Pest Managment Journal of Ethiopia

Occurrence and Pathogenicity of Entomopathogenic Nematode Isolates in Maize Growing Regions of Ethiopia

Tesfaye Hailu — 2021-10-01

The objective of this study was to find and test entomopathogenic nematodes (EPNs) native to regions of Ethiopia where maize is grown with the aim of developing a biocontrol program against fall armyworm (FAW) Spodoptera frugiperda (Smith) and other arthropod pests. Six hundred seventy-nine soil samples were collected from eight regional states of Ethiopia between August and October 2019. From these collections, 28 EPN isolates, 13 from Steinernema genera and 15 from Heterorhabditis genera have been identified. All the 28 isolates identified from the survey and nine Ambo Agricultural Research Center’s isolates were tested using a single dose (500 infective juveniles ml^-1(IJ)/ml) under laboratory conditions using FAW larvae in completely randomized design. Isolates, such as Aso-Tes-287 from Steinernema genera and Am-Ger-Tes-74, Am-Adm-Tes-369, and Z9 from Heterorhabditis genera caused significant larval mortality within eight days. Moreover, the LT₅₀ values i.e., 3.5 to 6.7 days showed that these isolates are more virulent. These most virulent isolates were further tested for their potential in a pot experiment under wire house conditions at three different concentration levels (250, 400, and 600 IJ/ml) in randomized complete block design. The isolates Aso-Tes-287 and Am-Ger-Tes-74 resulted in higher mortality of 74.7% and 78.3%, respectively at 600 IJ/ml. The EPN isolates Aso-Tes-287 and Am-Ger-Tes-74 which caused higher mortalities within shorter periods, were promising bio-agents for the management of FAW. A confirmatory study is suggested to use the two promising bioagents for the management of FAW and other arthropod pests.

Detection and molecular identification of some plant parasitic nematodes associated with ornamental plants from Jimma, Ethiopia

Abebe W. Aseffa — 2021-10-01

There has been a concerning presence of phytoparasitic nematodes on annual and biennial ornamental plants at Jimma University's agriculture campus. Rhizosphere soil samples were collected to elucidate the presence of plant parasitic nematodes associated with ornamental plants. The samples were collected from three locations of eleven different ornamental species, including Agapanthus africanus, Canna generalis, Cuphea ignea, Dahlia hybrids, Dianthus barbatus, Gerbera jamesonii, Impatiens balsamina, Impatiens hybrids, Pelargonium spp., Tagetes erecta and Zinnia elegans. Nematodes were extracted from 100 ml aliquot soil using the modified Baermann tray method. The study identified ten genera of plant parasitic nematodes, including Helicotylenchus, Hemicycliophora, Hoplotylus, Meloidogyne, Mesocriconema, Paratylenchus, Paratrichodorus, Scutellonema, Telotylenchus, and Trichodorus. Helicotylenchus was the most dominant genus with a mean population density of 126 individuals/100 ml soil, a frequency of occurrence (FO) of 64%, and a prominence value (PV) of 101 among all sampled ornamental plant species. Meloidogyne and Scutellonema followed with mean population densities of 129 and 70 individuals/100 ml soil, FOs of 48% and 39%, and PV of 89 and 44, respectively. The least important genera were Paratylenchus and Trichodorus, with an FO of 3% and mean nematode population densities of 10 and 17 individuals/100 ml soils, respectively. Molecular identification based on 18S small subunit (SSU) ribosomal DNA (rDNA) gene sequences revealed the species identity of Scutellonema bradys, Hemicycliophora conida and Telotylenchus ventralis. This study provides valuable information on nematodes associated with ornamental plant species vital for developing management plans in future landscape maintenance.

Applying Aqueous Crude Leaf Extracts and Organic Soil Amendments Manages Meloidogyne incognita on Hot Pepper

Beimnet Abegaz — 2021-10-01

The root-knot nematode, Meloidogyne incognita, can severely damage hot pepper plants (Capsicum annum and C. frutescens). Therefore, it is crucial to develop effective management strategies. The impact of aqueous crude leaf extracts from Vernonia amygdalina and Lantana camara and organic soil amendments with vermicompost and poultry manure was investigated in an open-field pot experiment on three pepper genotypes (Oda Haro, Acc.03, and Melka Awaze). The growth performance, yield, and nematode population were assessed. Twenty-seven treatments, including the untreated checks, were arranged in a factorial RCBD in three replications. Plots treated with leaf extracts and/or organic soil amendments resulted in significantly lower number of root galls, egg masses, and nematode populations than the untreated checks in all the pepper genotypes. The combined treatments were more effective than individual treatments in all the genotypes. The lowest nematode population was on the genotype Melka Awaze Lantana camara with vermicompost on genotype Melka Awaze, L. camara with poultry manure on genotype Oda Haro, and V. amygdalina with vermicompost on genotype Acc.03 sustained fewer root galls, egg masses and nematode populations. On the genotype ‘Oda Haro’, the untreated control gave significantly lower values for the number of pods, marketable pods, number of branches and plant height than the remaining treatments except V. amygdalina applied without soil amendments for number of branches. Similarly, on the genotype‘Acc.03’, except L. camara without soil amendments for number of branches and V. amygdalina and poultry manure for plant height, values were significantly lower in the untreated control than the other treatments. Vermicompost enhanced the growth and yield of pepper and reduced the number of root galls, egg masses and nematode populations. Therefore, applying leaf extracts and organic soil amendments appeared promising to control M. incognita.

Insecticidal Potency of a New Bioactive Dipeptide from Bacillus velezensis AR1 Culture Supernatant Against Myzus persicae

Regassa Ayana Bayisa — 2021-10-01

The green peach aphid (Myzus persicae) has become a worldwide challenge causing high yield losses through direct plant attack and transmission of plant pathogens. A widespread resistance development against synthetic agrochemicals by the aphid and the negative impact of the chemicals used to manage the pest on human health, other organisms and the environment are other problems. Therefore, the aphicidal potency of the secondary metabolite from Bacillus velezensis AR1 was investigated under in-vitro conditions. The purification process was conducted using solid-phase extraction by Strata SI-1 column, thin-layer chromatography (TLC) and high-performance liquid chromatography (HPLC). Then, the purified EA3T3 fraction was analysed with the nuclear magnetic resonance (NMR ¹H,¹³C, H-H COSY, HSQC, and HMBC) and the metabolite was identified as 5-N-tyrosinylornithine. The aphicidal potency of the metabolite on Myzus persicae mortality was tested using three concentrations over 24 to 72h periods of exposure in a laboratory bioassay in comparison with a biopesticide E-II. The biopesticide EII caused the highest mortality of the aphids; 89% at 72 hr. The purified metabolite caused a mortality rate of 40.74±6 to 66.67±5% at 1 to 4µg mL^-1 concentrations after 72h of exposure. The aphid mortality increased with the increase in concentration and duration of exposure to EA3T3. The lowest LD₅₀ was attained at 72h of exposure. Therefore, the bioactive metabolite produced by B. velezensis AR1 is potent against the green peach aphid Myzus persica and has the potential to be used for the management of aphids.

Insecticides for the Management of Tef Epilachna (Chnootriba similis Thunberg, Coleoptera: Coccinellidae) in Barley in Wolaita Zone, Southern Ethiopia

Workneh Wotaro — 2021-10-01

Tef epilachna, Chnootriba similis, is an important pest of cereal crops in Ethiopia. It causes significant yield loss on barley under heavy infestation. The efficacy and application time of five foliar insecticides were evaluated to control C. similis on barley in two districts of Wolaita, southern Ethiopia during the short “Belg” and the main “Meher” rainy seasons of 2020. The trial was factorial in a randomized complete block design with three replications. The treatments were combinations of five insecticides (carbaryl, diazinon, imidacloprid, λ-cyhalothrin, malathion) and two application times (early and late). Early applications (tillering stage) of insecticides were either better or on par with the late applications (booting stage) in the two seasons and locations in terms of mortality of larvae, leaf damage and grain yield. Higher larval mortalities were recorded for the insecticides λ-cyhalothin (87 - 100%), carbaryl (84 – 100%), diazinon (78 – 99%), malathion (86 – 100%), and imidacloprid (71 – 97%). Barley protected with insecticides against C. similis had lower leaf damage and resulted in significantly higher yield. The insecticides carbaryl, λ-cyhalothrin, malathion, diazinon, and imidacloprid, applied at the early tillering stage of barley can effectively control C. similis on barley. The insecticide λ-cyhalothrin that consistently provided higher protection and gave the highest return is the best choice for the control of C. similis.