Dispersal of Adult \u3ci\u3eDiatraea grandiosella\u3c/i\u3e (Lepidoptera: Crambidae) and Its Implications for Corn Borer Resistance Management in \u3ci\u3eBacillus thuringiensis\u3c/i\u3e Maize

Dispersal of the southwestern corn borer, Diatraea grandiosella Dyar, was examined by release and recapture of dye-marked adults and by capture of feral adults in and around 50-ha center pivot irrigated fields of Bacillus thuringiensis (Bt) maize. Pheromone and blacklight traps were used to capture the adults. In 1999, 2000, and 2001, a total of 177, 602, and 1,292 marked males, and 87, 231, and 1,045 marked females were released in four irrigated Bt maize fields, respectively. Recapture beyond release point was 2.13, 6.17, 3.16, and 17.91% for males and 0, 0, 2.23, and 4.18% for females in the four fields, respectively. One male was recaptured over native vegetation outside the field perimeter, and one was caught in a neighboring maize field, 457 m from the release point. An exponential decay function explained recapture of marked adults across the dispersal distance. More than 90% of adults were recaptured within 300 m of the release point. Large numbers of feral adults were captured throughout the study fields and over native vegetation between fields. The feral adult dispersal could be described with a linear model. Virgin females (38% marked and 14% feral) were captured throughout the study fields. The recapture of marked insects suggests that the dispersal was limited. However, capture of feral adults throughout Bt maize fields indicates that the actual dispersal may be more extensive than indicated by recapture of marked adults. Potential refuge sources for the feral adults were 587-1,387 m from the edge of the fields. There seems to be some dispersal of D. grandiosella from the nontransgenic “refuge” fields into the transgenic fields, which may allow for some genetic mixing of the Bt-resistant and -susceptible insects to help suppress potential evolution of pest resistance to transgenic maize. However, it is not clear whether the dispersal recorded in this study is sufficient to support the current resistance management strategy for corn borers

Oil-Soluble Dyes Incorporated in Meridic Diet of \u3ci\u3eDiatraea grandiosella\u3c/i\u3e (Lepidoptera: Crambidae) as Markers for Adult Dispersal Studies

Mark-release-recapture experiments to study insect dispersal require the release of marked insects that can be easily identified among feral conspecifics. Oil-soluble dyes have been used successfully to mark various insect species. Two oil-soluble dyes, Sudan Red 7B (C.I. 26050) and Sudan Blue 670 (C.I. 61554), were added to diet of the southwestern corn borer, Diatraea grandiosella Dyar, and evaluated against an untreated control diet. Survival, diet consumption, larval and pupal weight, development time, fecundity, longevity, and dry weight of the adults were measured. Adults reared on the three diets were also tested for mating success. Some minor effects were observed for southwestern corn borers reared on the marked diets. Eggs, larvae, pupae, and adults were all reliably marked and readily identifiable. Adults retained color for their entire life span. Adults from each diet mated successfully with adults from the other diets. F1 progeny from the different mating combinations survived to the second instar but tended to lose the marker after 3-4 d on untreated diet. Both Sudan Red 7B and Sudan Blue 670 can be used to mark southwestern corn borer adults and thus should be useful for mark-release-recapture dispersal studies. The dyes will also be useful for short-term studies with marked larvae and oviposition behavior

Rubidium Chloride and Cesium Chloride Sprayed on Maize Plants and Evaluated for Marking \u3ci\u3eDiatraea grandiosella\u3c/i\u3e (Lepidoptera: Crambidae) in Mark–Recapture Dispersal Studies

Experiments were undertaken to determine the potential for using rubidium chloride (RbCl) or cesium chloride (CsCl) to mark southwestern corn borer, Diatraea grandiosella Dyar, for use in applied ecological studies. Maize, Zea mays L., plants were sprayed with aqueous solutions of RbCl or CsCl at rates of 100, 1000, or 10,000 µg/g and inoculated with D. grandiosella neonates. Rubidium and cesium were successfully absorbed and translocated in maize plants. There were only a few minor effects of the treatment on maize or on southwestern corn borers.Rb and Cs were detected in plants, but not in insects, by using Flame atomic absorption spectrophotometry. Graphite furnace-atomic absorption spectrophotometry (GF-AAS) and neutron activation analysis (NAA) allowed identification of Rb and Cs in adults. Rb and Cs were detected by GF-AAS in feral unmarked adults, and they contained higher levels of Rb than Cs. Males and females contained similar amounts of Rb, but Cs levels were higher in males than in females. Adults recovered from field maize treated with 1000 µg/g Cs had higher levels of Cs than did those from untreated plants. Using NAA, neither Rb nor Cs was detected in adults recovered from greenhouse-grown untreated maize. Males and females recovered from maize treated with 1000 µg/g RbCl and CsCl contained similar amounts of Rb, but females contained more Rb than Cs. We conclude that application of 1000 µg/g RbCl or CsCl on plants is effective in marking adults of D. grandiosella with Rb or Cs and would be useful for mark-recapture dispersal studies

Predatory Mite, Amblyseius Swirskii (Acari: Phytoseiidae), for Biological Control of Asian Citrus Psyllid, Diaphorina Citri (Hemiptera: Psyllidae)

The Asian Citrus Psyllid (ACP), Diaphorina citri Kuwayama (Hemiptera: Psyllidae) is a serious pest of citrus in many citrus-producing regions. It vectors the bacterium 'Candidatus Liberibacter asiaticus' thought to be the causal agent of the devastating "Huanglongbing" (HLB) or citrus greening disease. Both pest and the disease are well established in Florida. Several insect predators, particularly lady beetles and the parasitoid Tamarixia radiata (Waterston) (Hymenoptera: Eulophidae), are known to cause significant mortality to ACP immatures. However, there are no reports on the effectiveness of predatory mites against ACP. We evaluated the suitability of D. citri eggs and nymphs as prey for the predatory mite Amblyseius swirskii Athias-Henriot (Acari: Phytoseiidae) in laboratory arenas, and its potential to reduce psyllid populations in the glasshouse on caged Murraya paniculata (L.) Jack plants. Mortality of D. citri eggs on M. paniculata shoots exposed to A. swirskii in plastic arenas was 4 times greater after 6 d compared to unexposed control plants. Mites were also observed sucking out body fluids of first instar nymphs. In the glasshouse, total number of D. citri adults collected over 8 wk from infested plants in ventilated cylinders with A. swirskii present averaged 80% less than the control without mites. These findings showed a significant negative impact of A. swirskii on D. citri under controlled conditions. Further research needs to focus on rates and frequency of release, impact of A. swirskii on D. citri populations in citrus and other hosts under field conditions, and interactions of A. swirskii and D. citri with native predatory mites

Sesame as an Alternative Host Plant to Establish and Retain Predatory Mirids in Open-Field Tomatoes

The silverleaf whitefly (Bemisia tabaci) and the South America tomato pinworm (Tuta absoluta) are two of the most destructive pests of tomato. Open-field tomato production frequently relies on chemical treatments, which has been shown to lead to pesticide resistance. The integration of biological control using predatory mirid bugs is an effective alternative method for managing these pests. However, methods to establish and maintain populations of zoophytophagous mirids are not adequately described. We explored the potential use of two mirids naturally occurring in Florida, Nesidiocoris tenuis and Macrolophus praeclarus. We conducted 6 field experiments over 4 consecutive years to develop a strategy to maintain the mirids. Pre-plant inoculation of tomato plants did not lead to their establishment, likely due to the low prevalence of prey. We explored the use of sesame (Sesamum indicum) to retain the mirids. Intercropping sesame maintained the populations of N. tenuis throughout the duration of the crop. Macrolophus praeclarus never established in any of the open-field experiments. Nesidiocoris tenuis damage was minimal (<1 necrotic ring/plant) and mirid damage was reduced in the presence of sesame. Our results show that intercropping sesame may provide a means to utilize mirids to manage B. tabaci, an established pest, and provide options to tomato growers should T. absoluta invade USA

Activación defensiva mediante exposición a volátiles en cítricos: efecto sobre el HLB y sus principales vectores

El huanglongbing (HLB) o greening de los cítricos es una enfermedad bacteriana que limita seriamente la producción de cítricos en la mayor parte de zonas citrícolas mundiales. Afortunadamente tanto la enfermedad como los dos principales insectos que transmiten esta enfermedad, los psílidos Trioza erytreae y Diaphorina citri, no están presentes en la citricultura mediterránea española. Trabajos recientes han demostrado como la acción del HLB puede limitarse mediante la activación de las defensas de las plantas, principalmente las desencadenadas a partir de la ruta de señalización del ácido salicílico (SA)

Interactions among three species of cereal aphids simultaneously infesting wheat

Interactions among greenbug, Schizaphis graminum (Rondani), Russian wheat aphid, Diuraphis noxia (Mordvilko), and bird cherry-oat aphid Rhopalosiphum padi (L.) were examined on wheat plants (Triticum aestivum L., cultivar TAM 107). Nymphs were released on the plants as conspecific and heterospecific pairs of either first or fourth instars and evaluated for survival, developmental time, fecundity, intra-plant movement, and affinity to plant tissues. Survival from first instar to onset of reproduction averaged 90–100% across all pair combinations. Diuraphis noxia developed faster as conspecifics than in any heterospecific combination, and faster as conspecifics feeding on the same plant tissue than on different tissues. Fecundity of S. graminum was higher for conspecifics that developed on the same plant tissue than for those feeding separately. There was evidence of amensalism (one species was harmed while the other was unaffected) in that D. noxia experienced delayed development feeding in tandem with S. graminum, and reduced fecundity with both S. graminum and R. padi. Furthermore, S. graminum nymphs had reduced survival when their mothers matured on a same plant with R. padi. Both D. noxia and R. padi changed position on the plant more often when developing with S. graminum. Survival of second generation S. graminum nymphs was reduced when this species developed and reproduced in tandem with R. padi. Preferred feeding locations were S. graminum - primary leaf, D. noxia - tertiary leaf and R. padi - stem and these were not altered in any heterospecific combinations. Heterospecific aphids had no impact on fecundity or progeny survival in any species combination when fourth instars matured and reproduced on plants not previously exposed to aphid feeding, supporting the inference that systemic, aphid-induced changes in plant physiology mediated the effects observed when first instars developed and reproduced on the same plants

Incidence of invasive Diaphorina citri (Hemiptera: Psyllidae) and its introduced parasitoid Tamarixia radiata (Hymenoptera: Eulophidae) in Florida citrus.

Diaphorina citri Kuwayama (Hemiptera: Psyllidae), vectors the bacterium Candidatus Liberibacter asiaticus, one of the causal organisms of the devastating citrus disease "huanglongbing" or citrus greening. In the United States, D. citri was first discovered in Florida, in 1998. Tamarixia radiata Waterston (Hymenoptera: Eulophidae) was imported from Asia and released in Florida in 1999-2001 to improve biological control of D. citri before citrus greening was detected in Florida in 2005. Florida citrus groves were surveyed during 2006-2007 for D. citri and T. radiata. Results showed that D. citri was established in all 28 citrus groves surveyed across 16 counties. Adult populations averaged 3.52, 1.27, and 1.66 individuals per "tap" sample at locations in the central, southwest, and eastern coastal regions, respectively. A tap sample consisted of 22- by 28-cm white paper sheet (on a clipboard) held under branches selected at random that were tapped three times. Averages of 67, 44, and 45% citrus shoots infested with psyllid eggs or nymphs were obtained in the central, southwest, and eastern coastal regions, respectively. T. radiata was recovered from fourth- and fifth-instar psyllid nymphs at 26 of the 28 locations. However, apparent parasitism rates were variable and averaged < 20% during spring and summer over all locations. Incidence of parasitism increased during fall at some locations, averaging 39% in September and 56% in November in the central and southwest regions, respectively. Further efforts are warranted to enhance the biological control of D. citri and thereby reduce psyllid populations and spread of citrus greening disease

Demographic analysis of fenpyroximate and thiacloprid exposed predatory mite Amblyseius swirskii (Acari: Phytoseiidae).

Knowledge of the impact of pesticides on predators is crucial for developing integrated pest management (IPM) programs. Amblyseius swirskii (Acari: Phytoseiidae) is a predatory mite used to control several species of pest including Tetranychus urticae (Acari: Tetranychidae) and arthropods. T. urticae is a major pest of multiple greenhouse-grown and field crops including apples in Iran. Lethal and sublethal effects of fenpyroximate and thiacloprid were investigated on A. swirskii, using these chemicals separately at recommended rates or in combination at reduced rates. Recommended tested rates of both pesticides negatively influenced the biological parameters of A. swirskii such as the net reproductive rate (R0) and the intrinsic rate of increase (r). However, the combined treatment of the two pesticides at their reduced rates was less hazardous to A. swirskii. Our findings indicate that the combined use of these chemicals may be compatible with IPM programs utilizing A. swirskii as biological control tool against phytophagous mites and other pests. However, semifield and field studies to investigate the effects of reduced rate treatments of fenpyroximate and thiacloprid alone and in combination on T. urticae and A. swirskii are required for developing IPM programs