We investigated kin relatedness and kin-recognition abilities of the Argentine ant, Linepithema humile (Mayr), an invader from North America that has pervaded Japan for 20 yr, using genetic analyses ...and behavioral bioassays. From these data and interactions among factors, we formulated an eradication and management time-scale pattern diagram. Relatedness within a colony using microsatellite markers was effectively zero, whereas relatedness estimated by multilocus DNA fingerprinting markers was relatively high. Specifically, relatedness of recently invaded populations was estimated at nearly 0.3. From the results of behavioral bioassays on the invading populations of the Argentine ant, all colonies except the Kobe supercolonies did not show clearly aggressive behaviors toward workers belonging to other colonies, even when distantly located. Because they are critical factors for eradicating and managing invasive organisms, we assessed the relationships among kin relatedness using multilocus DNA fingerprinting and microsatellite markers, with aggressiveness, in 2011 and 2012, including the establishment durations, and distances among supercolonies. A generalized linear model (GLM) analysis, with establishment durations as an explanatory variable, strongly contributed to explaining estimated relatedness from the two methods. Specifically, models using kin relatedness for both multilocus DNA fingerprinting and microsatellite markers provided the strongest contribution to explaining the establishment durations. Within 3 yr after establishment in a native area, eradication is possible because of their low genetic diversity and small colony size. After 15 yr, eradication will be more difficult, but it is preferable to just monitor the impact for a nonnative ecosystem.
The sterile insect technique uses males that have been mass-reared in a controlled environment. The insects, once released in the field, must compete to mate. However, the mass-rearing condition ...supposes a loss of fitness that will be noticeable by wild females. To compare the fitness of wild males and mass-reared males, three competition settings were established. In setting 1, wild males, mass-reared males and wild females were released in field cages. In setting 2, wild females and wild males were released without competition, and in setting 3, mass-reared males and mass-reared females were also released without competition. Male fitness was based on their mating success, fecundity, weight and longevity. The fitness of the females was measured based on weight and several demographic parameters. The highest percentage of mating was between wild males and wild females between 0800 and 0900 h in the competition condition, while the mass-reared males started one hour later. The successful wild males weighed more and showed longer mating times, greater longevity and a higher number of matings than the mass-reared males. Although the mass-reared males showed the lowest percentage of matings, their fecundity when mating with wild females indicated a high fitness. Since the survival and fecundity of wild females that mated with mass-reared males decreased to become similar to those of mass-reared females that mated with mass-reared males, females seem to be influenced by the type of male (wild or mass-reared).
Accelerometer, electret microphone, and piezoelectric disk acoustic systems were evaluated for their potential to detect hidden insect infestations in soil and interior structures of plants. ...Coleopteran grubs (the scarabaeids Phyllophaga spp. and Cyclocephala spp.) and the curculionids Diaprepes abbreviatus (L.) and Otiorhynchus sulcatus (F.) weighing 50–300 mg were detected easily in the laboratory and in the field except under extremely windy or noisy conditions. Cephus cinctus Norton (Hymenoptera: Cephidae) larvae weighing 1–12 mg could be detected in small pots of wheat in the laboratory by taking moderate precautions to eliminate background noise. Insect sounds could be distinguished from background noises by differences in frequency and temporal patterns, but insects of similarly sized species could not be distinguished easily from each other. Insect activity was highly variable among individuals and species, although D. abbreviatus grubs tended to be more active than those of O. sulcatus. Tests were done to compare acoustically predicted infestations with the contents of soil samples taken at recording sites. Under laboratory or ideal field conditions, active insects within ≈30 cm were identified with nearly 100% reliability. In field tests under adverse conditions, the reliability decreased to ≈75%. These results indicate that acoustic systems with vibration sensors have considerable potential as activity monitors in the laboratory and as field tools for rapid, nondestructive scouting and mapping of soil insect populations.
In North Carolina, Tomato spotted wilt tospovirus (family Bunyaviridae, genus Tospovirus, TSWV) is vectored primarily by the tobacco thrips, Frankliniella fusca (Hinds), and the western flower ...thrips, Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae). TSWV overwinters in winter annual weeds from which it is spread to susceptible crops in spring. Because most susceptible crops are destroyed after harvest before winter weeds emerge in the fall, infected summer weeds are thought to be the principal source for spread of TSWV to winter annual weeds in fall. A survey of summer weeds associated with TSWV-susceptible crops in the coastal plain of North Carolina conducted between May and October revealed that relatively few species were commonly infected with TSWV and supported populations of F. fusca or F. occidentalis. F. occidentalis made up >75% of vector species collected from 15 summer weed species during 2002. The number of F. occidentalis and F. fusca immatures collected from plant samples varied significantly among plant species. Ipomoea purpurea (L.) Roth, Mollugo verticillata L., Cassia obtusifolia L., and Amaranthus palmeri S. Wats supported the largest numbers of immature F. occidentalis. Richardia scabra L., M. verticillata, and Ipomoea hederacea (L.) supported the largest numbers of F. fusca immatures. TSWV was present at 16 of 17 locations, and naturally occurring infections were found in 14 of 29 weed species tested. Five of the TSWV-infected species have not previously been reported as hosts of TSWV (A. palmeri, Solidago altissima L., Ipomoea lacunosa L., I. purpurea, and Phytolacca americana L.). Estimated rates of infection were highest in I. purpurea (6.8%), M. verticillata (5.3%), and I. hederacea (1.9%). When both the incidence of infection by TSWV and the populations of F. occidentalis and F. fusca associated with each weed species are considered, the following summer weed species have the potential to act as significant sources for spread of TSWV to winter annual weeds in fall: I. purpurea, I. hederacea, M. verticillata, A. palmeri, C. obtusifolia, R. scabra, Ambrosia artemisiifolia L., Polygonum pensylvanicum L., and Chenopodium album L.
This study examined the responses of two termite species, the Formosan subterranean termite, Coptotermes formosanus Shiraki, and the eastern subterranean termite, Reticulitermes flavipes (Kollar), to ...three types of wood decay fungi: a brown rot fungus, Gloeophyllum trabeum (Persoon: Fries) Murrill; a white rot fungus, Phanerochaete chrysosporium Burdsall; and a litter rot fungus, Marasmiellus troyanus (Murrill) Singer. We also examined the responses of termites to these three types of fungi grown on different substrates. For all three fungal species, both termite species showed a strong preference for fungus-infected sawdust over uninfected sawdust. In choice tests, both termite species preferred sawdust infected with either M. troyanus or P. chrysosporium over G. trabeum. However, termites did not show any preference for fungus-infected potato dextrose agar over uninfected potato dextrose agar. Tunneling activity of C. formosanus was greater in sand treated with methanol extracts of fungus-infected sawdust than in sand treated with extracts of uninfected sawdust. Because chemicals in the fungal extracts caused termites to tunnel further into treated sand than untreated sand, these chemicals could potentially be used to direct termite foraging toward bait stations in the field.
The tunneling responses of two subterranean termite species, Coptotermes formosanus Shiraki and Reticulitermes flavipes (Kollar), to the presence of sound wood in laboratory arenas were studied. ...Branching pattern and the speed of tunnel construction between R. flavipes and C. formosanus also were compared. Patlak’s residence index (ρ) was generated using the length, width, speed of construction, and area of the primary tunnels built by termites. In the same allotted time, C. formosanus built wider and shorter primary tunnels, whereas R. flavipes built thinner and longer primary tunnels. The presence of wood did not affect termite tunnel formation. This lack of variation in tunnel formation parameters was evidenced by the inability of the termites to locate wood sources over distance, even as short as 2.5 mm, and by the similar tunneling behaviors in areas of the arena with or without wood. Patlak’s model predicted the densities of tunnels with an error between 9 and 28%, in experiments with R. flavipes exposed to a range of 0–8,000 g of wood, and between 61 and 87% in experiments with C. formosanus. These results indicated that the residence index can provide a qualitative measure of the effect of habitat heterogeneity on the individual termite tunnels. The tunneling construction strategy of these subterranean termites is discussed.
Plastic screens with UV absorbancy in the UV-A and UV-B range (bionets), were compared with conventional nets of the same mesh size for their protective capacity against vegetable insect pests and ...the spread of virus. Conventional and bionet screens with densities of 16- and 30-mesh were not effective in preventing the penetration of Bemisia argentifolii Bellows & Perring and Aphis gossypii Glover into walk-in tunnels covered with these nets. However, 50-mesh bionet screens significantly reduced the penetration of whiteflies into tunnels as well as the spread of tomato yellow leaf curl virus (TYLCV). Fifty days after planting, 30% disease incidence was recorded in unsprayed tomatoes Lycopersicon esculentum grown under 50-mesh bionet screens compared with 80% incidence in tunnels covered with conventional 50-mesh net. Fifty-mesh bionet screens were significantly more effective than the conventional screens of the same mesh size in protecting tomato against leafminers (Liriomyza trifolii Burgess) and red mites (Tetranychus telarius L.) as well as in protecting cucumbers (Cucumis sativus) against A. gossypii. None of the tested bionet screens was superior to the conventional screens against the western flower thrips, Frankliniella occidentalis Pergande. The size of thrips populations under the different screens was similar and unaffected by either the mechanical or optical properties of the net. The use of insect-proof bionet screens as a tool of integrated pest management in vegetable crops is discussed.
Lythrum salicaria L., purple loosestrife, an invasiveEurasian perennial, is degrading wetlands across temperate NorthAmerica. Chemical, physical, and mechanical methods failed to providelong-term ...control. Therefore, four host-specific insect species (twoleaf feeders, a root feeder, and a flower feeder) were introduced asbiological control agents. To increase the availability of adults ofthe root feeding weevil Hylobius transversovittatus Goezefor field releases, we developed a semiartificial diet. Suitability ofdifferent diet formulations (varying vitamin mixes, salt mixes,antimicrobials, water content, root content) and temperatures forlarval development were evaluated. We also monitored how rearing onartificial diet and the number of larvae per container affected larvaldevelopment time, larval survival, adult weight, and incidences ofdeformities. Rearing larvae on artificial diet reduced development timefrom 1–2 yr to 2–3 mo. Larval development was fastest and survivalrates highest under constant temperatures of 25°C. Hatch rate andlarval survival decreased if eggs were surface sterilized. Using FABCOantimicrobials could not prevent fungal contamination; use of methylparaben and sorbic acid was successful in suppressing fungal andbacterial growth throughout larval development time to <10%. Themoisture content of the diet did not significantly affect larvalsurvival, development, or adult weight. Decreasing the proportion ofpurple loosestrife roots in the diet reduced adult weight and theproportion of larvae completing development, and increased developmenttime; no larvae were able to complete development in root-free diet.With an increase in the number of larvae per cup, survival rates werereduced. The experiments revealed a female biased sex ratio: femalesconsistently developed faster and were heavier than males. Incidence ofadult deformities was consistently below 5%. Increased availability ofadults for field release as a result of mass production using thesemiartificial diet will accelerate the biocontrol program targetingpurple loosestrife. We are able to produce several hundred weevils perweek and have adapted the diet to rear other root-feeding weevils.
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