Leaf Damage Scores Research Articles

Control Efficacy of the Bt Maize Event DBN3601T Expressing Cry1Ab and Vip3Aa Proteins against Beet Armyworm, Spodoptera exigua (Hübner), in China.

The beet armyworm, Spodoptera exigua (Hübner), is a major pest of maize, cotton, soybean, and many other crops globally. Despite the widespread deployment of Bt transgenic maize for pest control worldwide, the efficacy of Bt lepidopteran-resistant transgenic maize in managing S. exigua remains rarely studied. In this study, we quantified the expression level of pyramided Cry1Ab and Vip3Aa toxins in Bt maize (event DBN3601T) and evaluated their control efficiency against S. exigua under both laboratory and field conditions. The enzyme-linked immunosorbent assay (ELISA) results showed that the expression levels of Cry1Ab and Vip3Aa proteins in DBN3601T maize tissues followed a decreasing order as follows: V5-leaf > V8-leaf > VT-tassel > R2-kernel > R1-silk. Diet-overlay assay results showed that the LC50 values of Cry1Ab and Vip3Aa proteins against S. exigua larvae were 11.66 ng/cm2 and 27.74 ng/cm2, respectively, with corresponding GIC50 values at 1.59 ng/cm2 and 7.93 ng/cm2. Bioassay using various tissues of the DBN3601T maize indicated that after 7 days of infestation, mortality rates of neonates and third-instar larvae ranged from 86% to 100% and 58% to 100%, respectively. Mortality was highest on V5 and V8 leaves, followed by R2-kernel, VT-tassel, and R1-silk. Field trials demonstrated that DBN3601T maize exhibited significantly lower larval density, damage rate, and leaf damage score compared to non-Bt maize. Field cage trial showed that the control efficacy of DBN3601T maize at the vegetative stage could reach 98%. These findings provide a theoretical basis for utilizing Bt transgenic maize to enhance the sustainable management of S. exigua in Asia.

Minimizing IP issues associated with gene constructs encoding the Bt toxin - a case study

BackgroundAs part of a publicly funded initiative to develop genetically engineered Brassicas (cabbage, cauliflower, and canola) expressing Bacillus thuringiensis Crystal (Cry)-encoded insecticidal (Bt) toxin for Indian and Australian farmers, we designed several constructs that drive high-level expression of modified Cry1B and Cry1C genes (referred to as Cry1BM and Cry1CM; with M indicating modified). The two main motivations for modifying the DNA sequences of these genes were to minimise any licensing cost associated with the commercial cultivation of transgenic crop plants expressing CryM genes, and to remove or alter sequences that might adversely affect their activity in plants.ResultsTo assess the insecticidal efficacy of the Cry1BM/Cry1CM genes, constructs were introduced into the model Brassica Arabidopsis thaliana in which Cry1BM/Cry1CM expression was directed from either single (S4/S7) or double (S4S4/S7S7) subterranean clover stunt virus (SCSV) promoters. The resulting transgenic plants displayed a high-level of Cry1BM/Cry1CM expression. Protein accumulation for Cry1CM ranged from 5.18 to 176.88 µg Cry1CM/g dry weight of leaves. Contrary to previous work on stunt promoters, we found no correlation between the use of either single or double stunt promoters and the expression levels of Cry1BM/Cry1CM genes, with a similar range of Cry1CM transcript abundance and protein content observed from both constructs. First instar Diamondback moth (Plutella xylostella) larvae fed on transgenic Arabidopsis leaves expressing the Cry1BM/Cry1CM genes showed 100% mortality, with a mean leaf damage score on a scale of zero to five of 0.125 for transgenic leaves and 4.2 for wild-type leaves.ConclusionsOur work indicates that the modified Cry1 genes are suitable for the development of insect resistant GM crops. Except for the PAT gene in the USA, our assessment of the intellectual property landscape of components presents within the constructs described here suggest that they can be used without the need for further licensing. This has the capacity to significantly reduce the cost of developing and using these Cry1M genes in GM crop plants in the future.

Screening of Popular Maize Hybrids against fall Armyworm, Spodoptera frugiperda

Fall armyworm (Spodoptera frugiperda) was the member of noctuidae family which has got economic importance as polyphagous and extreme pest of many important crops, including maize in India and elsewhere. In this context, screening experiment was conducted by using 15 different maize cultivars viz., CP 818, NK 6240, GPMH 1110, GH 0727, 900 M Gold, NK 6801, SM- 2, S- 4717, GK 3207, KMH 225, KMH 8333, Sunny NMH 777, 30 B07, PMH 2244 and Kaveri minchu in MARS, Dharwad. The results revealed that PMH 2244 was recorded the least mean larval load (0.67 larvae per plant) compared to rest of the cultivars. Among fifteen different cultivars screened, Kaveri minchu recorded the highest mean leaf damage score (4.62) whereas, the hybrid PMH 224 recorded the least mean leaf damage score (0.73). The cultivars, PMH 2244, NK 6801 and 900 M Gold were recorded with the least egg mass (0.33 per plant) whereas, the hybrids SM- 2 and Kaveri minchu were recorded with the highest egg mass of 0.63 and 0.61 per plant, respectively. Biophysical parameters of plant such as plant height, leaf area, stem girth and trichome density have been implicated in maize resistance to the fall armyworm. All the plant characters except leaf area which are mentioned above showed significant negative correlation with fall armyworm infestation whereas, leaf area was found significantly positive correlation.

Effect of Date of Sowing on Incidence of Fall Armyworm, Spodoptera frugiperda in Maize

Fall armyworm (Spodoptera frugiperda) is a member of the Noctuidae family which has economic importance as a polyphagous and extreme pest of many important crops, including maize in India and elsewhere. In this context, an experiment regarding the influence of different dates of sowing on the incidence of fall armyworm was conducted in MARS, Dharwad. The results revealed that the least mean larval load of fall armyworm was recorded in crop sown during the July 2nd fortnight (0.75 larvae per plant) and the highest was recorded in crop sown during the August 2nd fortnight (1.53 larvae per plant). Whereas, the lowest mean leaf damage score of 2.95 was observed in crop sown during 2nd fortnight of July and the highest was recorded in the crop sown during 2nd fortnight of August (4.82).

Exploring host plant resistance in chilli (Capsicum spp) against Southeast Asian thrips (Thripsparvispinus Karny)

Southeast Asian thrips (Thrips parvispinus Karny), poses a significant threat to chilli crop production causing severe economic losses. They feed heavily on leaves, flowers and young fruits causing severe damage to the crop. Exploring host plant resistance is the best ecofriendly management strategy to combat this pest. Large-scale field screening of 481 germplasm accessions, followed by further screening of selected accessions under polyhouse conditions led to identification of fourteen accessions that showed resistance against Southeast Asian thrips. Among the screened accessions, IIHR-B-HP-79 showed the highest level of Southeast Asian thrips resistance with significantly low leaf and fruit damage scores of 0.28 and 0.13, respectively. Further, screening of selected fourteen field resistant accessions was performed through whole plant bio-assay where in four accessions i.e., IIHR-B-HP-79 (C. frutescens), IIHR 4550, IIHR 4501 & IIHR 4410 (C. chinense) showed good level of resistance. Multi-choice leaf disc assay, demonstrated that IIHR-B-HP-79 exhibited a high level of resistance with the lowest percent of scraping damage during both the vegetative (10.98) and flowering stages (15.31). The identified resistant accession IIHR-B-HP-79 (C. frutescens), has the potential to be a valuable genetic resource as donor in breeding for Southeast Asian thrips resistance.

A Review on Fall Army Worm <I>Spodoptera frugiperda</I> (J E Smith) Invasion in Ghana: Current Status

The fall army worm Spodoptera frugiperda (J E Smith) (Lepidoptera: Noctuidae) which invaded Africa in 2016 continue to pose food security threat due to its destructive effect on maize. This article assesses current research outputs, management strategies and future projections. Levels of infestation vary across districts, ranging from 12 to 88% with corresponding leaf damage score of 2 to 7 and larval density of 0.16 – 1.44/ plant on farmers’ maize field. Infestation and damage levels were higher in 2021 than in 2020 possibly due to gradual withdrawal of free insecticide by government. Several indigenous practices were employed by farmers during early invasion but synthetic insecticides usage assumed high acceptance. Some commercial microbials and botanicals showed significant efficacy. Results from indigenous entomopathogenic nematodes and fungi are satisfactory and are under field validation. A number of predators and parasitoids identified have shown varied level of suppression. Mass release of parasitoids, complemented with entomopathogens will put the infestation below economic threshold levels in most maize fields.

Silicon and growth regulator induced defence against maize fall armyworm, Spodoptera frugiperda (J.E. Smith)

A microplot field experiment was conducted to study the effect of silicon sources and growth regulator against maize fall armyworm, Spodoptera frugiperda at Thoppur village of Virudhunagar district during Rabi, 2021-22. Basal application of different doses of calcium silicate and foliar application of silicic acid and potassium silicate were carried out. The results revealed that 150 kg of calcium silicate/ha + 0.2% silicic acid at 15 d after sowing (DAS) + 50 ppm GA at 30 DAS was found to be effective in reducing fall armyworm (FAW) population (1.23 larvae/plant) followed by treatment with 75 kg of calcium silicate/ha + 0.2% silicic acid at 15 DAS + 50 ppm GA at 30 DAS (1.27 larvae/plant). Regarding leaf and cob damage, the treatment with 150 kg of calcium silicate/ha + 0.2% silicic acid at 15 DAS + 50 ppm GA at 30 DAS was found to be most effective and significantly superior over all other treatments by recording lowest mean leaf damage score of 1.63/plant and mean cob damage score of 1.13/plant followed by the treatment with 75 kg of calcium silicate/ha + 0.2% silicic acid at 15 DAS + 50 ppm GA at 30 DAS with 1.66 leaf score/plant and 1.35 cob score/plant.

Field evaluation of whorl application of sand mixed entomopathogenic nematodes for the management of invasive fall armyworm, Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae) in sweet corn

BackgroundFall armyworm (FAW) Spodoptera frugiperda, also called ‘whorlworm’ is a global pest threatening maize production. Larvae stay in the whorl of maize/sweet corn and efficient delivery of insecticides or bio-agents is the major issue for its successful management. Biological control of FAW through entomopathogenic nematodes (EPNs) offers promise, as EPNs are soil colonizers and commercially available in various formulations, soil or sand can ideally be exploited as natural substrate targeting FAW under field conditions.ResultsIn the present study, field evaluations were carried out using the aqueous suspension of Steinernema carpocapsae and Heterorhabditis indica in two cropping seasons. The Infective Juveniles (IJs) stages of EPNs mixed with sand at different doses were applied to the whorl region of sweet corn twice during cropping season, i.e. on 25th and 40th day after sowing. For comparison, a recommended insecticide, Chlorantraniliprole 18.5 SC mixed in sand was taken as check. S. carpocapsae @ 500 IJs, significantly reduced the larval population and leaf damage score. It was statistically on par with Chlorantraniliprole 18.5 SC whorl application. Principal component analysis revealed that there was a relationship between larval population and leaf damage score. Survival of S. carpocapsae was significantly greater than the H. indica in the three media tested. Soil was found to be the best media followed by sand and frass.ConclusionsField study of whorl application of sand mixed EPNs supported by laboratory studies on the persistence connoted that EPNs could be used as an eco-friendly option through whorl application for the management of FAW.

Screening of Tropical Maize Inbred Lines by Artificial Infestation for Resistance against Invasive Fall Armyworm in India

Aim: This study was aimed to find resistance sources against FAW.
 Study Design: Randomised Block Design.
 Place and Duration of Study: The Present study was conducted at Maize Research Centre, Hyderabad with promising germplasm during Kharif-2021, Rabi-2021-22 and Kharif-2022. Methodology: Field-collected FAW egg masses were reared using maize leaf- and stalk-based diet at 27 ± 1 °C, 60 ± 5% relative humidity and 12 h day length. The resulting neonates were used to infest the seedlings of 34 diverse tropical maize inbred genotypes.
 Results: A total of 15 genotypes were found to have recorded a leaf damage score of less than 5 with the least score recorded in BML 2 (3.24), followed by BML 11 (3.34), BML 7(3.37), BML 5 (3.37), BML 8 (3.49), CM 201 (3.60), BML 32-2 (3.91), CM 132 (3.97), BML 10 (4.01), BML 6 (4.02), BML 13 (4.34), CM202 (4.34), CM 131 (4.68), BML 90 (4.82), BML 45 (4.95) and displayed moderate resistance.
 Conclusion: Out of 34 inbred lines studied 15 were found to be moderately resistant to fall armyworm based on LIR and cob damage score under artificial infestation.

Occurrence, Distribution, Damage Potential, and Farmers’ Perception on Fall Armyworm, Spodoptera frugiperda (J.E. Smith): Evidence from the Eastern Himalayan Region

The fall armyworm (FAW), Spodoptera frugiperda (J.E. Smith), is a polyphagous non-native pest identified as a serious threat to crop production and food security globally, including in India. Its unintentional introduction and quick coverage in large areas is a serious concern to millions of farmers in the eastern Himalayan region. However, detailed understanding of farmers’ perceptions and the biological attributes associated with the meteorological factors for FAW is limited. The present investigation, which aimed to create baseline data on this pest, concurs with the idea that the FAW is widely dispersed throughout the maize ecosystems of Tripura, with an average infestation rate of 21.33 percent. The severity ranged from 0 to 1.40, with an average leaf damage score of 1 on a 0–4 categorical scale. The findings indicate that pheromone trap catch was significantly correlated with the evaporation rate as other meteorological factors influenced variably. The biological attributes imply that the life cycle was completed in 32.82 ± 0.08 days, with a high fecundity potential (1068.57 ± 4.35 numbers) in controlled conditions (25 ± 1 °C, 70 ± 5% RH). Indigenous natural enemies, such as entomopathogens, spiders, and wasps, were found to be the first defence against this invasive pest. A minority of the population (17.51%) was aware of the incidence of FAW. Furthermore, respondents’ socio-demographic variables were associated significantly with FAW status. This is the first scientific report from the eastern Himalayan region about farmers’ knowledge and awareness of the invasiveness of FAW. This finding enumerates a detailed understanding of FAW from diverse perspectives. Further, the concerted data provide an important baseline that could help the development of holistic management strategies for FAW.

Effects of seed treatments and storage duration on Myzus persicae (Hemiptera: Aphididae) and amaranth fresh leaf yield.

The green peach aphid, Myzus persicae (Sulzer) (Hemiptera: Aphididae), is a key insect pest of amaranth in East Africa. Pest management has been restricted to indiscriminate application of insecticides to foliage. Applying systemic insecticides to seeds has been shown to manage aphid infestations in other crop systems. We evaluated two commercially available seed treatments in East Africa, Apron Star (thiamethoxam 20 g/kg + metalaxyl-M 20 g/kg + difenoconazole 2 g/kg) and Menceron (imidacloprid 233 g/L + pencycuron 50 g/L + thiram 107 g/L) for their efficacy against M. persicae and impact on fresh leaf yield with two Amaranthus species, Amaranthus blitum (2 selections), Amaranthus hybridus (4 selections) and untreated control. Two storage periods (24 h and 3 months) with seed treatments were used. Each amaranth selection was treated individually with Apron and Monceren or untreated, and seeds were planted either 24 h or 3 months after treatment. Significant reduction in live aphids was observed with A. blitum and A. hybridus selections grown with seed treatment, at 6, 8 and 10 d after infestation (DAI) when compared with seeds grown without seed treatment. Untreated seeds of A. hybridus (selection 5) had significantly higher number of live aphids up to 243, greater percentage of damaged leaves and leaf damage score up to 84% and 64% respectively when compared with treated seeds of specific amaranth at 10 DAI. No significant difference was noted between seed treatment and storage time. Amaranth seeds treated with Monceren offered more protection against infestations of Myzus persicae than amaranth seeds treated with Apron under high tunnel experiments.

Genetic Analysis of Agronomic and Fall Armyworm-Resistance Traits in Maize Hybrids with Varying Levels of Resistance to Stem Borers

Stem borer (SB) and more recently, fall armyworm (FAW) are serious economic pests in maize production in sub-Saharan Africa. It is hypothesized that SB-resistant germplasm may confer resistance against FAW. However, the performance of SB-resistant lines in hybrid combinations and the inheritance of FAW-resistant traits under variable FAW infestations have not been reported. This study was conducted to (i) obtain information on the inheritance of agronomic and FAW-resistant traits under variable FAW infestations; (ii) identify hybrids combining high grain yield (GYLD) and stability under FAW infestations; and (iii) determine the effects of FAW damage on GYLD. Three SB-resistant lines (1393, CKSBL10060 and CML 331) as testers and six open-pollinated varieties (OPVs) as lines were crossed in a line tester scheme to generate eighteen test crosses. The test crosses together with two tester × tester crosses and two checks were evaluated under artificial FAW infestation (AI), natural infestation (NI) and pesticide-protected condition (PC) in Nigeria. Additive and non-additive effects were significant for GYLD, most agronomic and FAW-resistant traits under AI and NI, except ear damage (EDAM) scores under NI, whereas only the non-additive effect was significant for GYLD under PC. Two testers (1393 and CKSBL10060) combined significant and positive GCA effects for GYLD with desirable GCA effects for FAW-resistant traits under AI and NI, whereas CML 331 combined significant and negative GCA effects of GYLD with undesirable GCA effects of FAW resistance under the test conditions. Three OPVs (AWR SYN-W2, AMATZBR-WC4 and TZB-SR) had a significantly positive GCA effect for GYLD and a desirable GCA effect for either leaf damage (LDAM) or EDAM score under AI. The FAW LDAM and EDAM significantly reduced GYLD under AI but not under NI. Three test crosses (AMATZBR-WC4 x CKSBL10060, TZB-SR x CKSBL10060 and TZBR Comp 1-WC2 × 1393) combined high yield with stability and FAW tolerance across the test conditions and thus were recommended for further testing.

Performance of the domestic Bt corn event expressing pyramided Cry1Ab and Vip3Aa19 against the invasive Spodoptera frugiperda (J. E. Smith) in China.

The invasive fall armyworm, Spodoptera frugiperda (J.E. Smith), has caused serious corn yield losses and increased the frequency of insecticide spraying on corn in Africa and Asia. Drawing lessons from the use of Bt corn to manage fall armyworm in the Americas, China released a certificate for the genetically modified corn event DBN3601T pyramidally expressing Cry1Ab and Vip3Aa19 for industrialization in 2021. Performance of the DBN3601T event against invasive fall armyworm in China was evaluated by plant tissue-based bioassays and field trials during 2019-2021. In the bioassays, tissues and organs of DBN3601T corn differed significantly in lethality to fall armyworm neonates in the order: leaf > husk > tassel and kernel > silk. In field trials, compared with non-Bt corn, DBN3601T corn greatly suppressed fall armyworm populations and damage; larval density, damage incidence, and leaf damage scores for DBN3601T corn were significantly lower than for non-Bt corn at different vegetative stages, and efficacy against larval populations during the 3 years ranged from 95.24% to 98.30%. A laboratory bioassay and 3-year field trials confirmed that DBN3601T corn greatly suppressed fall armyworm populations and has high potential as a control of this invasive pest, making it a key tactic for integrated management of fall armyworm in China. © 2022 Society of Chemical Industry.

Reproductive potential of fall armyworm Spodoptera frugiperda (J.E. Smith) and effects of feeding on diverse maize genotypes under artificial infestation.

Fall armyworm (FAW) Spodoptera frugiperda (J.E. Smith) has become a major threat to maize production in Africa. In this study, six maize genotypes were assessed for their resistance to FAW under artificial infestation in both laboratory and net house conditions. These included two FAW-tolerant hybrids (CKHFAW180294 and CKH191221), two commercial hybrids (WE2115 and CKH10717), and two open-pollinated varieties (ZM523 and KDV4). Larval development time and reproductive potential were assessed on maize leaves in the laboratory and a life table for FAW was constructed. The maize genotypes were also artificially infested with three FAW neonates at two phenological stages (V5 and V7) and reproductive stage (R1) in the net house. Leaf and ear damage scores were recorded on a scale of 1-9. Larval development time varied significantly between maize genotypes with the highest on CKH191221 (16.4 days) and the lowest on KDV4 (13.7 days). The intrinsic rate of natural increase for life tables varied from 0.24 on CKH191221 to 0.41 on KDV4. Mean generation time of FAW ranged from 17.6 to 22.8 days on KDV4 and CKH191221, respectively. Foliar damage was the lowest on CKH191221, and the highest on KDV4 at V7 infestation stage in week 1. CKH191221 had the lowest ear damage score, whereas ZM523 had the highest scores at V5 infestation stage. The highest and lowest yield reductions were observed on ZM523 (64%) at V7 infestation stage and CKHFAW180294 (6%) at R1 infestation stage, respectively. The results indicated the potential for developing tropical mid-altitude maize germplasm with native genetic resistance to FAW.

Biocontrol potential of entomopathogenic nematodes for the sustainable management of Spodoptera frugiperda (Lepidoptera: Noctuidae) in maize.

The occurrence of Spodoptera frugiperda (J.E. Smith) in Asia was reported for the first time from Karnataka in 2018. This pest is widely distributed in India, causing significant damage to maize. Management of this recent invasive pest in maize-growing regions of India relies on chemical control. Resistance is the greatest obstacle to the successful use of chemical insecticides to control this pest. Indiscriminate use of chemical insecticides destroys beneficial natural enemies, therefore effective and sustainable alternative control strategies are needed. In this case, the use of biological control agents is the alternative option to mitigate this pest. Thus, this study aimed to select virulent entomopathogenic nematodes (EPNs) isolates based on the laboratory assay and further to test the efficacy of virulent isolates in the field conditions along with commonly used chemical insecticide emamectin benzoate against S. frugiperda. Laboratory results revealed that both Heterorhabditis indica 1 NBAIIH38 and Steinernema carpocapsae NBAIRS59 caused 100% mortality in third- and fourth-instar larvae of S. frugiperda, while these two species caused 85% and 72% mortality in pupae, respectively. When pupae of S. frugiperda were exposed to EPNs, pupae died after metamorphosis to malformed adults. All the nematode species were able to penetrate and reproduce within S. frugiperda larvae, but the reproduction rate for Heterorhabditids was higher than that of Steinernematids. Field trial results showed that H. indica 1 NBAIIH38 significantly reduced the number of larvae and leaf damage scores compared to S. carpocapsae NBAIRS59. Emamectin benzoate was more effective in reducing the larval population compared to EPN species. The cob yield was significantly higher in EPN- and emamectin benzoate-treated plots than in untreated control plots. Overall, these experiments suggest H. indica 1 NBAIIH38 is a promising biocontrol agent against S. frugiperda in maize production. © 2022 Society of Chemical Industry.

Genomic Analysis of Resistance to Fall Armyworm (Spodoptera frugiperda) in CIMMYT Maize Lines.

The recent invasion, rapid spread, and widescale destruction of the maize crop by the fall armyworm (FAW; Spodoptera frugiperda (J.E. Smith)) is likely to worsen the food insecurity situation in Africa. In the present study, a set of 424 maize lines were screened for their responses to FAW under artificial infestation to dissect the genetic basis of resistance. All lines were evaluated for two seasons under screen houses and genotyped with the DArTseq platform. Foliar damage was rated on a scale of 1 (highly resistant) to 9 (highly susceptible) and scored at 7, 14, and 21 days after artificial infestation. Analyses of variance revealed significant genotypic and genotype by environment interaction variances for all traits. Heritability estimates for leaf damage scores were moderately high and ranged from 0.38 to 0.58. Grain yield was negatively correlated with a high magnitude to foliar damage scores, ear rot, and ear damage traits. The genome-wide association study (GWAS) revealed 56 significant marker–trait associations and the predicted functions of the putative candidate genes varied from a defense response to several genes of unknown function. Overall, the study revealed that native genetic resistance to FAW is quantitative in nature and is controlled by many loci with minor effects.

Spatial orientations of common bean (Phaseolus vulgaris L.) influence the activity and population dynamics of bean stem maggot (Ophiomyia phaseoli) and bean foliage beetle (Ootheca mutabilis)

Common bean (Phaseolus vulgaris L.) is an important legume for food and income for smallholder farmers all over the world. Pests such as bean stem maggot BSM (Ophiomyia phaseoli) and bean foliage beetle BFB (Ootheca mutabilis) pose a serious challenge to production. Many practices have been employed to manage these pests. However, little or no emphasis has been on basic agronomic practices such as plant spacing as a tool for pest management. In the present study, the role of plant orientation (plant spacing) on the activities and population dynamics of BSM and BFB was examined in a pesticide-free field trial in Bamenda, Cameroon from March to July, 2020. Different plant orientations namely 15cm x 15cm (~442500 plants/ha), 20cm x 20cm (~250000 plants/ha), 30cm x 30cm (~110000 plants/ha) and 40cm x 40cm (~62500 plants/ha) were test in a randomized complete block design with 4 replicates. Data was collected on oviposition holes on leaves of common bean by BSM, BSM population dynamics, leaf damage score by BFB, and population dynamics of BFB. The number of oviposition holes, the mean cumulative number of BSM, the mean leaf damage scores and the mean cumulative number of BFB were significantly higher (P < .05) in dense plots (15cm x 15cm) than in the other plots. The activity of BSM and BFM increased over time. The Principal Component Analysis revealed that the first two components accounted for 99.17% of the variation. Linear discriminant analysis with Mahalanobus distances with an 87.5% cross-validation by Jacknife procedure revealed that spatial orientation of 20cm x 20cm and 30cm x 30cm were very similar and significantly (F = 99.27, df = 3, 12, P < .001) different from the others. For pest management purposes, plant orientations of 20cm x 20cm and 30cm x 30cm can be recommended since they recorded low BSM and BFB activity. For future perspective, it is important assess the effect of different plant orientation on yield and pest parameters concurrently.

Evaluation of pearl millet (Pennisetum glaucum L. (R. Br.)) landraces for resistance to stem borer (Coniesta ignefusalis Hampson.) infestation

Characterisation of germplasm collection is imperative for identification and selection of new resistance sources in any crop breeding programmes. Thus, evaluation of pearl millet germplasm for resistance to stem borer infestation was carried out in view of the challenges of poor yield and quality reduction of pearl millet, elicited by its feeding activities. Thirty-five (35) pearl millet accessions were collected from different states where the crop is majorly cultivated in Nigeria. The accessions were characterised for resistance to stem borer infestation on the field. Further confirmation for selected potentially resistant accessions under artificial screen house conditions was done using a randomised complete block design (RCBD) with ten replications each. The field estimated selection index showed that out of the 35 accessions screened, 15 accessions were potentially resistant; 13 resistants with range value of 0.00 to 0.40 and 2 moderately resistant. Further nursery screening confirmed 9 of the 15 accessions to be resistant under artificial infestation. NS-JIL-01 accession was most highly resistant with significant least leaf damage score of 0.25. Significant and positive correlation (r = 0.32) was obtained between days to anthesis and number of larvae per plant at p &lt; 0.01. Negative correlation of percentage internodes damage with panicle diameter (-0.26) and panicle weight (-0.25 gn) at p &lt; 0.01 as well as weight of 1000 seeds (r = -0.19, p &lt; 0.05) were also significant. The identification of potentially resistant accessions on field and confirmation of some of the accessions under artificial screen house conditions indicated, gene for resistance to stem borer infestation in pearl millet could be obtained from the natural eco-type germplasm.

Screening cultivated eggplant and wild relatives for resistance to sweetpotato whitefly (Bemisia tabaci) and to two-spotted spider mite (Tetranychus urticae)

Whiteflies and spider mites are amongst the most harmful eggplant (Solanum melongena) pests. Considering the need for reduction of chemical applications for whitefly and spider mite control, the exploitation of wild relatives of eggplant as sources of pest resistances represents an important strategy in order to improve cultivated eggplant. The objectives of this study were to evaluate 15 accessions from 11 species of eggplant wild relatives together with seven S. melongena accessions for resistance to sweet potato whitefly (Bemisia tabaci) and to two-spotted spider mite (Tetranychus urticae). Resistance to whitefly was evaluated based on number of eggs, nymph, puparium and whitefly adults in a choice bioassay, while for two-spotted spider mite it was based on leaf damage scores in the choice and no-choice bioassays. The results revealed significantly (P < 0.05) different levels of resistance to the two pests among the accessions evaluated. Considering all screening parameters in the whitefly choice bioassay, the highest levels of resistance in wild eggplant relatives were detected in Solanum dasyphyllum (DAS1) and S. pyracanthos (PYR1), although one of the cultivated S. melongena (MEL2) accessions also displayed similar resistance levels. In addition, S. campylacanthum (CAM8) and S. tomentosum TOM1 were also resistant to whitefly based on numbers of puparium and adult whiteflies. Two accessions of S. sisymbriifolium (SIS1 and SIS2) exhibited strong resistance to two-spotted spider mite based on the choice and no-choice bioassays. High levels of spider mite resistance were also detected in the no-choice assay in S. dasyphyllum (DAS1) and S. torvum (TOR2) accessions. These resistant accessions can be used in pre-breeding program aiming to breed pest-resistant cultivars in cultivated eggplant. Moreover, to our knowledge, this study represents the first report on potential sources of resistance to whitefly and two-spotted spider mite in wild relatives of eggplant.

Evaluation of XL370A-Derived Maize Germplasm for Resistance to Leaf Feeding by Fall Armyworm1

The fall armyworm, Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae), is an economically important insect with larvae damaging maize (Zea mays L.) leaves and ear tissue. The pest has become resistant to several classes of insecticide and Bt-maize grown in some geographical areas. Once discovered and characterized, native sources of maize resistance to this pest could be effectively integrated with existing control tactics. The objective for this study was to test experimental lines derived from maize germplasm XL370A for resistance to leaf feeding by fall armyworm. Plants were grown in the field in 2018 and 2019, artificially infested with fall armyworm, and leaf damage scores recorded. Average 14-day scores for experimental maize lines GEMN-0095 (5.8), GEMN-0096 (5.7), and GEMN-0133 (5.6) were moderately resistant and 7- and 14-day scores for these entries were not significantly different across both years. Cuba 94 was not significantly different from the three entries with the exception of having greater 7-day damage scores in 2019. GEMN-0048 was not resistant but variability was observed in 14-day scores between 4 (resistant) and 8 (susceptible) in individual plants. The experimental lines are adapted for growth in temperate regions and might provide maize breeding programs with useful levels of resistance to fall armyworm.