Evaluation of secondary killing effect of Imidacloprid Gel Baits to control Blattella germanica (Linné 1767) (Blattaria: Blattellidae)

Blattella germanica (L.) (Blattodea: Blattellidae) is one of the major household pests worldwide, commonly named German cockroach. Application of gel baits is one of the most efficient management methods. This study investigated the effect of 3 commercially available Imidacloprid gel baits on the palatability of dead cockroaches and, consequently, on the efficacy of secondary killing. German cockroaches killed by the gel baits and others killed by freezing were offered to conspecifics, the numbers of cannibalistic cockroaches and dead cockroaches, as well as weight loss were recorded. Despite the content of Imidacloprid is identical in all the baits, the palatability of the cockroach killed by the gel consumption and used as food was different between the 3 commercial products, with consequences on the secondary killing effect. These results suggest as the bait co-formulants play an important role not only on the palatability of the bait but also in the palatability of the dead cockroaches which are eaten by conspecifics, and therefore, in the result of a pest control application.

Differential microbial responses to antibiotic treatments by insecticide-resistant and susceptible cockroach strains (Blattella germanica L.)

The German cockroach (Blattella germanica L.) is a major urban pest worldwide and is known for its ability to resist insecticides. Past research has shown that gut bacteria in other insects can metabolize xenobiotics, allowing the host to develop resistance. The research presented here determined differences in gut microbial composition between insecticide-resistant and susceptible German cockroaches and compared microbiome changes with antibiotic treatment. Cockroaches received either control diet or diet plus kanamycin (KAN) to quantify shifts in microbial composition. Additionally, both resistant and susceptible strains were challenged with diets containing the insecticides abamectin and fipronil in the presence and absence of antibiotic. In both strains, KAN treatment reduced feeding, leading to higher doses of abamectin and fipronil being tolerated. However, LC50 resistance ratios between resistant and susceptible strains decreased by half with KAN treatment, suggesting gut bacteria mediate resistance. Next, whole guts were isolated, bacterial DNA extracted, and 16S MiSeq was performed. Unlike most bacterial taxa, Stenotrophomonas increased in abundance in only the kanamycin-treated resistant strain and was the most indicative genus in classifying between control and kanamycin-treated cockroach guts. These findings provide unique insights into how the gut microbiome responds to stress and disturbance, and important new insights into microbiome-mediated insecticide resistance.

Level of Pyrethroid-resistance Associated with Cytochrome P450 Expression in German Cockroach Blattella germanica (Blattodea: Ectobiidae) in the Field Collected Strains

Background: Cytochrome P450-dependent monooxygenases are a very important metabolic system involve in insecti­cide resistance. This study was conducted to find the association between the expression level of cytochrome P450 (CYP450) and permethrin-resistance level among four strains of the German cockroach Blattella germanica (L) (Blat­todea: Ectobiidae). Methods: Three field strains of German cockroach with different frequency of exposure to pesticides, and a laboratory susceptible strain were used in the present study. Insecticide susceptibility bioassays were carried out to detect re­sistance to permethrin. The concentration of CYP450 in each strain was determined using ion-exchange HPLC chroma­tography. Biochemical assays was performed to analyse CYP450 activities. Results: The resistance ratios (RR) to permethrin among three field strains were 3.29, 4.10 and 6.17-fold comping with the susceptible stain. The CYP450 activity of three field strains was 1.6, 2.4 and 2.7 times higher than in the sus­ceptible stain. The amount of CYP450 per mg of protein was significantly different between the susceptible and the three re­sistant strains. The resistant cockroaches showed a relatively high expression of CYP450 enzymes. A strong corre­la­tion was found between permethrin resistance level and total concentration of CYP450 enzymes. Conclusion: The results of current study show that more frequent usage of a pyrethroid insecticide cause the metabolic insecticide resistance to rise in German cockroach. Therefore, there is a ratio correlation between resistance level and monooxygenases activities in insect. Thus, the control program must be managed according to history of pesticide us­age.

Effect of insect growth regulators on two german cockroach strains and pharaoh ants

When eating poisoned baits based on 0.1–1.0 % pyriproxyfen, within 6 weeks killed up to 50 % of German cockroaches of the S-NIID strain, and 12 % of cockroaches of the OBN strain. The resulting oothecae turned out to be defective and the second generation of cockroaches did not hatch. Morphological changes consisted were in the deformation of the wings (rudimentary, curved, twisted) and in the inability of the larvae to transform into adults. In experiments with an alternative food, similar results were obtained, females formed more oothecae, but the emergence of new generation larvae was not recorded. The consumption of pyriproxyfen-based baits by Pharaoh ant led to the elimination of colonies. A significant decrease in brood number was recorded at 3–6 weeks, and complete death of brood was observed at 6–8 weeks in all treated colonies. The absence of brood can be explained by both mortality as a result of developmental disorders and the cessation of egg laying by queens. Keywords: insect growth regulators, German cockroach, Pharaoh ant, pyriproxifen, hydroprene.

Infection With The Pinworm Blatticola Blattae And Survival of Starving German Cockroaches, Blattella Germanica

The German cockroach, Blattella germanica, is often infected with the pinworm, Blatticola blattae. To investigate the effect of pinworm infection on cockroach survival, we artificially manipulated the pinworm infection status of two lines of German cockroaches kept in the laboratory and compared survival rates in starvation. Of the two lines of German cockroaches WATn and NIIDp bred in the laboratory, the WATn line was not infected with pinworm, and the NIIDp line was naturally infected with pinworm B. blattae. The WATp line was created by artificially infecting the pinworm B. blattae with this WATn line. The NIIDn line was created by treating the NIIDp line with anthelmintic drugs. The 50% survival days of uninfected WATn line of starving cockroaches was 8 days, and infected WATp line of starving cockroaches was 13 days. The 50% survival days of naturally infected NIIDp line of starving cockroaches was 6 days, and that of anthelmintic-treated NIIDn line of cockroaches was 4 days. The survival days were significantly longer in pinworm-infected cockroaches than uninfected or anthelmintic-treated cockroaches. These results suggest that pinworm infection enhances the survival of cockroaches under starving conditions.