Leaf Feeding Damage Research Articles

Philippine Traditional Maize with Resistance to Asian Corn Borer [Ostrinia furnacalis (Guenée) (Lepidoptera: Crambidae)] Leaf and Stalk Feeding Damage

Maize has been identified as an excellent alternative to rice as a staple food in the Philippines. The Asian corn borer (ACB; Ostrinia furnacalis Guenée), one of the most destructive insect pests of maize, damages plants throughout their vegetative and reproductive stages. Most open-pollinated varieties are threatened by pests and diseases. The CGUARD program investigated the potential of traditional Philippine maize as a source of resistance to major insect pests, including ACB. This paper evaluated the response of the selected 149 Philippine traditional maize accessions to ACB at vegetative and reproductive stages through laboratory bioefficacy procedures for potential resistance without the presence of Bt leaf and stalk-feeding resistance were determined through mean larval survival and mean tunnel length, respectively, after 5 d using laboratory- reared second-instar larvae. Improvements in screening procedures for laboratory assays are detailed in this report. Fourteen (14) accessions were identified to have promising leaf-feeding resistance, whereas 30 accessions were identified for stalk-feeding resistance. The resistance of APN 0088, a white glutinous type of maize from Palawan, to both leaf and stalk feeding of ACB was also validated. The results demonstrate the presence of natural resistance to ACB in traditional maize that has been exposed to the threat of the pest for decades. These promising accessions may be utilized to generate ACB-resistant or-tolerant maize, in addition to other breeding programs. Several pigmented varieties with ACB resistance were also identified, which may be further examined for their nutritional properties and potential as functional foods. By utilizing our traditional varieties, we are boosting local maize production that will benefit small-scale farmers and ultimately providing them with a high-performing variety that is crucial in this time of changing climate.

Resistance of germplasm enhancement of partially inbred maize lines to fall armyworm and corn earworm

ABSTRACT Maize (Zea mays L.) is an important crop worldwide. In the southern area of the United States the two major pests of maize are fall armyworm (Spodoptera frugiperda (J.E. Smith)) and corn earworm (Helicoverpa zea (Boddie)). Fall armyworm primarily attacks maize leaves and corn earworm damages the upper part of the ear. An effort to obtain new sources for resistance is conducted through Germplasm Enhancement of Maize (GEM) project. Plants were infested at the whorl growth stage with fall armyworm neonates and evaluated for leaf-feeding damage 14 days after infestation. Plants were evaluated for ear-feeding damage based on natural infestation by corn earworm. Leaf-feeding damage values in Tifton were lower than at Mississippi State. GEMN-0259, GEMS-0311, and GEMS-0312 exhibited similar resistance levels with the resistant check on leaf-feeding damage in Tifton. Ear-feeding ratings in Tifton and Mississippi State were similar. GEMS-0311 showed the most resistance to ear-feeding damage in both environments. GEMS-0311 with resistance to both insects could be used for new germplasm development.

Efficacy of Conventional and Biorational Insecticides against the Invasive Pest Thrips parvispinus (Thysanoptera: Thripidae) under Containment Conditions.

In 2020, the invasive Thrips parvispinus (Karny) was first detected in Florida, United States. In response to the implemented regulatory restrictions, we conducted laboratory experiments under containment conditions. Thrips larvae and adults were exposed to 32 products (conventional and biorational insecticides) either directly or indirectly. Direct exposure was performed using a Spray Potter Tower, while indirect exposure was conducted by evaluating residue toxicity against the thrips. Water served as a control. We assessed mortality and leaf-feeding damage 48 h post-treatment. Among the conventional insecticides, chlorfenapyr, sulfoxaflor-spinetoram, and spinosad caused high mortality across all stages in both direct and residue toxicity assays. Pyridalyl, acetamiprid, tolfenpyrad, cyclaniliprole-flonicamid, acephate, novaluron, abamectin, cyantraniliprole, imidacloprid, cyclaniliprole, spirotetramat, and carbaryl displayed moderate toxicity, affecting at least two stages in either exposure route. Additionally, chlorfenapyr, spinosad, sulfoxaflor-spinetoram, pyridalyl, acetamiprid, cyclaniliprole, cyclaniliprole-flonicamid, abamectin, and acephate inhibited larvae and adult's leaf-feeding damage in both direct and residue toxicity assays. Regarding biorational insecticides, mineral oil (3%) and sesame oil caused the highest mortality and lowest leaf-feeding damage. Greenhouse evaluations of spinosad, chlorfenapyr, sulfoxaflor-spinetoram, and pyridalyl are recommended. Also, a rotation program incorporating these products, while considering different modes of action, is advised for ornamental growers to avoid resistance and to comply with regulations.

Evaluation of Germplasm Lines of Maize for Resistance to Fall Armyworm1 and Southwestern Corn Borer2 Leaf-Feeding Damage

Evaluation of Germplasm Lines of Maize for Resistance to Fall Armyworm1 and Southwestern Corn Borer2 Leaf-Feeding Damage

Evaluating Founding Landraces of Maize Population PI 674097 for Resistance to Leaf-Feeding Spodoptera frugiperda1

A maize (Zea mays L.) pest native to the Americas, the fall armyworm, Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae), is a recent invasive of Africa, Asia, and Oceania. Resistant to several insecticide classes and toxins of Btmaize, the insect damages maize by feeding on leaf, tassel, and ear tissue. Using native resistance in maize along with existing tactics could improve control outcomes. The objective for the study was to evaluate resistance to leaf-feeding fall armyworm in maize population PI 674097 and founding landraces used to develop this germplasm. Plants grown in the field and artificially infested at the seven/eight-leaf stage were visually scored for leaf-feeding damage at 7 and 14 days post infestation. All scores for NSL 283507, PI 498583, PI 583912, and PI 674097 were less (i.e., more resistant) than the susceptible check, GEMN-0131. In 2022, 14-day scores for PI 674097 were not different than the resistant check, Mp708 (3.6 ± 0.5 and 2.7 ± 0.5, respectively). PI 674097 was variable in its response to fall armyworm leaf feeding with individual plants receiving a range of 14-day scores from 2 (resistant) to 7 (susceptible) across both years of testing. This variability might be useful when selecting for greater resistance to the pest.

Impact of zein and lignin‐PLGA biopolymer nanoparticles used as pesticide nanocarriers on soybean growth and yield under field conditions

AbstractNanoparticles are being utilized in agriculture as fertilizers, pesticides, and agrochemical‐carriers. Designed to be biocompatible and degradable, biopolymer nanoparticles were developed as an alternative to metallic nanoparticles, and though safe‐by‐design, polymeric nanoparticles must be field‐tested prior to largescale use. Several field studies were conducted to observe detrimental effects of biopolymer nanoparticles on plant growth and yield using soybean, Glycine max (L.) Merr., as a model system. Biopolymer nanoparticles made from lignin or zein were applied as seed treatments to soybean seeds or as foliar sprays (zein only) to soybean plants. Studies using biopolymer nanoparticle seed treatments (nano‐STs) measured the germination rates and seedling growth were evaluated in the laboratory, while stand counts, plant height, growth stage, yield, and hundred‐seed weight were measured in the field. Foliar treatments assessed nanoparticle impact on flower abortion and pod production. To ensure nano‐STs would not compromise the plant's defensive capabilities, herbivore feeding was assessed using a leaf bioassay for defoliators and a seed damage index for pod feeders. Growth rate, percent germination, or root length were not impacted by nano‐STs. In the field, nano‐STs had no impact on stand counts, heights, growth stage, yield, and hundred‐seed weights. Leaf feeding assays and damage indices indicate plant susceptibility to herbivore attack was not increased due to nano‐STs. Foliar applications of zein nanoparticles did not increase flower abortion or decrease pod set. These results indicate that biopolymer nanoparticles have no negative effects on growth, yield, and herbivore susceptibility and should be suitable for use in agriculture.

Cadmium contamination triggers negative bottom-up effects on the growth and reproduction of Frankliniella occidentalis (Thysanoptera: Thripidae) without disrupting the foraging behavior of its predator, Orius sauteri (Heteroptera: Anthocoridae).

Heavy metal contaminants may influence tri-trophic interactions among plants, herbivores, and their natural enemies and affect the results of pest management practices. We examined how the widely distributed heavy metal cadmium (Cd) could modify interactions between kidney bean, Phaseolus vulgaris L., western flower thrips, Frankliniella occidentalis Pergande, and a predator, Orius sauteri (Poppius) by examining Cd effects on the feeding damage on leaves, the growth and reproduction of the thrips, and the feeding and plant location selection behaviors of predators. Leaf feeding damage was significantly reduced only at the highest Cd treatment (625mg L-1). Survival, reproduction, and population growth of thrips decreased with the increase of Cd treatment concentration (0, 25, and 625mg L-1). The reproduction rate of thrips from the highest Cd treatment group was reduced to less than 30% of the controls. Predator choice of plants was not impacted at the lowest level of Cd treatment (25mg L-1) when prey were excluded, but the predators were deterred from plants treated at the high level of Cd (625mg L-1). However, the predators responded strongly to the presence of prey, and the Cd-based deterrence was effectively eliminated when prey were added. Thus, the presence of Cd can cause a bottom-up effect on the fitness of pests without disrupting the foraging behavior of its predator. Our results provide baseline data on the toxic impacts on the pest and predator, and indicate that the ecology of the system and the biological control efficiency would be potentially impacted by high levels of Cd (625mg L-1).

Assessment of Beauveria bassiana for the biological control of corn borer, Ostrinia furnacalis, in sweet maize by irrigation application

Kernels of sweet maize are directly consumed by humans. This high value crop is grown in arid and semi-arid regions of western Jilin Province, China where trickle irrigation is widely used and larvae of the corn borer, Ostrinia furnacalis Guenée (Lepidoptera: Crambidae), can cause significant kernel damage. Low humidity in arid regions is less conducive to the efficacy of the biological control agent, Beauveria bassiana (Balsamo) Vuillemin (Hypocreales: Cordycipitaceae). Simulated semi-arid conditions in greenhouse experiments were conducted comparing B. bassiana application on a granule carrier or in aqueous suspension to sweet maize. Applications of B. bassiana adhered to granules and in suspension reduced O. furnacalis leaf feeding damage, number of boreholes and tunneling length. Treatments with a granular carrier showed the most significant reductions in maize damage when applied once at whorl stage and in combination with a second application at the ear. The greatest reductions in boring and tunneling attributed to these treatments occurred at internodes around the ear. Although reduced damage was greatest following granular compared to aqueous applications, the latter also provided significant reductions in feeding damage compared to controls. This study demonstrates the utility of B. bassiana as a biological control agent for the reduction in damage caused by second-generation corn borer to sweet maize and existing irrigation equipment could be adapted for efficacious aqueous treatments by growers.

Biological control of fall webworm larva (Hyphantria cunea Drury) and growth promotion of poplar seedlings (Populus × canadensis Moench) with Bacillus licheniformis PR2

The production of Populus × canadensis Moench seedling, as an important restoration resource has been constrained by the invasion of Hyphantria cunea Drury, a polyphagous pest that causes leaf feeding damage on nursery seedling production. This study investigated the larvicidal potential of cuticle degrading chitinase and protease enzymes secreted by the Bacillus licheniformis PR2 against H. cunea larvae. In addition, we investigated the growth promotion of P. canadensis seedling through the auxin belonging to plant growth hormones. Treatment of H. cunea larvae with either the bacterial crude enzymes or bacterial culture broth from B. licheniformis PR2 under laboratory conditions resulted in larvae mortality due to the severe degradation of the cuticle characterized by the loss of setae, swelling of sockets, and rupturing of the epicuticle and procuticle, and also caused a repellent effect from leaves, when the larvae suffered minor lacerations only in the epicuticle except the procuticle. Application of B. licheniformis PR2 culture broth on P. canadensis seedlings in the greenhouse experiment caused a mortality rate of 34.4 % and a repellency rate of 75.0 % against H. cunea larvae and reduced the leaf damage rate by 3.7-folds to only 25.9 % compared to 96.3 % in the control group. Accordingly, treatment with B. licheniformis PR2 improved seedling growth by reducing foliar damage caused by H. cunea larvae. In addition, B. licheniformis PR2 produced indole-3-acetic acid (IAA), which improves root hair growth and lateral root development to increase the surface area for nutrient uptake. Thus, inoculation of B. licheniformis PR2 improved the leaf chlorophyll content (photosynthetic rate) of the P. canadensis seedlings by 1.9-folds to 43.26 units compared to 23.26 units in the control group. Consequently, the application of B. licheniformis PR2 also improved the shoot, root, and leaf dry weights by 3.4-, 1.5- and 1.6-folds compared to the control group, respectively. Therefore, this study demonstrates the dual larvicidal and plant growth-promoting potential of B. licheniformis PR2, as an environmentally friendly alternative to chemical pesticides in the control of H. cunea larvae and production of healthy P. canadensis seedlings in the forest nursery.

Investigation of Metabolic Resistance to Soybean Aphid (Aphis glycines Matsumura) Feeding in Soybean Cultivars.

Simple SummaryThis project examined the interaction between soybean aphids and Ontario-grown soybean cultivars to determine which leaf metabolites were most associated with aphid resistance. Tolerance and resistance were determined by measuring the growth and reproduction of aphids and leaf feeding damage over 10-day and 4-week infestation periods. Chromatographic techniques were used for the analysis of legume-specific plant natural products and isoflavonoids, and high-resolution mass spectrometry was used for the identification of free amino acids in aphid-resistant, tolerant, and susceptible soybean cultivars. There was a low correlation between isoflavonoid leaf concentrations and aphid resistance in the soybean varieties studied; however, the aphid-resistant cultivars were determined to have lower free amino acid concentrations, indicating that lower nutrient quality could be responsible for the resistance observed. Identifying these cultivars is important for managing aphid populations and provides an additional tool for soybean integrated pest management.Soybean aphid (Aphis glycines) is a major soybean (Glycine max) herbivore pest in many soybean growing regions. High numbers of aphids on soybean can cause severe reductions in yield. The management of soybean aphids includes monitoring, insecticide applications when required, and the use of resistant cultivars. Soybean aphid-resistant soybean varieties are associated with genes that confer one or more categories of resistance to soybean aphids, including antibiosis (affects survival, growth, and fecundity), antixenosis (affects behaviour such as feeding), and tolerance (plant can withstand greater damage without economic loss). The genetic resistance of soybean to several herbivores has been associated with isoflavonoid phytoalexins; however, this correlation has not been observed in soybean varieties commonly grown in southern Ontario, Canada. Isoflavonoids in the leaves of 18 cultivars in the early growth stage were analyzed by HPLC and the concentration by fresh weight was used to rate the potential resistance to aphids. Greenhouse and growth cabinet trials determined that the cultivars with greater resistance to aphids were Harosoy 63 and OAC Avatar. The most susceptible cultivar was Maple Arrow, whereas Pagoda and Conrad were more tolerant to aphid feeding damage. Overall, there was a low correlation between the number of aphids per leaf, feeding damage, and leaf isoflavonoid levels. Metabolite profiling by high-resolution LC-MS determined that the most resistant cultivar had on average lower levels of certain free amino acids (Met, Tyr, and His) relative to the most susceptible cultivar. This suggests that within the tested cultivars, nutritional quality stimulates aphid feeding more than isoflavonoids negatively affect aphid feeding or growth. These findings provide a better understanding of soybean host plant resistance and suggest ways to improve soybean resistance to aphid feeding through the breeding or metabolic engineering of leaf metabolites.

QTL Mapping of Traits Associated with Dual Resistance to the African Stem Borer (Busseola fusca) and Spotted Stem Borer (Chilo partellus) in Sorghum (Sorghum bicolor).

Sorghum (Sorghum bicolor (L.) Moench) is an important food crop in semi-arid tropics. The crop grain yield ranges from 0.5 t/ha to 0.8 t/ha compared to potential yields of 10 t/ha. The African stem borer Busseola fusca Fuller (Noctuidae) and the spotted stem borer Chilo partellus Swinhoe (Crambidae), are among the most economically important insect pests of sorghum. The two borers can cause 15% - 80% grain yield loss in sorghum. Mapping of QTLs associated with resistance traits to the two stem borers is important towards marker-assisted breeding. The objective of this study was to map QTLs associated with resistance traits to B. fusca and C. partellus in sorghum. 243 F9:10 sorghum RILs derived from ICSV 745 (S) and PB 15520-1 (R) were selected for the study with 4,955 SNP markers. The RILs were evaluated in three sites. Data was collected on leaf feeding, deadheart, exit holes, stem tunnels, leaf toughness, seedling vigour, bloom waxiness, and leaf glossiness. ANOVA for all the traits was done using Genstat statistical software. Insect damage traits and morphological traits were correlated using Pearson's correlation coefficients. Genetic mapping was done using JoinMap 4 software, while QTL analysis was done using PLABQTL software. A likelihood odds ratio (LOD) score of 3.0 was used to declare linkage. Joint analyses across borer species and sites revealed 4 QTLs controlling deadheart formation; 6 controlling leaf feeding damage; 5 controlling exit holes and stem tunneling damages; 2 controlling bloom waxiness, leaf glossiness, and seedling vigour; 4 conditioning trichome density; and 6 conditioning leaf toughness. Joint analyses for B. fusca and C. partellus further revealed that marker CS132-2 colocalised for leaf toughness and stem tunneling traits on QTLs 1 and 2, respectively; thus, the two traits can be improved using the same linked marker. This study recommended further studies to identify gene(s) underlying the mapped QTLs.

Evaluation of 21 Thailand Maize Germplasms for Resistance to Leaf Feeding Spodoptera frugiperda (Lepidoptera: Noctuidae)

Native to the Americas, the fall armyworm, Spodoptera frugiperda (J.E. Smith) (Lepidoptera:Noctuidae), is a recent invasive pest of Africa and Asia. This insect causes economic damage to maize (Zea mays L.) primarily through leaf and ear tissue feeding. The pest is resistant to several classes of insecticide and several Bt-maize toxins. Native resistance in maize to fall armyworm could be used with existing control tactics to enhance control of this insect. The objective for this study was to evaluate maize germplasm, developed from Thailand and maintained by the U.S. National Plant Germplasm System, for resistance to leaf feeding fall armyworm. Plants were grown in the field and artificially infested at the seven-leaf stage with fall armyworms. Visual rating scores for leaf feeding damage were recorded at 7 and 14 days post infestation. Scores for maize germplasm Ames 26254 were not different than the resistant check, GT-FAWCC(C5), and germplasm PI 506347 and PI 690324 were not significantly different from Ames 26254. In total, five Thailand maize germplasms received 14-day damage scores of ≤ 6.0 across both years of testing and were considered moderately resistant to fall armyworm leaf feeding. These maize germplasms are tropical and require breeding to adapt progeny for research in temperate areas.

Mapping Quantitative Trait Loci for Resistance to Fall Armyworm (Lepidoptera: Noctuidae) Leaf-Feeding Damage in Maize Inbred Mp705.

The fall armyworm, Spodoptera frugiperda (J. E. Smith), is an agronomically important pest that severely limits maize (Zea mays (Linnaeus) [Poales: Poaceae]) production. This migrant insect devastates maize plants in many countries threatening the livelihood of millions. Quantitative trait loci (QTL) were mapped to identify chromosomal regions that control resistance to fall armyworm leaf-feeding and to identify molecular markers linked to the target loci for use in marker-assisted selection (MAS). A bi-parental mapping population, comprising 243 F2:3 families from the cross Mp705 (resistant) × Mp719 (susceptible), was evaluated for fall armyworm leaf-feeding damage under artificial infestation over 3 yr. A linkage map comprised of 1,276 single-nucleotide polymorphism and simple sequence repeat molecular markers was constructed. Quantitative trait loci analyses identified two major QTL in bins 4.06 and 9.03 that when combined, explained 35.7% of the phenotypic variance over all environments. Mp705 was responsible for the leaf-feeding damage reducing alleles for both large effect QTL and most of the small effect QTL identified in this study. The QTL identified in bin 9.03 co-locates with a previously identified QTL that controls resistance to leaf-feeding damage in maize by fall armyworm and other lepidopteran insects. The QTL in bin 4.06 is a new source of resistance identified in this study. Beneficial alleles derived from Mp705 for the application of an integrated QTL-MAS approach could accelerate breeding efforts to minimize fall armyworm leaf-feeding in maize.

Larval Migration Behaviour of Busseola fusca (Lepidoptera: Noctuidae) on Bt and Non-Bt Maize under Semi-Field and Field Conditions.

Busseola fusca (Fuller) (Lepidoptera: Noctuidae) is a destructive pest of maize throughout the African continent. Bt maize is an effective control measure for this pest, however, selection pressure for resistance evolution is high. This necessitates the implementation of insect resistance management (IRM) strategies such as the high-dose/refuge strategy. This IRM strategy relies on the validity of several assumptions about the behaviour of pests during insect-hostplant interactions. In this study, the migration behaviour of B. fusca larvae was evaluated in a semi-field (greenhouse) and field setting. The effect of factors such as different Cry proteins, plant growth stage at infestation, and plant density on the rate and distance of larval migration were investigated over four and five week periods. Migration of the larvae were recorded by using both a leaf feeding damage rating scale and destructive sampling at the end of the trials. Results indicated that B. fusca larval migration success was significantly affected by plant growth stage and plant density—while limited larval migration was recorded in plots inoculated with larvae at a late growth stage (V10), higher plant density facilitated increased interplant migration. The results also suggest that B. fusca larvae do not migrate extensively (rarely further than two plants from the natal plant) and that larval mortality is high. Implications for IRM strategies are discussed.

Diallel analysis for aflatoxin accumulation and fall armyworm leaf-feeding damage in maize

ABSTRACTTwo major impediments to profitable maize, Zea mays L., production in the southern United States are from feeding by fall armyworm, Spodoptera frugiperda (J.E. Smith), and losses from the production and accumulation of aflatoxin in maize grain. A diallel cross was produced by making all possible crosses among five germplasm lines developed as sources of resistance to fall armyworm leaf feeding and five lines developed as sources of resistance to aflatoxin accumulation. For resistance to both leaf feeding and aflatoxin accumulation, general combining ability (GCA) was a significant source of variation. Specific combining ability (SCA) was significant for fall armyworm feeding only. Estimates of GCA effects for reduced aflatoxin accumulation were significant for Mp715 and Mp719, two lines selected for resistance to aflatoxin accumulation. The GCA effects for reduced fall armyworm damage were significant for all five lines selected for fall armyworm resistance: Mp707, Mp708, Mp713, Mp714, and Mp716.

English

Stem borers, Busseola fusca (Fuller) Noctuidae, Lepidoptera and Chilo partellus (Swinhoe) Pyralidae, Lepidoptera, are serious insect pests of maize. However, genotypes showing exclusive resistance to each of these borers and with resistance to both species have not been identified in Kenya. The objective of this study was to evaluate tropical maize inbred lines for resistance to the two species. 112 maize inbred lines were artificially infested with the stem borers at three sites in Kenya. Each row of each line received three different treatments in different parts, namely infestation with B. fusca larvae, infestation with C. partellus larvae, and protection with beta 25 g/L cyfluthrin pesticide. Data was collected on leaf feeding damage rating, cumulative stem tunnel length, number of exit holes, number of dead-hearts, stalk strength and selected agronomic traits. There were significant differences among the test genotypes, (p<0.01) for resistance to B. fusca and C. partellus, for all the traits measured. The results also showed that most of the test genotypes were susceptible to B. fusca and less so to C. partellus. Twenty one (21) lines showed resistance to both B. fusca and C. partellus in at least two sites, and only four lines showed resistance to both species across the locations. Among all the test genotypes, 26 lines showed resistance to C. partellus only, while five entries had resistance to B. fusca only. Furthermore, 84 and 28 entries showed susceptibility to B. fusca and C. partellus, respectively. The others were categorized as either moderately resistant or moderately susceptible to either species. The identified inbred lines variously resistant to B. fusca and C. partellus may be used as parents in hybrid breeding programmes that emphasize stem borer resistance or as sources of resistance in breeding programs.   Key words: Busseola fusca, Chilo partellus, combined resistance, tropical maize inbred lines.

Response to S1 recurrent selection for resistance to two stem borers, Busseola fusca and Chilo partellus, in two tropical maize populations

AbstractStem borers, Busseola fusca and Chilo partellus, are among the key devastating lepidopteran insect pests of maize causing grain yield losses. Recurrent selection studies for stem borer resistance in maize are limited. However, maize populations carrying resistance genes to these stem borers have not been exploited fully in breeding programmes. The objective of the study was to separately improve resistance to B.fusca and C.partellus stem borers for two maize populations CML395/MBR C5 Bc and CML444/MBR/MDR C3Bc and therefore grain yield after two cycles of S1 progeny recurrent selection. Cycle 0 and the advanced generations (cycle 1-susceptible, cycle 1-resistant and cycle 2-resistant) were evaluated at three locations in Kenya using a 35 × 12 α-lattice design with 2 replications. The net reductions in cumulative tunneling, number of exit holes and leaf feeding damage scores ranged from 0 to 69 % for both populations after two cycles of selection. In the two populations, each cycle of selection for borer resistance improved grain yield by 0.5–0.8 t ha−1. Actual net gains in grain yield with reference to cycle 0 were 43 % for population CML395/MBRC5 Bc under B. fusca infestation and 70 % under C. partellus infestation. For population CML444/MBR/MDR C3Bc, the actual net gains in grain yield were 25 % under B. fusca infestation and 36 % under C. partellus infestation. The reductions in the injurious effects attributable to leaf feeding damage, cumulative stem tunneling and number of exit holes contributed towards the 43 and 70 % net genetic gain in grain yield under B. fusca and C. partellus infestation respectively, for both populations. Broad sense heritability (H2) for grain yield ranged from 2 to 98 % in both maize populations. The study showed that two cycles of S1 progeny recurrent selection was effective in accumulating favourable alleles for B. fusca and C. partellus stem borer resistance.

Insect leaf-chewing damage tracks herbivore richness in modern and ancient forests.

The fossil record demonstrates that past climate changes and extinctions significantly affected the diversity of insect leaf-feeding damage, implying that the richness of damage types reflects that of the unsampled damage makers, and that the two are correlated through time. However, this relationship has not been quantified for living leaf-chewing insects, whose richness and mouthpart convergence have obscured their value for understanding past and present herbivore diversity. We hypothesized that the correlation of leaf-chewing damage types (DTs) and damage maker richness is directly observable in living forests. Using canopy access cranes at two lowland tropical rainforest sites in Panamá to survey 24 host-plant species, we found significant correlations between the numbers of leaf chewing insect species collected and the numbers of DTs observed to be made by the same species in feeding experiments, strongly supporting our hypothesis. Damage type richness was largely driven by insect species that make multiple DTs. Also, the rank-order abundances of DTs recorded at the Panamá sites and across a set of latest Cretaceous to middle Eocene fossil floras were highly correlated, indicating remarkable consistency of feeding-mode distributions through time. Most fossil and modern host-plant pairs displayed high similarity indices for their leaf-chewing DTs, but informative differences and trends in fossil damage composition became apparent when endophytic damage was included. Our results greatly expand the potential of insect-mediated leaf damage for interpreting insect herbivore richness and compositional heterogeneity from fossil floras and, equally promisingly, in living forests.

Seasonal Activity, Within-Tree Distribution, and Ovipositional and Feeding Preference of the Elm Leafminer, Fenusa ulmi (Hymenoptera: Tenthredinidae)

Seventy-six different elm taxa were visually rated for elm leafminer (Fenusa ulmi Sundevall) defoliation. European elm taxa were more found to be more susceptible to feeding damage by the elm leafminer compared to Asian and North American elm taxa. European elms U. glabra, U. elliptica, U. sukaczezii, and elms with U. glabra-wallichiana parentage were highly susceptible to elm leafminer leaf feeding damage. Of the 37 Asian elm taxa evaluated, only U. laciniata was highly susceptible to feeding damage. The North American species U. rubra was the only North American elm susceptible to elm leafminer feeding. Adult emergence, initial leafmining, and cessation of leafmining were highly correlated with indicator plant full bloom phenology providing an accurate degree-day (DD) model for practitioners in predicting and monitoring for elm leafminer life stage development and related plant damage. Elm leafing out phenology of susceptible European elms was highly correlated with elm leafminer adult emergence and oviposition. Less susceptible European elm taxa, such as U. procera, and U. carpinifolia and cultivars, consistently leaf out later after peak adult leafminer emergence. Interestingly, the majority of Asian elm taxa such as U. davidiana, U. japonica, U. lamellosa, and U. pumila leaf out at the same time as susceptible elm taxa, but experience no or negligible feeding damage. Two Asian species, U. wilsoniana and U. parvifolia, leaf out later after peak adult emergence and oviposition has passed. No consistent pattern was observed for within tree ovipositional wounds and subsequent leafminer feeding damage for tree height or cardinal direction for both small and large elm tree species. Results from this study indicate there is a large number of Asian and North American elm taxa that provide a rich genetic pool for future elm breeding programs.

Efficacy Evaluation of Two Transgenic Maize Events Expressing Fused Proteins to Cry1Ab-Susceptible and -Resistant <I>Ostrinia furnacalis</I> (Lepidoptera: Crambidae)

The Asian corn borer, Ostrinia furnacalis (GuenCe), is a major pest of maize in China. Transgenic Bt maize could provide an effective way to control this pest. However, the potential of resistance evolution has been documented in the laboratory-a CrylAb-resistant strain of Asian corn borer (Asian corn borer-AbR) could survive well on two Bt maize events, that is, MON810 and Bt11. Pyramided transgenic crops with multiple dissimilar Bt insecticidal proteins offer a superior route for pests control compared with that with one Bt single gene. In this study, two novel transgenic Bt maize events (N30 and V3), which contained a fused gene Cry1Ab/Cry2Aj and CrylAb /Vip3DA, respectively, were evaluated for their efficacy on protection against CrylAb-susceptible Asian corn borer (Asian corn borer-BtS) as well as their potential for dealing with the Asian corn borer-AbR. In laboratory bioassay, no neonate larvae of Asian corn borer-BtS fed on the whorl leaves, tassels, husks, silks, and kernels of N30 and V3 could survive at 96 h after infestation. In contrast, only 2.0-8.7% larvae died as they fed on non-Bt maize tissues. As Asian corn borer-AbR neonate larvae fed on N30 and V3 silks and kernels, 95.0% even more larvae were killed at 96 h after infestation, and all died at 168 h after infestation, while 10.0-11.67% larvae survived on non-Bt control. In the field test under artificial infestation at middle whorl leaf and silking stages of maize, there were no significant leaf, silk, and stalk damage on Bt maize plants by comparison with severe leaf feeding, stalk born, and ear damage in control, in addition, the expression profiles of a fused protein of CrylAb/Cry2Aj or CrylAb/Vip3DA in different tissues of N30 and V3 were also confirmed. In conclusion, it is clear that both Bt maize events (N30 and V3) show great potential for protecting maize from attack by Asian corn borer that has resistance to Cry1Ab protein.