No-choice Experiments Research Articles

Plant defence responses in oilseed rape MINELESS plants after attack by the cabbage moth Mamestra brassicae.

The Brassicaceae family is characterized by a unique defence mechanism known as the 'glucosinolate-myrosinase' system. When insect herbivores attack plant tissues, glucosinolates are hydrolysed by the enzyme myrosinase (EC 3.2.1.147) into a variety of degradation products, which can deter further herbivory. This process has been described as 'the mustard oil bomb'. Additionally, insect damage induces the production of glucosinolates, myrosinase, and other defences. Brassica napus seeds have been genetically modified to remove myrosinase-containing myrosin cells. These plants are termed MINELESS because they lack myrosin cells, the so-called toxic mustard oil mines. Here, we examined the interaction between B. napus wild-type and MINELESS plants and the larvae of the cabbage moth Mamestra brassicae. No-choice feeding experiments showed that M. brassicae larvae gained less weight and showed stunted growth when feeding on MINELESS plants compared to feeding on wild-type plants. M. brassicae feeding didn't affect myrosinase activity in MINELESS plants, but did reduce it in wild-type seedlings. M. brassicae feeding increased the levels of indol-3-yl-methyl, 1-methoxy-indol-3-yl-methyl, and total glucosinolates in both wild-type and MINELESS seedlings. M. brassicae feeding affected the levels of glucosinolate hydrolysis products in both wild-type and MINELESS plants. Transcriptional analysis showed that 494 and 159 genes were differentially regulated after M. brassicae feeding on wild-type and MINELESS seedlings, respectively. Taken together, the outcomes are very interesting in terms of analysing the role of myrosin cells and the glucosinolate-myrosinase defence system in response to a generalist cabbage moth, suggesting that similar studies with other generalist or specialist insect herbivores, including above- and below-ground herbivores, would be useful.

Soybean aphid intrabiotype variability based on colonization of specific soybean genotypes.

The soybean aphid, Aphis glycines Matsumura (Hemiptera: Aphididae), is one of the most destructive insect pests on soybeans in the United States. One method for managing this pest is through host plant resistance. Since its arrival in 2000, 4 aphid biotypes have been identified that are able to overcome soybean aphid resistance (Rag) genes. A soybean aphid isolate collected from Moline, Illinois readily colonized soybean plants with the soybean aphid resistance gene Rag2, unlike biotypes 1 and 2, but similar to soybean aphid biotype 3. Two no-choice experiments compared the virulence of the Moline isolate with biotype 3. In both experiments, differences in aphid population counts were not significant (P > 0.05) on soybean genotypes LD08-12957a (Rag2) and LD11-5413a (Rag2), but the aphid counts for the Moline isolate were significantly (P < 0.05) lower than the aphid counts for the biotype 3 isolate on the soybean genotypes Dowling (Rag1), LD05-16611 (Rag1), LD11-4576a (Rag1), and PI 567598B (rag1b and rag3). The Moline isolate was a variant of aphid biotype 3, which is the first report showing that soybean aphid isolates classified as the same biotype, based on virulence against specific Rag genes, can differ in aggressiveness or ability to colonize specific host genotypes.

Systemic deterrence of aphid probing and feeding by novel β-damascone analogues.

β-Damascone appeared a weak attractant close to not active to Myzus persicae, but modifications of its structure caused the avoidance of treated leaves by aphids during settling and reluctance to probe in simple choice- and no-choice experiments in previous studies. Here, the electrical penetration graph (EPG) technique, which allows monitoring of aphid probing within plant tissues, was applied to explore the biological background and localisation in plant tissues of the deterrent activities of β-damascone and its analogues. Activity of β-damascone and β-damascone-derived compounds depended on their substituents, which was manifested in the variation in the potency of the behavioural effect and differences in aphid probing phases that were affected. β-Damascone appeared a behaviourally inactive compound. The moderately active β-damascone ester affected aphid activities only during the phloem phase. The highly active deterrents—dihydro-β-damascol, β-damascone acetate, δ-bromo-γ-lactone, and unsaturated γ-lactone—affected pre-phloem and phloem aphid probing activities. The most effective structural modification that evoked the strongest negative response from M. persicae was the transformation of β-damascone into δ-bromo-γ-lactone. The behavioural effect of this transformation was demonstrated in frequent interruption of probing in peripheral tissues, which caused repeated failures in finding sieve elements, and reduction in the ingestion time during the phloem phase in favour of watery salivation. The inhibition of aphid probing at both the pre-phloem and phloem levels reveals the passage of the compounds studied through the plant surface and their distribution within plant tissues in a systemic way, which may reduce the risk of the transmission of non-persistent and persistent viruses.

Host plant resistance towards the cabbage whitefly in Brassica oleracea and its wild relatives

The cabbage whitefly (Aleyrodes proletella) is a phloem-feeding insect that is a serious problem in Brassica oleracea crops like Brussels sprouts, kale and savoy cabbage. In order to develop whitefly-resistant varieties it is essential to identify effective sources of resistance. In this study, we screened a large collection of 432 accessions, including wild material and landraces of Brassica oleracea as well as crop wild relatives, to determine whitefly performance in a no-choice field experiment. Putatively resistant accessions were further tested under greenhouse conditions. Resistant accessions were identified among B. oleracea var. capitata (cabbage) landraces and in the species B. villosa, B. incana and B. montana. Whereas resistance in cabbage is only expressed in plants of at least 12 weeks old, some wild relatives were already starting to express resistance at 6 weeks. This could open up possibilities for breeding cabbages that are resistant at a young(er) plant age. Our research also shows again the importance of crop wild relatives for finding pest resistances.

Affordable Essential Oils for Management of the Asian Citrus Psyllid

Plant essential oils are commonly used to manage insects; they are widely available and some are inexpensive.&nbsp; In this research we have selected five botanical oils costing less than $100 US per kilogram, to evaluate for repellency to Asian Citrus Psyllid (ACP), the insect vector of the causal pathogens of huanglongbing.&nbsp; In olfactometer assays, fir oil was repellent; clove and camphor oils were attractive; and litsea and citronella oils elicited no response from ACP females.&nbsp; In no-choice settling experiments, neither the low nor high fir oil treatment deterred ACP from settling.&nbsp; Subsequently, ACP were presented with a choice test between control plants and fir oil plants with a single dose of fir oil contained in a polyethylene vial.&nbsp; In this case, ACP disproportionately settled on control plants, avoiding fir oil baited trees completely.&nbsp; Finally, we conducted a field trial using yellow sticky traps baited with a high or low dose of clove or camphor oil deployed from seven mL polyethylene vials.&nbsp; We expected that the botanical oil baited yellow traps would catch more ACP than unbaited controls.&nbsp; There was no significant increase in trap capture over the course of our experiment in male, female, or total ACP capture.&nbsp; We hypothesize that this result may have been caused by sub-optimal release rates or the overriding visual cue elicited by yellow sticky traps. Our ongoing experiments are designed to improve the behavioral activity of release devices for these essential oils, which may have practical utility for ACP management.

Biology, Behavior, and Larval Morphology of Salbia lotanalis (Lepidoptera: Crambidae), a Potential Biological Control Agent of Miconia calvescens (Myrtales: Melastomataceae) from Costa Rica

Abstract The leaf roller Salbia lotanalis Druce (Lepidoptera: Crambidae), a potential biological control agent of Miconia calvescens de Candolle (Melastomataceae), was studied in Costa Rica. Larvae were collected from a field site near San José and the insect was reared in the laboratory to study its biology and behavior. Chaetotaxy and morphology of final-instar larvae were described. Using head capsule width measurements, we determined five larval instars in S. lotanalis. The insect was easily reared in the laboratory on M. calvescens seedlings and the life cycle of the insect was completed in 71.3 and 66.4 d for females and males, respectively. Dissection of ovarioles indicated that females could lay&amp;gt;400 eggs. Larvae are initially gregarious, but become solitary as third instars. First- to fourth-instar larvae prefer to use leaf rolls already formed by other larvae, but fifth-instar larvae prefer to make a new leaf roll rather than using leaf rolls already made and occupied by other larvae. Pupation occurs in leaves, where prepupae build a pupation chamber. Host-specificity tests, including larval feeding tests and two-choice and no-choice oviposition experiments in the laboratory, indicate that S. lotanalis has a narrow host range restricted to Miconia spp. and other Melastomaceae. Levels of parasitism in the native habitat of S. lotanalis in Costa Rica were low. In locations like Hawaii, where there are no native Melastomataceae, S. lotanalis has the potential of being an effective biological control agent against M. calvescens, but interference from resident natural enemies of Lepidoptera could be high.

Learned predation risk management by spider mites

Predation is a prime selective force shaping prey behavior. Investment in anti-predator behavior is traded-off against time and energy for other fitness-enhancing activities such as foraging or reproduction. To optimize this benefit/cost trade-off, prey should be able to innately and/or by experience modulate their behavior to the level of predation risk. Here, we assessed learned predation risk management in the herbivorous two-spotted spider mite Tetranychus urticae. We exposed spider mites coming from benign (naive) or high immediate predation risk (experienced) environments to latent and/or no risk and assessed their site choice, activity and oviposition. Benign environments were characterized by the absence of any predator cues, high immediate risk environments by killed spider mites, physical presence of the predatory mite Phytoseiulus persimilis and associated chemosensory traces left on the surface, and latent risk environments by only predator traces. In the no-choice experiment both naive and experienced spider mites laid their first egg later on leaves with than without predator traces. Irrespective of predator traces presence/absence, experienced mites laid their first egg earlier than naive ones did. Naive spider mites were more active, indicating higher restlessness, and laid fewer eggs on leaves with predator traces, whereas experienced mites were less active and laid similar numbers of eggs on leaves with and without predator traces. In the choice experiment both naive and experienced spider mites preferentially resided and oviposited on leaves without predator traces but experienced mites were less active than naive ones. Overall, our study suggests that spider mites experienced with high predation risk behave bolder under latent risk than naive spider mites. Since predator traces alone do not indicate immediate risk, we argue that the attenuated anti-predator response of experienced spider mites represents adaptive learned risk management.

Efficiency of Orius minutus for control of Tetranychus urticae on selected potato cultivars

The influence of host plant traits of five potato cultivars: Savalan, Agria, Morene, Kondor and Diamant on the population density of two-spotted spider mite (TSM) Tetranychus urticae Koch, and ovipositional preference, predation rate and life history parameters of its predator Orius minutus L. were studied under laboratory conditions (23 ± 1°C, 50 ± 5% RH and 14L:10D). The density of TSM adults on Savalan, Agria and Morene was significantly lower than on Kondor and Diamant. In both no-choice and free-choice experiments, the females of the predator laid more eggs on TSM-infested leaves of Savalan (6 eggs/leaf and 24 eggs/plant) than on Agria, Morene, Kondor and Diamant. In predation rate experiments, the females of O. minutus consumed more TSM on the infested leaves of Savalan (32 TSM/predator during 48 hours) than on Agria, Morene, Kondor and Diamant. In performance experiments, the predator nymphs developed faster when reared on TSM-infested leaves of Savalan (16 days) than on Kondor and Diamant. Moreover, the survival rate, from egg to adult, of O. minutus on TSM-infested leaves of Savalan (52.8%) was better than on Kondor and Diamant. The fecundity of O. minutus reared on TSM-infested leaves of Savalan (11.7 eggs/female) was significantly higher than on Agria, Morene, Kondor and Diamant. The intrinsic rate of natural increase and the population growth rate of O. minutus were highest when reared on TSM-infested leaves of Savalan (rm = 0.089 day−1 and λ = 1.094 day−1). These results suggest that using Savalan cultivar integrated with O. minutus could result in improved efficacy of this predator and lead to effective and more sustainable management of T. urticae in potato fields.

Effects of Spider Chemotactile Cues on Arthropod Behavior

Predation risk can strongly affect the behavior of prey species. However, empirical evidence for changes in behavior driven by spider cues is restricted to relatively few taxa. Here, we conducted a series of behavioral experiments to test for changes in activity among a wide range of terrestrial arthropods. We confronted 13 insect and eight spider species with chemotactile cues of three spider species. We applied two different experimental setups: In the ‘no-choice experiment’ prey individuals were either put on control filter papers or on filter papers previously occupied by a spider. In the ‘choice experiment’, the prey individuals were able to choose between filter paper halves with and without spider cues. In both setups, the response to spider cues depended significantly on prey species, with some species increasing and others decreasing their activity. Surprisingly few prey species responded to the spider cues at all. Our results indicate that predator recognition upon contact with cue bearing filter papers is strongly prey-specific and that behavioral effects driven by spider chemotactile cues are an exception rather than the rule among terrestrial arthropods.

Evaluation of Chinese Centipedegrasses and other Turfgrass Taxa for Potential Resistance to Twolined Spittlebug, Prosapia bicincta (Say)

Warm season turf taxa of centipedegrass [Eremochloa ophiuroides (Munro) Hack], bermudagrass [Cynodon L.C. Rich, spp.], St. Augustinegrass [Stenotaphrum secundatum (Walt.) Kuntze], and zoysiagrass [Zoysia Willd. spp.] were evaluated for tolerance to adult twolined spittlebug (Prosapia bicincta Say) feeding in choice and no-choice experiments, and for their ability to support nymphal development (antibiosis potential). Among 133 selections evaluated, few showed evidence of potential antibiosis and/or improved tolerance over commercially available cultivars. Most of the centipedegrass taxa evaluated were susceptible to the spittlebug. However, some potential antibiosis among Chinese centipedegrass taxa was identified, and there was a gradient in the ability to tolerate spittlebug feeding. Among centipedegrasses, TC 358 and TC 362 showed moderate tolerance and recovery in no-choice and choice trials. The most tolerant bermudagrasses in no-choice trials were 00 - 23, 03 - 14, and 03 - 15. Centipedegrasses overall were the best hosts for nymph development, but TC 379, TC 422 and E. ciliaris did not support nymph development, and TC 341 and TC 399 showed very low numbers of nymphs. The bermudagrasses 00 - 23 and 00 - 28 and the St. Augustinegrasses T638 and Mercedes failed to support nymph development.

Association of Pepper with Arbuscular Mycorrhizal Fungi Influences Populations of the Herbivore Frankliniella occidentalis (Thysanoptera: Thripidae)

The symbiosis of plants with arbuscular mycorrhizal fungi can improve crop growth by enhancing nutrient uptake and by increasing plant tolerance to certain pests. Pest populations also can be affected, but the effects of mycorrhizal colonization of plant hosts on species of thrips are unknown. We inoculated 2-week-old bell pepper seedling roots with a commercial mycorrhizal mixture of Glomus species (Glomales: Zygomycotina) and evaluated the effects 8 wks later on the bell pepper pest, western flower thrips (Frankliniella occidentalis (Pergande)). Females that were 10-days-old after adult emergence significantly preferred plants inoculated with arbuscular mycorrhizae compared with noninoculated plants in a laboratory choice experiment. Their numbers were greater on inoculated plants 48 h after release into cages containing inoculated and noninoculated plants. A no-choice laboratory experiment compared performance of F. occidentalis on noninoculated and inoculated bell pepper plants. Females that were 10-days-old after adult emergence were released into cages containing individual plants, and there were significantly greater total thrips (larvae, pupae, and adults) on treated plants. Further testing over a range of plant host fertility levels is needed to evaluate the potential for increased pest damage from F. occidentalis on crops growing in mutualistic symbiosis with arbuscular mycorrhizal fungi. Additional interactions with other microorganisms and natural enemies are possible under field conditions.

Effects of trichomes on the behavior and distribution of Platyprepia virginalis caterpillars

AbstractTrichomes are an important physical resistance mechanism of plants, as they reduce insect herbivore movement, feeding, and digestion. However, we know little about how trichomes influence herbivore distributions and populations. We conducted laboratory and field experiments to evaluate the preferences of Platyprepia virginalis (Boisduval) (Lepidoptera: Arctiidae) caterpillars to natural and manipulated densities of trichomes on their primary food, Lupinus arboreus Sims (Fabaceae). We then conducted field surveys to determine whether variation in trichome density among lupine bushes affected caterpillar spatial distribution on the landscape. Platyprepia virginalis caterpillars preferred lupine leaves with fewer trichomes in choice and no‐choice experiments. In the field, caterpillar feeding damage was found more often on leaves with fewer trichomes. These preferences scaled up to the level of bushes in the landscape such that more caterpillars were found on bushes with lower trichome densities than on bushes with higher trichome densities. This is one of few studies to show the potential for trichome density to influence herbivore population size and distribution in a natural system at a landscape level. The results are consistent with trichomes functioning as a resistance mechanism with consequences for herbivore choice, performance, and distribution.

Halyomorpha halys (Hemiptera: Pentatomidae) Feeding Injury on Cotton Bolls

The invasive brown marmorated stink bug, Halyomorpha halys (Stål), is rapidly spreading from the mid-Atlantic region southward into cotton (Gossypium hirsutum L.) producing areas of the U.S. Stink bugs are one of the most economically damaging insect pests of cotton and feeding by stink bugs on cotton bolls can result in a reduction of lint yield and quality at harvest. Field cage studies were conducted in Virginia to determine if boll size influenced H. halys adult and nymphal feeding behavior. In 2011 and 2012, no-choice feeding experiments were conducted with three boll sizes (1.8, 2.8, and 3.2 cm diameter). The 2011 no-choice experiment also included the adult life stage of the native green stink bug, Chinavia hilaris (Say). In addition to the experiments with adults, two feeding choice experiments were conducted during 2012 with H. halys nymphs. The insects were placed into cages enclosing entire cotton plants with different boll sizes. Results of the no-choice experiment from 2011 indicated that feeding injury caused by C. hilaris was not significantly different among the different boll sizes offered, whereas injury by H. halys increased as boll size increased. Results from the choice experiment also revealed increasing feeding damage by H. halys as boll size increased. These data indicate that the addition of H. halys to the current stink bug complex in cotton might warrant a reevaluation of the current field scouting methods and management recommendations that show that large cotton bolls (&gt; 3.2 cm diameter) are safe from stink bug feeding injury.

Feeding damage by Bagrada hilaris (Hemiptera: Pentatomidae) and impact on growth and chlorophyll content of Brassicaceous plant species

Bagrada hilaris Burmeister is an invasive species native to the old world and is currently threatening commercial vegetable production in the southwestern USA. A series of no-choice experiments were conducted to investigate multiple plant responses in six Brassica crops to feeding by B. hilaris. Varying numbers of adults were caged onto cotyledon, 2-true leaf, and 4-true leaf-stage plants of broccoli, green cabbage, red cabbage, cauliflower, kale, and radish for a 48-h infestation period. Feeding damage on leaf surfaces, total leaf area, and relative chlorophyll content on plants of each crop were measured before and after the 48-h infestation period. In addition, dry weights and total leaf area for the 4-leaf-stage plants were measured at 21 days post-infestation to estimate the residual impacts on older plants. In all crops tested, feeding damage increased with greater numbers of B. hilaris adults caged on cotyledon and 2-leaf-stage plants. Significantly more feeding damage occurred on the upper (younger) two leaves than on the lower (older) two leaves of the 4-true leaf plants for all host plants suggesting that B. hilaris feeds preferentially on newer leaf tissue. Significant reductions in leaf area, relative chlorophyll content, and dry weight in all crops indicated negative impacts on plant growth by B. hilaris. Moreover, cotyledon and 2-leaf plants were more severely impacted by B. hilaris-induced injury than the 4-leaf plants, and kale appeared to be less sensitive to B. hilaris feeding than the other five Brassicaceous hosts.

Cryptocephaline Egg Case Provides Incomplete Protection from Generalist Predators (Coleoptera: Chrysomelidae)

The egg case ofCryptocephalus rufipes(Goeze) is described and illustrated. In laboratory trials, eggs of field-collectedC. rufipeswere observed for larval emergence (untreated control) or exposed to two species of generalist predators,Chrysoperla carnea(Stephens) orXylocoris flavipes(Reuter) in no-choice experiments. The behaviour of the predators upon contact with theC. rufipeseggs was observed. The number of hatching larvae was counted and compared. In the presence of each of the two species of predators, larval emergence was significantly reduced. Eggs that were not protected by an egg case were completely consumed by the predators.C. rufipeseggs were therefore incompletely protected from the studied generalist predators. This is the first study showing experimentally the protective function of cryptocephaline egg case.

Reduced consumption of protein-rich foods follows immune challenge in a polyphagous caterpillar.

Advances in ecological immunity have illustrated that, like vertebrates, insects exhibit adaptive immunity, including induced changes in feeding behavior that aid the immune system. In particular, recent studies have pointed to the importance of protein intake in mounting an immune response. In this study, we tested the hypothesis that the polyphagous caterpillar Grammia incorrupta (H. Edwards) (Family: Erebidae) would adaptively change its feeding behavior in response to immune challenge, predicting that caterpillars would increase their intake of dietary protein. We further predicted that this response would enhance the melanization response, a component of the immune system that acts against parasitoids. We challenged the immune system using either tachinid fly parasitoids or a bead injection technique that has been used in studies to simulate parasitism, and measured feeding before and after immune challenge on diets varying in their macronutrient content. To evaluate the effects of diet on melanization, we quantified melanization of beads following feeding assays. Contrary to our prediction, we found that parasitized or injected caterpillars given a choice between high- and low-protein foods reduced their intake of the high-protein food. Furthermore, in a no-choice experiment, caterpillars offered food with a protein concentration that is optimal for growth reduced feeding following immune challenge, whereas those offered a low-protein food did not. Although variation in protein intake did not change the caterpillars' melanization response, increased carbohydrate intake did increase melanization, suggesting a prophylactic role for carbohydrates. We discuss alternative mechanisms by which variation in protein intake could negatively or positively affect parasitized caterpillars, including nutritional interactions with the caterpillar's self-medication response.

Comparison shopping: detectability and mate preferences in a fiddler crab

Females commonly exhibit mating preferences when they are allowed to choose between two alternative courtship signals. However, they also commonly approach any courtship signal when presented on its own (no-choice experiments). This could have consequences for male and female fitness. Males with nonpreferred stimuli may successfully attract females if they are, fortuitously, far enough away from competing males to prevent direct comparison. In the banana fiddler crab, Uca mjoebergi, we show, using a combination of no-choice and two-choice experiments, that there was interplay between detectability and preference. We found that preferred stimuli were not more detectable at a distance. Females were more likely to exhibit a preference when they could directly compare two stimuli that were close together and viewed in the same field of vision. Once the decision to approach one male over another had been made, it was not changed, even when more information became available.

Are kaolin and copper treatments safe to the olive fruit fly parasitoid Psyttalia concolor?

Kaolin particle films and copper-based products can be considered as possible alternatives to traditional agrochemicals used for controlling the dominant pest of olive grove areas of the Mediterranean Basin, the olive fruit fly, Bactrocera oleae (Rossi) (Dip. Tephritidae), to which this pest has already evolved resistance. Psyttalia concolor (Szepligeti) (Hym. Braconidae) is a koinobiont larval–pupal endoparasitoid of many Tephritidae of economic importance. It has been routinely used in the Mediterranean Basin for augmentative releases against B. oleae. Detailed knowledge of lethal and sublethal effects of these agrochemicals on non target arthropods is required for effective integrated pest management programmes. The aims of this study were to evaluate direct mortality caused by kaolin and copper salts on the parasitoid and the sublethal effects on emergence of adults from treated pupae and on beneficial capacity of females through four different experiments, three at laboratory level and one in semi-field conditions. Dual choice and no-choice experiments in the case of kaolin were also performed to test kaolin oviposition repellence. The results indicated that the tested agrochemicals were not harmful to the parasitoid. No lethal toxicity or effects on beneficial capacity were recorded. The behavioural experiments, however, showed that when females could choose between parasitising through a kaolin-treated surface and a water-treated one, there was a slight reduction in the percentage of parasitised hosts for kaolin. No differences were detected when females were not given a choice.

Genetic mapping of two components of reproductive isolation between two sibling species of moths, Ostrinia nubilalis and O. scapulalis

We report the quantitative trait loci (QTL) mapping of reproductive isolation traits between Ostrinia nubilalis (the European corn borer) and its sibling species O. scapulalis (the Adzuki bean borer), focusing on two traits: mating isolation (mi) and pheromone production (Pher). Four genetic maps were generated from two backcross families, with two maps (one chromosomal map and one linkage map) per backcross. We located 165-323 AFLP markers on these four maps, resulting in the identification of 27-31 linkage groups, depending on the map considered. No-choice mating experiments with the offspring of each backcross led to the detection of at least two QTLs for mi in different linkage groups. QTLs underlying Pher were located in a third linkage group. The Z heterochromosome was identified by a specific marker (Tpi) and did not carry any of these QTLs. Finally, we considered the global divergence between the two sibling species, distortions of segregation throughout the genome, and the location and effect of mi and Pher QTLs in light of the known candidate genes for reproductive isolation within the genus Ostrinia and, more broadly, in phytophagous insects.

Acyrthosiphon pisum (Harris) (Homoptera: Aphididae) feeding preference and performance on cool-season food legumes in northwestern Ethiopia

Pea aphids severely constrain food legume production in Ethiopia. Pea aphid preference and performance on common legume crops (field pea, faba bean, lentil and grass pea) were tested with no-choice, dual- and multiple-choice experiments under greenhouse conditions in northwestern Ethiopia. The results revealed that pea aphids preferred field peas, lentils and grass peas more than faba bean. Growth rate of pea aphids varied with crop variety and plant growth stage. Field pea and lentils died within 30 d. Cumulative pea aphid load was higher on field pea and grass pea than on faba bean and lentil. In the no-choice experiment, the mean pea aphid number per five plants ranged between 1.8 at 5 d after aphid infestation (DAI) on improved faba bean and 321.5 at 20 DAI on local field pea. In the dual- and multiple-choice experiments, aphids required less than 1 d to infest field pea, lentil and grass pea plants, and 4–11 d to infest faba bean. No variety was immune to infestation, but overall, field peas and grass peas were good hosts for culturing pea aphids. Growing susceptible crops in pea aphid hot spot areas may have to be avoided in favor of less preferred ones.