Gavin Wilson, Technical and Marketing Manager for Liphatech, explains the value of using LD50 data when it comes to choosing a rodenticide.
With a range of rodent control products on the market, what factors should pest managers use to select a high performing product? It is not uncommon for pest managers to consider LD50 as an indicator of the efficacy of a rodent control product. Whilst it indicates the potential toxicity of a substance, it doesn’t really tell you much about product performance. Importantly, it does not guarantee that the product will be consumed by the rodent.
To understand why so many people make that mistake, you first need to understand what the LD50 is and what it’s for.
The LD50 (LD stands for lethal dose) indicates the potential toxicity of a substance. The LD50 is the dose at which a substance is lethal for 50% of the animals in a tested group. It is general given in milligrams of a chemical substance administered per kilogram of body weight. To determine the oral LD50 value of a substance, toxicologists prefer to use laboratory rats that are force fed the substance in a single dose. These studies aim to identify the acute toxicity of substances and classify them according to their hazard level (the higher the LD50, the less the toxic the product is).
As Dr Eric Blouin, toxicology expert at Physiotow (France), explains, “The LD50 is mainly used to develop emergency procedures (generally by poison control centres) in case of accidental human exposure, to create directives on the use of appropriate clothing and safety equipment for people when handling the substance, to regulate labelling, issue caution statements and transport conditions, and to help establish limits for professional exposure.”
The LD50 should be considered with care. First, its value may be determined based on various factors, such as the animal species in question as well as the sex, age and weight of the animals used in the test. Furthermore, there are several test protocols and methods available to calculate the LD50 which gives different results for the same product tested.
“You have to remember that LD50 is not a numerical value that corresponds to the toxicity class of a substance,” added Dr Blouin. “It cannot be used to determine a rodent control product’s efficacy because it does not take all criteria into account. To be effective, you should know that a rodenticide must only be both toxic for rodents (all rodenticides on the market are), but they must also be palatable; if not, the rodents simply won’t eat it! In other words, a rodent control product may actually be completely ineffective because rodents don’t like its taste.”
To really assess the efficacy of a rodenticide, you should trust the results of field tests. To choose a rodent control product, the question you need to ask is: “Will the rodent eat the bait?” Only field studies can provide the answer.
Liphatech’s R&D department has developed palatability and field efficacy protocol trials to assess how well its products are consumed and to compare their efficacy against other products on the market. These protocols replicate the real-world use conditions that customers face. For example, baits are placed on sites where food competition is high (with the presence of grains and cereals) and the target rodents are wild rats that are free to choose their food source. The efficacy of the rodent control product is then measured based on the level of consumption and the absence (or not) of rodents at the end of the treatment.
Performance of Liphatech rodent baits in situations where there are high levels of food competition is certainly a good indicator of high palatability, but Liphatech have also developed a 30-day field palatability test protocol to assess performance versus competition. During the field trials, Liphatech baits and those from a leading competitor are stacked side by side (or mounted in piles on two rods). Consumption is checked every three days to compare palatability of the different baits.
Pest managers can have confidence that Liphatech rodent control products deliver in real world situations – performance is not theoretical, it is proven. So don’t focus on LD50 data when selecting a product, focus on efficacy in the field. Following label instructions and best practice advice will ensure in the success of a treatment.
