Estimating the relationship of sugarcane borer larvae and crop damage based on adult captures and climate variables

Abstract

Sugarcane borer Diatraea saccharalis (F.) is the primary sugarcane pest in Brazil.To estimate the relationship between larvae in sugarcane stalks and captures of male adults of D. saccharalis, we collected samples weekly: (1) adults with one delta trap with three virgin females and three female pupae and (2) larvae in 120 stalks per plot of 12.6 hectares (355 × 355 m).The study was conducted in two sites with five plots each, in the municipalities of Nova Ponte and Tupaciguara, Minas Gerais State, Brazil, from July 2016 to May 2017. Relationships between (1) males trapped per week and the number of larvae outside of stalks (LOS) were estimated and(2) we evaluated climate variables, namely average temperature, average relative air humidity, hours with relative air humidity below 30 %, rainfall and number of rainy days, and adults and larvae of D. saccharalis. We obtained generalized linear models for LOS in autumn and for larvae inside the stalks (LIS) in spring and autumn and trapped males in both sites. A significant and direct relationship between LIS and males trapped allows predicting larvae density based on captures of males. In addition, plant damage can be estimated based on accumulated captures of males. There was a negative relationship between hours of air humidity < 30 % and larvae outside of stalks. Densities of LIS can be estimated from male captures and by the humidity variables in the trapping week. Nevertheless, the models require validation in the field.

Stem borer herbivory dependent on interactions of sugarcane variety, associated traits, and presence of prior borer damage

“…2(B)). Such discrepancies may be due to this dataset containing more years of observations compared to literature values as borer populations fluctuate with year and weather conditions, 89 influencing the resistance classifications in any given year 90 . In particular, the variety release for HoCP 09‐804 notes that borer pressure was abnormally low during the years of evaluation, potentially obfuscating the appropriate resistance classification 50 .…”

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

“…Four delta traps (Biocontrole, Indaiatuba, SP) with a sticky floor were installed around each plot. Due to the lack of commercial sex pheromones for D. saccharalis , cylindrical mesh plastic cages containing 5 virgin females and 3 female pupae were kept hung inside the traps, similar to Assis et al (2022) to infer infestation. The insects were replaced every 3–4 days to guarantee maximum efficiency of pheromone release by females (Pinto 2021).…”