Bioactivation manages disease transmitted by Dalbulus maidis in corn

Acadian Plant Health (APH) has conducted a study in partnership with the Brazilian UNESP (São Paulo State University) that revealed the effectiveness of bioactivators based on Ascophyllum nodosum. 

This seaweed grows exclusively in the cold waters of the North Atlantic.

According to Samir Filho, Market Development Coordinator for APH in Brazil, although not a direct agent in combating the corn leafhopper (Dalbulus maidis), the extract from Ascophyllum nodosum contributes to the strengthening and growth of the crop.

"The application of the seaweed extract has shown positive effects on the development and yield of corn, resulting in more robust plants with reduced oxidative stress, which can contribute to greater tolerance to infections," he explained.

Brazil is one of the world's largest corn producers. According to estimates from the National Supply Company (Conab), the 2024/2025 production could reach 119.8 million tons.

However, the outcome could be better. Besides climatic issues, pests are major villains of the harvest. "One of the main problems with this crop is Dalbulus maidis, an insect that is difficult to manage and the primary vector of diseases in the corn stunt complex and corn stripe, which drastically impact corn yield," Filho stated.

Ascophyllum nodosum is unique to the cold waters of the North Atlantic. It grows in intertidal zones under harsh conditions: during tide changes, it is submerged in saltwater at high tide and then exposed to dehydration at low tide. It faces extreme temperatures in summer (up to 40°C) and winter (-20°C). These characteristics have led to the development of survival mechanisms, producing bioactive compounds that provide defense against such extreme environmental conditions.

"Our goal was to evaluate the effectiveness of the Ascophyllum nodosum extract in activating resistance metabolism against biotic and abiotic stresses in corn. The study investigated the foliar application of the solution in combination with biological insecticides under field conditions in Brazil during the 2023 and 2024 seasons," the expert commented.

During the study period, the effects of Acadian Plant Health's seaweed extract on corn development and yield were evaluated, comparing it with a positive control (plants protected from leafhopper attack), a negative control (plants exposed to leafhopper attack), as well as a biological insecticide alone and combined with Ascophyllum nodosum extract. According to APH, notable results included:

- Crop Vigor: The seaweed extract, alone or combined with a biological insecticide, significantly increased the vigor of corn plants compared to the negative control in both growing seasons (2023 and 2024). The positive control showed the highest vigor index due to being completely free from leafhopper attack.

- Corn Stunt Disease (CSD): Untreated corn plants (negative control) showed the highest rates of CSD. The seaweed extract did not reduce the incidence of the disease but improved plant development even in the presence of CSD;

- Phytoalexins: The seaweed extract significantly increased the production of zealexin, a phytoalexin produced by the plant's secondary metabolism in response to biotic stress. Phytoalexins are defense substances against pathogenic fungi and bacteria. In this case, the production of zealexin was elicited by the Ascophyllum nodosum extract.

- Photosynthetic Pigments: The seaweed extract, especially when combined with biological insecticides, increased chlorophyll production, even surpassing the positive control. Plants with higher CSD severity showed lower chlorophyll levels;

- Oxidative Stress: The use of the seaweed extract resulted in lower concentrations of hydrogen peroxide (H₂O₂) and lipid peroxidation (MDA), indicating reduced oxidative stress.

- Antioxidant Enzymes: The activity of the superoxide dismutase (SOD) enzyme was higher in plants affected by CSD, with no difference between treatments. The application of the seaweed extract increased catalase activity.

Yield Components and Production: The combined application of seaweed extract and biological insecticides increased yield components, such as the number of kernels per row and per ear, leading to a higher final grain yield. The Ascophyllum nodosum extract alone mitigated yield losses compared to the negative control.

(Editing by Leonardo Gottems, reporter for AgroPages)