Comparative studies of predation among feral,commercially-purchased,and laboratory-reared predators

The predatory activities of commercially-purchased adult Hippodamia convergens Guérin-Méneville and two laboratory-reared strains of adult Geocoris punctipes (Say) were compared with their feral counterparts. In single prey choice feeding tests, commercially-purchased and feral H. convergens were provided copious amounts of silverleaf whitefly, Bemisia argentifolii Bellows & Perring adults or eggs of pink bollworm, Pectinophora gossypiella (Saunders). Commercially-purchased H. convergens devoured more pink bollworm eggs and at a faster rate than the feral H. convergens. In contrast, feral H. convergens consumed more adult whiteflies and at a faster rate than commercial H. convergens. In multiple feeding choice tests, two distinctly different laboratory-reared strains and feral G. punctipes were provided a cotton leaf disk containing copious amounts of silverleaf whitefly eggs, nymphs, and adults. Virtually no predation was observed on whitefly eggs, but both laboratory strains of G. punctipes fed on more whitefly nymphs and adults than the feral G. punctipes. Moreover, both of the laboratory strains had a significantly faster feeding rate on adult whiteflies and spent significantly less time feeding on plant tissue than the feral strain. These results suggest that the augmentative biological control candidates retained their ability to prey on these selected prey items, even after being displaced from their overwintering site (H. convergens) or being reared in captivity (G. punctipes) for over 40 generations. Handling editor: Patrick De Clercq. This article reports the results of research only. Mention of a proprietary product does not constitute an endorsement or a recommendation for its use by the USDA.     

Geocoris punctipes as a predator of Bemisia tabaci: a laboratory evaluation

Geocoris punctipes (Say), a predaceous lygaeid not previously docmented as a whitefly predator, was tested in the laboratory as a natural enemy of the sweet potato whitefly, Bemisia tabaci (Genn.). Its stalking behavior with whiteflies as prey was similar to that observed with aphids. A previously unobserved behavior was noted that involves the predators using salivary secretions to fasten the wings of prey to various surfaces, allowing labial probing and feeding. Prey consumption as a function of prey number appeared to follow the pattern of the Holling type II functional response. Handling time per prey item ranged from about 180 to 240 seconds. No changes were observed in handling time devoted to earlier versus later catches. Nutritional quality of whiteflies was measured using crude protein, lipids and carbohydrates as criteria. Performance, in terms of predator behavior, total daily handling time, functional response, energy budget and nutritional quality all support the hypothesis that G. punctipes is a promising candidate for biological control of sweet potato whiteflies.     

Phosphorus-32 bioelimination by arthropod predators fed labeled eggs ofHeliothis virescens [Lep.: Noctuidae]

Adults ofGeocoris punctipes (Say),Tropiconabis capsiformis Germar,Nabis roseipennis Reuter andColeomegilla maculata (DeGeer) were confined inside petri dishes and fed phosphorus-32 (^32p)-labeledHeliothis virescens (F.) eggs. Observations of bioelimination of^32p over a 72 h period allowed derivation of equations for predicting the number ofH. virescens eggs ingested by each species. Twenty-four to 72 h after eggs were eaten, the percentages of^32p eliminated ranged from ca. 14% forG. punctipes to 42 % forT. capsiformis. Cautious use of the results will aid researchers in assessing predation on^32p labeledHeliothis. Publication N^o 5935. Mississippi Agricultural and Forestry Experiment Station, Mississippi State, MS 39762.     

Intraguild predation on Eretmocerus sp. nr. emiratus,a parasitoid of Bemisia tabaci,by three generalist predators with implications for estimating the level and impact of parasitism

Intraguild predation (IGP) is pervasive in many managed and unmanaged ecosystems and may have negative, neutral or positive effects on the biological control of pest insects. Both generalist predators and aphelinid parasitoids attack Bemisia tabaci (Gennadius) Biotype B (=B. argentifolii Perring & Bellows) on cotton in the southwestern USA. Free-choice and no-choice laboratory assays were conducted to quantify prey consumption patterns and preference by three representative generalist predators, Geocoris punctipes (Say), Orius insidiosus (Say), and Hippodamia convergens Guérin-Méneville, offered fourth instar B. tabaci nymphs and nymphs parasitized by Eretmocerus sp. nr. emiratus. All three predators showed a significant preference for larval and pupal stage parasitoids over early fourth instar nymphs, but G. punctipes and O. insidiosus were non-discriminating when offered a choice of larval parasitoids and late fourth instar nymphs. The potential implications of these observed patterns for the field were examined through sensitivity analyses of existing field life table data. First, preference for parasitized hosts alters the methods required for calculating marginal rates of parasitism. Incorporating a preference variable in the estimation procedure had a very small positive effect (0.02–1.13% change) on total generational mortalities observed in previous life table studies. However, further hypothetical analyses suggested that under circumstances of lower generational mortality and higher levels of either apparent parasitism or predation, high levels of predator preference for parasitized prey could alter estimates of total mortality as much as 14%. Second, although intraguild predation was demonstrated, the implications for biological control are unclear. Based on field life table data the rate of IGP ranged from 0.019 to 0.126 depending on predator species and prey comparison, but accounting for these levels of IGP had only small negative effects on total generational mortalities (0.193–1.278% change).     

Prey selection and dietary response by wolves in a high-density multi-species ungulate community

Studies on predation by the wolf (Canis lupus) have often reported contradictory results about the role of prey density and vulnerability on wolf prey use. We investigated dietary response and prey selection by wolves in a high-density and multi-species ungulate community, analysing scats collected over a period of 11 years in the Casentinesi Forests, Italy. The second most abundant species, wild boar (Sus scrofa), was found to be the main wolf prey, and we did not observe any dietary response of wolves to variations in the density of either primary or secondary prey species. Selection patterns were uniform throughout the study period. Wolves strongly selected for wild boar piglets, while roe deer (Capreolus capreolus) fawns and adults, red deer (Cervus elaphus) adults and fallow deer (Dama dama) adults were avoided. Wolf preference for wild boar was inversely density dependent. Within each species, juveniles were preferred to adults. Medium-sized, young individuals of both wild boar and roe deer were optimal prey, although with different selection patterns related to the different anti-predator strategies adopted by each prey species. The results of this study suggest that in productive ecosystems with high density and high renewal rates of prey, selection patterns by wolves are determined by prey vulnerability, which is connected to prey age and body size. The different patterns of wild boar versus cervids use by wolf across Europe seems to be related to their relative abundances, while the strong selection of wild boar in Italian Apennines with respect to the more frequent avoidance in central-eastern Europe is better explained by higher piglet productivity and smaller body size of adults boar in Mediterranean temperate forests.     

Populations of Predaceous Natural Enemies Developing on Insect-Resistant and Susceptible Tomato in North Carolina

Naturally occurring populations of immature and adultGeocoris punctipes,adultColeomegilla maculataand immature coccinellids were monitored on field-grown tomato lines susceptible and resistant toManduca sextaandHelicoverpa zea. Helicoverpa zeaandHeliothis virescenseggs and small larvae that serve as prey for these predators also were monitored. MoreH. zeaandH. virescenseggs and small larvae were found on resistant than on susceptible plant lines. However, similar populations of largeH. zeaandH. virescenslarvae were found on resistant and susceptible plants. The number of adultGeocoris punctipes,adultColeomegilla maculataand immature coccinellids on resistant plants was always as high or higher than the number on susceptible plants. The data demonstrate no incompatibility of host-plant resistance with biological control provided by these predaceous insects, but indicate that the number ofG. punctipesand coccinellids required to provide effective biological control may develop too late in the season to be of practical value. Large populations of stilt bugs (Jalysus wickhami,Hemiptera: Berytidae) and spiders were observed to occur earlier in the growing season than eitherG. punctipesor coccinellids and may be a significant source of mortality forH. zeaeggs and small larvae.     

Expression of Bacillus thuringiensis Cry1Ac protein in cotton plants, acquisition by pests and predators: a tritrophic analysis

1. Studies have shown that Cry proteins of the bacterium Bacillus thuringiensis expressed in transgenic plants can be acquired by nontarget herbivores and predators. A series of studies under field and controlled conditions was conducted to investigate the extent to which Cry1Ac protein from Bt transgenic cotton reaches the third trophic level and to measure the amount of protein that herbivores can acquire and expose to predators. 2. Levels of Cry1Ac in Bt cotton leaves decreased over the season. Among herbivores (four species), Cry1Ac was detected in lepidopteran larvae and the amount varied between species. Among predators (seven species), Cry1Ac was detected in Podisus maculiventris and Chrysoperla rufilabris. 3. In the greenhouse, only 14% of the Cry1Ac detected in the prey (Spodoptera exigua larvae) was subsequently found in the predator P. maculiventris. Detection of Cry1Ac protein in Orius insidiosus, Geocoris punctipes and Nabis roseipennis was probably limited by the amount of prey consumed that had fed on Bt cotton. 4. Purified Cry1Ac was acquired by the small predatory bug G. punctipes but at much higher concentration than found in plants or in lepidopteran larvae. 5. Bt protein was shown to move through prey to the third trophic level. Predatory heteropterans acquired Cry1Ac from prey fed Bt cotton, but acquisition was dependent on the concentration of Cry1Ac conveyed by the prey and the amount of prey consumed. The type and availability of prey capable of acquiring the protein, coupled with the generalist feeding behaviour of the most common predators in the cotton ecosystem, probably constrain the flow of Cry1Ac through trophic levels.     

Feeding Fitness and Quality of Domesticated and Feral Predators: Effects of Long-Term Rearing on Artificial Diet

Predatory geocorids, Geocoris punctipes Say (Geocoridae: Hemiptera), that had been reared (domesticated) for over 6 years (60 continuous generations) on an artificial diet were compared with feral (F₁) counterparts to determine possible domestication-associated losses in predatory capabilities. Using adult female predators provided with either tobacco budworm larvae, Heliothis virescens F., or pea aphids, Acyrthosiphon pisum Harris, as prey, I measured predator weights, handling time with a single prey, amount extracted, consumption rate, and feeding (gut) capacity. Domesticated females were significantly smaller than ferals, weighing 4.53 mg versus 5.09 mg, respectively. Domestication did not significantly influence handling times, which averaged 131 (domesticated) and 122 min (feral) for predators feeding on H. virescens larvae and 106 (domesticated) and 94 min (feral) for G. punctipes feeding on A. pisum. Although there were significant differences in the weights of the two kinds of prey (H. virescens larvae being about twice as heavy as the A. pisum), both prey species exceeded the ingestion capacity of the predators. Amounts extracted by predators were 1.12 to 1.20 mg and were not significantly influenced by rearing background, prey biomass, or prey type. Consumption rates of 11.86 and 12.91 μg/min were nearly identical for both domesticated and feral predators regardless of prey species.     

Does body size difference in the leeches Glossiphonia complanata (L.) and Helobdella stagnalis (L.) contribute to co-existence?

The effect of predator and prey body size on the feeding success of the British lake-dwelling leeches Glossiphonia complanata and Helobdella stagnalis was examined in the laboratory, and any involvement of size difference between the leeches in allowing coexistence in the field assessed. G. complanata breeds in advance of H. stagnalis and maintains a body size advantage throughout their annual life-cycle. In experiments, conducted at 14 °C and a photoperiod of 16 hrs L: 8 hrs D, three size classes of leeches of each species were each exposed to each of three size classes of each of five prey species, viz. Tubifex sp., Chironomus sp., Asellus aquaticus, Lymnaea peregra and Potamopyrgus jenkinsi. For each prey species, three different types of experiments were performed: one leech exposed to four prey individuals; four leeches of the same species with sixteen prey; and two leeches of each species with sixteen prey. In the first experiment, all sizes of G. complanata were capable of feeding on all sizes of the prey types offered; the same was true for H. stagnalis with exceptions of feeding on large A. aquaticus and large L. peregra. For both species, but especially for G. complanata, there was a trend within each size class of leech for decreasing proportions of fed leeches with increasing prey size, and within each size class of prey for an increasing proportion of fed leeches with increasing leech size; however there were several exceptions to these trends. Both leeches fed extensively on Tubifex sp. but there were significant differences in the proportions feeding on other prey types; G. complanata fed more on A. aquaticus and the two snail species, and less on Chironomus, than H. stagnalis. The effect of increasing the number of leech individuals from one to four individuals, of the same or mixed species, had little effect on the proportion of leeches which had fed. It is concluded that large G. complanata will have access to large individuals of certain prey taxa denied H. stagnalis, which may lessen the intensity of interspecific competition.     

Prey selectivity of Piona exigua,a planktonic water mite

Summary Females, males and nymphs of Piona exigua were observed during prey capture and ingestion. The encounter radius of the mite was very small, allowing the escape of some crustaceans, such as the calanoid copepod Boeckella. Cladocerans, such as Bosmina or Chydorus, with little or no pre-contact escape response were the most vulnerable to mite predation. Preference values in size-selection experiments varied widely between individual mites. Adult mites presented with two sizes of Daphnia carinata generally preferred the smaller prey. When four sizes were presented simultaneously, however, the preferences of female mites for each size were not significantly different. Patterns of prey selection varied with predator age and sex; for example, female mites preferred Daphnia to Simocephalus, Ceriodaphnia and Chydorus, while nymphs showed a strong preference for Chydorus over Ceriodaphnia. When two prey types were present in equal proportions, differences in total prey density (range 5 or 10/1 – 30 or 50/1) did not alter preferences between the prey species. The preference of female mites for a particular prey type generally increased with increasing relative abundance of the prey type in each of three experiments (Daphnia: Ceriodaphnia, Ceriodaphnia: Chydorus, and Daphnia: Simocephalus). These results imply switching behaviour in these mites. Our results indicate the value of direct observation of predatory behaviour as an adjunct to prey selection experiments. It is also apparent that predatory behaviour in the presence of more than one prey type may not be predictable from that observed in single-prey situations. Predation rates on particular prey species were sometimes reduced in the presence of another species. The relative proportions of prey eaten when two species were present could not be predicted from the number of each species eaten when they were presented separately.     

Predation on eggs and larvae ofHeliothis virescens [Lep.: Noctuidae] by an adult predator complex in cage studies on cotton

Predation by a predator complex consisting of adults of the lygaeidGeocoris punctipes (Say), the nabidsNabis roseipennis Reuter and/orTropiconabis capsiformis Germar and the coccinelids,Hippodamia convergens Guerin-Meneville andColeomegilla maculata (DeGeer) onHeliothis virescens (F.) eggs, 1st-instar larvae or both on late pinhead square and early bloom stage cotton was evaluated in field cages in Mississippi. Prey densities of 4 (11, 512/ha) or 8 per cage and predator: prey (P:p) ratios of 1∶1, 2∶1, 3∶1, 4∶1 and 5∶1 were used. Prey were labeled with phosphorus-32 or carbon-14 to determine predator ingestion and effectiveness. Average percent egg predation as a function of P:p ratio ranged from 2.1 to 12.1 for a 48 h period. The average percent predation on larvae as a function of P:p ratio ranged from 5.3 to 22.0. The hemiptera fed more than the coleoptera on larvae, andG. punctipes was the best egg predator. For the range of predator densities used, the average area of discovery for the predator complex was 6.98 × 10⁻³ m/day and 2.34 × 10⁻² m/day when exposed to eggs and larvae, respectively. Publication N^o 5936-Mississippi Agricultural and Forestry Experiment Station, Mississippi State, MS 39762.     

Experience affects performance of ten-spined sticklebacks foraging on zooplankton

To study the effects of short-term experience on prey size-selection ten-spined sticklebacks (Pungitius pungitius) were fed 7–13 days with five differing diets of novel prey, Daphnia magna. The diets consisted either of a mixture of two prey size classes (1.7 and 2.2 mm) or of single-sized (1.7 and 2.2 mm) prey. Before and after the diets, the sticklebacks' prey size selection was tested with a 1:1 ratio of 1.7 and 2.2 mm D. magna. Sticklebacks made more attempts to capture large than small prey, but their foraging success was better for small than for large prey. Sticklebacks fed with a diet of both prey sizes chose significantly more large prey on the 13th day than on the 7th day or at the beginning of the experiment. Handling times for both Daphnia size classes decreased slightly with increasing foraging experience. Inexperienced sticklebacks made more unsuccessful strikes on large prey than did experienced fish. Foraging success on large prey improved somewhat with increasing experience in all but one diet group. The results indicate that experience affected ten-spined sticklebacks' prey selection.     

Interspecific somatic hybrids <Emphasis Type="Italic">Solanum bulbocastanum</Emphasis> (+) <Emphasis Type="Italic">S. tuberosum</Emphasis> H-8105

Interspecific somatic hybrids between a dihaploid potato clone H-8105 susceptible to Phytophthora infestans (Mont.) de Bary and a resistant diploid tuberizing species Solanum bulbocastanum were generated and analysed. Only ten regenerants displaying the intermediate morphology with dominating characteristics of the wild parent (simple leaves, anthocyanin pigmentation) were produced in 15 weeks after a single PEG-mediated fusion event. The RAPD patterns confirmed the hybridity of all of them. The hybrids rooted poorly and grew slowly in vitro. The cytological analysis revealed a high degree of aneuploidy in the hybrids with morphological and growth anomalies in vitro, while the morphologically normal hybrids were tetraploids. All the S. bulbocastanum (+) H-8105 hybrids were unstable in culture and three of them were consequently lost during three years of propagation in vitro. The possible reasons for instability of somatic hybrids between the distantly related species are discussed.     

Seasonal diet and prey selection of black‐backed jackals on a small‐livestock farm in South Africa

The extent to which black‐backed jackals (Canis mesomelas) selectively consume domestic sheep (Ovis aries) compared to wild prey is unknown. Using faecal analysis and prey surveys, we determined the seasonal diet and prey selection of jackals on a small‐livestock farm in South Africa. Sheep comprised 25–48% of the biomass consumed by jackals across seasons, and consumption peaked during the lambing seasons, indicating sheep often were the main food resource for jackals. Another main food resource was wild ungulates <50 kg, primarily springbok (Antidorcas marsupialis) and steenbok (Raphicerus campestris), which comprised 8–47% of the biomass consumed. Other important food items were mammals 1–3 kg (4–16%), which included hares (Lepus spp.) and springhares (Pedetes capensis), and small rodents (10–14%). Compared to the biomass available, jackals selectively consumed mammals 1–3 kg over sheep across all seasons, whereas wild ungulates <50 kg were selectively consumed over sheep in most seasons. Our results showed that jackals selectively consumed different food items throughout the year and that wild prey were consistently selected over sheep.     

Spatial variation in the density and vulnerability of preferred prey in the landscape shape patterns of Amur tiger habitat use

Theoretical and empirical research suggests that carnivore distributions are largely determined by prey availability. Availability depends not only on prey density but also on prey accessibility which is affected, in part, by the configuration of landscape attributes that make prey vulnerable to predation. Exactly how spatial variation in these processes shape patterns of carnivore habitat use at the home range scale remains poorly understood. We examined the influence of prey density (negative binomial resource selection function) and vulnerability (kill site resource selection function), mapped separately for each of three species of primary prey, on habitat use patterns within the home range for Amur tigers Panthera tigris altaica in Far East Russia over 20 winters. We developed spatially‐explicit mixed linear regression models to assess these patterns and found that models with parameters for specific primary prey were more robust than models with composite parameters for all primary prey species. This emphasizes the importance of evaluating predation dynamics at a species‐specific level. We also found that Amur tigers used habitat within the home range where red deer Cervus elaphus and wild boar Sus scrofa were dense. These two species were clearly preferred by tigers accounting for 72% (201 of the 278) of the tiger kills detected. The effect of red deer density however, was modulated by the vulnerability of red deer in the landscape. Amur tigers tended to establish their home ranges on habitat where red deer were most vulnerable to predation, but would use habitat where red deer were dense in the peripheral regions of their home ranges. This suggests that tigers may utilize two separate strategies for acquiring prey. As the configuration of resource patches within the home range influences carnivore survival and reproduction, our analysis has implications for tiger conservation that extend beyond our improved understanding of tiger‐prey ecology.     

Intraguild Predation on the Whitefly Parasitoid Eretmocerus eremicus by the Generalist Predator Geocoris punctipes: A Behavioral Approach

Intraguild predation (IGP) takes place when natural enemies that use similar resources attack each other. The impact of IGP on biological control can be significant if the survival of natural enemy species is disrupted. In the present study, we assessed whether Geocoris punctipes (Hemiptera: Lygaeidae) engages in IGP on Eretmocerus eremicus (Hymenoptera: Aphelinidae) while developing on whitefly nymphs of Trialeurodes vaporariorum (Hemiptera: Aleyrodidae). In choice and non-choice tests, we exposed G. punctipes to parasitized and non-parasitized whitefly nymphs. We found that G. punctipes does practice IGP on E. eremicus. However, choice tests assessing G. punctipes consumption revealed a significant preference for non-parasitized T. vaporariorum nymphs. Subsequently, we investigated whether E. eremicus females modify their foraging behavior when exposed to conditions involving IGP risk. To assess this, we analyzed wasp foraging behavior under the following treatments: i) whitefly nymphs only (control = C), ii) whitefly nymphs previously exposed to a predator ( = PEP) and, iii) whitefly nymphs and presence of a predator ( = PP). In non-choice tests we found that E. eremicus did not significantly modify its number of attacks, attack duration, oviposition duration, or behavior sequences. However, E. eremicus oviposited significantly more eggs in the PEP treatment. In the PP treatment, G. punctipes also preyed upon adult E. eremicus wasps, significantly reducing their number of ovipositions and residence time. When the wasps were studied under choice tests, in which they were exposed simultaneously to all three treatments, the number of attacks and frequency of selection were similar under all treatments. These results indicate that under IGP risk, E. eremicus maintains several behavioral traits, but can also increase its number of ovipositions in the presence of IG-predator cues. We discuss these findings in the context of population dynamics and biological control.     

Spatial and temporal avoidance of risk within a large carnivore guild

Within a large carnivore guild, subordinate competitors (African wild dog, Lycaon pictus, and cheetah, Acinonyx jubatus) might reduce the limiting effects of dominant competitors (lion, Panthera leo, and spotted hyena, Crocuta crocuta) by avoiding them in space, in time, or through patterns of prey selection. Understanding how these competitors cope with one other can inform strategies for their conservation. We tested how mechanisms of niche partitioning promote coexistence by quantifying patterns of prey selection and the use of space and time by all members of the large carnivore guild within Liuwa Plain National Park in western Zambia. Lions and hyenas specialized on wildebeest, whereas wild dogs and cheetahs selected broader diets including smaller and less abundant prey. Spatially, cheetahs showed no detectable avoidance of areas heavily used by dominant competitors, but wild dogs avoided areas heavily used by lions. Temporally, the proportion of kills by lions and hyenas did not detectably differ across four time periods (day, crepuscular, early night, and late night), but wild dogs and especially cheetahs concentrated on time windows that avoided nighttime hunting by lions and hyenas. Our results provide new insight into the conditions under which partitioning may not allow for coexistence for one subordinate species, the African wild dog, while it does for cheetah. Because of differences in responses to dominant competitors, African wild dogs may be more prone to competitive exclusion (local extirpation), particularly in open, uniform ecosystems with simple (often wildebeest dominated) prey communities, where spatial avoidance is difficult.     

Spatial and temporal dynamics of oviposition behavior of bollworm and three of its predators in Bt and non-Bt cotton fields

Host plants exhibiting insect resistance traits have long been known to influence within‐plant distributions of pests and their natural enemies. Sites and timing of egg deposition are particularly important for synchrony of predators and their prey in the field. Temporal and spatial distribution of eggs of the cotton bollworms [Heliothis virescens (F.) and Helicoverpa zea (Boddie) (Lepidoptera: Noctuidae)] and that of the predators Geocoris punctipes (Say) (Heteroptera: Geocoridae), Chrysoperla rufilabris (Burmeister) (Neuroptera: Chrysopidae), and Micromus spec. (Neuroptera: Hemerobiidae) were determined during three cotton seasons, from 2002 to 2004, by collecting and examining plants throughout each season. Comparisons also were made between Bt and non‐Bt cotton to investigate possible changes in oviposition behavior on Bt cotton. The study was conducted in commercial fields with insecticide use to manage pests when economic thresholds were exceeded in both cotton types. Egg densities for predators and bollworms varied among years, but were similar on Bt and non‐Bt cottons. Oviposition of bollworms and G. punctipes correlated spatially within plants, with most eggs laid on structures in the top five nodes of cotton plants and on the three outermost leaves on lateral branches regardless of cotton type. Bollworm oviposition dynamics exhibited two peaks within the season (early July and early August). Eggs of all predators and bollworms collected from the field and incubated in the laboratory had high hatching rates throughout each season (74–100%). Temporal association of predator with bollworm oviposition showed a significant correlation with green lacewings, a delay of 10 days for big‐eyed bugs, and no correlation with brown lacewings. Furthermore, Bt cotton plants exerted no significant effect on temporal or spatial patterns of oviposition of bollworms or the predators, indicating no change in oviposition behavior of bollworm females within plant structures after almost one decade of widespread planting of Bt cotton.     

Ability of selected accessions of Phaseolus vulgaris L. to restrict nodulation by particular rhizobia

Plant genotypes that limit nodulation by indigenous rhizobia while nodulating normally with inoculant-strain nodule occupancy in Phaseolus vulgaris. In this study, eight of nine Rhizobium tropici strains and six of 15 Rhizobium etli strains examined, showed limited ability to nodulate and fix nitrogen with the two wild P. vulgaris genotypes G21117 and G10002, but were effective in symbiosis with the cultivated bean genotypes Jamapa and Amarillo Gigante. Five of the R. etli strains restricted in nodulation by G21117 and G10002 produced an alkaline reaction in yeast mannitol medium. In a competition experiment in which restricted strains were tested in 1:1 mixtures with the highly effective R. etli strain CIAT632, the restricted strains produced a low percentage of the nodules formed on G2117, but produced over 40% of the nodules formed on Jamapa. The interaction of the four Rhizobium strains with the two bean genotypes, based on the percentage of nodules formed, was highly significant (P<0.001).     

Identifying inter‐ and intra‐guild feeding activity of an arthropod predator assemblage

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