Posted on June, 12, 2024 at 09:39 am
You have likely heard about the infamous “insect apocalypse,” in which insect populations are drastically decreasing due to climate change. However, not all insects are expected to die. Quite the contrary, many insect pests are predicted to thrive, but this group is vastly understudied. In particular, the impacts of climate change on stored-product insect pests are not well known.
The lack of research likely stems from the over-generalized assumption that stored-product pests live only in buffered environments such as food facilities. However, this is often not the case because such species find shelter in and travel through the landscape. Additionally, many storage areas are imperfectly sealed from the environment.
If stored-product pests will be affected by climate change, then it is vital to know how. Will changes prompt populations to expand, shrink, move, or stay put? This information is essential so proper management and surveillance programs can be implemented.
The larger grain borer (Prostephanus truncatus, often abbreviated as LAGB) is a highly destructive beetle that is native to the forests of Central America and Mexico. It is a wood-boring insect that adapted to stored corn. Populations can readily destroy 40 percent of grain in just a three-month storage period. LAGB was accidentally introduced to Tanzania, Africa, in the late 1970s and again to Togo, Africa, through commerce. In Africa, LAGB additionally adapted to consuming cassava, an important crop used for various purposes, including food and medicine. Losses of stored cassava from LAGB are estimated to be 52-74 percent.
Even though the beetle thrives in grain storage facilities, it persists in and moves through forests. Thus, if infestations are eradicated in a storage facility via pesticides or biocontrol, insects in the surrounding environment can readily move back into the facilities.
LAGB is a major threat. Can it survive anywhere else? What will likely happen in the future under climate change?
At the U.S. Department of Agriculture’s Agricultural Research Service (USDA-ARS), my colleagues and I teamed up to find answers to these questions and more. Alison Gerken, Ph.D., and Rob Morrison, Ph.D., are experts in stored-product pest management and modeling population dynamics. During his time at Texas A&M University, Dalton Ludwick, Ph.D., provided essential details concerning LAGB occurrence in the southern United States. Last, I am postdoctoral fellow interested in insect behavior in disturbed landscapes. Our work is supported by the Oak Ridge Institute for Science and Education and the USDA-ARS SCINet scientific computing initiative. Together, we published an article this month in the Journal of Economic Entomology with the results of our research modeling the potential effects of climate change on the range of the larger grain borer.
We used the species distribution model MaxEnt through the software platform Wallace to create models that predict the areas of potential suitability on a global scale. We informed the model with the known locations of LAGB and which bioclimatic variables are important to the insect. Bioclimatic variables include measurements of temperature and precipitation that are recorded on a global scale, are important to organism survival and growth, and are predicted to modulate with climate change. In general, the model takes this information, generates a niche space of the organism, and projects this to other areas and future climate scenarios. This projection creates a suitability map that ranges from 0 to 100, with higher numbers indicating higher suitability. Higher suitability means that if a population of the insect arrives in that area, the population is more likely to establish; thus, the maps also show the potential distribution of the insect.
Well, if LAGB is connected to an apocalypse, it is not because insect populations are dying.
The current global projection reflects the species’ origins, as highly suitable areas are primarily tropical, subtropical, and coastal areas. Chiefly, extreme levels of precipitation and low temperatures during the coldest times of the year made areas less suitable, which makes sense for a tropical species that thrives in hotter, wetter conditions.
In the future, highly suitable areas will likely expand away both from the equator and more inland. Greater expansion is likely to occur under high climate change scenarios. Importantly, the greatest change is expected by 2050, with little change in the following 20 years.
The models show that monitoring efforts are needed now and should be targeted along the coast and within shipping ports. Surveys are necessary for the United States, as areas in the Corn Belt region will likely become more suitable for LAGB survival. The pest is also likely to survive in Asia, Europe, and Oceania if it is accidentally brought there via cargo ships and is not quarantined. These areas are leading producers of corn and cassava, and the destruction caused by the pests could be devastating.
Source: Entomology