Pervasive Resistance to Pyrethroids in German Cockroaches (Blattodea: Ectobiidae) Related to Lack of Efficacy of Total Release Foggers.

Despite limited efficacy data, do-it-yourself (DIY) insecticide products often promise low-cost alternatives to professional pest control. Total release foggers (TRFs, 'bug bombs'), which are prominent DIY products, were recently shown to be ineffective at reducing German cockroach (Blattella germanica L.) infestations, in contrast to highly effective baits. However, the reason(s) for TRF failure remain unknown. Therefore, we investigated insecticide resistance of apartment-collected cockroaches from homes where TRFs failed. In topical (direct) application assays, resistance to cypermethrin (a common active ingredient in TRFs) was 202 ± 33 times that of a laboratory insecticide-susceptible population (based on LD50 ratios), while resistance to fipronil, a common bait active ingredient, was considerably lower at 14 ± 2 times that of the laboratory insecticide-susceptible population. The addition of PBO, a P450 inhibitor that synergizes pyrethroids, enhanced the efficacy of cypermethrin, but only at high doses of cypermethrin. Additionally, >96% of screened cockroaches possessed at least one copy of the L993F mutation in the voltage-gated sodium channel, known to confer resistance to pyrethroids (knockdown resistance, kdr). Because TRF treatments killed insecticide-susceptible sentinel cockroaches but failed to kill apartment-collected cockroaches, these results suggest that pyrethroid resistance is a major factor contributing to the failure of TRFs. Multiple mechanisms of resistance, including metabolic detoxification of the pyrethroids and kdr mutations that confer target-site insensitivity, suggest that TRFs would lack efficacy against German cockroaches in residential settings, where high levels of pyrethroid resistance have been documented globally.

Nuclear DNA PCR-RFLPs that distinguish African and European honey bee groups of subspecies. I: Comparison of long PCR and standard PCR to screen for polymorphisms.

Nuclear DNA RFLPs betweenAfrican and European honeybees (Apis mellifera L.) were sought by amplifying short (1-2 kbp) and long (> 5 kbp) anonymous regions of DNA and digesting the respective PCR products with a collection of restriction enzymes. Three short and three long regions were each screened with 26-31 enzymes. From a total of 163 locus enzyme combinations (LECs), seven revealed informative polymorphisms. One of these LECs came from one of the three short regions (S-3 with AluI), producing a total of seven alleles, five of which were African-specific. The search for useful RFLPs was far more effective within the long regions. The other six inforrmative LECs came from the three long regions (L-1 with AluI, L-2 with AvaI and HaeIII, and L-5 with HaeIII, DdeI, and SpeI), producing a total of 43 alleles, of which 18 were African-specific, 13 were European-specific, and two were predominantly found in the European samples. Among the European alleles, two were predominantly found in west European honey bee subspecies. Strong associations between alleles generated by pairs of enzymes at a locus were found.

Nuclear DNA PCR-RFLPs that distinguish African and European honey bee groups of subspecies. II: Conversion of long PCR markers to standard PCR.

Nuclear DNA PCR-RFLPs previously found in amplifications of three long (> 5 kbp) anonymous regions of DNA were made analyzable using standard PCR procedures. RFLP analyses were simplified by restricting the amplifications to sections, within each locus, that contained most of the informative polymorphic sites. AluI digests of locus L-1 section 2 (L-1S2) revealed three suballeles of which one was African-specific (Apis mellifera scutellata Lepeletier) and one was east European-predominant (A. m. ligustica Spinola, A. m. carnica Pollman, and A. m. caucasica Gorbachev). Alleles found originally at locus L-2 with AvaI were determined in RFLP analysis of two sections, L-2S1int and L-2S2, resulting in two African-specific and two east European-predominant suballeles. Suballele identity was determined by the combination of banding patterns from both fragments. Polymorphisms revealed by HaeIII in locus L-2 were analyzed in amplifications and digests of L-2SM1int. an 830 bpfragment within L-2S1. Seven suballeles were found of which two were African-specific and three were east European-specific or predominant, including one suballele specific to the east European subspecies A. m. caucasica. In locus L-5, RFLPs were detected with HaeIII, DdeI, and SpeI. HaeIII polymorphisms were analyzed by amplification and digestion offragments L-5S1xt and L-5S1ter: Five suballeles were found of which three were African-specific and one east European-predominant. For DdeI, all five alleles originally found with long PCR could be identified in RFLP analyses of three sections. Two African-specific, one east European-specific, and one west European-predominant (A. m. mellifera L. and A. m. iberica Goetze) suballeles were found. A west European-predominant suballele was also found in RFLP analysis of L-5S3 with SpeI. Allele frequency data from Old World and US. populations are presented.