperda larvae was 2.1 (on a scale of 5, with 5 being the highest damage level) when sporulated cells were used in spraying. Additionally, leaf integrity was higher, with an intact surface area of 220.78 cm², reinforcing the efficacy of spores in pest management. Both results showed significant differences compared to the control. To further evaluate Btk S76 in field conditions, an experiment was conducted in association with diazotrophic bacteria that promote plant growth and nitrogen uptake. The trial took place at Embrapa Agrobiologia’s Experimental Field in Seropédica, RJ, using a randomized block design. The study included six inoculation treatments and four nitrogen application rates (15, 40, 80, and 120 kg ha⁻¹), with and without Btk S76 spraying.  The results indicated that inoculation with some bacteria, such as the CNPAB mix (Azospirillum argentinense) and the commercial inoculant of A. brasilense (Ab-V5 and Ab-V6), as well as the S76 strain of B. thuringiensis, had a significant impact on stalk weight. However, most biometric parameters, except for ear weight, did not show statistically significant variation. The interaction between the spraying of the Btk S76 strain and the nitrogen rates proved to be relevant for ear weight, with the 80 kg ha-1 N rate providing the greatest results. The gains in productivity, as observed in grain weight, showed a positive response as a function of the four nitrogen rates (15, 40, 80 and 120 kg ha-1). In summary, both studies pointed to the potential use of the Btk S76 strain and the combination of bacterial inoculation with adequate nitrogen doses in optimizing pest management and field-grown corn production.

COMMITTEE MEMBERS:
Presidente - ***.864.458-** - JOSÉ IVO BALDANI - UFRRJ
Interna - 2223814 - ELEN DE LIMA AGUIAR MENEZES
Externa à Instituição - FRANCINE YURIKO OTSUKA ROCHA