Genetic Evidence for Multiple Invasions of Coptotermes formosanus (Blattodea: Rhinotermitidae) in California.

New infestations of the Formosan subterranean termite, Coptotermes formosanus Shiraki (Blattodea: Rhinotermitidae), were discovered in southern California, namely in Rancho Santa Fe and La Mesa (San Diego County) and Highland Park (Los Angeles County) in 2021. We investigated whether these new infestations were related to the previous infestations in La Mesa (2018) and Canyon Lake, Riverside County (2020). We used two mitochondrial genes (COI and COII) and seven polymorphic microsatellite markers to infer the genetic relationship between southern California colonies and their breeding systems. The samples collected from seven localities belonged to five colonies (inter-colony distances ranged from ~160 m to 185 km, with an average of 97 km). Of these five colonies, two were simple families, and three were extended families. Structure analyses of microsatellite genotypes grouped the termite samples into three distinct genetic clusters, suggesting at least three independent introduction events in southern California.

Genetic Analysis of Formosan Subterranean Termite (Blattodea: Rhinotermitidae) Populations in California.

A new infestation of the Formosan subterranean termite, Coptotermes formosanus Shiraki (Blattodea: Rhinotermitidae), was discovered in Canyon Lake, Riverside County, California. We used three mitochondrial DNA (COI, COII, and 16S) and seven polymorphic microsatellite markers to characterize the genetic relationship of the colony with two other colonies that were collected in 1992 and 2018 in La Mesa, San Diego County. Maximum likelihood phylogeny of C. formosanus based on concatenated COI and COII sequences revealed that the two La Mesa populations (CA01 and CA02) and the Canyon Lake population (CA03) were from different maternal lineages. Based on the 14 COII haplotypes of C. formosanus found world-wide, CA01 and CA02 belonged to a haplotype widely distributed across the United States, while CA03 was grouped under a haplotype predominantly found in Asia. Microsatellite allele frequencies across all loci for both La Mesa populations were relatively similar, but significant genetic differences were found between CA02 and CA03 colonies (FST = 0.24; Dest = 0.30; G″ ST = 0.55; P < 0.01).

Lethal and Sublethal Effects of Selected Systemic and Contact Insecticides on Nephaspis oculata (Coleoptera: Coccinellidae), in a Tri-Trophic System.

Nephaspis oculata (Blatchley, 1917) is a whitefly predator which has been reported feeding on several whitefly species. In South Florida, it attacks rugose spiraling whitefly, an invasive pest of urban trees which was first reported in the United States in 2009. The management of rugose spiraling whitefly relies heavily on the use of insecticides which may negatively impact biological control agents. We studied the effect of bifenthrin (spray) and imidacloprid (drench) application on survival, fecundity, and behavior of N. oculata in the laboratory. Adult beetles survived significantly longer in control and systemic imidacloprid compared to bifenthrin treatment, but there was no significant difference between control and systemic imidacloprid applications. However, the fecundity of beetles in the imidacloprid treatment was significantly lower than the control. There was no significant difference between the survival of beetles in bifenthrin and control treatments 3 mo post application. Beetles avoided bifenthrin-treated leaves but did not avoid systemic imidacloprid-treated in a no-choice test. Also, beetles' feeding rate on bifenthrin-treated rugose spiraling whitefly nymphs was significantly lower in a no-choice test. In the choice test, there was a significant difference in feeding rates on whiteflies between choices of bifenthrin/control but no significant difference in the control/control or in imidacloprid/control treatments. The results from this study shows that while systemic imidacloprid has sublethal effects on N. oculata, it does not significantly affect mortality of adult beetles in the tri-trophic system tested. Therefore, using systemic imidacloprid and N. oculata for controlling rugose spiraling whitefly might be compatible or at least not significantly incompatible.

Evaluation of Low-Energy Microwaves Technology (Termatrac) for Detecting Western Drywood Termite in a Simulated Drywall System.

Detecting drywood termites in structures is very challenging. Microwaves technology (Termatrac T3i) is a nondestructive method for detecting drywood termites in structures. Termatrac device and its mobile application provide a bar as well as a line graph when detecting insect movements, but interpreting these graphs is very subjective. In this paper, Termatrac's output signal is quantified using a new method to study the effect of wall layers, wood type, and termite density on signal strength measured as area under curve in a simulated drywall system in laboratory. Two experiments were conducted on Termatrac T3i at its maximum sensitivity (Gain: 10). In experiment I, HEXBUG Nano was used as a source of movement/vibration and two wood types were used in which the wall layers significantly predicted signal strength, but wood type did not. In experiment II, two different densities of live western drywood termites, Incisitermes minor (Hagen) (Isoptera: Kalotermitidae), were used to study the effect of termite density on signal strength. Interestingly, termite density did not significantly predict signal strength. The maximum reliable wood depth for detecting termites was 5 cm. Microwaves produced by Termatrac also showed good penetration into drywall and produced detectable signals even on a single drywood termite which confirms manufacturer's claim. Suggestions on using and improving microwaves technology for detecting termites is provided which can potentially be applied to other types of insects and noninsect animals.

Effect of Aggregation and Cage Setting on Some Life-History Parameters of Aleurodicus Rugioperculatus (Hemiptera: Aleyrodidae).

Fecundity is defined as the number of progeny produced by an organism. In our study, we used three different experimental settings to measure the fecundity of rugose spiraling whitefly (Aleurodicus rugioperculatus Martin), a recent invasive insect in Florida, on Strelitzia nicolai host plants. The adult longevity was significantly different among treatments, with females surviving significantly longer in groups in whole-plant cages and individual females in clip cages compared with individual females in whole-plant cages. Females laid 34.5 ± 8.4, 156.4 ± 18.3, and 225.2 ± 18 eggs, on average, when kept individually in whole-plant cages, in a group in whole-plant cages, and individually in clip cages, respectively. In all treatments, there was a significant correlation between the longevity and fecundity of females. Males emerged earlier than females in all treatments. Virgin females produced only males in the F1, while mated females produced both males and females, which suggests an arrhenotokous parthenogenesis. The egg-to-adult survival of the whitefly was 29 ± 4%, and the highest mortality occurred at the crawler stage when reared on S. nicolai. The results showed a significant effect of aggregation and cage setting on longevity and fecundity of this whitefly. To conclude, the experimental setting of the group fecundity treatment is more similar to what occurs in the landscape. Such a significant effect of cage setting and aggregation on the life-history parameters should be always taken into account when designing experiments or interpreting results.