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Eva Judith Hueso, Jaime Molina-Ochoa, Jalil Fallad-Chávez, Roberto Roberto Lezama-Gutiérrez, Marilú López-Edwards and Javier Farías-Larios

Scyphophorus acupunctatus is the main pest of Agave tequilana. Its adults are vectors of Erwinia carotovora, which causes plant destruction. The susceptibility of S. acupunctatus larvae to various strains of entomopathogenic nematodes has been demonstrated previously (Molina et al., 2004). In the current paper, the use of seven different concentrations: 0, 10, 20, 50, 100, 200, and 500, of infected juveniles per larva in petri dishes containing a filter paper against Steinernema carpocapsae strains All, Ca, and Fl, and also against native insolated N1, N2, N4, belonging to the genera Steinernema sp. The studies were conducted under laboratory conditions to determine the susceptibility of S. acupunctatus larvae to entomopathogenic nematodes. One hundred percent mortality of S. acupunctatus larvae was achieved by S. carpocapsae strains All, Ca, and Fl with exposure to 100 infected juveniles. In the case of native isolates, N2 registered 95% mortality, and for N4 and N1, mortality registered was 75%. An analysis of variance was conducted in order to determine whether strain or isolate had the highest virulence against S. acupunctatus larvae. Means for S. acupunctatus larvae by entomopathogenic nematodes presented significant differences (F = 57.01; df = 55, 223; P < 0.0001), resulting in two levels. At the first level, S. carpocapsae All, Fl, and Ca are statistically the same as isolate N4. At the second level, the isolates N4 and N1 are statistically the same. The results indicate the high susceptibility of S. acupunctatus larvae. The infectivity of native isolates as well as S. carpocapsae strains All, Fl, and Ca are associated with the symbiotic bacterium Xenorharbdus sp., suggesting they have potential for use against S. acupunctatus larvae.

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Roberto Lezama-Gutierrez, Jaime Molina-Ochoa, Oscar L. Contreras-Ochoa, Martin Gonzalez-Ramirez, Oscar Rebolledo-Dominguez and M. Lopez-Edwards

The susceptibility of third-instar larvae of Anastrepha ludens (Loew) to the entomopathogenic nematodes Steinernema carpocapsae (Weiser) (All and Tecomán strains), S. feltiae (Filiipjev), S. glaseri (Steiner) (NC strain), S. riobrave (Cabanillas, Poinar & Raulston), and Heterorhabditis bacteriophora Poinar (NC, Patronato, and Tecomán strains), was evaluated under laboratory conditions. Sterile distilled water (1.0 mL) with 4000 infective juvenile nematodes were applied on 300 g of moistened sterile soil into 1000-mL pots, and 20 third-instar larvae were placed on the soil surface, 1 mL of distilled water without nematodes was applied as control. Each nematode treatment was replicated four times. After nematode application, pots were incubated at 25 °C. Mortality of larvae and pupae was evaluated 6 and 12 d after inoculation. Cadavers of larvae and pupae were dissected and examined for the presence of nematodes. Our results showed that Mexican fruit larvae were susceptible to entomopathogenic nematodes. S. riobrave and S. carpocapsae All strain caused 90% of larval and pupae cumulative mortality, H. bactetiophora NC strain and S. feltiae killed more than 80%, whereas H. bacteriophora Tecomán and S. glaseri caused a 52.5% mortality. These results suggest that the nematodes S. riobrave and S. carpocapsae All strain have a potential as biological control agents against A. ludens.

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James J. Luby, Peter A. Alspach, Vincent G.M. Bus and Nnadozie C. Oraguzie

Incidence and severity of fire blight [Erwinia amylovora (Burr.) Winslow, Broadhurst, Buchanan, Krumwiede, Rogers, and Smith] following field infection were recorded using families resulting primarily from open-pollination of Malus sylvestris (L.) Mill. var.domestica (Borkh.) Mansf. cultivars and a few other Malus Mill. sp. The families were structured as three sublines, planted in three successive years (1992 to 1994), of a diverse population of apple germplasm established at HortResearch, Hawkes Bay, New Zealand. The incidence of fire blight varied among the sublines with the oldest planting exhibiting more fire blight. Flowering trees were more likely to be infected than nonflowering trees, in terms of both incidence and severity. Furthermore, the level of fire blight was related to flowering date, with later flowering trees having higher levels. Thus, family means and narrow-sense heritability estimates were computed after first adjusting the fire blight score for flowering date by fitting a linear model. Provenance of origin of the maternal parent explained little variation except that M. sieversii Lebed. families were more resistant than M. sylvestris var. domestica families in one subline. Family means computed using all trees, and those from only flowering trees were highly correlated. Families from open-pollination of M. honanensis Rehder and M. xhartwiggii Koehne females were among the more susceptible. Those from several European M. sylvestris var. domestica cultivars as well as from M. baccata (L.) Borkh. and M. toringoides (Rehder) Hughes females were among the more resistant families. Narrow-sense heritability estimates ranged from 0.05 to 0.85 depending on the subline, with most estimates between 0.12 and 0.36. They were higher in the two older sublines that consisted primarily of open-pollinated families from M. sylvestris var. domestica, and lower in the younger subline that consisted primarily of M. sieversii, due to lower incidence and severity in the latter subline. Breeders who consider potential complications of juvenility, tree size, and flowering date in relation to infection periods should be able to exploit field epidemics to perform effective selection.

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Aekaterini N. Martini, Maria Papafotiou and Stavros N. Vemmos

addition, the season of explant collection has been found to affect the survival of explants through effects on microbial contamination ( Thomas and Ravindra, 1997 ). The present study investigated the effect of explant origin (juvenile, adult), explant

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Madhurababu Kunta, John V. da Graça, Nasir S.A. Malik, Eliezer S. Louzada and Mamoudou Sétamou

. Discussion With the exception of bark in which higher Ca. L. asiaticus concentration was recorded in HLB-infected sweet orange trees relative to their grapefruit counterparts and juvenile tissue (not sampled from sweet orange), we found no significant

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Michael W. Smith, William D. Goff and M. Lenny Wells

( Sparks and Payne, 1977 ). Observations also suggest most seedling trunks (juvenile growth) are less prone to damage than cultivar trunks (adult phase growth) when mechanically thinning fruit. In hurricane-prone areas of the Southeast, whip-grafted trees

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Michael C. Long, Stephen L. Krebs and Stan C. Hokanson

Powdery mildew (PM) is a common foliar disease of genus Rhododendron ( Basden and Helfer, 1995 ; Coyier, 1986 ; Kenyon, 1995 ). Although PM is known to cross-infect broad taxonomic groups within the genus ( Beales, 1997 ; Galle, 1987

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Erick X. Caamano, Raymond A. Cloyd, Leellen F. Solter and Declan J. Fallon

viability or percentage of live, active infective juveniles (IJs) in an EPN suspension ( Grewal and Peters, 2005 ). Gaugler et al. (2000) evaluated the viability and pathogenicity of different commercial EPN products, which were shipped to three different

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Phillip D. Griffiths, Laura Fredrick Marek and Larry D. Robertson

effectively. The aim of this research was to evaluate crucifer species at the juvenile stage to quantify the presence, frequency, and potential use of accessions for introgression of Xcc resistance. To achieve this, the crucifer accessions from the NC-7 (Ames

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Wenhao Dai, Victoria Magnusson and Chris Johnson

control these diseases. These diseases and infected trees can only be removed. Therefore, utilization of disease-resistant plants is the best method to manage these diseases. Conventional approaches for chokecherry breeding is generally difficult and time