The 'black weevil of the soya' (Rhyssomatus subtilis) is currently the most important pest affecting the crop in the northwest region of Argentina (NOA). This species has a significant potential to cause damage, resulting in a 75 percent loss in yield if not controlled properly.
 
National Institute of Agricultural Technology (Inta) of Argentina warned that it is already affecting more than 730 thousand hectares. Experts recommended curing seeds and foliar applications of insecticides to control the pest.
 
It is in a process of expansion since it has been detected in certain areas and is dispersing rapidly from east to west in the NOA region. It was detected in 53 localities of the provinces of Salta, Tucumán and Santiago del Estero, affecting an area of 737,280 hectares.
 
The black weevil attacks the soybean and the bean. 
 
Primarily, monoculture soybean should be avoided as it can promote a steady increase in the population of insects, especially black weevil. Insecticides offer an efficient way to control this pest but only for a limited time.
 
During the initial vegetative phase, the damage caused by the adults in the cotyledons and shoots leads to the death of the plants, consequently reducing the number of plants in the lot.
 
In more advanced vegetative stages, the damage and the death of shoots determine a decrease in the height of the plants and a modification of its structure. In the initial reproductive stage (R3 - R4), they cause the pods to fall.
 
In stages of filling of the grains (R5-R6) and up to the phenological states R7 and R8, the pest can also affect the external tissue of the seed, causing problems during germination. If the grain destination is the industry, the material can be considered as damaged grain, causing loss in quality besides economic loss.