Locusts and grasshoppers (Orthoptera: Acridoidea) are among the most dangerous agricultural pests. Their control is critical to food security worldwide and often requires governmental or international involvement. Although locust and grasshopper outbreaks are now better controlled and often shorter in duration and reduced in extent, large outbreaks, often promoted by climate change, continue to occur in many parts of the world. While some locust and grasshopper control systems are still curative, the recognition of the damage these pests can cause and the socioeconomic consequences of locust and grasshopper outbreaks have led to an increasing paradigm shift from crop protection to preventive management. Effective preventive management strategy relies on an improved knowledge of the pest biology and ecology and more efficient monitoring and control techniques.

Grasshopper outbreaks cause significant damage to crops and grasslands in US. Chemical control is widely used to suppress these pests but it reduces environmental quality. Biological control of insect pests is an alternative way to reduce the use of chemical insecticides. In this context, two entomopathogenic fungi, Metarhizium brunneum strain F52 and Paranosema locustae were evaluated as control agents for the pest migratory grasshopper Melanoplus sanguinipes under laboratory and greenhouse conditions. Third-instar grasshoppers, reared in the laboratory, were exposed up to fourteen days to wheat bran treated with different concentrations of each of the fungi alone or the two pathogens combined. In the greenhouse, nymphs were placed individually in cages where they were able to increase their body temperatures by basking in the sun in an attempt to inhibit the fungal infection, and treated with each pathogen alone or in combination. Mortality was recorded daily and presence of fungal outgrowth in cadavers was confirmed by recording fungal mycosis for two weeks’ post-treatment (PT). For combination treatment, the nature of the pathogen interaction (synergistic, additive, or antagonistic effects) was also determined. In laboratory conditions, all treatments except P. locustae alone resulted in grasshopper mortality. The application of the pathogen combinations caused 75% and 77%, mortality for lower and higher concentrations, respectively than each of the pathogens alone. We infer a synergistic effect occurred between the two agents. In greenhouse conditions, the highest mortalities were recorded in combination fungal treatments with a M. brunneum dose (60% mortality) and with a combination of the two pathogens in which M. brunneum was applied at high rate (50%) two weeks after application. This latter combination also exhibited a synergistic effect. Exposure to the P. locustae treatment did not lead to mortality until day 14 PT. We infer that these pathogens are promising for developing a biopesticide formulation for rangeland pest grasshopper management.

This study contributes to the body of knowledge on the Moroccan locust (Dociostaurus maroccanus) in Tajikistan, exploring its distribution, population dynamics, economic significance, and management. Our research covers the period from 2012 to 2023. Over this period, there has been a documented increase in the size of the infested areas, with southern Tajikistan being the most severely affected. Outbreaks of economic importance happened each year throughout the timeframe. The total area impacted by infestations reached 752,130 hectares in southern Tajikistan alone. The paper places emphasis on the necessity of cross-border and regional collaboration and the adoption of environmentally sustainable control methods, such as the use of biopesticides.