Key Pest Of Maize Research Articles

CHEMICAL COMPOSITION AND INSECTICIDAL EFFICACY OF VITEX NEGUNDO L. ESSENTIAL OIL AGAINST FALL ARMYWORM, SPODOPTERA FRUGIPERDA (J. E. SMITH)

The fall armyworm, Spodoptera frugiperda, is a key pest ofmaize crops in tropical and subtropical regions and has developed resistanceagainst synthetic pesticides and Bacillus thuringiensis toxins. Thus,the experiments were designed to evaluate the chemical analysis andinsecticidal efficacy of Vitex negundo against S. frugiperda.Chemical analysis of V. negundo essential oil revealed a total of 36compounds, and the oil contained more monoterpenes (68.16%) than sesquiterpenes(22.21%) and diterpenes (13.56%). For the ovicidal and insecticidal activities,the essential oil was found to be most effective, with a median lethalconcentration (LC50) value of 51.31 µL/mL and 0.29 L/larvae, respectively.Larval antifeedant and growth inhibitory activity of essential oil werepositively correlated (R2 = 0.9645) and (R2 = 0.9727) with oil concentrations,respectively. Therefore, the V. negundo essential oil can be used forthe development of bioinsecticides to control S. frugiperda, a highlyinvasive and polyphagous pest, which will replace chemical pesticides.

Viability and virulence of freeze-dried Beauveria bassiana, Metarhizium acridum, and Hirsutella thompsonii isolates under non-refrigerated conditions in Ghana

ABSTRACT The necessity of cold storage for mycoinsecticides poses a logistical challenge in tropical Africa, where maintaining consistent refrigeration is a major obstacle. To investigate alternative preservation methods, our study evaluates conidial-based freeze-dried formulations of Beauveria bassiana (IMI 389521), Metarhizium acridum (IMI 330189), and mycelial-based freeze-dried formulations of Hirsutella thompsonii (IMI 327488 and IMI 391722). Propagules were cryoprotected with lactose, mannitol, and raffinose, encapsulated, and freeze-dried in plastic and glass vials. Bioformulations in glass vials were cryoprotected with mannitol only. Viability (CFU/g each day) of bioformulations, following 16-weeks-storage, and their virulence (at 1 × 107 conidia mL−1 in six days) against key pests of maize and cassava in Africa (larger grain borer, variegated grasshopper and cassava green mite) were determined under ambient laboratory conditions in Ghana. Our results show that non-freeze-dried conidia of B. bassiana and M. acridum had significantly higher viability and efficacy than freeze-dried versions, when stored under non-refrigerated conditions (averaging 27.7°C, 78.8% RH). Freeze-dried H. thompsonii mycelia were neither viable nor virulent against cassava green mite. Freeze-dried B. bassiana and M. acridum in plastic vials remained viable for 12 weeks, while in glass vials they were viable for seven weeks. Freeze-dried B. bassiana in both plastic and glass vials caused 38–43% mortality in larger grain borer, and M. acridum caused 45–82% mortality in variegated grasshopper. Further, conidia cryoprotected with lactose had significantly higher viability and mortality than raffinose and mannitol. Our research contributes to mycoinsecticide development, particularly in the context of storage and application challenges in tropical climates.

Efficacy of Beauveria bassiana against adults of Prostephanus truncatus (Horn), Sitophilus zeamais Motschulsky and Teretrius nigrescens Lewis in stored maize

The larger grain borer, Prostephanus truncatus (Horn) and the maize weevil, Sitophilus zeamais Motschulsky continue to cause tremendous losses to stored maize. Research in the UK has identified Beauveria bassiana, IMI 389521 as a suitable control agent for grain storage pests in the UK. The pathogenicity of B. bassiana, IMI 389521 was evaluated against adult P. truncatus, S. zeamais and Teretrius nigrescens in Ghana. Fifty adults of each insect species were treated with 0.5 g dry conidia powder of this isolate at 8.65 × 108 conidia/g for 1 minute and mortality recorded daily for 14 days. The results indicated that B. bassiana, is pathogenic against P. truncatus and S. zeamais, inducing over 90% mortality by day 7. Teretrius nigrescens was, however less susceptible to the fungus with 30% mortality. To determine the most effective concentration of B. bassiana for the control of P. truncatus, a laboratory dose response experiment using four concentrations of B. bassiana (108–1011 cfu/kg maize) was also conducted. Maize grains (250 g) in separate jars were treated with the four concentrations of the product. Fifty adults of P. truncatus were placed into the jars containing the treated maize and mortality was assessed weekly for 3 weeks. The most effective dose was 1010 cfu/kg maize, which resulted in 96% and 100% mortality of P. truncatus after 2 and 3 weeks, respectively. This study shows that B. bassiana could effectively be integrated into bio-control programme of these two key pests of maize in Ghana after further field trials.

MON 95379 Bt maize as a new tool to manage sugarcane borer (Diatraea saccharalis) in South America.

BackgroundThe sugarcane borer (SCB), Diatraea saccharalis (Lepidoptera: Crambidae), is a key pest of maize in Argentina, and genetically modified maize, producing Bacillus thuringiensis (Bt) proteins, has revolutionized the management of this insect in South America. However, field‐evolved resistance to some Bt technologies has been observed in SCB in Argentina. Here we assessed a new Bt technology, MON 95379, in the laboratory, greenhouse and field for efficacy against SCB.ResultsIn a laboratory leaf disc bioassay, both MON 95379 (producing Cry1B.868 and Cry1Da_7) and Cry1B.868_single maize (producing only Cry1B.868) resulted in 100% mortality of SCB. The level of Cry1B.868 in the Cry1B.868_single maize is comparable to that in MON 95379 maize. However, the Cry1Da_7 protein does not have high efficacy against SCB, as evidenced by < 20% mortality on Cry1Da_7_single leaf tissue. Total (100%) mortality of SCB in a Cry1B.868_single tissue dilution bioassay indicated that Cry1B.868_single maize meets the criteria to be classified as a high dose. Similar median lethal concentration (LC50) values were observed for MON 89034‐R and susceptible SCB strains exposed to Cry1B.868 protein. MON 95379 also controlled SCB strains resistant to MON 89034 (Cry1A.105/Cry2Ab2) and Cry1Ab. Under field conditions in Brazil and Argentina, MON 95379 maize plants were consistently protected from SCB damage.ConclusionMON 95379 maize will bring value to maize growers in South America by effectively managing SCB even in locations where resistance to other Bt‐containing maize technologies has been reported. © 2022 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Impact of the fall armyworm, Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae), invasion on maize and the native Spodoptera litura (Fabricius) in East Java, Indonesia, and evaluation of the virulence of some indigenous entomopathogenic fungus isolates for controlling the pest

BackgroundThe fall armyworm, Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae), is an invasive alien species in Indonesia. This study aimed to assess the impact of its invasion in Indonesia by measuring the damaged area caused by the pest in maize fields located across East Java and simultaneously determine whether S. frugiperda outcompetes the native Asian armyworm Spodoptera litura (Fabricius). Secondly, the virulence of 14 entomopathogenic fungus (EPF) isolates against S. frugiperda larvae was evaluated in an effort to find effective biocontrol agent candidates.ResultsThe damaged area caused by S. frugiperda was generally higher than that caused by S. litura during the survey period from August 2019 to December 2021. It indicated that S. frugiperda may have dominated the native armyworm and become the primary key pest of maize in Indonesia. Based on a single-concentration assay (106 conidia ml−1), the tested EPF isolates displayed varying degrees of virulence against S. frugiperda larvae, causing larval mortality of 3.5 to 71% at 10-day post-treatment, with the highest mortality rates provided by Beauveria bassiana sensu lato and Trichoderma asperellum sensu lato. At a concentration of 108 conidia ml−1, B. bassiana s.l. and T. asperellum s.l. elicited high larval mortality of 76 and 81%, respectively, at 10-day post-treatment. Nevertheless, the probit analysis based on a concentration–response assay revealed that T. asperellum s.l. had lower LC50 and LC90 values than B. bassiana s.l.ConclusionsThe attack and invasion of S. frugiperda seem to be a continual threat to the maize agro-ecosystem in Indonesia. As a consequence, Indonesia should mitigate and be well-prepared for future outbreaks of S. frugiperda. Indigenous EPF isolates used in this study may act as promising biocontrol agents of S. frugiperda, especially T. asperellum s.l. This study also serves as the first report documenting the direct lethality of Trichoderma fungus on S. frugiperda larvae.

Spatial distribution and sequential sampling plan for Diceraeus melacanthus (Hemiptera: Pentatomidae) in maize at the vegetative stage

Diceraeus melacanthus has become a key pest of maize in Brazil, primarily during the early vegetative growth stages. This study examined the spatial distribution of D. melacanthus in maize and developed a sequential sampling plan for monitoring the pest in maize at the vegetative stage. The samples were collected from six fields of 1250 m2 each in the second crop seasons of 2012 and 2013. The sampling unit consisted of five randomly chosen plants per plot, which were visually examined for D. melacanthus on a weekly basis, totaling 250 plants evaluated per field on each sampling date. To construct the sampling plan, an economic threshold of 0.8 stink bugs per sample unit (five plants) was adopted. According to the indices of dispersion and by fitting the frequency data to mathematical distributions, the spatial distribution of D. melacanthus in maize is aggregated. From the obtained data, two decision lines were generated, one of which, S1 = 3.5683 + 0.5702 N, recommends taking control action, whereas the other, S0 = −3.5683 + 0.5702 N, suggests that no control action is needed. The sequential sampling plan indicated an expected maximum number of 26 sampling units (∼130 plants) to determine whether to control the pest with prefixed precision level of 95%. This sampling plan may help the decision-making for the control of D. melacanthus in maize, contributing for a sustainable management of this herbivore to increase farmers’ profit.

Evaluating Artificial Diets for the Fall Armyworm, Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae) through Nutritional Indices and an Age-Stage, Two-Sex Life Table Approach

Spodoptera frugiperda (J.E. Smith) is an invasive and key pest of maize, which has been recently introduced to South India. There are two strains reported, viz. rice strain and maize strain. Though several diets were tried in different parts of the world, none of them contained rice leaf powder as a component from natural host. Hence a study was conducted to evaluate the biology, nutritional indices, age-stage and two-sex life table to assess the suitability of the different artificial diets for S. frugiperda larval development. Six differently modified artificial diets were tested to evaluate the following biological parameters: duration of larva and pupae, survival of larvae and pupae, pupal weight, sex ratio, fecundity, adult pre-oviposition period, total pre-oviposition period, adult longevity and total lifespan. The following nutritional indices were determined: growth rate, relative growth rate, consumption rate, consumption index, approximate digestibility, efficiency of conversion of ingested food, efficiency of conversion of digested food and metabolic cost. Larval development showed a significant difference among the diets, in relation to the life table parameters. The results indicated that optimal growth, development and food utilisation by S. frugiperda occurred in the mixture of rice leaf powder and chickpea flour-based diet followed by the mixture of maize leaf powder and common bean powder-based diet. Evaluated diets also had a significant effect on the net reproductive rate, gross reproductive rate, intrinsic rate of increase, finite rate of increase, mean generation time and population doubling time. The values of these parameters were higher in the mixture of rice leaf powder and chickpea flour-based diet followed by mixture of maize leaf powder and common bean powder-based diet. Based on the results, the most adequate diet for rearing in the laboratory was the mixture of rice leaf powder and chickpea flour-based diet.

Sustainability of strategies for Ostrinia nubilalis management in Northern Italy: Potential impact on beneficial arthropods and aflatoxin contamination in years with different meteorological conditions

The European corn borer (ECB), Ostrinia nubilalis Hübner (Lepidoptera: Crambidae), is a key pest of maize (Zea mays L.). In Northern Italy, larvae of the 2nd generation may damage cobs and kernels and the feeding activity can promote the proliferation of aflatoxigenic fungi, such as Aspergillus flavus, the major producer of aflatoxin B1 (AFB1).During 2017–2018, the efficacy of two strategies to control ECB in maize was assessed. Biological control strategy (Trichogramma brassicae Bezdenko and Bacillus thuringiensis Berliner), conventional chemical strategy (chlorantraniliprole) and an untreated control were compared to assess: i) the effect of the strategies on ECB infestation; ii) the association of ECB and AFB1 kernels contamination; iii) the impact of the strategies on beneficial arthropods.The conventional chemical strategy demonstrated the best control of ECB infestation, followed by biological control strategy and the untreated control. No significant differences in maize yield were found among strategies. The role of ECB on AFB1 concentration was demonstrated only in 2017, when higher level of infestations occurred simultaneously with an extended period of drought and high temperatures, sanctioning the important role of meteorological conditions on AFB1 contamination.The activity density of ground beetles, rove beetles and spiders and the mean number per leaf of the most abundant beneficial insects dwelling on plants (coccinellids, predatory thrips and lacewings) did not show significant changes between pre-and post-treatment with chlorantraniliprole, highlighting the selectivity of this pesticide in the short time.This study provides some contribution for the reduction of non-renewable input in Italian maize fields, demonstrating that biological control strategy, although less effective than conventional chemical control, can be a feasible approach to control ECB second larval generation, without any increment of AFB1 level in grains and yield loss.

Biocontrol-based management of fall armyworm, Spodoptera frugiperda (J E Smith) (Lepidoptera: Noctuidae) on Indian Maize

Spodoptera frugiperda (J E Smith) (fall armyworm) (Lepidoptera: Noctuidae), is a key pest of maize that has recently entered in India causing damage and yield loss. A biocontrol-based integrated pest management (IPM) strategy was designed and evaluated in farmer’s field during rabi and kharif season (2018–2019). IPM strategy comprising installation of controlled release FAW pheromone traps, four releases of Trichogramma pretiosum Riley, two sprays of neem oil, one spray of each Bacillus thuringiensis (NBAIR-BT25) and Metarizium anisopliae (NBAIR Ma-35) resulted in 76 and 71.64% egg mass; 80 and 74.44% larval population reduction at 60 days after treatment during rabi and kharif season, respectively. Cob yield per acre in biocontrol-based IPM field was higher than the farmer’s practice (6–7 sprays of emamectin benzoate 5% SG) during both the seasons, and it resulted in 38.3 and 42.29% gain in yield per acre during rabi and kharif, respectively. Therefore, this module forms a base to manage the fall armyworm in an eco-friendly and farmer friendly manner. Future research with other alternatives has also been discussed.

Oviposition behavior of Telenomus busseolae, Telenomus isis and Trichogramma bournieri on eggs of east African cereal stemborers

The oviposition behavior of the scelionids Telenomus busseolae, Telenomus isis and the trichogrammatid Trichogramma bournieri was studied on eggs of lepidopteran cereal stemborers, which included the noctuid Busseola fusca, Sesamia calamistis, Sesamia nonagrioides, the crambid Chilo partellus, and the pyralid Eldana saccharina. Unlike Tr. bournieri, Telenomus spp. did not attack eggs of C. partellus and E. saccharina. Five distinct behavioral steps were observed, which included foraging, drumming with the antennae on the eggs, ovipositor insertion, egg marking, and walking and resting. Foraging, walking and resting were observed less frequently than the other behaviors. There was a clear hierarchy of behavioral steps leading to successful parasitism, which culminated in marking of eggs. Self-superparasitism (i.e., oviposition in an egg previously parasitized by the same female) was between 2.7–5.9% indicating that the three parasitoids were able to discern eggs that were already parasitized. Earlier studies on the bionomics and host finding ability together with the present findings on the oviposition behavior of the different parasitoids cannot explain differences in parasitism rates by the parasitoids in the field. It is suggested that the plant species and alternative hosts occurring in crop and natural habitats may play an important role in the population dynamics of the parasitoids and affect their importance in controlling key pests of maize.

Effects of entomopathogenic fungi (EPFs) and cropping systems on parasitoids of fall armyworm (Spodoptera frugiperda) on maize in eastern central, Tanzania

ABSTRACTFall armyworm (FAW), Spodoptera frugiperda is a key pest of maize in Africa including Tanzania. Field trials were conducted to determine the incidence of species of parasitoids and their rate of parasitism on selected IPM treatments. The experiment was conducted at crop Museum of Sokoine University of Agriculture, Morogoro, Tanzania for two cropping seasons and arranged in a split – split-plot design with three replicates. The treatment combinations were push–pull without application of pesticides, push–pull and Beauveria bassiana, push–pull and Metarhizium anisopliae sensu lato, push–pull and flubendamide, cowpea + maize without application of pesticides, and cowpea + maize and Beauveria bassiana. Others were cowpea + maize and Metarhizium anisopliae sensu lato, cowpea + maize and flubendamide, maize sole crop without application of pesticides, maize sole and Beauveria bassiana, maize sole and Metarhizium anisopliae, and maize sole and flubendamide. The results showed that one species of egg-larva parasitoids (Chelonus bifoveolatus) and two species of larva parasitoids (Coccygidium luteum and Cotesia sp.) were recovered from the sampled fall armyworm eggs and larvae. The percentage of parasitism of C. bifoveolatus and C. luteum differed significantly among intercropping systems (p < .001). The results also showed that the percentage of larval parasitism of Cotesia sp. differed significantly (p < .001) among intercropping systems only. These results confirm biological control of fall armyworm through the conservation of natural enemies in Tanzania.

Practical Resistance of Ostrinia nubilalis (Lepidoptera: Crambidae) to Cry1F Bacillus thuringiensis maize discovered in Nova Scotia, Canada

Transgenic maize, Zea mays L., modified to express insecticidal proteins from the bacterium Bacillus thuringiensis Berliner, was introduced in 1996 to control Ostrinia nubilalis Hübner (Lepidoptera: Crambidae), a key maize pest in North America. The high-dose/refuge concept, developed to delay or prevent resistance evolution to this technology, has been exemplified by O. nubilalis as no cases of practical resistance were identified in >20 years. This study documents the first case of practical resistance to Cry1F Bt maize by O. nubilalis in North America. Four collections of O. nubilalis were made from Cry1F maize in Nova Scotia, Canada with unexpected injury (UXI) ranging from 30–70%. Greater survival of UXI collections was observed when larvae were exposed to the highest concentration of 200 ng Cry1F cm−2 in diet-overlay bioassays compared to susceptible laboratory colonies. Larvae also fed and survived on Cry1F leaf tissue in 7 d bioassays. A collection from non-Bt maize, 120 km west of the UXI region, also survived 200 ng Cry1F cm−2, but was susceptible to Cry1F leaf tissue. Detection of Cry1F-resistant O. nubilalis in what might be considered an insignificant maize-growing region indicates that a number of preventable causal factors may have been related to inadequate stewardship of Bt maize technology.

Pest categorisation of Diabrotica barberi.

The EFSA Panel on Plant Health performed a pest categorisation of Diabrotica barberi (Coleoptera: Chrysomelidae), the northern corn rootworm, for the EU. D. barberi is a univoltine species occurring in mid‐western and eastern USA and Canada, where it reproduces on maize (Zea mays), the preferred larval host. A small proportion of individuals can develop to a lesser extent on spelt (Triticum spelta), rice (Oryza sativa), millet (Panicum miliaceum) and a few North American wild grasses. Eggs are laid in the soil of maize fields, where they overwinter and can enter a diapause which can extend for more than one winter. Larvae hatch in late spring and early summer. Adult emergence peaks in the summer to feed on maize tassels, silks and ear tips. Adults abandon maize fields looking for other feeding hosts and return to maize for oviposition during late summer and autumn. D. barberi is considered a key pest of maize, together with other rootworm species of the same genus. D. barberi is regulated in the EU by Directive 2000/29/EC (Annex IAI). Within this Directive, a general prohibition of soil from most third countries prevents the entry of D. barberi larvae. However, adults carried on sweetcorn or green maize are potential pathways for entry into the EU. Climatic conditions and the wide availability of maize provide conditions to support establishment in the EU. Following establishment, impact on maize yields is anticipated. Phytosanitary measures are available to inhibit entry of this pest. D. barberi satisfies the criteria, which are within the remit of EFSA to assess for it to be regarded as a potential Union quarantine pest. D. barberi does not meet the criteria of occurring in the EU nor plants for planting being the principal means of spread for it to be regarded as a potential Union regulated non‐quarantine pest.

Pest categorisation of Diabrotica virgifera zeae.

The EFSA Panel on Plant Health performed a pest categorisation of Diabrotica virgifera zeae (Coleoptera: Chrysomelidae), the Mexican corn rootworm, for the EU. This is one of two subspecies of D. virgifera which occurs in Central America, Mexico and central southern parts of the USA (Texas, Oklahoma and New Mexico). The preferred larval host is maize (Zea mays) roots, although larvae can feed on the roots of sorghum and other grass species. Adults feed on the leaves, silks, immature seeds of maize, and pollen of up to 63 plant genera. Eggs are laid in the soil of maize fields in late summer/early autumn and hatch in late spring. Adults are found in and near maize fields from May until frosts appear later in the year. D. virgifera zeae is univoltine except where maize is grown continuously when there can be multiple overlapping generations each year. In the Americas, D. virgifera zeae is considered a key maize pest. D. virgifera zeae is regulated by Directive 2000/29/EC (Annex IAI). A general prohibition of soil from most third countries prevents the entry of immature stages of D. virgifera zeae. However, adults could be carried on sweetcorn or green maize. Maize is grown widely across the EU, but establishment may be limited to warmer parts of southern EU. Should it establish in the EU, impact on maize yields is anticipated. Phytosanitary measures are available to inhibit entry of this pest. D. virgifera zeae satisfies the criteria, which are within the remit of EFSA to assess for it to be regarded as a potential Union quarantine pest. D. virgifera zeae does not meet the criteria of occurring in the EU, nor plants for planting being the principal means of spread, for it to be regarded as a potential Union regulated non‐quarantine pest.

Life-History Parameters of Striacosta albicosta (Lepidoptera: Noctuidae) Under Laboratory Conditions.

Striacosta albicosta (Smith) is a key pest of maize and dry beans in North America. It has expanded its distribution from the western Great Plains of the United States to the Great Lakes region in the United States and Canada. There has been limited research on the baseline biological aspects of this insect under controlled conditions. The objective of this study was to detail the biological parameters of S. albicosta feeding on an artificial diet under laboratory conditions. Overall survival from neonate to adult at 26.6 ± 1°C was 36.72% and the total developmental time was approximately 110 d. Survival of the egg, larval, prepupal, and pupal stages were 75.71, 98.50, 51.78, and 95.10%, respectively. Average duration of the egg, larval, prepupal, and pupal stages was 4.64, 28.20, 41.50, and 25.91 d, respectively. During the larval stage, 92.50% of larvae developed through seven instars and the remaining through six instars. Larvae that developed through six and seven instars exhibited a mean growth ratio of 1.60 and 1.47, respectively; however, there was no difference in pupal weight. Eggs laid by field-mated moths showed a fertility of 75.71%, compared with 4.18% from laboratory-reared moths. These data suggest that S. albicosta develop primarily through seven instars and the most vulnerable developmental stage is the prepupa. Laboratory conditions strongly affected fertility success. Information presented here greatly expands our understanding of S. albicosta biology, which can be used to improve the efficiency of laboratory bioassays and management techniques for this critical crop pest.

Fusarium graminearum Mycotoxins in Maize Associated With Striacosta albicosta (Lepidoptera: Noctuidae) Injury

Western bean cutworm, Striacosta albicosta (Smith; Lepidoptera: Noctuidae) has become a key pest of maize, Zea mays (L.), in Ontario, Canada which is challenging to control due to its lack of susceptibility to most Bt-maize events. Injury by S. albicosta may exacerbate Fusarium graminearum (Schwabe; Hypocreales: Nectriaceae) infection through provision of entry points on the ear. The objectives of this study were to: investigate the relationship between injury by S. albicosta and deoxynivalenol (DON) accumulation; evaluate non-Bt and Bt-maize hybrids, with and without insecticide and fungicide application; and determine optimal insecticide-fungicide application timing for reducing S. albicosta injury and DON accumulation. The incidence of injury by S. albicosta and ear rot severity were found to increase DON concentrations under favorable environmental conditions for F. graminearum infection. Incidence of S. albicosta injury was more important than severity of injury for DON accumulation which may be due to larval consumption of infected kernels. The Vip3A × Cry1Ab event provided superior protection from the incidence and severity of S. albicosta injury compared to non-Bt or Cry1F hybrids. Insecticide application to a Vip3A × Cry1Ab hybrid did not reduce injury further; however, lower severity of injury was observed for non-Bt and Cry1F hybrids when pyrethroids or diamides were applied at early VT or R1 stages. DON concentrations were reduced with application of prothioconazole fungicide tank-mixed with insecticide at late VT (before silk browning) or when insecticide was applied at early VT followed by prothioconazole at R1. The application of an insecticide/fungicide tank-mix is the most efficient approach for maize hybrids lacking high-dose insecticidal proteins against S. albicosta and F. graminearum tolerance. Results demonstrate that reducing the risk of DON accumulation requires a strategic approach to manage complex associations among S. albicosta, F. graminearum and the environment.

Monitoring of Sesamia nonagrioides resistance to MON 810 maize in the European Union: lessons from a long-term harmonized plan.

Use of MON 810 maize (Zea mays), which expresses the insecticidal protein Cry1Ab from Bacillus thuringiensis (Bt maize), is a highly effective method to control Sesamia nonagrioides (Lefèbvre), a key maize pest in Mediterranean countries. Monitoring programs to assess the potential development of resistance of target pests to Bt maize are mandatory in the European Union (EU). Here we report the results of the S. nonagrioides resistance monitoring plan implemented for MON 810 maize in the EU between 2004 and 2015 and reassess the different components of this long-term harmonized plan. No major shifts in the susceptibility of S. nonagrioides to the Cry1Ab protein have occurred over time. The reassessment of this long-term program has identified some practical and technical constraints, allowing us to provide specific recommendations for improvement: use reference strains instead of susceptibility baselines as comparators for field-collected populations; shift from dose-response bioassays to diagnostic concentrations; and focus monitoring on areas with high adoption rates, such as the Ebro basin in Spain. There are no signs of field resistance of S. nonagrioides to the Cry1Ab protein of MON 810 maize. Specific recommendations for improvement are provided, based on the knowledge and experience accumulated through the implementation of this unique EU-wide harmonized plan. © 2017 Society of Chemical Industry.

Farmers knowledge and perception on maize stem borers and their indigenous control methods in south western region of Cameroon.

BackgroundAgriculture is a major contributor to the Gross Domestic Product (GDP) of Cameroon, The South West region of Cameroon is known for its potential in the production of major agricultural commodities, but farmers’ yields from various speculations are low, dwindling over time due to some major constraints. Maize production is hampered by adverse socio-economic factors, several pests and diseases as well as high rainfall with low solar radiation. Lepidopterous maize stem borers are a major threat to increase maize production. Therefore we hypothesized that the farmers of the South West region: (1) also perceived stem borers as an important pest of maize; (2) they have their own indigenous methods of control; (3) they use chemical pesticides because they have no alternative, but would prefer plant materials if these were standardized.MethodsA semi-structured questionnaire survey was administered in four villages: Maumu, Lower Bokova, Ekona and Bonduma. A total of 151 (male and female) farmers were randomly interviewed to document farmers’ perception on stem borers, and their use of indigenous knowledge to manage key pests of maize.ResultsStem borers were present throughout the maize growing areas in the Fako division and ranked as one of the most important pests of the crop. Most farmers (82.1 %) perceived that stem borers caused significant damage on maize and were responsible for yield reductions in the crop. The increased impact of these pests was due to improper/untimely use of expensive conventional insecticides given the lack of a cheaper alternative method of control. About 50 % of respondent admitted not having any indigenous knowledge of stem borer control, while only 20 % had tried plant products. The most relevant indigenous stem borer control was the use of wood ash. Most (90 %) of the respondent would prefer plant-based insecticides in future because they are safer, cheaper and readily available.ConclusionsFarmers’ knowledge would contribute in understanding the activities of stem borers and use of plant insecticides. Research is therefore needed to standardize the methods of using plant-based products and also identify the active ingredients of these plants to ensure their effectiveness against maize stem borers and other pests.

Spatial and numerical relationships of arthropod communities associated with key pests of maize

AbstractPest management largely focuses on managing individual pest species with little concern for the diverse communities that co‐occur with key pests and potentially shape their population dynamics. During anthesis, we described the foliar arthropod communities on 53 maize farms throughout the region of eastern South Dakota. The resulting communities were examined for trends in local associations in the abundances of taxa with key pests in the system (rootworms [Diabrotica spp.], European corn borers [Ostrinia nubilalis], aphids and Western bean cutworm [Striacosta albicosta]) using regression analyses. Regional spatial clustering in the abundances of key pests with members of the community was explored using Moran's I test statistic. The distributions of rootworms and European corn borer were mapped. A total of 37 185 arthropods representing at least 91 taxa were collected in South Dakota maize; there was an average of 5.06 predators and 8.29 herbivores found per plant. Key pests were never found at economically threatening levels (with one exception for Diabrotica). Numerous species were consistently numerically associated with each of the key pests across the farms during anthesis. Occasionally, these pests shared species with which they were locally associated with; for example, coccinellid egg abundances were predictive of the abundances of all key pest species except rootworm adults. Spatial analysis across the region suggested that species co‐occurred with key pests based on local characteristics surrounding the fields, rather than as a result of regional characteristics. Exceptions were documented; namely aphids and Western bean cutworms that spatially clustered with a handful of other members of the community. The results of the study point out that the abundances of key pests of maize were interconnected through indirect associations in the abundances of other members of the community. These associations may be useful for manipulating maize agroecosystems to minimize the effects of maize pests.

Downregulation and mutation of a Cadherin gene associated with Cry1Ac resistance in the Asian Corn Borer, Ostrinia furnacalis (Guenée).

Development of resistance in target pests is a major threat to long-term use of transgenic crops expressing Bacillus thuringiensis (Bt) Cry toxins. To manage and/or delay the evolution of resistance in target insects through the implementation of effective strategies, it is essential to understand the basis of resistance. One of the most important mechanisms of insect resistance to Bt crops is the alteration of the interactions between Cry toxins and their receptors in the midgut. A Cry1Ac-selected strain of Asian corn borer (ACB), Ostrinia furnacalis, a key pest of maize in China, evolved three mutant alleles of a cadherin-like protein (OfCAD) (MPR-r1, MPR-r2 and MPR-r3), which mapped within the toxin-binding region (TBR). Each of the three mutant alleles possessed two or three amino acid substitutions in this region, especially Thr1457→Ser. In highly resistant larvae (ACB-Ac200), MPR-r2 had a 26-amino acid residue deletion in the TBR, which resulted in reduced binding of Cry1Ac compared to the MPR from the susceptible strain, suggesting that the number of amino acid deletions influences the level of resistance. Furthermore, downregulation of OfCAD gene (ofcad) transcription was observed in the Cry1Ac resistant strain, ACB-Ac24, suggesting that Cry1Ac resistance in ACB is associated with the downregulation of the transcript levels of the cadherin-like protein gene. The OfCAD identified from ACB exhibited a high degree of similarity to other members of the cadherin super-family in lepidopteran species.