Alissa Welsher, Ph.D Poultry Technical Consultant

Dr. Alissa Welsher graduated from the University of Pittsburgh with a degree in Biological Science and received her Master's in Poultry Science and Ph.D in Molecular Biology from the University of Arkansas. Her areas of expertise include pre-harvest food safety interventions, vaccines and insecticides. 

Can Darkling Beetles be an Indicator of Pre-Harvest Salmonella Load?

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Posted by Alissa Welsher, Ph.D. on 15 May, 2024

Darkling beetles are a proven vector for several poultry diseases and pathogens and can cause considerable damage to poultry houses if the pests are not properly controlled. While the poultry industry is well versed in the implications of insect presence in the poultry house, what has recently been revealed through new preliminary research is a correlation between darkling beetle populations and Salmonella loads in poultry houses, deepening our understanding of how beetle presence can not only spread disease, but also impact food safety.

The preliminary research also reinforces the importance of establishing and maintaining a strong integrated pest management program as a key strategy in managing pre-harvest Salmonella.

First, understanding darkling beetle behaviors and how the pests transmit disease can help producers and their technical teams better prevent the threat pests pose to bird health, food safety and poultry house infrastructure.

Examining Darkling Beetle Behaviors

If darkling beetle populations are not properly treated, the insects can thrive in a poultry house. Factors that are often naturally found in the poultry houses provide a favorable environment and cause populations to proliferate, including:

  • Dark houses: Darkling beetles like dark environments. They are typically nocturnal but can be active at any time of day in a dark poultry house.
  • Litter: Beetles often congregate in large areas and burrow down in litter in cold weather as an escape mechanism.
  • Heat: Darkling beetles can typically be found under feed lines and feeders where there is heat, moisture, grain source and bird protection.

Darkling beetles can also be found inside walls and the center of the house when there is no more room under the feed lines. When beetles are found in the center of the house, it indicates a high population.

How Darkling Beetles Can Transmit Salmonella

Darkling beetles spend much of their life cycle in and around poultry housing, feed, and litter. The insects are exposed to pathogens found in the litter and can internalize pathogens and carry pathogens on their exoskeleton.

Much like rodents and flies, darkling beetles can then spread pathogens either through touching feed that is ingested by birds, or by birds ingesting contaminated beetles themselves.

Chickens may sometimes feed on beetles. When they ingest the beetles, they can become the intermediate host of intestinal parasites and become impacted as reservoir for numerous poultry diseases.

Additionally, beetles and larvae can bite chicks and adult birds as they look for moisture or food. The bites can cause mortality in young chicks and sores or scabs in older birds which can lead to condemnations at the processing plant.

When producers and their teams understand where darkling beetles are commonly found and how they transmit disease, taking steps to eradicate beetle presence becomes more successful.

While eradicating beetle populations can help improve health outcomes for the birds, we now also have new research that takes mitigation incentives a step further: by showing a potential correlation between beetle populations and Salmonella load.

A Look at New Preliminary Data

Pests are a source of pathogens and Salmonella can harbor in pests, but there has never been data showing that the amount of pathogen carried influences things such as incoming Salmonella load to a processing plant. 

When exploring the potential correlation between beetle populations and Salmonella load, the initial hypothesis was that broiler house beetle populations would influence Salmonella load in birds at the end of the grow-out period.

To guide the study, two objectives were noted:

  1. Quantify the relationship between house-level beetle populations and Salmonella load in birds prior to processing.
  2. Compare Salmonella serotypes found in beetles to those found in (paired) plant rinse samples.

Samples included:

  • On Farm: 6 feathers-on rinse, 6 cloacal swabs and beetles
  • In Plant: 6 hot rehang rinse, 6 pre-scald rinse, beetles for serotyping

The current study looks at the correlation between beetle load in a house and feathers on rinses data from that same house, revealing that beetle load in house can likely be used as a diagnostic tool indicating pre-harvest Salmonella load. Elanco teams are currently collecting additional on-farm samples and will move to correlating plant samples as a second study objective.

While further research is developed, the preliminary results show a clear benefit to eradicating beetle presence in the poultry house through biosecurity measures.

Next Steps for Producers

As producers seek to control pests in the poultry house, biosecurity measures and an integrated pest management program (IPM) are essential components to the insect mitigation strategy.

Producers should leverage an IPM strategy that includes the following:

  • Walk the houses and pick up organic material
  • Repair water leaks and damaged feeders that are dropping feed
  • Check for potential insect breeding sites and remove them
  • Keep grass low near the buildings
  • Remove excess moisture from inside and outside of houses
  • Remove debris from ventilation fans
  • Check insulation and roofing
  • Leverage insecticides and rotate chemical classes to avoid chemical resistance among the population

Insecticides, most commonly used when birds are not present in a house, can be used on the perimeter of the poultry house to control populations in the soil and grass, on walls, below feed lines and any other areas that beetles congregate. Insecticide classes should also be rotated regularly to prevent resistance.

From preliminary data gathered, we can better understand the importance of biosecurity measures to help address preharvest food safety.


Food Safety


Darkling beetle

Pest control

Salmonella control