Research shows that losses caused by the pest can halve production, depending on the hybrid. It is the first time this kind of estimate is performed with the caterpillar in sorghum crops. Recorded losses varied according to hybrid and management choices. The recommendation is to adopt control measures if crop infestation reaches 3% or over. The pest goes unnoticed by many farmers due to the fact it grows within plant culms. The sugarcane borer (Diatraea saccharalis) can be considered one of the main sorghum pests, depending on the insect's population density in the field. That is the conclusion of the first study to determine its level of economic damage in grain sorghum and to effectively show the amount of yield that can be compromised due to borer infestation. In general, the results of this study, which used commercial hybrids that are commonly sown in Brazil, showed grain sorghum's susceptibility to the sugarcane borer (also known as stalk borer) under high levels of infestation, causing substantial yield losses when not they are not treated with an insecticide. The paper entitled "What is the potential of sugarcane borer in reducing sorghum fitness and grain production?" and published on the Journal of Applied Entomology rrecords the findings of a study performed in three crop seasons between 2021 and 2023 at Embrapa Maize and Sorghum, in Sete Lagoas, Minas Gerais, Brazil. The study is part of the PhD thesis by Camila da Silva Fernandes Souza, for the Federal University of Lavras (Ufla), under the supervision of professor Bruno Henrique Sardinha de Souza, and Simone Martins Mendes, a researcher at Embrapa. “Lately we have been talking a lot about the sorghum aphid (Melanaphis sorghi), obviously, because it has caused great damage to this cereal's plantations as it is difficult to control. However, this study shows the damage caused by the stalk borer in sorghum cultivation, for comparison”, the Embrapa scientist reports. She says that the borer often goes unnoticed due to its growth habit. It grows hidden within the stalk of sorghum plants. Such crop losses were measured for the first time in this study and, depending on the sorghum hybrid, they can reach around 50% of the yield. Photo by: Simone Mendes and Otávio Araújo (pest in its caterpillar stage, within a plant culm) Many of such economic losses have been controlled through the use of insecticides, both against fall armyworm (Spodoptera frugiperda) and against the sorghum aphid. “However, it is fundamental to be cautious of the borer in sorghum crops, as the damages often go unnoticed by farmers”, Mendes reveals. The sugarcane borer was able to cause yield losses of up to 100% in more severe cases, when the plants were not treated with insecticide in a less tolerant hybrid. The most productive and tolerant hybrid recorded a loss of 50%. This shows how sorghum hybrids can behave differently in the field under the same pest infestation. Therefore, it is also important for farmers to be attentive to whether the pest is infesting their fields, as the use of a susceptible hybrid combined with the non-use of insecticides can lead to severe losses. According to Camila Souza, despite the importance of this insect pest species, little was known about the relationship between borer infestation and reduced grain sorghum yield. Another research question was to learn the economic threshold and the level of economic damage for pest control decision-making. “As per the study, we carefully measured both pest infestation and crop yield parameters. We assessed the length of the galleries caused by the borer’s feeding, plant height, panicle length and weight, as well as stalk borer injury and compromised grain yield. The sugarcane borer infestation was higher when the sorghum plants were not treated with insecticide, resulting in lower yield,” Souza explains. With the use of insecticide to control the pest, the researchers observed an increase in plant height mostly due to the decrease in the galleries (holes) caused by the borer in the plant culms, which prevents the translocation of photoassimilates (compounds resulting from photosynthesis) through the plant and thus increases panicle length and weight. More resistant hybrid Dois híbridos comerciais apresentaram redução na produção de grãos com o aumento do comprimento da galeria, enquanto o sorgo BRS 373 não apresentou correlação significativa, o que pode sugerir certo nível de tolerância ao ataque da broca-da-cana-de-açúcar. O estudo foi pioneiro ao determinar o limiar de ganho e o nível de dano econômico causado pelo ataque dessa lagarta em híbridos de sorgo granífero. Essa informação é fundamental para os agricultores porque permite planejar melhor o cultivo, sabendo que é necessário tomar medida de controle se a infestação da praga atingir 3% de intensidade”, pontua Camila Souza. Gráfico: Produtividade média (kg/ha) de híbridos de sorgo granífero, em três safras consecutivas de 2021 a 2022 sob infestação da broca-da-cana (Diatraea saccharalis) e sem infestação dessa praga. Autores: Camila Souza e Simone Mendes Análise econômica O nível de dano econômico é a menor densidade de insetos, ou de seus danos, que causam prejuízos econômicos. “Quando o custo do controle da praga é igual à perda de produtividade causada pela densidade populacional da broca-da-cana-de-açúcar. Os valores de mercado podem mudar ao longo do tempo de acordo com as condições econômicas atuais”, relata Souza. Os cálculos foram baseados em dados médios dos últimos cinco anos. Para o valor de uma saca de 60 kg de grãos de sorgo, em dólares, o valor considerado foi US$ 8,62. E o custo médio de aplicação via solo por hectare, para controle da broca-da-cana-de-açúcar, US$ 25,90, levando-se em consideração o preço do inseticida comercial por hectare aplicado. Foram realizadas cotações nos principais revendedores para uma aplicação, conforme o Mercado Físico - Sorgo, em 2022.