Pattern of attack of a galling insect reveals an unexpected preference-performance linkage on medium-sized resources

Pattern of attack of a galling insect reveals an unexpected preference-performance linkage on medium-sized resources. The Plant Vigor Hypothesis (PVH) predicts oviposition preference and higher offspring performance on longer and fast-growing shoots, and although several studies have tested its predictions, long-term studies concerning the patterns of host selection by galling species are still lacking. The PVH was tested in this study using Bauhinia brevipes (Fabaceae) as the host of a leaf gall midge, Asphondylia microcapillata (Diptera, Cecidomyiidae) during three consecutive years. Shoots were collected from the same 80 plants between 2001 and 2003 and shoot length, number of healthy and galled leaves, gall number, and mortality factors were recorded. Nearly 600 galls were found on the 5,800 shoots collected. Medium-sized shoots supported from 46 to 70% of all galls, with greater gall survival rate in 2002 and 2003. A decrease in parasitism rate coupled with an increase in gall predation lead to a constant similar gall survivorship rate in all years (x = 22.7%). Although gall abundance varied among years (122 in 2001, 114 in 2002 and 359 in 2003) preference for longer shoots was not observed because the percentage of galled shoots and galled leaves were higher on medium shoot length classes in all years. The observed distribution of gall abundance and galled shoots were always greater than the expected distribution on medium shoot length classes. These findings do not support the PVH, and show that A. microcapillata can maximize the female preference and larval performance on medium-sized shoots of B. brevipes.

Identity and combinations of arbuscular mycorrhizal fungal isolates influence plant resistance and insect preference

1. Accumulating evidence indicates that plant resistance against above-ground herbivores can be affected by the presence of arbuscular mycorrhizal fungi (AMF) in association with the host plant. Little is known, however, about how AMF composition can influence herbivore choice to feed on a particular plant. 2. Unravelling the preference-performance hypothesis in a multitrophic context is needed to expand our knowledge of complex multitrophic interactions in natural systems. If given mycorrhizal fungal genotypes increase attractiveness for a herbivore (reduced plant resistance), then the benefits of increased unpalatability provided by the mycorrhizal fungi (increased plant resistance) might be outweighed by the increased herbivore recruitment. 3. This was addressed by designing three experiments to test the effects of different AMF genotypes, inoculated either alone or in combination, to measure intraspecific AMF effects on plant resistance and insect herbivore preference. Using strawberry (Fragaria vesca L.) plants that were colonised by eight different combinations of Rhizophagus irregularis isolates, we measured effects on plant growth, insect growth and survival, as well as feeding preferences of a generalist herbivore caterpillar (Spodoptera littoralis Boisduval). 4. Overall, it was found that: (i) AMF influenced plant resistance in an AMF genotype-specific manner; (ii) some AMF inoculations decreased insect performance; (iii) insects preferentially chose to feed more on leaves originating from non-mycorrhizal plants; but also that (iv) in a whole plant bioassay, insects preferentially chose the biggest plant, regardless of their mycorrhizal status. 5. Therefore, AMF-mediated trade-offs between growth and resistance against herbivores have been shown. Such trade-offs, particularly driven by plant attractiveness to herbivores, buffer the positive effects of the mycorrhizal symbiosis on enhanced plant growth.

Feeding and oviposition preferences of the diamondback moth Plutella xylostella (Lepidoptera: Plutellidae) on six Brassicaceae host plant species

Plutella xylostella (diamondback moth, DBM) is a globally distributed Lepidopteran that feeds and oviposits almost exclusively on plants in the Brassicaceae family. DBM disperses from the southern United States and Mexico into Canada in the spring and summer. Establishment of DBM in Ontario is partially dependent upon the quantity and quality of host plants available and the preference of DBM for different hosts. Host plants include many crops such as broccoli, canola and cabbage, as well as landscape ornamentals and wild plants. It has previously been established that DBM are attracted to host plants by chemicals, specifically glucosinolates. I examined the preference of DBM among crop, wild and ornamental host plant species and how preference varies with insect life stage (3rd and 4th instar larvae and adults). Experiments included exposing DBM larvae from five populations coming from different locations in Canada to six Brassicaceae species and evaluating the preferences and weight gain over one hour. Then adult females were exposed to these same plant species and their oviposition preferences were examined. Populations from Alberta, Saskatchewan and Ontario were compared to assess differences in preference associated with geographic region or species of host plant. The ultimate goal of my study was to understand the potential of various Brassicaceae species to act as reservoirs to sustain and promote population growth of DBM, as well as sinks that may decrease DBM abundance. Results showed that garden cress (Lepidium sativum) was highly preferred over other species (wintercress, black mustard, aubretia, broccoli and ornamental kale) for both food and oviposition sources. Previous studies report that garden cress contains saponins, chemicals shown to be toxic to developing DBM larvae, however no studies have yet shown a preference for garden cress. These results provide information on a novel host plant with the potential to control DBM population growth. No difference in preferences was found among populations of DBM from various sources in Canada.

Host selection and performance of the giant willow aphid, Tuberolachnus salignus (Gmelin) - Implications for pest management

1 The recent increase in planting of selected willow clones as energy crops for biomass production has resulted in a need to understand the relationship between commonly grown, clonally propagated genotypes and their pests. 2 For the first time, we present a study of the interactions of six willow clones and a previously unconsidered pest, the giant willow aphid Tuberolachnus salignus. 3 Tuberolachnus salignus alatae displayed no preference between the clones, but there was genetic variation in resistance between the clones; Q83 was the most resistant and led to the lowest reproductive performance in the aphid 4 Maternal effects buffered changes in aphid performance. On four tested willow clones fecundity of first generation aphids on the new host clone was intermediate to that of the second generation and that of the clone used to maintain the aphids in culture. 5 In the field, patterns of aphid infestation were highly variable between years, with the duration of attack being up to four times longer in 1999. In both years there was a significant effect of willow clone on the intensity of infestation. However, whereas Orm had the lowest intensity of infestation in the first year, Dasyclados supported a lower population level than other monitored clones in the second year.

Feeding non-preference by Spodoptera frugiperda and Spodoptera eridania on tomato genotypes

Lagartas do gênero Spodoptera spp. são altamente polífagas, podendo causar danos econômicos em diversas culturas agrícolas. em vista de sua emergente importância na cultura do tomate, principalmente o destinado à indústria, este trabalho teve por objetivo avaliar a não preferência, para alimentação, de lagartas de Spodoptera frugiperda (J. E. Smith, 1797) e Spodoptera eridania (Cramer, 1782) por genótipos de tomateiro, e classificá-los quanto aos graus de resistência. Como padrão susceptível, utilizou-se o cultivar comercial Santa Clara e, como resistente, a linhagem PI 134417, sendo avaliadas, ainda, as linhagens PI 134418, PI 126931, LA 462 e LA 716. Realizaram-se testes de não preferência, para alimentação, com e sem chance de escolha, avaliando-se a atratividade dos genótipos de tomateiro para as lagartas, em tempos pré-estabelecidos após sua liberação, além da massa foliar consumida. em geral, os genótipos LA 716 e PI 126931 foram os menos atrativos para a S. frugiperda, enquanto Santa Clara foi o mais atrativo e consumido. Quanto a S. eridania, os genótipos PI 126931, LA 462, LA 716 e PI 134418 foram os menos preferidos, para a alimentação, pelas lagartas, e Santa Clara e PI 134417 foram os mais atrativos e consumidos. Os genótipos LA e PI 126931 são moderadamente resistentes, do tipo não preferência para alimentação, para a S. frugiperda e S. eridania; PI 134418 e LA 462 são moderadamente resistentes a S. eridania; PI 134417 é susceptível a S. frugiperda e S. eridania; Santa Clara é altamente susceptível a S. frugiperda e S. eridania.

Adult attractiveness and oviposition preference of Bemisia tabaci (Genn.) (Homoptera: Aleyrodidae) B-biotype in cotton genotypes

Considerada importante praga do algodoeiro, a mosca-branca Bemisia tabaci biótipo B pode através de sua alimentação, diminuir o vigor das plantas, trasmitir vírus e prejudicar a qualidade da fibra. Visando avaliar a resistência de genótipos de algodoeiro, Gossypium hirsutum (L.), à mosca-branca Bemisia tabaci biótipo B, realizaram-se testes de atratividade e não-preferência para oviposição, com e sem chance de escolha, em telado, a temperatura ambiente. Verificou-se baixa atratividade das plantas dos genótipos Fabrika, CNPA Ita 90, Makina, Coodetec 407 e IAC 01-639 CPA 02-24 a adultos dessa mosca-branca, o que pode representar um componente de resistência destes materiais genéticos ao inseto. Os genótipos BRS Aroeira, Coodetec 406, Fabrika e Coodetec 401 apresentaram resistência do tipo não-preferência para oviposição, nos testes com e sem chance de escolha. Os números de tricomas e de glândulas de gossipol por cm² não foram adequados para se avaliar a não-preferência para oviposição de adultos da mosca-branca em genótipos de algodoeiro.

Variation in the host preferences and responses of Ascia monuste orseis Godart (Lepidoptera: Pieridae) to cultivars of collard greens Brassica oleracea (L.) var. acephala

This work evaluated the preference of Ascia monuste orseis among 29 cultivars of collard greens through free- and no-choice assays using female adults (attractiveness and oviposition) and third-instar larvae (feeding preference), in both laboratory and greenhouse conditions. In free-choice tests with female adults, the L, V, Y, H, A, and Z cultivars produced oviposition non-preference in butterflies. Cultivars R, P, C, and D produced feeding non-preference in third-instar larvae of A. monuste orseis in free- and no-choice tests. Our findings may be useful for genetic improvement focusing on the development of B. oleracea var. acephala cultivars resistant to A. monuste orseis.

Attractiveness and oviposition preference of Glycaspis brimblecombei Moore in Eucalyptus spp.

The red gum lerp psyllid Glycaspis brimblecombei Moore (Hemiptera: Psyllidae) was first recorded in Brazil in 2003 and since then has caused serious damage in Eucalyptus forests. The damage is mainly due to defoliation, sooty mold and dieback, thus requiring the development of efficient management strategies. The settling and ovipositional preference of G. brimblecombei by species and clones of Eucalyptus were evaluated in free- and no-choice tests. Preliminary tests were done to determine the density of psyllid couples that produced the greatest densities of eggs, leaf position selection for oviposition, and whether oviposition was affected by preimaginal conditioning. Apical leaves were used more frequently for oviposition by the psyllid, and the number of eggs decreased from the apex to the base. The densities of 10 and 15 psyllid couples per seedling produced the highest oviposition. There was no evidence of preimaginal conditioning. In the free-choice test, E. grandis, E. urophylla, VM-1, I-144, C-219 and H-13 were less attractive to G. brimblecombei adults, with H-13, E. grandis and E. urophylla having the least oviposition. In the no-choice test, E. urophylla, GG-100 and E. grandis also demonstrated a lower oviposition, but E. camaldulensis and 3025 were highly susceptible. The low preference for the genotypes E. grandis and E. urophylla suggests the occurrence of a non-preference type resistance against the red gum lerp psyllid. Our results can be utilized for the development of management programs for G. brimblecombei in Eucalyptus forests. © 2012 Springer Science + Business Media B.V.

Oviposition preference assessment of Diabrotica speciosa (Coleoptera: Chrysomelidae) for different soybean genotypes

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Feeding preference of Nezara viridula (Hemiptera: Pentatomidae) and attractiveness of soybean genotypes

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Heterorhabditis amazonensis RSC5 (Rhabditida: Heterorhabditidae) movement and host recognition

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Host race formation in Hyalesthes obsoletus (Signoret 1865)

Die Winden-Glasflügelzikade Hyalesthes obsoletus (Cixiidae, Glasflügelzikaden) nutzte in Deutschland ursprünglich die Ackerwinde Convolvulus arvensis als Wirtspflanze, allerdings nahm in den letzten zwei Dekaden die Abundanz auf der Großen Brennnessel Urtica dioica stark zu, zusammen mit der Inzidenz der Schwarzholzkrankheit Bois noir auf Weinreben. Bois noir wird durch ein Phytoplasma verursacht, das durch H. obsoletus von C. arvensis und U. dioica auf Weinreben übertragen wird. Es stellte sich daher die Frage, ob H. obsoletus Wirtsrassen entwickelt hat, die möglicherweise die Bois noir-Epidemiologie beeinflussen. In der vorliegenden Studie wurden folgende Fragestellungen bearbeitet: rn(1) Gibt es in Deutschland und Europa genetisch unterscheidbare Wirtsrassen von H. obsoletus auf den beiden Wirtspflanzen C. arvensis und U. dioica? Es wurden sieben Mikrosatellitenmarker entwickelt und etabliert, um H. obsoletus Populationen aus Deutschland und Europa genetisch zu analysieren. Es zeigte sich eine deutliche Differenzierung zwischen Populationen von beiden Wirtspflanzen in Deutschland, jedoch nicht in den historischen Ursprungsgebieten der deutschen Populationen, in der Schweiz, Italien oder Slovenien.rn(2) Wo sind die deutschen Wirtsrassen von H. obsoletus entstanden? Eine Einwanderung von südlichen, bereits an U. dioica angepassten Individuen stand einer lokalen Wirtsrassenevolution gegenüber. Die engere genetische Verwandtschaft der deutschen Population auf U. dioica zu denen auf C. arvensis, im Vergleich zu den übrigen Populationen auf U. dioica, impliziert einen lokalen Prozess im nördlichen Verbreitungsgebiet. Eine Immigration südlicher Tiere scheint nicht zur Diversifizierung beigetragen zu haben, führte aber möglicherweise einen U. dioica-spezifischen Phytoplasma-Stamm ein. Durch Wirtsrassenevolution entwickelten sich spezifische, vektorbasierte epidemiologische Kreisläufe der Schwarzholzkrankheit Bois noir. rn(3) Welche Präferenzen zeigen die beiden Wirtsrassen von H. obsoletus für die Wirtspflanzen C. arvensis und U. dioica und unterscheiden sich diese? Die Präferenz von H. obsoletus aus beiden deutschen Wirtsrassen in Bezug auf den Geruch der Wirtspflanzen wurde in einem Y-Olfaktometer untersucht, zusätzlich wurden beide Pflanzen direkt zur Wahl gestellt. Bei beiden Untersuchungen zeigte die Population von C. arvensis eine signifikante Präferenz für ihre native Wirtspflanze. Die Population von U. dioica wies dagegen keine Präferenz für den Geruch einer Wirtspflanze auf, bevorzugte im direkten Test jedoch signifikant ihre native Wirtspflanze. Dies weist darauf hin, dass die Anpassung an den „neuen“ Wirt noch nicht vollständig ist.rn

Sea anemone host selection by the symbiotic saddled cleaner shrimp Periclimenes holthuisi

A preliminary field survey was conducted to determine the distribution of ectosymbiotic shrimp Periclimenes holthuisi on the sea anemone Stichodactyla haddoni in Moreton Bay (Queensland, Australia). Laboratory experiments were also carried out to verify whether the shrimp show a preference for one anemone host. In the field, 45 individuals of P. holthuisi were found to be associated with 70% of the specimens of S. haddoni (n=20). We inferred this shrimp population was not space-limited because not all anemones were colonized. After having been isolated from their natural host for 2 weeks, when placed between individuals of S. haddoni and Macrodactyla doreensis (an anemone that is sympatric with S. haddoni), shrimp overwhelmingly selected S. haddoni (92%). To establish whether M. doreensis may serve as an alternative host for P. holthuisi, unacclimated shrimp were forced to associate with this anemone. Macrodactyla doreensis showed little tentacle reaction during this association; shrimp were found on the anemone's tentacles and the column. The finding that M. doreensis can serve as an alternative host for P. holthuisi demonstrates that this anemoneshrimp is adaptable to another anemone host and thus may not be highly host specific.

Intra-specific variation for host plant use in Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae): Implications for management

The polyphagous moth Helicoverpa armigera (Hubner) is one of the world's most important agricultural pests. A number of existing approaches and future designs for management of H. armigera rely on the assumption that moths do not exhibit either genetically and/or non-genetically based variation for host plant utilization. We review recent empirical evidence demonstrating that both these forms of variation influence host plant use in this moth. The significance of this variation in H. armigera in relation to current and future pest management strategies is examined. We provide recommendations on future research needs and directions for sustainable management of H. armigera, under a framework that includes consideration of intra.-specific variation for host use relevant in this and other similar pest species. (C) 2004 Elsevier Ltd. All rights reserved.

Oviposition and reproductive performance of a generalist parasitoid (Trichogramma pretiosum) exposed to host species that differ in their physical characteristics

The response of generalist egg parasitoids to alternative natural hosts that are present simultaneously is not well known. We investigated the behavior of Trichogramma pretiosum Riley (Hymenoptera: Trichogrammatidae) in relation to two field hosts Helicoverpa armigera Hubner and Spodoptera litura Fabricius, in choice and no choice tests. We quantified the effects of natal host species and post-emergence adult age on the oviposition preference of the parasitoids. H. armigera eggs were consistently preferred over S. litura eggs, regardless of the natal host and adult age. When only S. litura eggs were available as hosts, they were parasitized at statistically similar rates to H. armigera eggs (average of 17 +/- 2.7 vs. 13 +/- 3.0, H. armigera to S. litura). The adult lifespan and lifetime fecundity of T. pretiosum were variable but were affected by natal host species and/or host species to which they were exposed. Mean lifespan and fecundity of parasitoids that had developed in H. armigera eggs and were exposed to H. armigera eggs for oviposition were 13.9 +/- 1.8 days and 98.7 +/- 11.0 adult offspring. By contrast, those that developed in S. litura eggs and were exposed to S. litura eggs for oviposition lived for 7 +/- 0.9 days and produced 53.8 +/- 8.0 adult offspring. The ovigeny index (OI) was significantly lower in the parasitoids exposed to H. armigera eggs than in those exposed to S. litura eggs, regardless of the natal host, indicating that H. armigera eggs sustain the adult parasitoids better than S. litura eggs. These results are used to predict parasitoid behavior in the field when both hosts are available. (c) 2006 Elsevier Inc. All rights reserved.