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.

Toxico-Pathological Studies of the Insecticide Metasystox-R (Oxydemeton-Methyl) in Rabbits

One of the widely used insecticides in agriculture and urban pest control is oxydemeton-methyl, which is an organothiophosphate compound. It has a high bioaccumulation effect due to its increased solubility and mobility. This study was carried out to investigate the effect of oxydemeton-methyl toxicity on the environment, and female New Zealand rabbits were used as a model. The rabbits were given oxydemeton-methyl orally in drinking water at a concentration of 34 ppm for six weeks. The clinical signs were diarrhoea, emesis, salivation, lacrimation, fasciculation, muscle tremors and weakness. The haematological parameters, such as the RBCs count, the Hb concentration and the PCV % were significantly decreased. On the contrary, the WBCs count were significantly increased. In addition, an acetylcholinesterase enzyme was inhibited, and a histopathological examination on the liver showed small areas of oval and bridge necrosis infiltrated with mononuclear cells. In the kidneys, there was a variable degree of nephrosis, and the heart showed foci of myocardial degeneration infiltrated with mononuclear cells. Therefore, it is concluded that oxydemeton-methyl is highly toxic to the environment.

Repellency of Novel Catnip Oils Against the Bed Bug (Hemiptera: Cimicidae)

The common bed bug, Cimex lectularius L., resurged as an important urban pest in the last 20 yr. Yet, there are no commercial repellent products labeled for bed bugs available in the United States. We evaluated the repellency of two catnip oils from newly developed cultivars, CR3 and CR9, and compared each to 10 and 25% N,N-diethyl-meta-toluamide (DEET). CR3 contains 63.4% E,Z-nepatalactone and 27.5% Z,E-nepatalactone, and CR9 contains 94.9% Z,E-nepatalactone. Arena studies showed that CR3 and CR9 oils were more effective than DEET within a 24-h period. At 10% concentration, both CR3 and CR9 oils exhibited a repellency of over 94% during the first 8 h. At 25% concentration, the repellency of CR3 and CR9 oils increased to 100%, and repellency of DEET was 92% during the first 24 h. Repellency of 25% CR3 and CR9 oils became lower than 25% DEET after being aged for 3 d. After 28-d aging, repellency of 25% CR3, CR9, and DEET reduced to 25, 64, and 92%, respectively. Soiled socks were placed above repellent treated bands to determine if the repellent can protect soiled socks from being infested. The 20% CR3 oil prevented 100% of bed bugs from infesting soiled socks showing that it was more effective than DEET. These results indicate that catnip oils from CR3 and CR9 cultivars are more repellent than DEET over a 24-h period following application, but their longevity is shorter than DEET after 72 h.

The Inhibition of Serine/Threonine Protein Phosphatase Type 5 Mediates Cantharidin Toxicity to Control Periplaneta americana (L.)

The American cockroach, Periplaneta americana (L.), is a notorious urban pest. It has developed insecticidal resistance to commonly used insecticides. Cantharidin (CTD) is a defensive toxin derived from blister beetles. It has been verified to have insecticidal toxicity in a range of pests. In this study, we determined the ingestion toxicity of CTD and norcantharidin (NCTD) to P. americana to test whether they had the potential to be effective against P. americana. Bioassays revealed that CTD produces toxicity against P. americana. The median lethal concentration (LC50) value of CTD was 50.92 μg/mL, while NCTD displayed nearly no toxicity against P. americana. The inhibition assays of serine/threonine protein phosphatases (PSPs) in P. americana indicated that CTD and NCTD could inhibit PSPs. The value of the half maximal inhibitory concentration (IC50) of CTD was 7.21 ± 0.94 μM, whereas that of NCTD was higher, at 31.65 ± 3.87 μM. Furthermore, the inhibition effect of CTD on the serine/threonine protein phosphatase type 5 of P. americana (PaPP5) was superior to that of NCTD. Specifically, the IC50 of CTD reached 0.39 ± 0.04 μM, while the IC50 of NCTD was 1.87 ± 0.23 μM. This study paves the way for insect-derived agents (CTD) to be applied toward controlling P. americana and contributes to the development of novel insecticides based on PP5 as a target.

Comparative Efficacy of Residual Insecticides against the Turkestan Cockroach, Blatta lateralis, (Blattodea: Blattidae) on Different Substrates

The Turkestan cockroach, Blatta lateralis (Walker) is an invasive urban pest prevalent throughout the Southwestern United States. Despite the presence of this cockroach in peridomestic areas, there is limited information on strategies that can be utilized by pest management professionals (PMPs) to effectively manage populations of this pest. We evaluated the efficacy of dry residues of liquid insecticides commonly used for household and structural insect pest control: Tandem (0.10% thiamethoxam, 0.03% lambda-cyhalothrin), Transport GHP (0.05% acetamiprid, 0.06% bifenthrin), Temprid SC (0.10% imidacloprid, 0.05% beta-cyfluthrin), Demand CS (0.06% lambda-cyhalothrin), Talstar P (0.06% bifenthrin), and Phantom (0.5% chlorfenapyr) on three different substrates against Turkestan cockroach nymphs. Except for Phantom and Talstar P, all insecticide formulations killed 100% of the cockroaches on concrete, 89–100% on tile, and 77–100% on wood within 4 days. The rate of cockroach mortality varied according to the substrates to which they were exposed. Temprid SC and Transport GHP killed cockroaches faster on tile than wood. Tandem provided a faster mortality rate than Transport GHP and Temprid SC on concrete. Demand CS and Tandem killed cockroaches at similar rates on the three substrates. This study provides information to guide PMPs in their selection of insecticide formulations for the management of Turkestan cockroach infestations.

Accumulation of Urban Insect Pests in China: 50 Years’ Observations on Camphor Tree (Cinnamomum camphora)

Since China experienced a rapid and unprecedented process of urbanization and climate change from 1978 onwards, pest outbreaks were frequently reported on urban forests, which reflects a significant imbalance between natural regulation and human control. Based on information extracted from all journal articles and reports about insect pests on camphor tree (Cinnamomum camphora) in urban China, we characterized historical patterns and trends in pest outbreaks over large areas. Our results suggested that (1) most distribution areas of C. camphora in urban China had pest records (14 provinces) over the last 50 years, especially at the south-eastern coastal areas; (2) pests on camphor tree in urban China showed an accelerated growth since the 1990s; and (3) pests on camphor tree in urban China were characterized by native and leaf-feeding species. Urbanization seems to positively correlate with urban pest outbreaks. Changes of urban pest outbreaks could largely be described by synchronic changes of socio-economic indicators, of which CO2 emissions as metric tons per capita is the most significant predictor, followed by GDP and human population. Thus, managers and city planners should allocate resources to socio-economic-related pest outbreaks for a sustainable ecosystem.

The jewel beetle Lamprodila (Palmar) festiva Linné, 1767, a new invasive urban pest of Cupressaceae in Cluj area (Romania) (Coleoptera: Buprestidae)

The jewel beetle Lamprodila festiva (Linné, 1767), in natural habitats of S Europe originally associated with Juniperus spp. (Juniper; Cupressaceae), has been recorded as a recent invasive pest in several European areas, affecting different genera of these coniferous trees and spreading rapidly during the last few years in many countries of Europe. The research was carried out in 2017-2018 in Cluj-Napoca area (Romania), in field and laboratory conditions. The aim of our studies was to identify and study some populations of this new invasive pest occurring in urban areas of NW Romania.