Effective mass trapping of pests attracted to farm fields on a large scale could be a way of generating low-cost protein for animal feed, according to a US Government research team.
As well as crop pests, agricultural environments can be attractive to pests which pose medical risks to humans, particularly wet environments such as rice fields, which are prone to attracting disease-carrying mosquitoes as well as other problem insects.
In two pieces of research published in Journal of Economic Entomology, the US Department of Agriculture scientists firstly make a case for using insect harvest technologies to collect large numbers of pests, then go on to assess the potential of their own novel trap in a field setting.
Combining benefits
The positives of the approach, they wrote, is that it provides a two-in-one solution addressed pressing issues for the sustainability of agriculture: reducing the presence of medically-significant insects in areas where people work and crop pests, while also providing a sustainable and nutritious source of protein for livestock such as poultry and ruminants. It also provide a stopgap insect feed alternative while the insect farming industry scales up production.
It’s a technique which is already used in some parts of the world, such as Mexico, where grasshoppers are harvested for food from alfalfa fields and around Lake Malawi, where non-biting midges are harvested and made into protein-rich cakes. However, the concept of combining pest control and a food source has declined in recent years.
Before any revival happens, there are still some challenges that need to be addressed, the researchers stressed. These include ensuring that trapped insects are free from contaminants, effective processing of the insects into usable feed and properly assessing how mass-trapped insect feed contributes to livestock nutrition.
Another key issue is ensuring trapping technologies are optimal for the task in hand. That’s where their USDA Biomass Harvest Trap (USDA-BHA) could come in, they say.
Suck it and see
The USDA-BHA is a modular suction trap using both carbon dioxide, which can be produced from either propane or dry ice, as well as an LED light to attract target insects. The team set up the traps at two locations near both water sources and farmland, aiming to test its performance against three other technologies commonly used in mass trapping initiatives: a Centers for Disease Control and Prevention (CDC) light trap, Encephalitis virus surveillance trap, and Biogents Sentinel trap.
They found that while the USDA trap collected a greater insect biomass than the others tested, they saw no difference in mosquito catch. And although the claim is that the trap minimises beneficial insect catch, it sucked in greater numbers than the other traps tested, including moths, ground beetles and spiders.
Care — and refinements — needed
However, while “remarkably few” beneficials were caught in the other models, numbers were also relatively low for the experimental device, and fewer were caught at night, where accidental catches of key pollinators such as bees could also be avoided. The team also noted that in areas of intensive farming or other environments disturbed by human activities, insect diversity tends to be reduced, so trapping there would likely minimise biodiversity risk.
“Although minimal, the USDA-BHT captures beneficial arthropods and collections depend upon the arthropod diversity in the sampling area. Thus, it would be advisable to assess the local arthropod diversity prior to collecting insect biomass for animal feed,” they suggested.
Sorting mosquitoes from other insects also took significantly longer using the USDA trap, while the mechanics of the system damaged more insects leading to difficulties in species identification. This led the team to conclude that the device was better suited to collecting high levels of insect biomass for use as feed than targeted mosquito surveillance initiatives.
“Further improvements are needed to increase insect collection if harvesting is to be used to supplement traditional commercial protein sources,” they added.
