Unraveling the effect of temperature and humidity on the life cycle of Diatraea saccharalis (Lepidoptera: Crambidae) and the impact on pest outbreaks

Temperature and humidity are considered the main abiotic factors that affect both the development and survival of ectothermic organisms. In this study, we estimated the development time as well as the thermal requirements of the sugarcane borer, Diatraea saccharalis (Fabricius, 1794; Lepidoptera: Crambidae), a key insect pest of sugarcane and discussed the influence of temperature and relative humidity and its infestation intensity in a scenario of climate change. The models Briere-1 and Ikemoto-Takai provided the best fit to the data of development rate versus temperature. The average life cycle (from egg to adult) ranged from 39.21 +/- 4.84 at 32 degrees C to 137.10 +/- 7.47 at 18 degrees C days. The thermal constant and average base temperature were 547.69 degree-days and 13.64 degrees C, respectively. The number of larval instars varied from 4 to 7 depending on the temperature, being higher at lower temperatures. The thermal range comprised the interval from 16.7 degrees C to 33.9 degrees C and the optimum temperature was estimated as 27.4 degrees C. Locations with elevated temperature (>= 25 degrees C) and high relative humidity (>= 70%) presented larger populations of D. saccharalis. Our findings show that the infestation pressure of this species is highly influenced by both temperature and humidity, and the studied models allow to forecast pest outbreaks. In the context of climate change, information about the thermal range and the optimum temperature contributes to predicting the spatial-temporal distribution of D. saccharalis and, consequently, aids decision making in pest management. Graphical Abstract Temperatura e umidade sao consideradas os principais fatores abioticos que afetam o desenvolvimento e a sobrevivencia de organismos ectotermicos. Neste estudo, nos estimamos o tempo de desenvolvimento, bem como os requerimentos termicos da broca da cana-de-acucar, Diatraea saccharalis (Fabricius, 1794) (Lepidoptera: Crambidae), uma praga-chave da cana-de-acucar e discutimos a influencia da temperatura e umidade relativa e sua intensidade de infestacao em um cenario de mudancas climaticas. Os modelos Briere-1 e Ikemoto-Takai forneceram o melhor ajuste aos dados de taxa de desenvolvimento versus temperatura. O ciclo de vida medio (do ovo ao adulto) variou de 39,21 +/- 4,84 a 32 degrees C ate 137,10 +/- 7,47 dias a 18 degrees C. A constante termica e a temperatura base media foram 547,69 graus-dia e 13,64 degrees C, respectivamente. O numero de instares larvais variou de 4 a 7 dependendo da temperatura, sendo maior em temperaturas baixas. A faixa termica compreendeu o intervalo de 16,7 degrees C a 33,9 degrees C e a temperatura otima foi estimada em 27,4 degrees C. Locais com temperatura elevada (>= 25 degrees C) e alta umidade relativa (>= 70%) tem populacoes maiores de D. saccharalis. Nossos resultados mostram que a pressao de infestacao desta especie e altamente influenciada pela temperatura e umidade e os modelos estudados permitem prever surtos da praga. No contexto das mudancas climaticas, informacao sobre a amplitude termica e a temperatura otima contribui para prever a distribuicao espaco-temporal de D. saccharalis e, consequentemente, auxilia na tomada de decisao no manejo de pragas.