Natural Infestation Conditions Research Articles

Tolerance in <i>Brassica juncea</i> Cultivars Vis-a-Vis Population Buildup of Mustard Aphid <i>Lipaphis erysimi</i> (Kalt.)

Current investigation deciphered the differential level of tolerance in diverse Brassica juncea cultivars, and variations in the preference and population buildup of Mustard aphid, Lipaphis erysimi. Cultivars RLC 3, NRCHB 101 and Pusa Mustard 27 were least preferred by L. erysimi. Further, total number of aphids and aphid resistance index under natural infestation condition were significantly lower on RLC 3, NRCHB 101, RH 725 and Pusa Mustard 27. However, under artificial conditions, total number of aphids, aphid resistance index and multiplication rates were significantly lower on DRMR 150-35, RH 0406, NRCHB 101, Pusa Mustard 27 and RLC 3. The cultivars DRMR 150-35, RH 0406, NRCHB 101, RLC 3, RH 725 and Pusa Mustard 27 were found with least preference, lower aphid resistance index, establishment, population buildup of L. erysimi under natural and/or artificial infestation conditions, thus can be used in Brassica improvement program.

Performance of some new soybean genotypes against the infestation of the cotton leaf worm, Spodoptera littoralis Boisd

Cotton leaf worm, Spodoptera littoralis (Lepidoptra: Noctuidae) is considered one of the most destructive insect pests in Egypt. A field trail was conducted at the experimental farm of Nubaria agricultural research station, Behaira Governorate, Egypt, during 2021 and 2022 seasons to evaluate the performance of 14 new genotypes and two check varieties under the cotton leaf worn natural infestation conditions. The experimental design was a randomized complete block design (RCBD) with three replicates. The combined results revealed that there were substantial differences across genotypes for all evaluated parameters. The genotypes (H7L39/2015, H6L49, and H6L28) were considered as more resistant ones over the resistant check variety (Giza 111) which recorded the least infestation (25.86, 27.57 and 32.14 %, respectively), with feeding damage area of 18.52, 19.58 and 18.58 %, respectively. These genotypes gave the highest leaf content of P%, K%, total phenolic compounds, yield, and its components. The correlations between infestation% and leaflet area damage% or N all were positive on one another. All other correlations, with the exception of plant height and branches no plant-1, had negative effects on one another. The results proposed that the genotypes (H7L39/2015, H6L49 and H6L28) are promising and could be planted at Nubaria region and used in the breeding programs.

Assessment of effectiveness of maize seed treated with cyantraniliprole and thiamethoxam for management of fall armyworm, Spodoptera frugiperda (J.E. Smith)

The effectiveness of maize seed treatments for management of fall armyworm (FAW) (Spodoptera frugiperda) was evaluated under natural infestation conditions in Zambia in 2019, 2020 and 2022. Two seed treatments were tested: cyantraniliprole (Fortenza® 600 FS) + thiamethoxam (Cruiser® 600 FS) (combination marketed as Fortenza® Duo) and Fortenza® 600 FS. Other treatments included each of the two seed treatments supplemented with threshold-based rotational sprays of Denim Fit® 50 WG (emamectin benzoate + lufenuron) and Ampligo® (chlorantraniliprole + lambda cyhalothrin), Denim Fit/Ampligo alone, untreated controls, Ecoterex® 0.5% GR (deltamethrin + pirimiphos methyl) and Mythic® FN SC (chlorantraniliprole). The incidence of FAW-infested plants and plant damage scores were recorded weekly for 4–5 weeks post-emergence. At harvest, grain yield, yield increase over untreated control and cost-benefit ratios were also determined. Although there were some seasonal variations in treatment effectiveness, plots established from Fortenza Duo-treated seed generally had significantly lower plant damage within the first 3–5 weeks of growth. The number of follow-on insecticide sprays were reduced from 2 to 1 in February 2022 plantings in plots established from Fortenza Duo-treated seed. Grain yields were highest in the Denim Fit/Ampligo plots (December 2021 plantings) and Fortenza Duo + Denim Fit/Ampligo plots (December 2021 and February 2022 plantings). In both plantings of the 2021-22 season, mean yield increase over untreated control was highest in Fortenza Duo + Denim Fit/Ampligo plots. Cost-benefit ratios were, however, highest where Fortenza Duo-treated seed was planted without any follow-on chemical sprays and lowest and negative in sole Fortenza plots. Due to method of application and systemic action, Fortenza Duo maize seed treatments may be a perfect fit in FAW integrated pest management (IPM) programs where there is need for judicious pesticide use.

‘Genotype by yield*trait’ (GYT) biplot approach to evaluate resistance of soybean cultivars to Helicoverpa armigera Hübner under natural infestation conditions

‘Genotype by yield*trait’ (GYT) biplot approach to evaluate resistance of soybean cultivars to Helicoverpa armigera Hübner under natural infestation conditions

COMPARATIVE EFFICACY OF FOUR FORMULATIONS BASED ON AROMATIC PLANT EXTRACT AND A SYNTHETIC FUNGICIDE AGAINST MYCOSPHAERELLA FIJIENSISMORELETCAUSAL AGENT OF BLACK LEAF STREAK DISEASE (BLSD), IN INDUSTRIAL DESSERT BANANA PRODUCTION

Black leaf streak disease (BLSD) caused by Mycosphaerella fijiensisa an ascomycete fungus is the most important foliar disease ofbananas (Musa sp.). Losses due to this pathogen can exceed 50% in case of no resistant cultivars and effective treatments. This study aimed to evaluate the efficacy of four biopesticides on the severity of Mycosphaerella fijiensis. It was conducted under natural infestation conditions in the industrial dessert banana plantation of the Agricultural Company KablanJoublin (SAKJ) at Elima (Aboisso). To make it possible some phytopathological, growth and agronomic parameters of banana plants were evaluated. The results showed that banana trees of plots treated with biopesticides had identical characteristics, about all the assessed parameters, with those of plots treated with the chemical fungicide. In addition, applications of biofungicide contributed to protecting banana leaves, slowed down the onset of necrotic first stage and significantly reduced the disease infestation level in the parcels. The use of aromatic plant essential oils-based biofungicides could be suggested as an ecological efficient solution to dessert banana and plantain producers against Mycosphaerella fijiensis responsible for the black leaf streak disease.

Field screening of chilli germplasm collections for resistance to chilli thrips, Scirtothrips dorsalis Hood

Forty chilli germplasm collections were field screened against chilli thrips, Scirthothrips dorsalis Hoodduring consecutive summer seasons of 2017-18 and 2018-19 under natural infestation conditions at All India Co-ordinated Research Project on Vegetable Crops, Odisha University of Agriculture and Technology, Bhubaneswar. Observations on the population of S.dorsalis were recorded at weekly interval from the appearance of the pest to last picking of the chilli fruits during all the seasons. Further the germplasm were visually rated for infestation of S.dorsalis in 0-4 point scale based on the ‘upward leaf curl’ damage symptom at 45, 60, 75, 90 and 105 DAT (Days After Transplanting). Meanpopulation of S.dorsalis and per cent leaf curl index were computed which were further pooled to get aggregate mean population and leaf curl index over two seasosns. On the basis of this aggregate mean population and per cent leaf curl index values, none of the germplasm was found in highly resistant category. The germplasm collections viz., BC-7-2-1, BC-25 were identified as resistant whereas the genotypes viz., BC-79-1, BC-27-2-2, Utkal Abha (RC), BC-21 and BC- 406 were identified as moderately resistant categories. These may be further utilized as donor parents in developing thecultivars resistant to S.dorsalis

Introgression of Resistance to Leafminer (Liriomyza cicerina Rondani) from Cicer reticulatum Ladiz. to C. arietinum L. and Relationships between Potential Biochemical Selection Criteria

The chickpea leafminer, Liriomyza cicerina (Rondani), is one of the most destructive insect pests of cultivated chickpea (Cicer arietinum L.) in the Mediterranean region under field conditions. For sustainable and environmentally friendly chickpea production, efforts have been devoted to managing the leafminer via decreasing the use of insecticides. Breeding of new resistant varieties is not only an efficient and practical approach, but also cost-effective and environmentally sensitive. To improve resistant varieties, breeders need reliable biochemical selection criteria that can be used in breeding programs. The first objective was to investigate the possible introgression of resistance to the leafminer from C. reticulatum Ladiz. (resistant) to C. arietinum (susceptible), then, to estimate inheritance of resistance to the leafminer for efficient breeding strategies, and finally, to study organic acid contents as selection criteria. Recombinant inbred lines (RILs) and their parents were evaluated using a visual scale of 1–9 (1 = free from leafminer damage and 9 = mines in more than 91% of the leaflets and defoliation greater than 31%) in the field under natural infestation conditions after the susceptible parent and check had scores of >7 on the visual scale. Superior RILs were found for resistance to the leafminer, and agro-morphological traits indicating that introgression of resistance to leaf miner from C. reticulatum to C. arietinum could be possible using interspecific crosses. The inheritance pattern of resistance to the leafminer in RILs was shown to be quantitative. Organic acids, including oxalic, malic, quinic, tartaric, citric and succinic acids in RILs grown in the field under insect epidemic conditions and in the greenhouse under non-infested conditions were detected by using high performance liquid chromatography (HPLC). In general, organic acids were found to be higher in resistant RILs than susceptible RILs. Path and correlation coefficients showed that succinic acid exhibited the highest direct effects on resistance to the leafminer. Multivariate analyses, including path, correlation and factor analyses suggested that a high level of succinic acid could be used as a potential biochemical selection criterion for resistance to leafminer in chickpea. Resistant RILs with a high seed yield resembling kabuli chickpea can be grown directly in the target environments under leaf miner infestation conditions.

Inheritance and Expressivity of Neoplasm Trait in Crosses between the Domestic Pea (Pisum sativum subsp. sativum) and Tall Wild Pea (Pisum sativum subsp. elatius)

The Neoplasm trait in pea pods is reported to be due to the lack of ultraviolet (UV) light in glasshouse conditions or in response to pea weevil (Bruchus pisorum L.) damage. This pod deformation arises from the growth of non-meristematic tissue on pods of domesticated peas (Pisum sativum L. subsp. sativum). Neither expressivity, nor the effect of pea weevil on neoplasm in the tall wild pea (P. sativum L. subsp. elatius (M. Bieb.) Asch. & Graebn.), have been adequately studied. We aimed to study the expression and inheritance of neoplasm in the tall wild pea and crosses between domesticated and tall wild peas grown in the glasshouse (without pea weevils) and in the field (with pea weevils) under natural infestation conditions. Neoplasm was found in all pods in tall wild peas when grown in the glasshouse, while it was not detected on pods of field-grown plants despite heavy pea weevil damage. In inter-subspecific crosses between P. sativum subsp. sativum and P. sativum subsp. elatius, all F1 plants had neoplastic pods, and the F2 populations segregated in a good fit ratio of 3 (neoplasm): 1 (free from neoplasm) under glasshouse conditions, which suggests that neoplasm on pods of the tall wild pea was controlled by a single dominant gene. Expressivity of neoplasm in the progeny differed from parent to parent used in inter-subspecific crosses. There was no relationship between neoplasm and damage by pea weevil under heavy insect epidemics under field conditions. The neoplasm occurring under glasshouse conditions may be due to one or to a combination of environmental factors. Since wild peas are useful genetic resources for breeding programs aiming at fresh pea production that could be utilized under glasshouse conditions, negative selection could be considered in segregating populations.

Evaluation of Common Bean (Phaseolous vulgaris L.) Varieties for the Reaction of Common Bean Anthracnose (Colletotrichum lindemuthianum) at Sirinka, Eastern Amhara, Ethiopia

Common bean (Phaseolous vulgaris L.) is the most important food legume consumed as source of protein and cash crop in Ethiopia. The production of the crops is constrained by biotic and abiotic factors. Common bean anthracnose caused by the fungus Colletotrichum lindemuthianum is a major production constraint in common bean growing regions of Ethiopia. Field experiment was conducted at Sirinka Agricultural research center during 2017/18 main cropping season to evaluate reactions of common bean varieties to the disease. The experiment consisted of twenty two common bean varieties evaluated for the reaction to anthracnose under natural infestation conditions. The highest disease severity (58%) was recorded from Awash-1 variety while the lowest disease severity (45%), was recorded from Awash Melka variety at final assessment day. The highest (3.03 t ha-1) yield was recorded from Awash Melka variety while the lowest (0.97 t ha-1) yield was recorded from KAT-B1 variety. From the present study, it is possible to conclude that, the advantage of screening resistant verities increases the opportunity to select for a broad range of anthracnose resistance and help to know the variability of the common bean anthracnose disease.

Resistance to red mite in Coffea arabica genotype introgressed with Coffea racemosa genes

The aim of this study was to assess the resistance to red mite (Oligonychus ilicis) in Coffea arabica genotypes with introgression of genes from a different species (Coffea racemosa). The experiment was conducted in a greenhouse at IAPAR (Londrina, PR, Brazil), between January 2016 and January 2017. The experiment was conducted in a completely randomized design with five genotypes, 12 replications of one plant per plot. The C. arabica cultivars IPR 100, IPR 99 and IPR 103 were evaluated as well as an F4 Arabica coffee line IAPAR H0113-40-26-10 with introgressed C. racemosa genes. Catuaí Vermelho IAC 99 cultivar, which is a pure C. arabica, was used as a susceptible control. In conditions of high natural infestation of red mite, the resistance of coffee genotypes was evaluated using a standard visual evaluation in January 2017. This evaluation was based on the percentage of leaf area with typical symptoms caused by this mite. Only one genotype, the F4 line IAPAR H0113-40-26-10 showed resistance to the red mite because present less leaf area with symptoms compared to other genotypes. The Arabica coffee cultivars IPR 99, IPR 100 and IPR 103 are as susceptible to red mite as to the susceptible control Catuaí Vermelho IAC 99.

Integrated Management of Tomato Whitefly Under Greenhouse Conditions

The whitefly Bemisia tabaci (Gennadius, 1889) is a major pest species in many agricultural crops worldwide. Growers from the Vale do Caí region, in Southern Brazil (Rio Grande do Sul state) have been facing severe economic losses due to the increasing damages caused by this sucking insect in their horticultural crops. Small-scale farming in the Vale do Caí region relies heavily on horticulture, with many families involved in the activity and a consumer market spread throughout the whole state. Virus transmission and other damages inflicted by B. tabaci are especially harmful to tomato plants, and the managing of the pest currently demands two thirds of all chemical insecticides used in the region. While chemical control remains the main strategy for whitefly management on tomato crops, control failures and lack of updated information have led tomato growers to raise the number of sprays per crop cycle, with selection of resistant populations and harmful effects on the environment as consequent risks. The aim of this work was to evaluate chemical compounds and bioinsecticides in the control of B. tabaci nymphs and adults on tomato plants grown in two different greenhouses and under natural infestation conditions. The most efficient treatment for the control of B. tabaci adults was cyantraniliprole + lambda-cyhalothrin (50+30 g a.i. ha-1) with 64% of average control efficiency. As for nymph control, the most efficient treatment was the Embrapa formula, a bioinsecticide composed of 0.5% flaxseed oil + 0.5% neutral detergent + 0.3% sodium bicarbonate, which resulted in 72% of whitefly control in average.

Host Suitability of Weeds to the Root Lesions Nematoid in Soybean Areas in the North of Goias, Brazil

Several studies have done more on weed and nematode hosts. It is important to know a host of weeds and P. brachyurus in areas cultivated with soy. This nematode can stay in weed roots even in the absence of plants grown in the off-season, making it difficult to control them. The objective was to evaluate the host suitability of emerged weed species in cultivated areas with a soybean crop to the P. brachyurus nematode under natural infestation conditions. The surveys were conducted in commercial properties located in the municipalities of Campinorte and Rialma, both in the northern region of the state of Goias, Brazil under the no-tillage and conventional system, respectively, with a history of high nematode population densities. We evaluated 19 weed species with the highest expressivity in the properties. The population densities of the nematode ranged RFom 23 to 17,113 and 55 to 4,221 specimens per 10 grams of roots respectively. All as weed species evaluated as hosts of P. brachyurus. As species, Hyptis suaveolens, Sida cardifolia, Senna occidentalis, Coneyza canadensis and Commelina benghalensis had low population densities.

Development of Oryzophagus oryzae (Costa Lima) in rice cultivars

ABSTRACT Insect-resistant cultivars are essential for improving the management of pests such as Oryzophagus oryzae (Coleoptera: Curculionidae), which significantly decreases flooded rice yields. However, the degree of benefit brought to the crop varies with the type of resistance. This study aimed to evaluate the resistance of rice cultivars to O. oryzae, inferring about antixenosis and antibiosis effects on the development of larvae and adults. Under natural infestation conditions, a biennial experiment was carried out using a latin square design, with six treatments (cultivars) and plots with 30 plants (five rows of six plants equidistant 20 cm) irrigated with water depth of 15 cm. The number and weight of larvae by size, as well as the number, weight, emergence rate, and sex ratio of adults, were evaluated using standard soil, plant and root samples. Except for adult sexual ratio, the cultivars differed (p ≤ 0.05) for the other variables, whose relationship evidenced antibiosis effects at the larval stage, making possible to conclude that: the BRS Firmeza cultivar has resistance to O. oryzae due to antixenosis and/or antibiosis effects; BRS Ligeirinho is susceptible to this insect species, resulting in a relatively higher number of well-developed larvae and adults; and IRGA 417 shows an antibiosis action, restricting the adult emergence rates. The weight of adults gives a greater accuracy to the evaluation of the harmful effects of rice cultivars on the O. oryzae development.

Revealing of resistant sources in Cicer species to chickpea leaf miner, Liriomyza cicerina (Rondani)

The chickpea leaf miner, Liriomyza cicerina (Rondani) (Diptera: Agromyzidae), is an important pest of cultivated chickpea (Cicer arietinum L.). A 2-year field study was carried out to screen a total of 126 Cicer germplasm for resistance to the leaf miner during the 2012 and 2013 growing seasons. Resistance was evaluated using a visual scale of 1–9, where 1 = highly resistant and 9 = very highly susceptible under natural infestation conditions. The results showed that two C. arietinum accessions, ILC 3397 and Sierra, had a score of 9 on the scale, being very highly susceptible. Three germplasm, one mutant (3304) and two breeding lines (LMR 140 and LMR 160) of C. arietinum, were found to be highly resistant with the scores ranging from 1.5 to 2 for resistance to the leaf miner. The mutant, 3304, was detected for the first time in this study as a highly leaf miner-resistant mutant of the cultivated chickpeas while the other two breeding lines had been previously reported as highly resistant against the leaf miner. In addition, two mutants and 14 breeding lines of C. arietinum and two mutants and one germplasm of C. reticulatum were identified as resistant having the scores from 2.1 to 3 on the 1–9 scale. The results suggest that these resistant germplasm may add a new dimension to chickpea breeding programs because they possess valuable traits for resistance against the pest. The resistant chickpeas that can be grown without using pesticides are important as environmental protection and reliable food source for human health.

The combining ability of popcorn S7 lines for Puccinia polysora resistance purposes

ABSTRACT The present study resulted from the lack of information on the genotypic expression ruling the resistance to rust and on the main traits of economic importance to the herein addressed crop. The combining ability of 16 popcorn lines and hybrids was assessed in partial diallel cross in two representative locations in Rio de Janeiro State, Brazil, where forty simple hybrids were obtained. The experiments followed a completely randomized block design with four repetitions and were conducted under natural infestation conditions in order to test the southern rust severity in the entire plant (SSW) and in the leaf of the first ear (SFPE), as well as the morpho-agronomic traits of greater interest: grain yield (GY) and popping expansion (PE). Additive gene effects prevailed in PE and the non-additive ones stood out in GY; however, both gene effects were important to the southern rust resistance characteristics (SSW and SFPE). Hybrids L65 × P10 and P7 × L70 presented appropriate specific combining ability (SCA) values in all traits; therefore, they were promising for the selection of superior genotypes. Lines L80, L76 and L77 expressed negative general combining ability (GCA) values in SSW and SFPE; line P10 recorded high and positiveGCA values in GY and PE.

Efficacy of <em>Metarhizium anisopliae</em> in the control of the horn fly, <em>Haematobia irritans</em> (<em>Diptera: Muscidae</em>), under natural infestation conditions

Veterinaria Mexico OA ISSN: 2448-6760 Cite this as: Cruz Vazquez C, Carvajal Marquez J, Lezama Gutierrez R, Vitela Mendoza I, Angel Sahagun CA. Efficacy of Metarhizium anisopliae in the control of the horn fly, Haematobia irritans ( Diptera: Muscidae ), under natural infestation conditions. Veterinaria Mexico OA. 2017;4(2). doi: 10.21753/vmoa.4.2.384 . The aim of this study was to determine the efficacy of the entomopathogenic fungus, Metarhizium anisopliae strain 134 (Ma134), for dairy cattle naturally infested with Haematobia irritans (L.) An aqueous formulation of 1 x 10 8 conidia/ml was applied by aspersion on a group of eight cows every seven days for a total of four applications, while a control group was sprayed with the same solution without conidial content. The degree of horn fly infestation was estimated daily in both groups by the direct count of adult flies found resting or feeding on the animals, and Abbott’s formula was used to calculate the effectiveness of the formulation. The Ma134 formulation resulted in a 68.6 % reduction of the fly infestation during the study period, and a significant reduction was observed from the first week post-application ( p < 0.05). The results show that the Ma134 formulation is effective in reducing infestations of horn fly, H. irritans , on dairy cattle under natural conditions. Thus, the fungus, Ma134, can be considered a candidate for biological control for the integrated management of H. irritans . Figure 1. Infestation index of horn flies, Haematobia irritans , on cows treated with the aqueous formulation of Ma134

GENE EXPRESSION INDUCED IN FABA BEAN (Vicia faba L.) BY Orobanche crenata AND ITS IMPACT ON THE FIELD LEVEL

Twenty five faba bean (Vicia faba L.) genotypes were evaluated under broomrape (Orobanche crenata L.) natural infestation conditions for their growth and yield characteristics as well as the gene expression of some tolerance genes. Analysis of variance of the morphological traits revealed highly significant differences among the genotypes for all the morphological traits. The results of some yield related traits such as number of pods/plant, number of seeds/pod and number of seeds/plant were significantly increased in the Egyptian broomrape-tolerant genotypes “Giza843”, “Misr1” and “Misr3” and in the foreign genotype “FAB476”. On the other hand, “Nubaria1” genotype was worst genotype to defeat broomrape growth in which the highest number of O. crenata spikes/row and O. crenata spikes/plant was obtained (broomrape-susceptible genotypes). Cluster analysis of yield related traits distingweshed between broomrape tolerant and susceptible genotypes as well as between Egyptian and foreigner genotypes. Gene expression was assessed using Reverse Transcriptase PCR (RT-PCR) to study genes transcript accumulation during early (35 days) and late stages (50 days) of infestation. RT-PCR results revealed a kind of coexpression in common defense genes such as (HMG gene) and broomrape specific defense genes such as (C4H gene) in the most tolerant genotype “Misr1”. It is possible to conclude that yield related traits and the molecular results revealed that faba bean cultivar “Misr1” was the most broomrape tolerant cultivar and “Nubaria1” was the broomrape susceptible cultivar.

Selección recurrente recíproca en maíz: tolerancia al ataque del gusano de la mazorca y el cogollero (Lepidoptera: Noctuidae).

The progressive selection of yield, agronomic characteristics and quantification of damages caused by Spodoptera frugiperda (J.E. Smith) and Helicoverpa zea (Boddie), were evaluated after four selection cycles on maize populations (Zea mays L., varieties Ohio S9, Ohio S10, Mayorbela and Diente de caballo, under chemical control and natural infestation conditions. The experiments were carried out at an experimental site in a tropical agriculture research station (TARS), a USDA station located in Isabela, Puerto Rico. The experimental design consisted of random entire blocks with five repetitions, and treatments were asigned according to a factorial arrangement with parcels divided at a density of 44.444 plants/ha. Significant differences were found among populations and selection cycles for yield, plant and cob height, and percentage of insect-related losses*. The highest yield was obtained from the Ohio S 10 population with 4.824 kg/ha, and 169 kg/ha - a profit of 1.2% per selection cycle. The latest selection cycles showed a greater yield and better agronomic characteristics than the initial selection cycle of each population under improvement. Losses in yield caused by S. frugiperda and H. zea oscillated between 3-21 % and 17-28%, respectively. Ohio S9 showed the greatest los s in yield caused by these insects.

Host suitability of soybean and corn genotypes to the root lesion caused by nematode under natural infestation conditions

ABSTRACT: Among the nematode management strategies, genetic resistance is one of the most appropriate and desirable. However, resistant soybean and corn genotypes resistant to Pratylenchus brachyurus are not available up to the moment. The objective of this study was to evaluate the host suitability of 50 soybean and 38 corn genotypes to P. brachyurus under natural infestation. Soybean genotypes BRSGO Chapadões, BRSGO Paraíso, M-Soy 7211 RR, M-Soy 8008 RR, Emgopa 313 RR, M-Soy 8411, BRSGO Juliana RR, Emgopa 316 RR, BRSGO Luziânia RR and TMG 103 RR, and corn genotype Agromem 30A06 reduced the nematode population during the evaluation period.

Efficiency of insecticide and bioinsecticide treatments against infestation of European corn borer and their effect on maize yield

During 2008 and 2009, efficacy of insecticidal products, based on thiamethoxam and imidacloprid, were tested. Furthermore, effects of entomophatogenic fungus Beauveria bassiana on the infestation intensity of European corn borer (Ostrinia nubilalis), were established over effects of both, 10 different treatments of maize seed (8 treatments and 2 controls) and the application of the fungal inoculum. Trials were carried out on maize crop under field conditions in accordance with the EPPO method. Results obtained in the studies with the product Cruiser 350 FS (350g l-1 thiamethoxam) applied in the amount of 0.9 l per 100 kg of seed and the products Imidor 600 FS and Gaucho 600FS (600g l-1 imidacloprid) applied in the amount of 0.7 l per 100 kg of seed, point out to satisfactory efficacy in controlling ECB and satisfactory effects on maize yields. The intensity of ECB infestation, expressed in percentages, ranged from 50.1% to 74.1%. The interrelation between average percentages of infested plants and obtained yields in both investigation years (2008-2009) in Zemun Polje was established. Results over treatments indicate that the highest percentages (62.2%) of infested plants were observed in the control variant (K1- Captan). Moreover, as expected, the lowest yield was also recorded in this variant. The treatment with the fungicide Maxim combined with the insecticide Criuser proved to be the most efficient. At the same time, the percentage of infested plants was the lowest in this treatment (53.32%) and the yield was the highest (8.610 t ha-1). The infestation level of maize plants in this treatment was significantly reduced over years of investigation in comparison with remaining treatments. Meteorological factors during the years of investigation, especially unfavourable agroecological conditions in 2009, affected the average yield of maize per hectare. The yield (8.314 t ha-1) recorded in the treatment with the inoculum of B. basssiana was almost equal to the one recorded in the treatment with the product Cruiser (8.610 t ha-1), while it was higher than the yield obtained in the treatment with the products Gaucho (7.506 t ha-1) and Imidor (8.259 t ha-1) combined with the fungicide Maxim. These differences were not statistically significant. Seed treatments with the fungal inoculum were not significantly different in any of observed parameters, except in the seed treatment with Captan. The comparison of data obtained in the two-year studies (2008-2009) under conditions of natural ECB infestation, shows prevalence of plants with damages of leaves (type H2) and tassels (type M3-4), which is indicated with the average score of 2.43. According to the average scores, it can be concluded that ECB infestation did not result in damages that would have significantly affected maize yield. In order to establish significance of certain observed parameters, they were compared and their correlations were determined. The greatest negative correlation with the 0.05 probability level (r= -0.96533) was established between the plant damage score and the recorded yield. Since recorded value of coefficients of correlation was approximately 1, it can be stated that the complete functional linear dependence existed among variables. Achieved results show efficiency of insecticides based on thiamethoxam and imidacloprid in the regulation of the infestation level in maize and also point to negative effects of the fungus B. bassiana on entomofauna of maize and its mycoinsecticide activity that could find an application in biocontrol of insect pests of maize.