Diabrotica speciosa is an important pest of several crops in South America, including soybeans. Adults cause severe defoliation in soybean plants, and damage is significant when cotyledons are attacked. This study evaluated feeding non-preference to D. speciosa adults using 10 soybean genotypes, testing (i) 15-day-old whole plants and (ii) leaf disks of 60-day-old plants, through assessments of soybean attractiveness and leaf area consumed (LAC). Foliar contents of flavonoids and nutrients, and leaf trichome density were quantified for potential correlations with soybean resistance to adult of D. speciosa. In the whole young-plant experiment, under free-choice conditions, the lowest LAC was observed in IAC 100 and PI 227687. In no-choice, PI 227687 and IGRA RA 626 RR showed lower LAC than the other genotypes. In the leaf disk test, in free-choice, the genotypes IAC 100, PI 274454, PI 227687, DM 339, and BR 16 were the least preferred by adult of D. speciosa. In no-choice, PI 274454 was one of the least preferred, similarly to IGRA RA 626 RR, Dowling, and PI 227687. In the whole plant experiment, a high rutin content and low amounts of zinc, calcium, sulfur and manganese were associated with less consumption of D. speciosa on leaves of resistant genotypes. In contrast, in the leaf disk test there was a significant influence of trichomes in soybean resistance to the pest. In conclusion, the PI lines herein assessed are also promising sources for developing cultivars resistant to D. speciosa.

Tuta absoluta (Meyrick) is considered as a major pest of tomato worldwide that causes significant losses in the crop production. This study aimed to evaluate integration of two effective and environmentally safe methods (host plant resistant and biological control) for sustainable management of the pest under greenhouse conditions. The experiment was conducted based on the factorial design with ten replicates under greenhouse conditions (22 ± 3°C, 50 ± 10 RH and 14 L:10 D photoperiod). Infestation to T. absoluta was conducted at the first-flowering stage of the plants by introducing a pair of newly emerged adults (one female and one male) per plant. Ten days later, the biological agent, Trichogramma brassicae, was released on the treatments by hanging a card contained 50 parasitized eggs in each replicate. Observation was performed weekly on ratio of infested leaves per plant (%), number of larvae/plant, number of mines/leaf and ratio of infested fruits/plant (%). Results indicated that the susceptible variety alone (Izmir) supported the highest ratio of infested leaves (42.92 ± 1.95%), number of larvae/plant (12.86 ± 0.71), number of mines/leaf (1.29 ± 0.07) and infested fruits/plant (18.8 ± 1.10%), whereas the lowest (6.12 ± 0.42%, 1.85 ± 0.13, 0.18 ± 0.02 and 0.12 ± 0.06%, respectively) were observed in combined resistant variety (Cherry) and parasitoid released treatment. Integration of these methods not only decreases damage caused on tomato leaflets and fruits, but also reduces insecticide applications which are adversely impact human health and environment.

Aphids are phloem-feeding insects that cause economic losses to crops globally. Whilst aphid interactions with susceptible plants and partially resistant genotypes have been well characterized, the interactions between aphids and non-host species are not well understood. Unravelling these non-host interactions can identify the mechanisms which contribute to plant resistance. Using contrasting aphid-host plant systems, including the broad host range pest Myzus persicae (host: Arabidopsis; poor-host: barley) and the cereal pest Rhopalosiphum padi (host: barley; non-host: Arabidopsis), we conducted a range of physiological experiments and compared aphid settling and probing behaviour on a host plant vs either a non-host or poor-host. In choice experiments, we observed that around 10% of aphids selected a non-host or poor-host plant species after 24 h. Using the Electrical Penetration Graph technique, we showed that feeding and probing behaviours differ during non-host and poor-host interactions when compared with a host interaction. In the Arabidopsis non-host interaction with the cereal pest R. padi aphids were unable to reach and feed on the phloem, with resistance likely residing in the mesophyll cell layer. In the barley poor-host interaction with M. persicae, resistance is likely phloem-based as phloem ingestion was reduced compared with the host interaction. Overall, our data suggest that plant resistance to aphids in non-host and poor-host interactions with these aphid species likely resides in different plant cell layers. Future work will take into account specific cell layers where resistances are based to dissect the underlying mechanisms and gain a better understanding of how we may improve crop resistance to aphids.

The tomato Mi-1 gene mediates plant resistance to whitefly Bemisia tabaci, nematodes, and aphids. Other genes are also required for this resistance, and a model of interaction between the proteins encoded by these genes was proposed. Microarray analyses were used previously to identify genes involved in plant resistance to pests or pathogens, but scarcely in resistance to insects. In the present work, the GeneChip™ Tomato Genome Array (Affymetrix®) was used to compare the transcriptional profiles of Motelle (bearing Mi-1) and Moneymaker (lacking Mi-1) cultivars, both before and after B. tabaci infestation. Ten transcripts were expressed at least twofold in uninfested Motelle than in Moneymaker, while other eight were expressed half or less. After whitefly infestation, differences between cultivars increased to 14 transcripts expressed more in Motelle than in Moneymaker and 14 transcripts less expressed. Half of these transcripts showed no differential expression before infestation. These results show the baseline differences in the tomato transcriptomic profile associated with the presence or absence of the Mi-1 gene and provide us with valuable information on candidate genes to intervene in either compatible or incompatible tomato–whitefly interactions.

Lipaphis erysimi (L.) Kaltenbach (Hemiptera: Aphididae) is one of the most important pests of brassica crops, mainly causing losses due to sap sucking, toxin injection and viral transmission. Knowledge about the main natural factors that regulate populations of this pest, as well as its critical mortality stage, is crucial for the development of integrated pest management of L. erysimi. Here, we determined the critical stage and key mortality factors for L. erysimi in cabbage using an ecological life table. Causes of mortality at each stage of L. erysimi development were monitored daily in the field for seven seasons. From the experimental data, we determined the key factor and critical stage of mortality through correlation and regression analyses. The nymphal stage, especially first instar nymphs, was critical for L. erysimi mortality. The key mortality factors were, in descending order of importance, physiological disturbances and predation by Syrphidae, Coccinellidae and Solenopsis ants. Therefore, control measures should target early stages of L. erysimi and the use of cabbage cultivars that have negative effects against L. erysimi may be a promising strategy for its management. Our results may be useful for plant geneticists who could develop new cabbage cultivars based on these findings. In addition, conservation measures of the main predators of L. erysimi may contribute to the natural control of this pest.

Continuous ingestion of the phloem sap of plants by aphids can remove a significant amount of photoassimilates. Based on our earlier works, we hypothesized that due to the reduced aphid feeding time caused by antibiosis, wheat plants may achieve growth tolerance to aphids. We tested this hypothesis using three wheat cultivars, XY22 (Xiaoyan22), AK58 (Bainongaikang58) and XN979 (Xinong979) and the grain aphid, Sitobion avenae. In the choice test, S. avenae did not show any preference among the three wheat cultivars. However, S. avenae had a lower body weight and a lower intrinsic rate of increase when feeding on XY22 than on AK58 and XN979. The electrical penetration graph results indicated that S. avenae had significantly shorter mean and total phloem ingestion periods on XY22 than on AK58 or XN979. The aphids required a similar time to reach the phloem sap on the three wheat cultivars, but required more time to establish sustained phloem ingestion on XY22. These results suggest that the resistance factors of XY22 may be phloem based. Moreover, XY22 suffered less biomass loss in response to aphid infestation compared with XN979, suggesting that XY22 also had a better growth tolerance to S. avenae than XN979. Wheat resistance level to S. avenae was partially correlated with plant photosynthetic rates, and peroxidase activities. These results confirmed that the limitation in aphid feeding from plant phloem in wheat cultivar XY22 was related to antibiosis but not antixenosis, which caused XY22 tolerance to S. avenae.

Genetically modified crops with insect resistance genes from Bacillus thuringiensis Berliner (Bt-plants) are increasingly being cultivated worldwide. Therefore, it is critical to improve our knowledge of their direct or indirect impact not only on target pests but also on non-target arthropods. Hence, this study evaluates comparative leaf consumption and performance of Spodoptera eridania (Cramer), a species that is tolerant of the Cry1Ac protein, fed with Bt soybean, MON 87701×MON 89788 or its non-Bt isoline. We also assessed the comparative performance of the egg parasitoid Telenomus remus Nixon on eggs of S. eridania produced from individuals that fed on these two soybean isolines as larvae. Results showed that Bt soybean reduced by 2 days larval development and increased by 3 days adult male longevity. Therefore, we conclude that the effect of Bt soybean MON 87701×MON 89788 on S. eridania development and reproduction is small, and favorable to pest development. These differences are less likely to directly result from the toxin presence but indirectly from unintended changes in plant characteristics caused by the insertion of the transgene. Our results should be viewed as an alert that S. eridania populations may increase in Bt soybeans, but on the other hand, no adverse effects of this technology were observed for the egg parasitoid T. remus which can help to prevent S. eridania outbreaks on these crops.

Aphids are, arguably, the single most damaging group of agricultural insect pests throughout the world. Plant tolerance, which is a plant response to an insect pest, is viewed as an excellent management strategy. Developing testable hypotheses based on genome-wide and more focused methods will help in understanding the molecular underpinnings of plant tolerance to aphid herbivory. As a first step in this process, we undertook transcript profiling with Affymetrix GeneChip Barley Genome arrays using RNA extracted from tissues of tolerant and susceptible genotypes collected at three hours, three days and six days after Diuraphis noxia introduction. Acquired data were compared to identify changes unique to the tolerant barley at each harvest date. Transcript abundance of 4086 genes was differentially changed over the three harvest dates in tolerant and susceptible barley in response to D. noxia feeding. Across the three harvest dates, the greatest number of genes was differentially expressed in both barleys at three days after aphid introduction. A total of 909 genes showed significant levels of change in the tolerant barley in response to D. noxia feeding as compared to susceptible plants infested with aphids. Many of these genes could be assigned to specific metabolic categories, including several associated with plant defense and scavenging of reactive oxygen species (ROS). Interestingly, two peroxidase genes, designated HvPRXA1 and HvPRXA2, were up-regulated to a greater degree in response to D. noxia feeding on tolerant barley plants, indicating that specific peroxidases could be important for the tolerance process. These findings suggest that the ability to elevate and sustain levels of ROS-scavenging enzymes could play an important role in the tolerant response.

The antibiotic effects of 12 different cotton genotypes on Bemisia tabaci (Gennadius) were studied during June–July and August–September 2003, with the objective to determine the biological parameters which are important to study the mechanism of antibiosis and to identify the genotypes in which antibiosis is operating. The detailed biology of whitefly, i.e. developmental period, survival, fecundity, longevity and sex ratio were studied under ‘no choice’ conditions, by confining the whiteflies in leaf cages. The study revealed that incubation period, nymphal developmental time, total developmental time, nymphal survival, total survival, fecundity and female longevity are the most important biological parameters for detecting the presence of antibiosis in resistant cotton genotypes against whiteflies. On the other hand, pupal period and survival, male longevity and sex ratio do not seem to play important roles in antibiosis. The combined effect of these parameters indicated that Gossypium arboreum genotype PA 183 was the most resistant while Bt 6304, TX Maroon 2–78 and F846 were the most susceptible ones. Other genotypes with moderate resistance include Supriya and LD 694.

The tomato–potato psyllid Bactericera [Paratrioza] cockerelli (Sulc) has recently caused losses exceeding 50% on fresh market tomatoes in California and Baja, Mexico by injecting a toxin that results in a condition known as ‘psyllid yellows’. The objectives of this study were to: (i) document oviposition preferences on a range of tomato cultivars; (ii) determine threshold levels for psyllid densities that would cause psyllid yellows on tomatoes within the first three weeks following transplanting; and (iii) identify the most important ‘psyllid yellows’ symptoms that might be used in surveying and monitoring for this pest. Plant lines tested included the commonly-planted commercial cultivars ‘Shady Lady’ and ‘QualiT 21’, an older, previously commercial cultivar ‘7718 VFN’, a common cultivar planted by consumers ‘Yellow Pear’, and a wild type plant accession, PI 134417. When given a choice, psyllids significantly preferred ‘Yellow Pear’ and avoided PI 134417 for oviposition. Under no-choice conditions psyllids laid significantly fewer eggs on PI 134417, but all the other plant lines were equally good substrates for laying eggs. Thus, oviposition preference is not likely to provide a functional management strategy in large plantings. On ‘Shady Lady’, psyllids preferred to oviposit on plants already infested with adults. On both ‘Shady Lady’ and ‘7718 VFN’ oviposition was significantly greater on plants previously infested by nymphs as compared to uninfested control plants. This suggests that, at least for some cultivars, there is a physiological change in plant attractiveness following psyllid feeding. ‘Yellow Pear’ and ‘QualiT 21’ were relatively tolerant of psyllids, requiring 18 nymphs per plant to produce the disease symptoms. Only eight nymphs per plant were needed on ‘Shady Lady’ and ‘7718 VFN’. For all cultivars, the pest density showed strong correlations with measurements such as the number of yellowing leaves and leaflets and distorted leaves, which were as good as or better than the first factor extracted from principal component analysis. Therefore, such measurements have the potential to simplify field surveys.

Allomerus octoarticulatus is a plant-ant that colonizes domatia of the understorey tree Hirtella myrmecophila in the Central Amazon and forages for invertebrates, including leaf herbivores, on the host plant. We conducted manipulative experiments to study the ant's recruitment response to damaged leaves and leaf extracts of the host and to extracts of Protium hebetatum, a non-myrmecophytic sympatric tree species. Artificial damage to leaves of H. myrmecophila caused an increase in the number of recruits to the leaf. Ant response was stronger in young than in mature leaves. Recruitment was restricted to damaged leaves. No increment in recruitment rates was observed in undamaged, adjacent leaves. Different levels of leaf damage did not elicit differences in recruitment rates. Aqueous extract of leaves, placed on undamaged leaves of the host plant, also led to increased recruitment compared with water (control), and more ants were recruited to extracts from young than from mature and old leaves. Extracts of both H. myrmecophila and Protium hebetatum induced recruitment. We discuss the evolutionary importance of plant leaf components for maintenance of the ant-plant mutualism.

Within the Aphidoidea, most species of Aphididae, as long as they are in small numbers and not carrying plant viruses, do little perceptible damage to their food plants. In species that cause toxicoses, it is usually assumed that some component of the saliva must be responsible. Paradoxically, however, the salivary enzymes of Aphididae are similar to those that already occur in plants – oxidases and enzymes that depolymerize polysaccharides – and the salivary enzymes are injected in very small amounts relative to their counterparts in the plant. Damage to plants triggers defensive, biochemical responses, and it is suggested that the injected enzymes serve mainly to divert or counter responses at the immediate interface of stylets and plant tissues. The saliva of Aphididae contains non-enzymic, reducing compounds which, in the presence of oxidases, can combine with and inactivate defensive phytochemicals – including those released in response to damage and transported in the phloem sieve tube sap on which Aphididae feed. Salivary and gut oxidases deactivate ingested phytochemicals by oxidative polymerization. Aphididae inject saliva into sieve tubes before sustained ingestion of sap, and this saliva has been presumed to condition the sieve tubes, but in what way remains unclear. It is suggested that there is a dynamic biochemical interaction between aphids and plants; that the interaction is usually well balanced for most of the Aphididae; hence, no outcome is readily observable. Where a significant imbalance occurs, however, either the aphid is unable to feed, i.e. the plant is resistant, and/or the aphid does not effectively counter a hypersensitive response. Not all plant responses are disadvantageous to aphids. Gall-forming Aphidoidea trigger and control abnormal growth in the plant to the insects' advantage, possibly by eliciting vigorous oxidation in selective meristematic tissues, thereby limiting supply of molecular oxygen and inhibiting oxygen-dependent growth-controls. Current problems and possible approaches for further research are reviewed.

S2 line and S2 test-cross recurrent selection procedures were initiated to improve the resistance of a maize (Zea mays L.) population to the spotted stemborer, Chilo partellus (Swinhoe) (Lepidoptera: Pyralidae). Thirty-five selections developed from the population were evaluated for resistance to the stemborer in western Kenya. Resistance was rated according to leaf feeding (LF), stem tunnelling (ST) and deadheart formation (DH) following artificial infestation with first-instar C. partellus. Larval establishment and growth were also assessed. The reduction in foliar damage ratings, percentage stem length tunnelled, and percentage of plants showing deadheart after one cycle of recurrent selection were 4.38 %, 74.80 % and 13.92 %, respectively. A very low larval establishment on all the selections was attributed to their resistance to C. partellus attack. Results from this study indicated low levels of larval growth and development. It is concluded that antibiosis was the type of resistance mechanism against C. partellus in the maize populations investigated and that more cycles of selection are required to significantly shift the gene frequencies for resistance.

Seedlings of 462 sorghum lines were screened to identify resistance to the sugarcane aphid, Melanaphis sacchari (Zehntner). About 7% of the lines exhibited resistance in the seedling stage in greenhouse trials. In an advanced screening experiment, 12 sorghum lines had resistance ratings of 1.0–3.0 (highly resistant or resistant). In a similar test, older and larger plants of the same lines were as resistant as in the seedling stage. Lines IS12664C, IS12609C, IS12158C, and IS12661C were highly resistant in preliminary and advanced screening trials. Antixenosis was shown to be a mechanism of resistance. Sorghum lines IS12664C, IS1144C, IS1598C, and IS12661C were less preferred than ‘Mtode’, a susceptible sorghum. Based on greenhouse and field trials, antibiosis adversely affected aphid longevity, days reproducing, and progeny production. On the least antibiotic sorghums, longevity, days reproducing, and number of nymphs produced were as high as 13.7, 6.0, and 26.6, respectively. On the most antibiotic sorghums, these values were 4.5, 0.0, and 0.0. Resistance appeared to be controlled by a dominant gene, but there were indications of modifiers linked to major genes.

Malathion tolerance of the rose-grain aphid Metopolophium dirhodum (Walker) reared on the ancient wheat variety Emmer (Triticum dicoccum L.) was tested by topical bioassay and found to be lower than that of aphids reared on the modern more susceptible variety Marts Kinsman (T. aestivum L.). On both varieties, tolerance was greater at stem elongation than at the tillering stage of plant growth. All statistically significant differences when plants were treated with Cycocel and MCPA showed that the two chemicals, respectively, reduced and increased aphid tolerance to malathion, in keeping with the effects of the chemicals on induced plant resistance to aphids reported in the literature. Probit mortality slopes were not progressively altered by changes in LC50, so that similar differences in aphid tolerance to malathion were found at both LC59 and LC90 levels.

Four soybean genotypes, PI 227687, PI 229358, Davis and Hardee were tested for their antixenosis and antibiosis to the soybean hairy caterpillar, Spilarctia casignata Koll. PI 227687 and PI 229358 showed greater antixenosis and strong antibiosis (high larval and pupal mortalities, reduced pupal weight, and a low growth index). Davis and Hardee were the favoured hosts as indicated by high larval preference based on increased feeding and low larval and pupal mortalities, increased pupal weight and a high growth index.

The main thrust of the article is to present the historical development of the idea of Integrated Pest Management (IPM) from the heyday of “pestophobia” (the insistence of elimination of any vestige of insect interference with the cosmetic appearance of our crops), which leads to the misuse and abuse of insecticides, to the era of employing IPM concepts, which leads to pest interventions which are necessarily knowledge-intensive. Illustrations are given using ICIPE's research experience in developing an IPM approach to the control of Chilo through adaptation of relevant intercropping patterns, plant resistant cultivars and biological control agents. In this task, the IPM specialist needs to have three assets to be successful in the tropics: he needs to be a first-class natural historian; he requires to build his new knowledge on the traditional knowledge of the rural farmer, and to rationalize it scientifically, and he needs to be able to manipulate new innovations—both technical and social.

Plants express evolutionary adaptations in response to overall environmental stresses (selection pressures), of which insect infestation usually represents only a minor component. The majority of insect-host plant relationships involves adaptations of insect species to existing plants. Over time, plants have evolved a variety of physical and chemical defence mechanisms against environmental stresses. Only some of these are active against insects, and then not against all species. Plants rarely seem to evolve defences specifically against insects. Parameters of plant resistance to parasites are classified as constitutive or inducible. Soybean resistance to agromyzid stem-miners involves both constitutive and inducible components. Expression of such resistance parameters involves controls ranging from single genes (e.g. for trichome traits) to various combinations of genes (e.g. for the metabolic pathway for phenyl-propanoids). Environmental stresses (e.g. high illumination) especially affect the expression of resistance parameters which involve dynamic metabolic pathways. Soybean (Glycine soja) resistance to beanflies is an example of ‘horizontal’ resistance. Thus, the expected stability is long-term. Such stability is attributable to its major parameters being fundamental components of the soybean's primary and secondary growth and differentiation. These kinds of parameters are major products of the soybean's successful evolutionary experience at survival.

The agroecosystem is the basic unit of consideration in the integrated pest management approach. The target crop within this ecological system and its level of susceptibility to insect pest species is of fundamental importance, and can be altered genetically through breeding for pest resistance. The relative level of pest resistance as influenced by pest density, demands a knowledge of pest density and plant damage (yield) relationships. An understanding of these relationships leads to the determination of economic injury levels and subsequently to the establishment of dynamic economic threshold levels. Comparing the economic injury level of insect resistant cultivars to that of susceptible cultivars defines the resistance level and provides the base-line data on which to quantify the effects of other direct control tactics and natural pest density suppressing agents.

Insect resistant sorghums are used as a model to examine the unique values of this tactic as a component in an integrated pest management strategy; the role they play, and how they influence other direct control and support tactics.

Differences in the susceptibility or resistance of different plants to an insect are reflected in the magnitude of its population established on them and the resulting damage. The population of an insect on a plant is determined by an interaction between its responses and the plant's characters. As explained previously, the following six main types of responses, operating in as many stages, are involved in the establishment of an insect on a plant: (1) orientation, determining the insect's arrival on or avoidance of a plant in response to its attractant or repellent stimuli; (2) feeding responses, determining the quantity of food ingested from the plant; (3) metabolic responses involving the utilisation of the ingested food and determining the insect's nutrition; (4) development of the insect, if in the larval stage, determined by the quantitative food-intake and nutrition; (5) egg-production in the adult stage, determined by the quantitative food-intake and nutrition; and (6) oviposition.

The first, second and last of the above mentioned responses are behavioural which determine the initial selection or rejection of a plant by an insect. In order, therefore, to understand the principles governing the susceptibility/resistance of plants to an insect species, it is necessary to compare the above mentioned responses to susceptible and resistant plants and, next, to examine the role of the plant characters in determining these responses.

On the basis of the existing literature on the subject, the role of different behavioural responses of insects to plants and their characters in determining their susceptibility or resistance to their insect pests has been considered in this paper.