Argentina issues Sternechus pinguis pest alert

By Leonardo Gottems, Reporter for AgroPages

Last month, the National Agricultural Technology Institute (INTA) of the Reconquista Region, Argentina, released a health alert about the presence of the insect, Sternechus pinguis, in soybeans in the province of Santa Fé, one of the main producers of this crop in the South American country. According to the institute, it is a pest that synchronizes its cycle with the soybean crop life cycle, with both larvae and adults causing damage.

“From October to December, 2020, adults emerge in stages following the rainy season,” said INTA's Agricultural Experiment Station in an official statement. According to its technicians, the larvae remain inside the stem, where they feed and develop from December until the end of the crop cycle.

Sternechus pinguis was mentioned for the first time in Brazil and acquired economic importance, and around 30,000 ha were sprayed with insecticides to control it. At the start of the 1990s, it was detected for the first time in Paraguay. In the north of Argentina, during the last campaign, there was an increase in the population of soybean weevil that affect the plant stands of the crop.

Since it was first detected, its population increase has been worrying. The attack by the pest is more intense during the direct seeding and minimum tillage lots, although it is also possible to find plants damaged by larvae and adults in soybeans during conventional tillage. According to information from Paraguay, the potential for damage is high, because both adults and larvae damage plants, especially when their numbers are high and occurs during the initial phase of cultivation. During this phase, there may be a partial or total loss of crops.

Insecticide evaluations carried out in Brazil showed efficient control with chlorpyrifos ethyl 480 g ai/ha, monocrotophos 150 g ai/ha, deltamethrin 7.5 g ai/ha, methyl parathion 400 g ai/ha, profenofos 400 g ai/ha and methidathion 200 g ai/ha.

“For now, it is only a secondary plague, but knowing the enemy is the best defense, since if it becomes a problem, we will have the artillery ready,” explained engineer María Ana Sosa, who added that management done in fields will depend on whether the pest spreads around or not, a concept that includes crop rotation, since sorghum, corn, sunflower and cotton are not food crops.

She also stressed that the key is to monitor the culture during the early stages to detect the presence of adults and early damage, which appears as the fraying of tissue. Regarding the expansion potential of the pest, Sosa stated, “It could expand by increasing the area of direct sowing. For now, we have located it as far as the Reconquista region, but we have no information about it reaching further south.”

One of the necessary actions for decision-making during pest control is early monitoring. “It is essential to detect the presence of the pest at the early stages of the crop. Check the lot at dawn and dusk,” said the experts.

According to the Argentine INTA, chemical leaf control with registered products must be carried out at dusk or even at night, since the target is the adult insect.