Using an IGR product alongside a gel bait is a winning combination when it comes to cockroach control.
German cockroaches are amongst the more problematic pests to control due to their small size, numerous harbourages and rapid rates of reproduction. Often there can be unfavourable conditions at the site of infestation, which both aid population growth and make treatments more challenging. Food handling establishments often provide competing food sources and may have irregular cleaning regimes, and some local government housing can suffer from significant hygiene issues. Either way, pest managers need to have a treatment regime they can trust and one that is backed by science.
Cockroach gels are a proven tool for use in German cockroach management. However, perceived wisdom has always suggested that to successfully gain control, it is necessary to minimise competing food sources and ensure a good hygiene regime is in place. However, recent research from Virginia Tech in the US suggests that this isn’t necessarily the case and that cockroach gels can deliver excellent German cockroach control, even in cases where there are competing food sources and poor hygiene practices.
The Virgina Tech research team led by Professor Dini Miller carried out field trials in blocks of units in lower socio-economic areas, which not only had large German cockroach infestations, but also had significant hygiene challenges, where units were infrequently cleaned and large amounts of rubbish, food and dirty dishes were left lying around. Using cockroach gel alone, the populations were controlled in 2-3 months, with the population kept to zero (or at least low levels) for the duration of the trial (over a year).1 The key to success was placing the bait in optimal positions and ensuring enough bait was applied.
Many pest managers are tempted to use a spray in conjunction with baits to “get faster results”. But the reality is, that using sprays, even non-repellent sprays, can impact cockroach behaviour and reduce the effectiveness of baits. In addition, the choice of spray needs to be considered, as often applications are taking place in food management facilities or in areas where children and pets may be present.
The better solution is to use an IGR (insect growth regulator) such as Sumilarv. Sumilarv can actually speed up the performance of cockroach baits. Female cockroaches rarely eat when they are carrying their ootheca. However, when pregnant female cockroaches come into contact with Sumilarv they drop their egg cases. Not only does this generally result in the death of the undeveloped nymphs, but it means the female cockroach starts eating straight away, allowing the bait to get to work.2
Importantly, Sumilarv has no impact on their sensory behaviour so it can be used in combination with baits, without impacting the cockroach foraging behaviour. Additionally, as Sumilarv is classed as an unscheduled poison, it can be used in sensitive areas. With pyriproxyfen, the active ingredient in Sumilarv, very stable and effective at very low concentrations, a single application of Sumilarv can last for many months.
So, when it comes to controlling German cockroaches, especially in tough situations, don’t just grab the ‘strongest’ spray possible. The science says a smart treatment regime using ‘softer’ products – cockroach gel bait plus IGR – is the way to go.
1 Miller, D.M and Smith, E.P (2019). Quantifying the Efficacy of an Assessment-Based Pest Management (APM) Program for German Cockroach (L.) (Blattodea: Blattellidae) Control in Low-Income Public Housing Units: Journal of Economic Entomology, Volume 113, Issue 1, February 2020, Pages 375–384
2 Schal, C. et al. (1997). Reproductive Biology of the German Cockroach, Blattella germanica: Juvenile Hormone as a Pleiotropic Master Regulator. Archives of Insect Biochemistry and Physiology 35:405–426.