Insect Cages Research Articles

An evaluation of the growth, development, reproductive characteristics and pest control potential of three Trichogramma species on Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae).

Tuta absoluta is an invasive alien species that has caused major losses in the Chinese tomato industry. Investigating the growth, development, reproduction and pest control effects of three native species of Trichogramma species on the eggs of T. absoluta could provide an ecological tool for preventing and controlling T. absoluta in China. In this study, we constructed age-stage two-sex life tables for three common species of Trichogramma and determined their relative abilities to control T. absoluta in greenhouse insect cages, thus allowing us to identify the species with the most effective ability to prey on T. absoluta eggs. Analysis showed that the net reproductive rate (R0), gross reproduction rate (GRR) and intrinsic rate of increase (r) of Trichogramma ostriniae were the highest of the three species at 22.85, 32.58 and 1.31, respectively. In the presence of 10 eggs and under ideal conditions, T. ostriniae, Trichogramma chilonis, and Trichogramma dendrolimi produced 9451.04, 5199.56, and 1902.95 offspring, respectively. Following the release of T. ostriniae, tomato leaves incurred a damage index of 1 after the first week, while the number of T. absoluta reduced to 24.60 individuals by week 10 (8.75% of the control treatment). Of the three species of Trichogramma tested in this study, T. ostriniae exhibited the best growth, development, reproductive capacity and predatory ability against T. absoluta, and has broad application prospects. © 2024 Society of Chemical Industry.

Refining Gastrophysa atrocyanea (Coleoptera: Chrysomelidae) identification using UV marking in whole-plant assessment

The host plant quality is crucial for assessing the environmental safety of weed biological control agents, as they rely on the phenotypic characteristics of test plants in host specificity tests and for mass-rearing before field release. In this study, we explored the feasibility of using potted plants by applying ultraviolet (UV) fluorescent pigment to the elytra of the leaf beetle Gastrophysa atrocyanea. They were released separately on Rumex acetosa as the target weed and Buxus sinica var. insularis as a non-target plant in insect cages. UV marking reduced detection time by 2.7 times and increased the detection rates of female leaf beetles on the target weed compared to visible light, resulting in only 7.41% missing leaf beetles. Similarly, UV application reduced detection time by 2.3 times on the non-target plant, with no missing leaf beetles. Further, marking different sexes with UV pigments facilitated identification 4.8 times faster than visual light. The UV mark and recapture method exhibits promising potential in whole-plant testing, simplifying the identification of a potential biological control agent, G. atrocyanea, in insect cages under no-choice tests. Thus, UV marking enables the possibility of mass-rearing weed biological control agents and monitors the foraging behavior of phytophagous insects cost-effectively and non-disruptively in laboratory settings.

Wettable sulphur application for Halyomorpha halys (Stål) (Hemiptera: Pentatomidae) management: laboratory and semi-field experiments.

The brown marmorated stink bug, Halyomorpha halys (Stål) (Hemiptera: Pentatomidae), is a significant threat to crop production. Alternatives to synthetic pesticides are needed for its management. Here we investigated the effect of sulphur on H. halys. Experiments were performed to evaluate both mortality and deterrence/repellence of H. halys following sulphur treatments in laboratory and semi-field conditions. Brown marmorated stink bug mortality was not influenced by sulphur applications. However, in two-choice experiments in insect cages and olfactometer, more H. halys adults moved toward the untreated control rather than the sulphur-treated food sources, with a high effect as the concentration increased. A semi-field experiment using potted apple plants confirmed the results observed in the laboratory, showing a deterrent and/or repellent effect of sulphur-based products on H. halys. Sulphur applications were associated with a deterrent/repellent effect on the brown marmorated stink bug. The use of sulphur-based products could represent a promising tool for Integrated Pest Management strategies against H. halys in fruit crops. © 2024 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Effects of Xenorhabdus and Photorhabdus bacterial metabolites on the ovipositional activity of Aedes albopictus

AbstractViral diseases like yellow fever, dengue, and Zika have an alarming impact on public health. These diseases can be transmitted by Aedes mosquito species, such as Ae. albopictus, which is now found in many countries outside its original range. Xenorhabdus and Photorhabdus spp. are enteric bacterial symbionts of insect-preying nematodes and are known to produce an array of natural products with various activities including larvicidal activity. In this study, the effects of natural products produced by four Xenorhabdus and one Photorhabdus bacteria on the ovipositional behavior of Ae. albopictus mosquitoes were assessed. Utilizing a binary choice assay in insect cages, gravid female mosquitoes were presented with two oviposition cups containing water supplemented with varying concentrations of bacterial supernatants (50–1% concentrations) versus control medium. After 72 h, the eggs deposited on filter papers were counted. The oviposition attractant index (OAI) feature of the bacterial supernatant was evaluated using the number of eggs laid in the cups. Notably, all tested supernatants exhibited concentration-dependent deterrence of oviposition. Xenorhabdus cabanillasii displayed the strongest deterrent effect, inhibiting egg-laying at 50–5% concentrations (OAI: − 0.87 to − 0.35), followed by X. nematophila (50–10%, OAI: − 0.82 to − 0.52). Xenorhabdus szentirmaii, X. doucetiae, and P. kayaii showed significant deterrence at ≥ 20% concentrations. Using promoter exchange mutants generated by the easyPACId approach, fabclavine from X. szentirmaii was identified as the bioactive compound with evident deterrent effects. Such deterrents targeting egg-laying could be valuable for controlling populations by disrupting their breeding in suitable habitats.

Managed pollination is a much better way of increasing productivity and essential oil content of dill seeds crop

Dill seeds (Anethumgraveolens L.) is the most valuable medicinal seed spice crop of Apiaceae. It bears small yellow flowers in the form of umbels. Being a cross-pollinated crop, floral visitors play vital role in pollination and seed sets. Hence, the present study was conducted at the ICAR-National Research Centre on Seed Spices, Ajmer (Rajasthan), India to discover the pollinator’s community, foraging behaviour and abundance of most frequent pollinators and different modes of pollination on seed yield and quality of this seed spice crop. The insect visitors community of dill seeds was composed of 28 insect species belonging to 14 families of 6 orders. Most of floral visitors started their foraging activity at 8.00 h, reached peak activity between 12.00 and 14.00 h and their activity ceased at 18.00 h. Apisflorea,A.dorsata,A.mellifera, solitary bee, Halictus sp. and two unidentified species of Hymenoptera; Episyrphusbalteatus (DeGeer), Episyrphus sp., Eristalis sp and two other Musca species of Diptera were identified as potential and regular floral visitors of dill seeds. The highest seed yield of 1505.63 kg/ha was recorded in the treated plots provided with only 10% jaggery solution and was at par with the open pollination. A lower seed yield of 1432.5 kg/ha was recorded in plots pollinated only with A.mellifera inside insect cages. Open pollination with 10% jaggery solution spray increased the seed yield of dill seed crop by 57%, one-thousand seed test weight by 96% and the essential oil content by 27% over control plots. These results show that managed pollination is a much better way to enhance yields and quality of dill seed crop than other treatments including only honeybee-based pollination.

Comparative Functional and Numeric Response of Two Coccinellids (Coccinella septempunctata and Cheilomenes sexmaculata) Preying Cowpea Aphid (Aphis craccivora)

Background: The cowpea aphid, Aphis craccivora Koch (Hemiptera: Aphididae), a plant lice known to commonly attack plants that causes loss by sucking sap from phloem and act as vector for viruses. The aphidophagous coccinellids are efficient in controlling the pestiferous population of aphids. The two coccinellid Coccinella septempunctata and Cheilomenes sexmaculata are efficient in predation of cowpea aphid, Aphis craccivora in southern Rajasthan. The present study determined the response of prey consumption at different prey densities. Methods: To compute the functional and numeric response of the lady bird beetle on cowpea aphid, experiment was conducted in vitro by using cowpea potted plant in caged conditions at Department of Entomology, Rajasthan College of Agriculture during 2019-20. The cowpea pea plants were sown in small pots and were placed in aluminium insect cages having 15 cm × 15 cm × 15 cm size. The predatory potential of coccinellid grubs and adults were evaluated at six different prey densities (aphids per arena): 25, 50, 75, 100, 125, 150 and 200 with 5 replications. Result: The grub and adults of C. septempunctata consumed more prey as compared to C. sexmaculata. Both the coccinellid showed Type II functional response when functional curve was plotted. The linear regression method suggested that C. septempunctata required less time to act upon prey as compared to C. sexmaculata. The C. septempunctata also showed more numeric response in terms of ECI [conversion efficiency of prey consumption (ECI) into biomass (egg)] at different prey densities. The fecundity in both the cases increased with the increased prey densities that eventually decreased after reaching the maximum egg laying capacity at prey density of 125 aphids. In all the cases it was found that consumption rate of predaceous beetle increased with increasing aphid population.

High population density of bee pollinators increasing Camelina sativa (L.) Crantz seed yield: Implications on the potential risk for insect-mediated gene flow

New Camelina sativa genotypes have been genetically engineered (GE) to produce unique high-value chemical compounds and biofuel products. However, baseline information on predictive environmental risk assessment on this plant is urgently needed to establish guidelines for commercial large-scale production. Pollinating insects such as bees could facilitate the spread of transgenes into the ecosystem and raises ecological concerns on insect-mediated gene flow. Thus determination of the potential impact of pollinating insects on C. sativa pollination and gene flow becomes important. A 4-year experiment conducted in Connecticut, USA (2017) and Yangzhou, China (2019–2021) was carried out to determine the pollination effect of different densities of honey bees (Apis mellifera L.) populations on C. sativa seed yield and assess their involvement on C. sativa pollen dispersal. Insect cages experiments with presence or absence of honey bees showed that C. sativa seed yield was not affected by a relatively low population density of honey bees (20 honey bees m−2). However, at a higher density of honey bee population, Camelina sativa seed yield (0.23 g plant-1 and 73.3 g m−2) was statistically greater than those of the uncaged control (0.21 g plant-1 and 68.9 g m−2), caged C. sativa plants without honey bees (0.20 g plant-1 and 66.3 g m−2) or with 20 honey bees m−2 (0.21 g plant-1 and 66.9 g m−2), although C. sativa is commonly assumed to be self-pollinated. Principle coordinate analysis (PCoA) made from SSR markers revealed that honey bee and bumble bee are able to transfer C. sativa pollen from pollen source to adjacent flowers of other species (e.g., Brassica juncea, Brassica napus) up to 10−15 m beyond the field edge, raising ecological concerns on insect-mediated gene flow between adjacent C. sativa fields particularly if GE C. sativa cultivars are involved. The new information in this study will help to better understand C. sativa pollination biology, environmental risks associated with insect-mediated gene flow, and develop management strategies to reduce gene flow and facilitate coexistence between GE and non-GE C. sativa under natural agroecosystem.

Variation in sex ratio of the leafminerPhytomyza plantaginisGoureau (Diptera: Agromyzidae) from Australia

AbstractParthenogenetic reproduction has only previously been demonstrated in two species of agromyzid leafminer flies (Diptera: Agromyzidae), both from the genusPhytomyza. The plantain leafminer,Phytomyza plantaginis, is Palaearctic in origin, and bisexual populations have been observed in this region. However, historically, only females had been collected in the Australasian, Nearctic, Neotropical and Oceanian regions. Here, we show that southern Australian samples of this species fromPlantagospp. can be composed of both parthenogenic and bisexual populations. In sites around Melbourne, males were present, although the sex ratio was female biased, with females comprising 75% of sampled individuals. In contrast, males were absent from collections in western and northern Victoria, Australian Capital Territory, New South Wales and Western Australia. FemaleP. plantaginisflies were reared from threePlantagohost plants (Plantago lanceolata,Plantago majorandPlantago coronopus), although females were particularly common fromPl. lanceolata. Insect cages set up with leafminers from sites where only females occurred produced only females, while cages with leafminers from sites where males occurred produced both sexes and mating was observed. Individuals from all populations were infected byWolbachiaendosymbionts, suggesting that the presence/absence ofWolbachiais not directly responsible for the parthenogenesis. However, there was an association between a mtDNA variant (PP.02) and sexual reproduction, in that this variant was absent in areas where only females were collected but present in all males and some females from areas with sexual populations. The mechanism responsible for parthenogenesis inP. plantaginisremains unknown but is linked to maternal factors.

The effect of chemical exudates of three larvivorous fish species on oviposition preference of Aedes aegypti and Aedes albopictus (Diptera: Culicidae).

Mosquito species Aedes aegypti and Aedes albopictus are vectors of dengue worldwide. Mosquito vector control through maintaining larvivorous fish in water bodies is generally suggested, however, its underlying role towards oviposition preference of these dengue vectors is unknown in the Sri Lankan context. The current study investigated the effect of chemical exudates from larvivorous fish species Poecilia reticulata, Rasbora daniconius and Applocheilus dayi on the oviposition preference of Aedes mosquitoes. The number of eggs laid by each mosquito species was determined using ovitraps that contained water conditioned by the fish species both separately and in combination. The ovitraps were placed inside insect cages containing engorged gravid Aedes females. Both the mosquito species had the least preference of oviposition in water conditioned by A. dayi followed by R. daniconius. The highest preference of oviposition was shown for water conditioned by P. reticulata. The current study indicated that oviposition site selection in Ae. aegypti and Ae. albopictus was reduced by A. dayi and R. daniconius, however, it was not influenced by the fish combinations used. Further studies are warranted to understand the chemical cues associated with larvivorous fish towards the oviposition preference in Aedes mosquitoes.

Transmission of Metarhizium anisopliae and Beauveria bassiana to adults of Kuschelorhynchus macadamiae (Coleoptera: Curculionidae) from infected adults and conidiated cadavers

Kuschelorhynchus macadamiae is a major pest of macadamias in Australia, causing yield losses of up to 15%. Our previous studies have shown the weevil is susceptible to Beauveria bassiana and Metarhizium anisopliae. The aim of this study was to investigate horizontal transmission of both fungal species to healthy weevils from both infected adults and weevil cadavers. In a confined environment the mortality of healthy adults caused by the transmission of conidia from live fungus-infected adults was < 50%. Under similar experimental conditions, the mortality of healthy adults reached 100% when exposed to conidiated cadavers. However, when conidiated cadavers were used in more spacious environments (insect cages), the mortality of adults was < 80%. Using scanning electron microscopy, it was observed that all healthy adults had conidia attached to all external parts of the body. This suggests that although the conidia were readily transferred to the adults, the lower mortality in the larger insect cages could be the result of an unfavourable environmental factor such as low humidity. The presence of conidia attached to all the adults indicated that they did not show any discriminatory behaviour such as avoidance of conidiated cadavers infected by these two fungal species. The results from this study show that there is potential for enhanced control of adult K. macadamiae via transmission from either fungus-infected adults or conidiated cadavers and this could strengthen sustainable pest management in macadamias.

USING BIPLOT ANALYSIS OF F1 FABA BEAN DIALLEL DATA TO PREDICT COMBINING ABILITY

This study was carried out under insect cages during 2017/18 and 2018/19 seasons at Giza Research Station, ARC, Egypt to investigate the combining ability possibility prediction and relationship between biplot graph and Griffing of half diallel data, and to identify promising genotypes. Six parental faba bean genotypes and their half diallel crosses (15 F1’s) were evaluated under a randomized complete block design in three replications. The results reflected significant differences for both GCA and SCA in most traits, indicating the important role of both additive and dominant components in the inheritance. Meanwhile, Baker’s ratio emphasized the preponderant role of additive gene action in controlling the most studied traits. Simple correlation results showed that seed yield may be raised through selecting most pods and seeds per plant, which recorded the highest heritability in broad and narrow sense (hb 2 and hn 2%) estimates coupled with highest genetic advance (GA %) in faba bean. Biplot graph (innovative) and Griffing (traditional) analysis exhibited equivalent results for gca and sca effects and are meaningful for identifying Giza 843 (P1), Misr 1 (P2) and Giza 40 (P6) as the best parents and Giza 843 x Misr 1 (C12), Giza 843 x Nubaria 1 (C15), Misr 1 x Giza 3 (C24), Giza 716 x Nubaria 1 (C35) and Nubaria 1 x Giza 40 (C56) as promising five crosses. Then, GT-biplot method is considered as the best alternative analysis for giving a complete picture about the interrelationships among genotypes and traits (for relative comparing genotypes based on multiple traits). Hence, number of pods and seeds per plant traits could be used for the improvement of seed yield. Besides, five faba bean crosses were distinguished which possess genetic factors for high yield and highly promising to be employed in the development of high yielding populations of faba bean breeding programs.

First Report of Gynmandrosoma aurantianum (Lepidoptera: Tortricidae) in Mandarin (Citrus reticulata) in the Inter-Andean Valleys of Ecuador

Mandarin (Citrus reticulata) is an economically important fruit for farmers of the inter-Andean valleys of Ecuador, South America. Insectinfested fruits were sampled in the locality of Perucho (Pichincha Province). The larvae obtained from the interior of the fruit were cultured in insect cages to obtain adults. Morphological observations of characteristics of the larval stage, and male and female genitalia at the adult stage confirmed the taxonomic description of the species Gynmandrosoma aurantianum (Lima) (Lepidoptera: Tortricidae). According to our knowledge, this is the first report of mandarin being infested by G. aurantianum in Ecuador.

Reducing biting rates of Aedes aegypti with metofluthrin: investigations in time and space

BackgroundIndoor residual spraying is key to dengue control in Cairns and other parts of northern Queensland, Australia, where Aedes aegypti is prevalent, but the strategy faces challenges with regards to slow application time and, therefore, community coverage. A faster potential improvement might be the use of polyethylene netting impregnated with the volatile pyrethroid metofluthrin (SumiOne™). This formulation was assessed in rooms in three houses in Cairns, Australia. One emanator was placed in each room and cages of 10 female Aedes aegypti were exposed at distances of 1 and 3 m. Knockdown and landings on a human hand were counted before metofluthrin exposure and at 10, 30, 60, 90 and 120 min during exposure. In addition, two trials continued over 48 h of exposure to assess the long-term sublethal effects of metofluthrin on caged mosquitoes.ResultsPercentage landing rates fell to 0–2.5% in the first 10 min of exposure. Knockdown was most evident between 10 and 30 min (54% at 1 m and 33% at 3 m). Distance from the emanator strongly affected the results: mosquitoes at 3 m exhibited less knockdown and more landings than those at 1 m. As room volume increased, knockdown decreased and the number of landing increased. There is a cumulative mortality and landing inhibition and, for mosquitoes exposed to metofluthrin for > 48 h, mortality was 100% at 1 m and 90% at 3 m. Of those still alive, a small number continued to land and bite. After being removed from metofluthrin-treated rooms, exposed insect cages were found to reducing landing rates for up to 2 h.ConclusionsDespite only moderate levels of knockdown during the initial hours of exposure, metofluthrin emanators were effective in reducing mosquito landing rates, especially within 1 m, even when exposed on an open veranda. The evaluation methods and results described in this paper will help inform the optimal conditions of deployment of metofluthrin emanators. These devices have the potential to reduce contact between humans and urban disease vectors faster than indoor residual spraying so supplement our current arsenal of dengue control tools.

Laboratory refugia preferences of the brown widow spider,Latrodectus geometricus(Araneae: Theridiidae)

During collecting episodes in urban southern California, brown widow spiders, Latrodectus geometricus C. L. Koch, 1841, were observed to reside most often in specific locations such as acute angles within patio furniture or on the underside of railings. In this laboratory study, we tested several variables to determine which factors brown widow females may use for web site selection. All tests were conducted with corrugated cardboard refugia in enclosed dome-shaped insect cages. Brown widows were found to significantly prefer: 1) 30o angles compared to 60o or 90o angles, 2) cavities of 75 and 100 mm depth compared to 25 or 50 mm depth, 3) cavities lined with single-faced corrugated cardboard compared to smooth surfaces, and 4) refuges that had previously housed a brown widow compared to similar but previously unoccupied refugia. These data provide unusually detailed information about microhabitat selection by an urban pest, with possible implications for the pest control industry for eradication or for home owners to avoid envenomations.

Eficacia de diferentes diodos emisores de luz (LEDs) unidos a trampas adhesivas amarillas para la captura de la mosca blanca Trialeurodes vaporariorum

Teniendo en cuenta que algunos adultos de insectos muestran preferencia a ciertas longitudes de onda, se ha considerado este comportamiento para desarrollar herramientas de monitoreo y estrategias de control de insectos plaga. Como ejemplo de ello, las tarjetas adhesivas amarillas han sido ampliamente usadas para monitorear población de moscas blancas a campo como invernadero. Este estudio tuvo como objetivo evaluar la efectividad de trampas adhesivas amarillas provistas con luces emitidas por diodos (LEDs) para el trampeo de adultos moscas blancas Trialeurodes vaporariorum (Westwood) (Hemiptera: Aleyrodidae). Los ensayos se llevaron a cabo en la EEA INTA Concordia en condiciones de umbráculo, donde se ubicaron jaulas de cría con plantas de tabaco, Solanum tabacum (L.) y poroto, Phaseolus vulgaris L. desde Junio hasta Julio del 2013. Las trampas adhesivas amarillas tuvieron una superficie de 64cm2 provistas con (LEDs) de diferentes longitudes de onda promedio (525 nm verde y 380 nm UV) y sin LED como testigo. Los ensayos mostraron que los adultos de mosca blanca fueron significativamente (p &gt;0,05) más atraídos por las trampas equipadas con LED 525nm verde (134 ± 7,4 adultos/tarjeta) comparadas con trampas equipadas con LED 380 nm UV (105 ± 7,4 adultos/tarjeta) y trampas sin LED (85,17 ± 7,4 adultos/tarjeta). Estos resultados muestran que los adultos de T. vaporariorum son atraídos a trampas dotadas con LED verde, las cuales podrían tener un promisorio uso en invernadero como detección, monitoreo y control de mosca blanca.

Use of insect exclusion cages in soybean creates an altered microclimate and differential crop response

Insect exclusion cages are commonly used in agricultural and ecological studies to examine plant-insect interactions in a field setting while maintaining control over insect populations. However, these insect cages can unintentionally alter the climate inside of the cage and impact plant physiology, growth and yield as well as insect populations. This can subsequently affect interpretations of experimental results obtained from caged experiments. To address this concern, we measured meteorological variables in conjunction with soybean physiology, growth, and yield over a two-year period. In a 2011 field study in southern Wisconsin, we compared photosynthetic rates, leaf area index (LAI), soil environmental conditions, and various components of yield for plants grown inside and outside of an industry standard insect cage (Lumite 32×32 mesh). Inside of cages, several variables were higher (P<0.05) including surface (0–6cm) soil moisture (38%), stomatal conductance (42%), and total plant biomass (30%), while LAI was 20% lower (P<0.001) inside of the cages. During the 2012 growing season, we measured wind speed, wind gusts, solar radiation, air temperature and relative humidity inside of cages compared to open field conditions. We found that wind speed and solar radiation were 89% and 42% lower, respectively, and air temperature, relative humidity and vapor pressure deficit were not significantly affected. There was also a significant (P<0.0001) effect of the time of day on differences in wind speed and radiation between cages and open field plots. Our findings suggest that commonly used insect cages significantly alter the microclimate inside of the cage, and create a radiation regime in which the amount of direct and diffuse radiation received by plants is altered compared to the open field. Plant physiological processes and growth are affected by these environmental changes, adding a confounding factor when comparing caged to open field plants. Because the effects are likely a function of the type of cage, and mesh size and color, we recommend that future studies more thoroughly measure the microclimate for a variety of common cage types used in experiments.

English

The whitefly Bemisia tabaci Genn. is an important pest worldwide because of its ability to cause damage by direct feeding and its role as a vector of plant viruses including geminiviruses. Yellow mosaic virus (MYV) is a serious disease of pulse crops including mungbean, blackgram, frenchbean, pigeonpea and soybean. Yellow mosaic diseases are one of the most important viral diseases in mungbean caused by mungbean yellow mosaic virus (MYMV) which lead to severe yield reduction and it necessitates development of MYMV resistant lines for improved crop yield. Basic studies were carried out to elucidate the characteristics of MYMV transmission by its vector, B. tabaci. Artificial transmission experiments with B. tabaci were conducted under greenhouse conditions using cylindrical nylon cages with wire mesh tops. After 24 h acquisition access period (ASP) on agroinfected mungbean plants, B. tabaci collected from these agroinfected mungbean plants were considered viruliferous and transferred to a separate cage with healthy mungbean plants as confirmed via agroinoculation. After 24 h inoculation access period (IAP), B. tabaci were removed and the plants were sprayed with an insecticide and kept for observations of symptom development for 10 to 25 days in insect cages. Studies concluded with mungbean accessions using ten whitefly adults with 24 h of ASP and IAP resulted in transmission of virus of 70.50, and percent in MYMVR 111 (At VA 221), MYMVR 29 (At VA 239) and MYMVR 29 (At VA 221) respectively. Ten viruliferous whitefly adults did not cause MYMV symptom in KMG 189 (At VA 221), ML818 (At VA 239) and MYMVR 57 (At VA 221). Twenty viruliferous whitefly adults were able to cause MYMV after 48 h ASP and 24 h IAP and resulted in the maximum transmission efficiency in MYMVR 55 (At VA 221) (85.00%) and MYMVR 55 (At VA 239) (83.50%). The virus was proven to be a persistent discrete fragment of 703 bp using the polymerase chain reaction method on viruliferous whitefly adults, while no bands were obtained from non-viruliferous B. tabaci adults reared on CO2 brinjal host. Key words: Mungbean yellow mosaic virus (MYMV), transmission, vector, Bemisia tabaci.

Planthopper‐rice interactions: unequal stresses on pure‐line and hybrid rice under similar experimental conditions

AbstractHybrid and pure‐line (inbred) rice [Oryza sativa L. (Poaceae)] varieties have distinct physiologies, particularly as related to their nutrient requirements. These differences could confound the results and interpretation of experiments that compare rice varieties grown in pots for their resistance and responses to herbivores. In this study, a series of experiments was conducted to identify potentially confounding interactions between pot size (soil volume), fertilizer regime, and the use of acetate insect cages with rice line type (hybrid, fertile parental inbred, and male sterile inbred) during bioassays with the brown planthopper, Nilaparvata lugens (Stål) (Hemiptera: Delphacidae). The growth of hybrid rice was often limited (relatively low biomass and low grain production) compared to fertile inbred lines even in large pots (7 200 ml) and when grown without added fertilizer. Several interactions between the effects of growth conditions and line type were detected. Acetate cages caused a significant reduction in grain yield in hybrids, but not in inbreds, mainly resulting from a cage‐induced decrease in grain weight (smaller grains). Hybrids and male sterile lines often had higher root or above‐ground biomass in the largest caged pots compared with fertile inbred lines, but biomass was similar in smaller pots, indicating that the large pots allowed longer unimpeded growth of fertile inbreds, but not other line types. There were no interactions between the presence or absence of planthoppers with line type or experimental conditions. All line types were equally susceptible to planthoppers. Often the effects of planthopper feeding on plant fitness (i.e., tolerance) were apparent when plants were grown in large pots but not in small pots, particularly for hybrid lines and under high nitrogen regimes. On the basis of these results we recommend that researchers ensure that plants are not unequally stressed by inadequate growth conditions during comparative studies with herbivores on physiologically distinct rice varieties or rice species. We recommend the use of large pots (soil volume) and lower fertilizer levels with young, non‐reproductive plants during comparative bioassays with planthoppers. Field cages are recommended for hybrid‐inbred comparisons during older plant stages but these are subject to a range of other confounding variables.

Lasioderma serricorne (Coleoptera, Anobiidae), Number of generations and phenology, in tobacco stores of Northern Greece (Macedonia)

Observation and study of Lasioderma serricorne (Coleoptera: Anobiidae) number of generations has taken place in the region of Thessaloniki (Macedonia – Greece) during the years 1966, 1997, 1998 and 1999. For every year of the experiment, four (4) insect cages (29 × 29 × 31 cm) placed inside the tobacco stores were used. Every cage containing Virginia-type dry tobacco leaves, treated by redrying method, was supplied with overwintering larvae, eggs as well as male and female pupae to avoid overlapping of generations. It was concluded that three (3) generations per year exist (April-May, June-July, August-September).

Screening and Breeding for Leafminer Resistance in Spinach

Leaf miner(Liriomyza spp.) is a major insect pest of many important vegetable crops, including spinach (Spinacia oleracea). Chemical control is not long lasting, and it is well documented that leafminers can develop a high degree of resistance to insecticides. Resistant varieties remain the most economical means of insect control. The purposes of the present experiments were to evaluate differences in spinach genotypes to leafminer damage, to compare results obtained from insect cages and from the field, and to study the association among different resistant traits. We screened 345 spinach genotypes from the USDA germplasm collection and 441 genotypes from CGN (Holland) and IPK (Germany) spinach collections for leafminer resistance in an outdoor insect cage and in the field. Significant genotypic differences were found for leafminer stings per unit leaf area, mines per plant, and mines per 100 g of plant weight. The sting result from the field was highly correlated (r = 0.770) with the result from the insect cage, demonstrating that a cage test could be used to screen for leafminer resistance in the field. Mines per plant were not correlated with plant weight, suggesting that leafminer flies did not lay their eggs randomly and oviposition-nonpreference occurred in these plants. Stings per unit leaf area was not correlated with mines per plant or per 100 g plant weight, which suggests that feeding-nonpreference does not necessarily mean oviposition-nonpreference for a spinach genotype and these two traits can be improved independently. These findings suggest that genetic improvement of spinach for leafminer resistance is feasible. A phenotypic recurrent selection method is used to increase the level of leafminer resistance in spinach.