Schizaphis Graminum Research Articles

Wheat and barley as banker plant in the mass production of Aphidius gifuensis Ashmead (Hymenoptera: Braconidae) parasitizing Schizaphis graminum Rondani (Homoptera: Aphididae)

In order to select a suitable banker plant to culture Aphidius gifuensis Ashmead in mass as a biological control agent, the reproductive potential of A. gifuensis parasitizing Schizaphis graminum Rondani reared on wheat, barley or oat was measured by the way of two-sex life table. Results showed that the intrinsic rate of increase (r) and net reproductive rate (R 0) of A. gifuensis reared on S. graminum that was fed wheat (0.4257 days−1 and 235.1 progeny per female) or barley (0.4117 days−1 and 193.1 progeny per female) were significantly greater than oat (0.3878 days−1 and 143.9 progeny per female). In conclusion, among the three cultivars that were tested in this study, A. gifuensis performed better on S. graminum fed on wheat and barley, and these two plants could serve as a suitable banker plant for rearing A. gifuensis in biological control programs.

Identification of allatostatins in the brown-winged green bug Plautia stali

Juvenile hormone (JH) biosynthesis is inhibited under short-day conditions in the brown-winged green bug Plautia stali. We investigated allatostatic molecules in the brain of P. stali. Methanol brain extracts strongly inhibited JH biosynthesis. The allatostatic activities of the brain extracts were heat stable but gently suppressed by trypsin treatment, indicating that the allatostatic molecules were peptides. Grybi-MIP1, found in Gryllus bimaculatus as an allatostatic molecule, inhibited JH biosynthesis in P. stali. In contrast, peptides such as Dippu-AST2, 8, and 9, found in Diploptera punctata, did not affect JH biosynthesis in P. stali. We found a cDNA sequence encoding a peptide precursor of myoinhibitory peptides (MIPs), which we named Plast-MIP. Three synthetic peptides, AWKDLSKAW-NH2 (Plast-MIP1), GWSDLQSAGW-NH2 (Plast-MIP5), and AADWGSFRGSW-NH2 (Plast-MIP8), deduced from the precursor sequence, showed clear inhibition of JH biosynthesis in P. stali. Analysis by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and tandem mass spectrometry showed that Plast-MIP8 resides in the brain. Expression of the Plast-MIP mRNA precursor was detected in the brain of insects reared under short- and long-day conditions. These results suggest that Plast-MIP is an allatostatic molecule and that MIPs are synthesized irrespective of photoperiod. To our knowledge, this is the first study to identify Plast-MIP as a functional allatostatin in hemipteran insects.

Effect of Water on Survival and Development of Diapausing Eggs of Apolygus lucorum (Hemiptera: Miridae)

The green mirid bug Apolygus lucorum is a regional pest of multiple crops in northern China, and the survival and development of diapausing eggs during winter plays an important role in the population dynamics of this species. The effect of water on the survival and development of A. lucorum eggs was investigated using laboratory-induced diapause. Diapausing eggs were exposed to various humidity regimes under three conditions: (1) termination of diapause with exposure to warm long-day (WLD) conditions (i.e., 26 ± 1°C and 75 ± 5% relative humidity (RH) under a photoperiod of 16 hours light and 8 hours dark), (2) termination of diapause by chilling at 4°C, or (3) during the post-diapause stage, i.e., from transfer to WLD conditions after chilling, until the hatching of nymphs. The results indicate that water availability is crucial for the post-diapause resumption of development of A. lucorum. However, exposure to excessive moisture was detrimental, as indicated by a decrease in diapause termination rate and a prolonged pre-hatching period of diapausing eggs, compared to limited moisture conditions. This implies that both too dry and too humid environmental conditions would suppress survival and postpone hatching of overwintered A. lucorum eggs, and might explain why this pest has not caused severe damage in either southern or western China where the respective climates are very humid or dry.

Resistance of the national collection of rice varieties to phytophagous pests

The results of the field evaluation of the national collection of rice varieties, for resistance to Cricotopus silvestris Fabr., Hydrelia grisseola Fall., Ephydra macellaria Egg. & Schizaphis graminum Rond. by using an improved method of determining all types (antixenosis, antibiosis, evasion and tolerance) and adaptive resistance, are provided. Under conditions of 2011, among the 23 examined samples 3 varieties turned out to be resistant (with a score of 6) to Cricotopus silvestris Fabr., 1 to Hydrelia grisseola Fall., 2 to Ephydra macellaria Egg. In 2012, complex resistance (among 41 rice varieties) was observed in: UIR 3482, Flagman, Snezhynka, KOP-383-93 (red), which can be harnessed in a program of breeding resistant varieties. Rice samples exhibited different sensitivity to the scheme: mixed herbicide penoksulam + tsyhalofop-butyl and insecticide lambda tsyhalotryn after 10 days.

Changing global risk of invading greenbug Schizaphis graminum under climate change

The geographical range, abundance, growth rate, survival and mortality of insects are largely influenced by abiotic factors such as temperature and humidity. When suitable, these factors can positively influence the abundance of insect pests. It is in this light that the influence of climate change, particularly global warming, has direct bearing to crop protection. In this study, we simulated the potential distribution of the greenbug or wheat aphid Schizaphis graminum (Rondani) (Aphididae), a major global pest of wheat, using the climate matching tool CLIMEX (CLIMatic indEX) in global warming scenarios. To predict the potential distribution of the insect on CLIMEX at time periods 2030, 2070 and 2100, we utilize two global climate models (GCMs) at two emission scenarios. The result of CLIMEX modelling shows that the favourable climatic areas for S. graminum are subtropical to temperate at the current time. With global warming, under different scenarios current suitable and highly suitable areas in the northern hemisphere are expected to expand to higher latitudes by 2030 towards 2100; while areas in the southern hemisphere, where the pest’s living areas already have high temperature ranges, the occurrence of the pest will contract by 2030 since temperatures will exceed its heat limits. This study assists in predicting the potential risk areas that may be threatened by this pest in the future, providing supportive information for agricultural management practices and aid in the preparation of strategic plans to avoid possible economic damage posed by future expansion of the pest population due to climate change.

Integrated pest management (IPM) in raspberries under subtropical climate in a year round production system

The raspberry crop in Australia is affected by different pests during its growth cycle. The main pests with an economic impact are: Queensland fruit fly (Bactrocera tryoni), two spotted mite (Tetranychus urticae), broadmite (Polyphagotarsonemus latus), grubs (Helicoverpa spp., loopers, cluster caterpillars, etc.), western flower thrip (Frankliniella occidentalis), green stink bug (Plautia affinis) and green vegetable bug (Nezara viridula). As raspberries are harvested daily, the ability to meet the withholding period requirements after each pesticide application becomes a challenge. Also, the use of agrochemicals as the only control method reduces the efficacy of the pest control program in the short and long term. That's why integrated pest management (IPM) should be considered as an essential strategy for the effective pest control in raspberry crops. However, avoidance of broad spectrum pesticides increases the likelihood of secondary pests becoming an issue (e.g., cotton seed bug (Oxycarensus luctuosus), and myrids). In Corindi, New South Wales (NSW), we have been working to establish an IPM program based on biological control agents and selective pesticides with low or no side effects on beneficial insects or mites. We have been testing biological control agents for pests that cannot be controlled by any selective pesticides currently available. As Corindi is located in a subtropical climate and we grow raspberries year round, pest control becomes quite complex and challenging, so we continue to search for new products and control techniques.

Incidence and distribution of insect pests in rain-fed wheat in eastern Africa

Insect pests are some of the major constraints limiting yield of wheat ( Triticum aestivum L.) in East Africa. The objective of this study was to determine the species composition and distribution of insect pests, and their natural enemies associated with wheat in Eastern Africa. A survey was conducted in farmers’ fields in Ethiopia, Kenya and Uganda during 2013 and 2014 cropping season. Wheat fields along roadsides were randomly selected at approximately 2 to 10 Km intervals, and in each field, several wheat plants in a cross diagonal line were examined for presence or absence of insect pests and associate natural enemies. Also, the type of insect was identified to species level and in situ population counts recorded. In Ethiopia, only 39% of the fields were infested by tef epilachna, Chnootriba similis Thurnberg (Coleoptera: Coccinellidae); while the remaining wheat fields were free of insect infestation. The Russian Wheat Aphid (RWA), Diuraphis noxia Kurdijumov (Hemiptera: Aphididae), was the most prevalent insect pest of wheat in Kenya and Uganda. The maximum number of RWA per tiller was 58 in Kenya and 38 in Uganda. Moreover, in Kenya the rose wheat (grass) aphid ( Metopolophium dirhodum Walker), oat-bird-cherry aphid ( Rhopalosiphum padi Walker) and corn leaf aphid (R. maidis Fitch) were prevalent, though at low densities ranging, from 0.1 to 9 per tiller. The greenbug ( Schizaphis graminum Rondani) and the green stink bug ( Nezara viridula L.) were recorded only in Uganda. The general aphid predators Cheilomenes spp., spiders, lacewings and the parasitoid Aphidius spp. were the natural enemies of aphids found in Kenyan wheat. However, the density of these natural enemies was too low to bring the aphid population to a level that causes economic damage. Key Words: Russian Wheat Aphid, Triticum aestivum

Incidence and distribution of insect pests in rain-fed wheat in eastern Africa

Insect pests are some of the major constraints limiting yield of wheat (Triticum aestivum L.) in East Africa. The objective of this study was to determine the species composition and distribution of insect pests, and their natural enemies associated with wheat in Eastern Africa. A survey was conducted in farmers’ fields in Ethiopia, Kenya and Uganda during 2013 and 2014 cropping season. Wheat fields along roadsides were randomly selected at approximately 2 to 10 Km intervals, and in each field, several wheat plants in a cross diagonal line were examined for presence or absence of insect pests and associate natural enemies. Also, the type of insect was identified to species level and in situ population counts recorded. In Ethiopia, only 39% of the fields were infested by tef epilachna, Chnootriba similis Thurnberg (Coleoptera: Coccinellidae); while the remaining wheat fields were free of insect infestation. The Russian Wheat Aphid (RWA), Diuraphis noxia Kurdijumov (Hemiptera: Aphididae), was the most prevalent insect pest of wheat in Kenya and Uganda. The maximum number of RWA per tiller was 58 in Kenya and 38 in Uganda. Moreover, in Kenya the rose wheat (grass) aphid (Metopolophium dirhodum Walker), oat-bird-cherry aphid (Rhopalosiphum padi Walker) and corn leaf aphid (R. maidis Fitch) were prevalent, though at low densities ranging, from 0.1 to 9 per tiller. The greenbug (Schizaphis graminum Rondani) and the green stink bug (Nezara viridula L.) were recorded only in Uganda. The general aphid predators Cheilomenes spp., spiders, lacewings and the parasitoid Aphidius spp. were the natural enemies of aphids found in Kenyan wheat. However, the density of these natural enemies was too low to bring the aphid population to a level that causes economic damage.Key Words: Russian Wheat Aphid, Triticum aestivum

Using Multispectral Imagery to Compare the Spatial Pattern of Injury to Wheat Caused by Russian Wheat Aphid1and Greenbug1

Abstract. The Russian wheat aphid, Diuraphis noxia (Kurdjumov), and greenbug, Schizaphis graminum (Rondani) (Hemiptera: Aphididae), are important insect pests of wheat, Triticum aestivum L. Outbreaks of both pests in commercial wheat fields occur almost every year in the Great Plains of the United States. Infestations of both pests in wheat fields are clumped in distribution, and as a result so is the injury to plants in the field. The spatial pattern of patches of plants injured by the two aphid pests can be detected using airborne multispectral imaging. This study used multispectral imagery of wheat fields infested by the two species of aphids analyzed using spatial-pattern metrics with the purpose of determining differences between species in the spatial pattern of injury to wheat plants in fields. Analyses using Students t-tests revealed patches of wheat within fields injured by Russian wheat aphid were larger, more complex in shape, and more isolated than patches of wheat injured by greenbug. Our fin...

Identification of an orthologous clade of peroxidases that respond to feeding by greenbugs (Schizaphis graminum) in C4 grasses.

Knowledge of specific peroxidases that respond to aphid herbivory is limited in C4 grasses, but could provide targets for improving defence against these pests. A sorghum (Sorghum bicolor (L.) Moench) peroxidase (SbPrx-1; Sobic.002G416700) has been previously linked to biotic stress responses, and was the starting point for this study. Genomic analyses indicated that SbPrx-1 was part of a clade of five closely related peroxidase genes occurring within a ~30kb region on chromosome 2 of the sorghum genome. Comparison of this ~30-kb region to syntenic regions in switchgrass (Panicum virgatum L.) and foxtail millet (Setaria italica L.) identified similar related clusters of peroxidases. Infestation of a susceptible sorghum cultivar with greenbugs (Shizaphis graminum Rondani) induced three of the five peroxidases. Greenbug infestation of switchgrass and foxtail millet plants showed similar inductions of peroxidases. SbPrx-1 was also induced in response to aphid herbivory in a greenbug-resistant sorghum line, Cargill 607E. These data indicate that this genomic region of C4 grasses could be valuable as a marker to assess potential insect resistance in C4 grasses.

The influence of temperature, photoperiod, and diet on development and reproduction in the four-spot lady beetle Harmonia quadripunctata (Pontoppidan) (Coleoptera, Coccinellidae)

This is the first report on the effects of temperature (from 17 to 30°C), photoperiod (from 10 to 16 h of light), and diet (the wheat aphid Schizaphis graminum and the green peach aphid Myzus persicae) on preimaginal developmental rates, adult body mass, preoviposition period, and female fecundity of the predatory lady beetle Harmonia quadripunctata (Pontoppidan) under the laboratory conditions. A constant temperature of 30°C was lethal to the embryos. Judging from the data obtained at 17, 20, and 25°C, the lower temperature threshold for total egg-to-adult development equaled 12.0°C and the respective sum of effective temperatures was 274 degree-days. Preimaginal development was somewhat faster under short-day conditions, the threshold for this quantitative photoperiodic response being approximately 14 h at the rearing temperatures of 20 and 25°C. At a temperature of 25°C, the mean body mass of newly emerged adults was greater for those individuals that during the larval stage had been fed on the green peach aphid (16.4 mg in males and 18.4 mg in females) than in those fed with the wheat aphid (13.8 mg in males and 15.3 mg in females). The preoviposition period (measured from adult emergence to the first egg laid) also depended on temperature and had a lower threshold of 13.4°C and a sum of effective temperatures of 152 degree-days. Maximum fecundity was observed at 25°C and 16-h day length; under these conditions, the oviposition period lasted over 100 d, and the average lifetime fecundity was about 800 eggs per female. Under short-day conditions, females of H. quadripunctata entered reproductive diapause. The photoperiodic threshold for this qualitative response at the temperatures of 20 and 25°C was about 14 h when fed on the peach aphid and 15 h when fed on the wheat aphid. Relatively small body size, low fecundity, and a strong photoperiodic response that hinders rapid adaptation to novel climates probably explain the fact that H. quadripunctata, in contrast to H. axyridis, has not become an aggressive invader.

Testing the fecundity advantage hypothesis with Sitobion avenae, Rhopalosiphum padi, and Schizaphis graminum (Hemiptera: Aphididae) feeding on ten wheat accessions.

The fecundity advantage hypothesis suggests that females with a large body size produce more offspring than smaller females. We tested this hypothesis by exploring the correlations between life-history traits of three aphid species feeding on ten wheat accessions at three levels of analysis with respect to the host plant: overall, inter-accession, and intra-accession. We found that fecundity was significantly correlated with mean relative growth rate (MRGR), weight gain, and development time, and that the faster aphid develops the greater body and fecundity, depending on aphid species, wheat accession, and analyses level. Larger aphids of all three species produced more offspring overall; this held true for Sitobion avenae and Schizaphis graminum at the inter-accession level, and for S. avenae, Rhopalosiphum padi, and S. graminum for three, five, and eight accessions respectively at the intra-accession level. Only one correlation, between intrinsic rates of natural increase (rm) and MRGR, was significant for all aphid species at all three analysis levels. A more accurate statement of the fecundity advantage hypothesis is that cereal aphids with greater MRGR generally maintain higher rm on wheat. Our results also provide a method for exploring relationships between individual life-history traits and population dynamics for insects on host plants.

Greenbug (Hemiptera: Aphididae) Biology, Ecology, and Management in Wheat and Sorghum

Greenbug, Schizaphis graminum (Rondani), is a major insect pest of wheat and sorghum on the southern Great Plains. In this review, we outline greenbug life history and biology, describe direct and indirect crop injury to wheat and sorghum, and discuss current management strategies such as biological control, cultural control focusing on host plant resistance, monitoring, and chemical control that can be incorporated into an integrated pest management program.

The Discovery of Resistant Sources of Spring Barley, Hordeum vulgare ssp. spontaneum, and Unique Greenbug Biotypes.

The genetic sources for host-plant resistance to the greenbug (Schizaphis graminum Rondani) in barley (Hordeum vulgare ssp. spontaneum) are limited in that only two single dominant genes Rsg1 and Rsg2 are available for the complex of greenbug biotypes. We evaluated four new barley lines from the Wild Barley Diversity Collection (WBDC) that previously showed potential for greenbug resistance. Three of those entries, WBDC 53, WBDC 117, WBDC 336, exhibited very dominant sources of resistance to older known biotypes B, C, E, F, H, I, and TX1, which also add to the host-plant differentials used to separate these greenbug biotypes. We also re-evaluated the earlier known set of greenbug biotypes that have been in culture for several years against the known host-plant differentials, and included seven newer greenbug isolates collected from Wyoming to the full complement of small grain differentials. This resulted in the discovery of five new greenbug biotypes, WY10 MC, WY81, WY10 B, WY12 MC, and WY86. Wyoming isolates WY4 A and WY4 B were identical in their phenotypic profile, and should be combined as a single unique greenbug biotype. These barley trials resulted in finding new sources of host-plant resistance, although more research needs to be conducted on what type of resistance was found, and how it can be used. We also document that the Wheatland, Wyoming area serves as a very conducive environment for the development of new greenbug biotypes.

Temporal Changes in Cereal Aphids (Hemiptera: Aphididae) Populations in Northern Rio Grande do Sul, Brazil

Cereal aphids (Hemiptera: Aphididae) are economically important pests in all wheat-producing regions of Brazil and about eight species can be found in wheat crops. Aphids acquired the condition of severe pest in wheat in the 1970s, due to the emergence of Metopolophium dirhodum and Sitobion avenae. A successful biological control program of wheat aphids was introduced in southern Brazil in 1978. This study describes temporal changes in aphid populations in a wheat producing area in the northern region of Rio Grande do Sul (RS) state, Brazil. Data from weekly samples (water traps of Moericke type) for the current (May to November 2008, 2009 and 2010) population frequency of each species was compared with 1970s populations. In addition, their seasonal fluctuations and the influence of rainfall and temperature on their populations were estimated. The species collected, and their frequencies, were as follows: Rhopalosiphum padi (57.6%), Sitobion avenae (31.0 %), Schizaphis graminum (7.7%), Metopolophium dirhodum (1.4%), Rhopalosiphum rufiabdominalis (0.9%), Rhopalosiphum maidis (0.6%), Sipha maydis (0.4%) and Sipha flava (0.4%). Aphids populations in winter cereals in northern RS have changed radically. The high populations of M. dirhodum in wheat in 1970s have been reduced to such levels that rarely have been found. Nowadays, R. padi was the predominant species. When the rainfall remained between 0-20 mm and temperatures between 15-20 ºC, aphid populations were more numerous than the average for the sampling period.

Integrative proteomics to understand the transmission mechanism of Barley yellow dwarf virus-GPV by its insect vector Rhopalosiphum padi.

Barley yellow dwarf virus-GPV (BYDV-GPV) is transmitted by Rhopalosiphum padi and Schizaphis graminum in a persistent nonpropagative manner. To improve our understanding of its transmission mechanism by aphid vectors, we used two approaches, isobaric tags for relative and absolute quantitation (iTRAQ) and yeast two-hybrid (YTH) system, to identify proteins in R. padi that may interact with or direct the spread of BYDV-GPV along the circulative transmission pathway. Thirty-three differential aphid proteins in viruliferous and nonviruliferous insects were identified using iTRAQ coupled to 2DLC-MS/MS. With the yeast two-hybrid system, 25 prey proteins were identified as interacting with the readthrough protein (RTP) and eight with the coat protein (CP), which are encoded by BYDV-GPV. Among the aphid proteins identified, most were involved in primary energy metabolism, synaptic vesicle cycle, the proteasome pathway and the cell cytoskeleton organization pathway. In a systematic comparison of the two methods, we found that the information generated by the two methods was complementary. Taken together, our findings provide useful information on the interactions between BYDV-GPV and its vector R. padi to further our understanding of the mechanisms regulating circulative transmission in aphid vectors.

Sticky Traps Baited with Synthetic Aggregation Pheromone Predict Fruit Orchard Infestations of Plautia stali (Hemiptera: Pentatomidae).

The brown-winged green bug, Plautia stali Scott, mainly reproduces on Japanese cedar or cypress cones in Japanese plantation forests during summer and autumn. It often depletes its food sources in forest habitats and moves to cultivated crops in large numbers. To establish an easy method for assessing the risk of fruit orchard infestation by P. stali, we conducted a 3-yr field survey that monitored the attraction of bugs to the synthetic P. stali aggregation pheromone using a sticky trap. We used a morphological indicator, variable body size depending on food intake, to estimate the nutritional status in nymphs, which showed that nymphs attracted to the synthetic pheromone were starving. Comparisons between increasing changes in the number of stylet sheaths left on the cones by P. stali and the number of trapped nymphs show that monitoring nymphs with the pheromone-baited sticky trap is useful for inferring conditions regarding food resources in forest habitats. The trend toward trapping second instars can provide a timely overview of resource competition for cones. Trapping middle-to-late (third-fifth) instars is a warning that the cones are finally depleted and that there is a high probability that adults will leave the forests and invade the orchards. In addition, trends in trapping adults suggest that there is a potential risk of orchard infestation by the pest and predict the intensity and period of the invasion. The pheromone-baited sticky trap is an easy but useful survey tool for predicting P. stali orchard infestations.

Recruitment of aphidophagous arthropods to sorghum plants infested with Melanaphis sacchari and Schizaphis graminum (Hemiptera: Aphididae)

A significant question in biological control is the extent to which indigenous natural enemies might be pre-adapted to exploit invasive species that constitute novel prey. We observed the recruitment of natural enemies to aphid microcosms – pots containing four sorghum plants infested with either Melanaphis sacchari (Zehntner), a newly invasive aphid, or Schizaphis graminum (Rondani), an established pest. The first cohort was monitored in open habitat along a tree line near riparian parkland and urban plantings, and the second, within a sorghum monoculture. Both aphid species were eliminated by natural enemies within 13days in the first cohort, but in the second, M. sacchari reached higher numbers than S. graminum and survived a week longer. Biological control was successful in both cases; neither aphid produced a generation of alates, nor did plants sustain significant damage. Syrphid larvae, primarily Allograpta obliqua (Say), caused most aphid mortality in the first cohort, whereas adult Coccinellidae, primarily Hippodamia convergens Guerin-Meneville, caused most mortality in the second. Eggs and larvae of Chrysoperla carnea Stephens were present in both cohorts, but appeared to suffer more intraguild predation in the first. Flower flies and velvet mites were present only in the first cohort, and flower bugs, only in the second. Aphelinus sp. successfully parasitized both aphids, but Lysiphlebus testaceipes Cresson did not develop in M. sacchari due to their infection with the secondary endosymbiont Hamiltonella defensa (confirmed by DNA analysis). Thus, sorghum infested with M. sacchari attracted the same guild of natural enemies as S. graminum and had similar biological control outcomes. The findings suggest that the capacity of indigenous aphidophagous guilds to respond to, and ultimately control, invasive aphid species may be underestimated.

Processed multispectral imagery differentiates wheat crop stress caused by greenbug from other causes

The greenbug, Schizaphis graminum (Rondani) (Hemiptera:Aphididae) is an important pest of small grains such as winter wheat (Triticum aestivum). The objective of this study was to determine the potential for multispectral imagery analyzed using spatial pattern metrics subjected to discriminant function analysis to differentiate patches of wheat plants within wheat fields infested by greenbug from stressed patches caused by other factors. Multispectral images of wheat fields were acquired using a Duncantech MS3100-CIR multispectral camera. Stress observed to wheat plants in wheat fields was grouped into categories: greenbug, drought and agricultural conditions. ERDAS Imagine software was used to process and analyze images, and FRAGSTATS was used to quantify spatial pattern. A set of 10 spatial pattern metrics were computed at the patch level for each stress factor. The analysis of spatial pattern metrics by discriminant function analysis revealed that the three types of stress could be reliably differentiated. The combination of multispectral data and spatial pattern metrics made it possible to differentiate patches in wheat fields infested by greenbug from patches caused by drought and agronomic conditions. The detection and differentiation of stressed patches may help in mapping stress within fields for the purpose of site-specific pest management and for monitoring systems to identify greenbug infestations at individual field and regional scales.

Sublethal effects of insecticide seed treatments on two nearctic lady beetles (Coleoptera: Coccinellidae).

Predatory insects often feed on plants or use plant products to supplement their diet, creating a potential route of exposure to systemic insecticides used as seed treatments. This study examined whether chlorantraniliprole or thiamethoxam might negatively impact Coleomegilla maculata and Hippodamia convergens when the beetles consumed the extrafloral nectar of sunflowers grown from treated seed. We reared both species on eggs of Ephestia kuehniella and then switched adult H. convergens to a diet of greenbugs, Schizaphis graminum, in order to induce oviposition in this species. Excised sunflower stems, either treated or control and refreshed every 48 h, were provided throughout larval development, or for the first week of adult life. Exposure of C. maculata larvae to chlorantraniliprole and thiamethoxam applied as seed treatments delayed adult emergence by prolonging the pupal period. When adults were exposed, thiamethoxam reduced the preoviposition period compared to chlorantraniliprole, whereas the latter treatment cause females to produce fewer clutches during the observation period. Larvae of C. maculata did not appear to obtain sufficient hydration from the sunflower stems and their subsequent fecundity and fertility were compromised in comparison to the adult exposure experiment where larvae received supplemental water during development. Exposure of H. convergens larvae to thiamethoxam skewed the sex ratio in favor of females; both materials reduced the egg viability of resulting adults and increased the period required for eclosion. Exposure of H. convergens adults to chlorantraniliprole reduced egg eclosion times compared to thiamethoxam and exposure to both insecticides reduced pupation times in progeny. The results indicate that both insecticides have negative, sublethal impacts on the biology of these predators when they feed on extrafloral nectar of sunflower plants grown from treated seed.