Identification et occurrence des fourmis dans les champs de manioc au centre de recherche de Mvuazi

Afrique SCIENCE 12(6) (2016) 383 – 390

ISSN 1813-548X, http://www.afnquescience.info

Identification et occurrence des fourmis dans les champs de manioc au centre de
recherche de Mvuazi

Desvid Kupesa B. MFÜÏl12‘, Heritier B a ton gu MEHAKUNTUÂLA2,

Emmanuel Nkulukuta BÂMBÂLA1, Hermane Kuavingids L0MG§2,

Toussaint B. KUSPESA2, et Albert Ki-Munseks LEMA2

‘ institut National pour l’Etude et ta Recherche Agronomiques, Centre de Mvuazi, SP2637, RD Congo
2institut Supérmur dCtudes Agronomiques de Mvuazi, RD Congo

* Correspondance, courriel : daviukupesa@gmait.com

Résumé

L’identification et l’abondance des fourmis colonisant les champs du manioc au centre de recherche de M VUAZI, en particulier dans les sites de Mankewa et celui de NdimbaVata a été l’objet de la recherche menée dans cette étude. Quatre sous familles comprenant six genres des fourmis ont été identifiés. Les sous familles des fourmis identifiées sont constitués de Doryîinea, Ponerinaejormicinae et Myrmicinae. Dans ces sous familles, les genres identifiés comprennent : Doryiusvç., Odontomachus Pheidoie^., Componotus vp.et Myrmicaria sp. En faisant une étude comparative entre la diversité des fourmis de Mvuazi avec celle du territoire de Tshela, infestée à la Cochenille Africaine des Racines et Tubercules (CART). Il a été constaté du point de vue écologique que si par risque il y aurait Infestation de Sa cochenille à Mvuazi, ce ravageur pourrait se maintenir suite à îa présence du genre Pheidoie vp. qui jouerait le rôle de partenaire secondaire en lieu et place de AnopioiepisypAaws la symbiose avec la CART.

Mots-clés : fourmis, identification, manioc, symbiose, Mvuazi.

Abstract

Identification and occurrence of ants m cassava fields at Mvuazi research center

Identification and abundance of ants colonizing cassava field in Mvuazi Research Center particularly in Mankewa and NdimbaVata sites were investigated in this study. Four subfamilies including six ant’s genera were identified. Genera identified were Doryius sp., Odontomachus sp., Pheidoie sp., Componotus sp. et Myrmicaria sp. belonged to subfamilies Dorylinea, Ponerinae, Formicinae and Myrmicinae respectively. Comparing ant diversity of Mvuazi w:th the one of Tshela territory infested by the African Root and Tuber Scale (ARTS). It is appeared obviousiythat there is a high risk for ARTS invades Mvuazi. This could he due to the ant genus Pheidoie sp. which could play a role of alternative partner to ARTS and maintained their symbiosis in replacement of Anopiofepisvg

Keywords : ants, identification, cassava, symbiosis, Mvuazi.

David Kopesa B. MF1JTI et ah

Auteur : David Mfuti Batoba Kupesa

Chercheur base à l’INERA Mvuazi

Situation actuelle : En formation de doctorat en Entomologie au Centre International de Physiologie et Ecologie des Insectes a Nairobi/Kenya

  1. Publications dans Ses journaux internationaux:

Mfuti, D.B.K., Subramanian, S., van Toi, R.W.H.M., Wiegers, G.L., De Kogel, W.J.,

Niassy, S., Du Plessis, H., Ekesi, S. and Maniania, N. K.                                  Spatial

separation of semiochemica! Lurem-TR and entomopathogenic fungi to enhance their compatibility and infectivity in an autoinoculation^system for_thrips management. Pest Management Science, 72^

D.B.K., Subramanian S., Niassy S., Saiifu D7, d^TPlessis H., Ekesi S., and Maniania N K. (2018) Screening for attractants compatible with Metarhizium anisopliae for use in thrips management. Accepted for publication in Journal of v . African Biotechnology, (fa

Mfuti D.B.K., Niassy S., Subramanian S., du Plessis H., Ekesi S., and Maniania N.K.(2016) Lure and infect strategy for application of entomopathogenic fungus for the control bean flower thrips in cowpea. Manuscript submitted to Journal of Pest Science.

  1. Conference proceedings:
  • Tata, H.K., Mfuti, Tuwizana, N., Lema, K.M. and Mahungu, N.M.

(2012) Thrips (Thripidae; Tysanoptera) infestation on cassava (Manihot esculenta Crantz) at Mvuazi research station, Bas Congo province in Democratic Republic of Congo, in: Tropica! Roots and tuber Crops and the challenges of globalization and climate changes, (ed. by R.U. Okechukwu & P. Ntawuruhunga) ‘STC-AB Memling hotel, Kinshasa, DRC pp. 406-410.

  • Mfutf Subramanian S., Niassy , du Plessis H., Ekesi S., and Maniania N
  1. (2913) Effect of spatial separation of semiochemicai LUREM-TR on persistence of Metarhizium anisopliae, thrips attraction and conidia! acquisition in an auto-dissemination device and prospects for the management of Megalurothrips sjostedti. Association of African Insect Scientists(AAIS), Octobre 24-28 2013; Yaounde, Cameroon
  • Maniania, N.K., Subramanian, , Dimbi, S., Migiro, L. N., Niassy, S., Mfuti, D.8.K.

and Ekesi S. (2014). Mutualistic affairs between biopesticides and semiochemicais against insect pests in horticulture. Entomoiogicai Society of Ame ncs Annua! Meeting. ESA 62nd Annua! Meeting, November 16 -19, Portland, Oregon, USA

 

  • Mfuti, B.K., Subramanian, S., Niassy, S., du Plessis, H., Ekesi, S. and Maniania,

N.K. (2015) Enhancing compatibility between entomopathogens and thrips semiochemicals. In Xthlnternational Symposium on Thysanoptera and Tospoviruses. Asilomar, conference grounds May16-20, California, USA.

  • Niassy, S., Ekesi, S., Subramanian, S., Fiaboe, K., Thibaud, M., Akutse, K.S.,

Muvea, A., Nyasani, J., Mutune, B., Mfuti, K., Hundessa, W., Azandémè- Hounmalcn, G. and Maniania, N.K. (2015) Improved biopesticide application strategies for insect pest management in Africa. Proceeding of the XVIIIth international Plant Protection Congress Mission possible – food for all through appropriate plant protection, at Berlin, Germany, 24 – 27th August 2015.

  • Mfuti 3.K., Subramanian S., Niassy S., Salifu D., du Plessis H., Ekesi S., and

Maniania N K. (2015) Screening for attractants compatible with Metarhizium anisopliae for use in thrips management. Association of African Insect Scientists(AAIS). October 19-23, 2015; Cotonou, Benin

  1. Publications dans les journaux nationaux:

3.1 Mfuti, D.B.K., Lema, K.M., Hanna, R., and Hauser, S. (2011) Abundance and diversity of ants in the fields of cassava under removal of hosts’ plants of African Root and Tuber Scale at secondary forest zone of Tshela in RD.Congo., Accepted for publication in Crop sciences faculty annals, UNIKIN, 2012. Annales de la faculté des sciences agronomiques 3-11

3.2 Mfuti, C.B.K., Hanna, R., uema, K.M., Eleko, N., Kiatoko, M., and Tuwizana, N., Hauser, S. (2011) Removal of hosts plants of African Root and Tuber Scale (ARTS) (Sf/ctococcus vassierei Homoptera:Stictococcidae) to reduce its density on cassava fielo at Tshela in DRC. Annales de la faculté des sciences

 

iTaJPcXA MfM/r

acadenücjournals

Vol. x(x), pp. xxxxx, x xx, 2016

DO1: xxxxxxxxxxxx

Article Number: xxxxx

issN 1684-5315                                                                                                              African Journal of Biotechnology

Copyright© 2016

Author(s) retain the copyright of this article

http:Mvww.academicjournals.org/AJB

 

Full Length Research Paper

Screening for attractants compatible wath
entomopathogenic fungus Metarhizium anisopliae for

use m thrips management

David Kupesa Mfyîf’2, Sevgan Subramanian*, Saliou Niassy1, Daisy SalifiP, Hannalene du

?jessis2> Sunday Ekes:1 and Nguya Kalemba Maniania1*

international Centre of Insect Physiology and Ecology (icipe), Duduville Campus, P. O. Box 30772-00100,
Nairobi, Kenya.

2Unit for Environmental Sciences and Management, North-West University, Private Bag X6001, Potchefstroom 2520,
South Africa.

Received 4 December, 2015; Accepted 21 March, 2016

Several thrips attractants were screened for compatibility with Metarhizium anisopliae (Metchnikoff) Sorokin (Hypocrsales: Clavicspitaceae) and a subset of these for attraction to Megalurothrips sjostedti Trybom (Thysanoptera: Thripidae). Conidial germination and germ tube length of M. anisopiiae were used as indicators of its compatibility with thrips attractant. Conidial germination and germ tube length differed significantly according to volatiles of different attractants. The highest conidial germination (76.5±3.5%) and longest germ tube length (130.3±13.4 pm) were recorded in the control, followed by methyl anthraniiate (63.8±3.8%; 103.8×8.4 pm), cis-jasmone (61.8+5.9%; 93.8±14.4 pm) and trans- caryophyllene (57.7×5.5%; 96.3±i5.5 pm) whicn were founo compatible with M. anisopiiae. A Pearson correlation test indicated a significant positive correlation oetween conidiai germination and germ tube length (r =0.6; P<0.0001). The attraction of M. sjostedti to selected thrips attractant also varied significantly among the attractants. Under field conditions, methyl anthraniiate was equally attractive to M. sjGsiedi as Lurem-TR and could be recommended as a thrips attractant that can be combined with M. anisopiiae in auto inoculation devices for potential control of M. sjostedti.

Key words: Semiochemicais, conidial germination, germ tuoe length, Megalurothrips sjostedti, attraction, persistence, field.

INTRODUCTION

 

 

 

*Corresponding author. E-mail: nmaniania@icipe.org. Tel: +254-20-8632072. Fax: +254-20-8632001/2.

Author(s) agree that this article remc’ns permanent!’/ open access under the terms of the Creative Commons Attribution License CO Internationa: foense

 

Biological Control 107 (2017) 7Ü–76

Contents lists available at SueneeDirect

Biological Control

journal homepage: www.elsevier.com/locate/ybcon

Lure and infect strategy for application of entomopathogenic fungus for the control of bean flower thrips in cowpea

David K. Mfuti ■ , Saîiou Niassy , Sevgan Subramanian , Hannalne du Plessis Sunday tkesia, Nguya K. Maniania •

 »International Cent re of Insect Physiology and Ecology (icipe), PO Box 30772-00100, Nairobi, Kenya

b Unit for Environmental Sciences and Management, North-West University, Private Bag X6001, Potchefstroom 2520, South Africa

HIGHLIGHTS » Spot and cover sprays of Metarhizium with attractant were compared for the control of Megalurothrips.

  • Spot spray was as effective as cover spray in reducing Megalurothrips populations on cowpea.
  • Both spot and cover application strategies resulted in yield increase as compared to the control.

» Spot spray application recorded the highest rates of benefit returns than cover spray.

 

 

 

ARTICLE INFO
ABSTRACT

 

 

The efficacy of spot spray and cover spray applications of Metarhizium anisopliae (Metsch.) Sorok. in com­bination with the thrips attractant Lurem-TR (methyl-isonicotinate) was compared in field experiments for the management of bean flower thrips (BFT), Megalurothrips sjostedti (Trybom), on a cowpea crop in two seasons (June-December 201 n). Treatments were applied five days after the placement of Lurem-TR in the field. During the first season, BFT densities per plant 5 days post-application were lower in spot spray (10.1 ±4.3) and cover spray (11.5±4.8) treatments than in the control treatment (41.8 + 15.2). In the second season, 5 days post-application, the spot spray treatment recorded the lowest BFT density of 32.5 ± 6.0, followed by cover spray with 40.9 + 7.0 thrips. The control treatment recorded the highest BFT density of 67.4 + 10.3 5 days post-application. Ccnidiai viability and thrips conidial acquisition did not differ between the two application methods. Grain yields of 1430.7 ± 114.2 kg and 1312.1 ± 87.7 kg were obtained in the cover and spot spray treatments, respectively, while 976.8 + 105.2 kg in the control during the second season. The cost benefit analysis indicated profits with the spot spray than cover spray application due to the reduction in labor and the quantity of inoculum used. Spot spray application of biopesticides could therefore be a viable option for small-scale farmers for the management of BFT on cowpea.

© 2017 Elsevier Inc. All rights reserved.

 

 

 

 

Î. Introduction

Cowpea, Vigna unguiciilata L. Walp. (Fabales: Fabaceae), is an important food and cash crop in different parts of the tropics ( i: 1997). It occupies a vital place in human nutrition as a source of protein, vitamins and minerals. In Kenya, cowpea is among the most consumed grain legumes. Its yield is, however, low and cannot satisfy the demand ( vlergor et ai.. 200′.). Annual

* Corresponding author.

E-mail addresses: tavinkupesa@gmail.com (D.K. Mfuti), saliou.niassy@up.ac.za (S. Niassy), ssnbramania@icipe.org (S. Subramanian), hannalene.duplessis@nwu.ac. i (H. du Plessis), M-l;csi@;ci>x’.-.:(S. Ekesi), nmariania@icipc.org (N.K. Maniania).

htipp/dx.doi.org/ id. 1016.’i.bioconirol. 2017,0! .011

1049-9644/© 20)7 Elsevier Inc. All rights reserved.

production of cowpea in Kenya declined from about 83,000 MT in 2007 to about 48,000 MT in 2008, despite an increase in area pianted from around 130,000 in 2007 to about 148,000 ha over the same period (Belmain et ai., 2013; «iprotich et al., 2015). Insect pests are the main factor responsible for the low grain legume pro­duction (Abate et al., 2012; Ajeigbe et aL, 2012), The bean flower thrips (BFT), Megalurothrips sjostedti (Trybom) (Thysanoptera: Thripidae), is considered as key pest that attacks the reproductive structures of cowpeas during plant development (Bzueh, 1381). BFT can cause yield losses ranging from 20 to 100% (Singh and Allen, 1980).

The control of BFT currently relies heavily on synthetic chemical insecticides (Abate and Ampofo, 1996; jackal and Daoust, 1986)

 

Teulon et al., 2014; Broughton et al., 2015). These semiochemicals can be integrated with other control strategies to improve thrips management in horticulture (Suckling et al., 2012; Sampson and Kirk, 2013).

Entomopathogenic fungi (EPF) are among the alternatives to synthetic chemical pesticides being considered for the management of thrips in horticulture (Ekesi and Maniania, 2007). EPF are generally applied through inundative spray, which requires high amount of inocula, thereby enhancing its cost (Jaronski, 2010). Further, the persistence of conidia applied on foliage is challenged by several environmental parameters such as UV light, rain, temperature (Inglis et a!., 2000; Jaronski, 2010). The use of ‘lure and Kill” strategy using autoinocuiation device or spot spray application could reduce the amount of inoculum, the cost and sustain fungal persistence in the field (Dimbi et al., 2003; Nana et al., 2014; Mfuti et al., 2015). However, me success of this technology depends on me use of powerful attractants and their compatibility with the entomopathogens. For example, the tick attraction-aggregation-attachment pheromone (AAAP) could attract adult ticks from a distance of 6 m (Nchu et al., 2009) but couid not be used in combination with conidia of Metarhizium anisopliae (Metschnikoff) Sorokin (Hypocreaies: Clavicipitaceae) because of inhibition of fungal conidia by the pheromone (Nana et al., 2012). Nlassy et al. (2012a) and Mfuti et ai. (2015) have also reported inhibitory effects of conidia of M. anisopliae by the semiochemical Lurem-TR in autoinoculation device in a screenhou.se and field experiments.

Considering the growing interest in integrating attractants with EPF in tnrips management (Niassy et ai. 2012a; Mfuti et al., 2015), there Is a need to identify compounds that are bom attractive to tnrips ano compatible with EPF. The objective of the present study was therefore to identify thrips attractants that are compatible with M. anisopliae In terms of conidia! germination and germ tube length since the latter plays a crucial role in fungal infection (Ortiz-Ribbing and. Williams, 2006).

MATERsALS AND METHODS

Thrips attractants

Seven compounds used for thrips attraction or with potential attraction for thrips were tested for their compatibility with M. anisopliae isolate ICiPE 63. They were selected on the basis of structural analogies to known attractant such as methyl isonicotinate (Lurem-TR) (Teulon ex al., 2007, 2010) but also based on previous studies of Koschier et al. (2000). Information on their chemical characteristics and manufacturers is presented in Table 1. The commercial atxractanx, Lurem-TR whicn was earlier reported to be toxic with xhe entomopathogen (Niassy et al. 2012a) was included in xhe study as a reference, it Is a commercial product which quantity and release rate is standardized: therefore, could not be diluted. In preliminary bioassays, no significant effect of different concentrations (0.1, 10 ana 100%) of attractants was observed on conidial germination and subsequently only the recommended concentration of 10% of the pure product was used in the screening bioassays. The pure concentration of all attractants was diluted in paraffin oil.

Crop

Cowpea, Vigna unguiculata L. Walp variety Ken-Kunde1, was planted in 80 m2 plots with an inter- and intra- row spacing of 10 and 45 cm, respectively, in Mbita Thomas Odhiambo Campus (ITOC) (0° 26’ 06.19” S, 34° 12’ 53.13” E; 1,137 above sea level) earlier during rainy season (March 2014). The size of the cowpea farm was about 94 * 22 m. The field experiment of selected attractants was conducted during flowering stage of the crop (45 days after planting). No fertilizers, organic matter or synthetic chemical insecticides were applied during the experiment.

Fungal culture

  1. anisopliae isolate ICIPE 69 was obtained from the Arthropod Germplasm Centre of icipe. It is currently commercialized as Campaign® by the Real IPM Ltd, Kenya, for the control of thrips, papaw mealy bug and fruit flies (http://www.realipm.com). It was cultured on Sabouraud Dextrose Agar (SDA) in 9 cm Petri dishes and incubated at 25 ± 2°C in complete darkness. Conidia were harvested from three week-old culture by scraping the surface using a spatula. Conidia were suspended in 10 ml sterile distilled water containing 0.05% Triton X-100 in universal bottles containing glass beads. Conidial suspensions were vortexed for 5 min to produce a homogeneous suspension. Spore concentrations were determined using a haemocytometer.

Effect of thrips attractants on conidiai viability and germ tube length of M. anisopliae

The conidial suspension was prepared as described earlier and titrated to 1*10 » conidia ml’1. The spores were retained on a nitrocellulose filter membrane (diameter 47 mm, pore size 0.45 pm, Sigma Chemicals) by pouring 10 ml suspension through a filter holder unit (MFS) under aspirator vacuum (Maniania, 1994). The nitrocellulose filter membranes were dried for 30 min under a laminar flow cabinet and transferred to glass desiccators (2.5 L) for exposure to the attractant volatile. Cotton wicks were soaked in 0.5 ml suspensions of each attractant diluted in paraffin oil and placed in desiccators to allow volatile diffusion. Cotton wicks were used as dispenser (Sidahmed et al., 2014). Fungus-treated nitrocellulose membranes were exposed to different thrips attractants and sampled for viability observation at different time intervals of 1, 2, 3, 6 and 8 days. An untreated control without thrips attractant was inciuded. The commercial thrips attractant, Lurem-TR was included as a check. Treatments were randomized and the experiment repeated three times over time.

To determine conidial germination, nitrocellulose filter membranes containing conidia were removed from the desiccators and transferred into 10 ml sterile distilled water containing 0.05% Triton X-100 and vortexed for 3 min to dislodge conidia. Suspension (0.1 ml) titrated to 3 * 106 conidia ml’1 was spread- plated on SDA plates. Piates were incubated at 26 ± 2°C, L12: D12 phoxoperiod and examined after 18 to 24 h for conidial germination and germ tube length thereafter. Samples that could not be processed the same day were fixed by pouring a drop of lactophenol cotton blue onto the plate to stop further growth. Percentage germination was determined by counting approx. 100 spores per plate under a microscope Leica DMLB at 40 X magnification. The iength of germ tubes was measured using a

 

Label Name Chemical

formula

CAS number
4-anisaldehyde C8H8O2 19486-/1-6
Ethyl benzoate CsH-l0O2 93-89-0
C/s-jasmone C V| L1160 488-10-8
Linalool CwHicO 78-70-6
Methyl anthranilate CsHgNOj 134-20-3
trans caryophyllene C15H24 87-44-5
Phenylethanol CsFhoO 60-12-8
Methyl-isonicotinate C7H7NO2 2459-09-8
Chemical

group

Company Purity

(%).

Aldehyde Sigma Aldrich Chemicals GmbH, Germany 98
Ester of benzoic acid                and

ethanol

Sigma-Aldrich Chemicals GmbH, Germany 99
Jasmonate

(organic

compound)

Sigma- Aldrich Chemicals

GmbH, Germany

> 99
monoterpene Sigma-Aldrich Chemicals GmbH, Germany 97
Ester                  of Sigma-Aldrich Chemicals 98
anthranilic GmbH, Germany
Sesquiterpene Sigma-Aldrich Chemicals GmbH, Germany >93.5
Alcohol Sigma-Aldrich Chemicals GmbH, Germany >99
Pyridine Pherobank Wageningen, The Netherlands.

Dilution range for thrips attraction and species attracted

0.1 10% (applied in 1 microliter paraffin oil) (Koschier et al.,2000) Frankliniella occidentalis

Thrips obscuratus; Thrips tabac/ (Koschier et al., 2000)

IOrng/200 microliters hexane J. obscuratus, T. tabaci (El- Sayed et al., 2009)

1-10% (in 1 microliter paraffin oil) F. occidentalis, T.tabaci (Koschier et al., 2000)

  1. coloratus, T. hawaiiensis (Murai et al., 2000; Imai et al., 2001)

1-10% (in 1 microliter paraffin oil) (Koschier et al., 2000)

  1. tabaci (Teulon et al., 2007)

Several thrips species such as F. occidentalis, T. tabaci (Davidson et al., 2007) F. schultzei, Hydatothrips adolfifriderici and Megalurothrips sjostedti (Muvea et al., 2014)                      ______________________________________

 

 

 

 

Leica Application Suite (LAS EZ V1.5.0). Average germ tube lengths were obtained from 5 spores taken at random in each cover slip (22 x 22 mm) and replicated three times.

Effect of selected thrips attractants on the attraction of

  1. sjostedti

Attractants that were found compatible with M. anisopliae from the screening experiment were selected for field experiment to evaluate the attraction of Bean Flower Thrips (BFT), M. sjostedti (Trybom) (Thysanoptera: Thripidae) on cowpea. Lurem-TR was included as reference. Attractants were diluted in Paraffin oil as indicated above. Each attractant suspension was poured in 5 ml Eppendorf tube and suspended in the middle surface of the blue sticky card (10 * 25 cm) (Plate 1). The two items were placed at 30 cm above ground level. Blue sticky cards were
separated 10 m from one another to avoid interference. An untreated blue sticky card with no attractant was used as a control. The experiment was conducted during flowering and podding stages of cowpea when BFT populations are high (Ezueh, 1981; Nyasani et al., 2013). Cards were replaced every three days. Numbers of adult BFT were recorded on each card and the experiment was replicated four times over time.

Statistical analysis

Data on conidial germination of M. anisopliae were normalized by arcsine transformation before subjecting them to linear mixed model. Data on M. anisopliae conidial germ tube length and M. sjostedti catches were also analyzed using linear mixed model. Means were separated using Student-Newman-Keuls (SNK) test. A Pearson
correlation analysis was carried out to relate conidial viability with the germ tube length. All data analyses were performed using R (R Development Core Team, 2014). The level of significance was maintained at 95%.

RESULTS

Effect of thrips attractants on conidial viability and germ tube length of M. anisopliae

Overall, the effects of thrips attractants on germination of conidia of M. anisopliae varied significantly between the attractants (F9i268 = 22.1; P<0.0001) (Table 2). The interaction day x attractant was statistically significant (F9 268 = 3.8;

 

este                          he surface of the blue sticky card baited with

its                           ■          .

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Table 2. Conidial germ ation :’d germ x.: sene of /letarhizium anisopliae after exposition to thrips attractants (temperature: 26 ± 2 °C ot .p<.       L’,2. 2′ 2 e cf m.cubaticr.: ‘.8-24 hours)

Treatments … -s.x t ; ge. msnation ±SE (transformed) Mean length ±SE
Control 62.4±3.5a 130.5±10.0a
Methyl anthranilate 53.7±3.5ab 103.8+10.0ab
Trans-Caryophyllene 51.2±3.5ab 96.3±10.0ab
Cis-jasmone 50.9+3.5ab 93.8±10.0ab
Solvent (paraffin oil) 48.4±3.5b 90.9±10.0b
Linalool 33.3±3.5bc 67.1±10.0°
Phenylethano! 32.4±3.5C 50.9±10.0°
4-Anisaldehyde 30.8+3.5° 45.5±10.0°
Lurem-TR 24.4±3.5° 37.1±11.7°
Ethyl benzoate 20.1 ±4.0° 36.1±10.0°
Means bearing the same small letters are not significantly different by the Student-Newman-Keuls test (SNK).

 

 

 

 

P<0.0001). The time of exposure had significant effects on conidiai germination, except at 1 day post-exposure when no significant effect was observed (F9i45 = 1.5; P = 0.2) (Table 3). Significant reduction in conidial germination was observed in all the treatments from day 2 (F9,45 = 6.1; P<0.0001), day 3 (F9,45 = 6.8; P<0.0001), Day 6 (F9i45 = 8.3; P<0.0001) and day 8 post-exposure (Fg,45 = 8.7;  P<0.0001) (Table 3). The conidial

germination was significantly higher in the control (62.5 ± 10.0%), followed by cis-jasmone (44.8 ± 16.6%). Solvent (paraffin oil) (42.8 ± 11.0%), methyl anthranilate (36.6 ± 8.0%) and trans-caryophyllene (31.3 ± 16.8%) treatments after 8 days of exposure and was significantly different (Table 3). No conidiai germination was observed in Lurem-TR treatment at Qay 8 post-exposure (Table 3).

The effect of thrips attractants on germ tube length followed the same trend as with conidial germination where treatments differed significantly (F9 268 = 12.6; P<0.0001) (Table 2). The interaction day x attractant was nor statistically significant (F9i268 = 10; P=0.5). Exposure time had significant effects on length of the germ tube of M. anisopliae at Qay 1 (F945 = 4.3; P= 0.003), Qay 2

 

I ré&ûïiëiit (Tin ips attractdriis) Day after exposure
1 2 3 6 8 ANOVA
Control 91.3+3.0aA 85.4±3.7aAB 78.3±4.0aB 65.5+10.0aC 62.5+10.0aC F4,22=14.65; PO.OOOI
4-anisaldehye 85.7±2.0aA 48.7±14.3bcdB 9.2±7.9dC 0.1±0.1cC 0.1±0.1cG F4,22=38.2, P<0.0001
Ethyl Benzoate 79.8+6.8aA 44.1±14.1abcB <71- i.r- -1 cdBC

I 7.5+6. I

11.9±4.4bcBC 7.5+3.4bcC FT,22=35.8, P0.0001
Jasmone 83.8+4.0aA 74.6±7.5abcA 61.1±12.9abAB 44.6+15.5abB 44.8±16.6aB F4.22=6.1; P=0.001
L inalool 75.5±4.3aA 63±3abcB 50.6±6.2abcC 2.5+1.4cD 0.5±0.5cD F4,22=195.5; P<0001
Methyl anthranilate 85.8+3.6aA 78.8±2.7abA 60.7±2.3abBC 56.8±4.6aB 36.6+8.0aC 1-4.22=28.2; P<0.0001
Phenylethanol 76.1 ±8.5aA 50.1+14.6bcdB 36.5+15.3bcdB 18.2+11,5bcC 5.5+4.1bcC 1-4,22=21.5; P0.0001
Trans caryophyllene 80.0+5.0aA 74.5±abc7.0A 53.8+16.6abcAB 49.3+16.4abAB 31.3±16.8abB [–4,22=6.2; P0.001
Lurem-TR 75.7+4,2aA 20.6+3.7dB 13.6+3.1cdC 0.03±0.0cD 0.0±0.0D 1-4,13=199.8; PO.OOOI
Solvent (paraffin oil) 82.0+3.0aA 72.7±5.2abcAB 58.6+7.1abB 43.9+11,0abC 42.8+11,0aC FT,22=14,7; P0.0001
ANOVA F9,45=1.5;P=0.2 F -9,45=6.1;P<0.0001 P9,45=6.8; PO.OOOI                                F 9.46=8.3;P<0.0001                                    F946=8.7;P0.0001
Vithin column, means (iSE) followed by tlie same small lettei s are not significantly ’ different Student- Newman- -Keuls test (SNK), Within rows, means (+SE) followed by the same capital

letters are not significantly different Student-Newman-Keuls test (SNK).

 

fïôatmei it (7 In ips atuactants) Day after exposure
1 2 3 6 8 ANOVA
Control 190.7±2.0aA 146.9±25.4aP 123.2±28.2aBn 102.4±2.8.9aBC 89.1+32.4aC F4.22=8.3; P-0.003
4-anisaldehye 102.5±19.0bcA 74.6+12.4bcA 27.7+1 G.2cB 11.5±0.0CB 11.5±0.0cB I-4,22=12.6; P<0.0001
Ethyl benzoate 77.8±20.4cA 40.9±13.4cB 26.8±5.4cB 20.5±4.6cB 14.4+2.0cB 1-4.22=7.2; P-0.0007
Jasmone 185.4±42.6sA 103.8±22.1abB 90.6±21.9abBC 47.3±16.3bcC 41.9+16.7bcC F4.22=13.5; P<0.0001
Linalool 122±26.4abrA 94.3±15.5abA 83.9±12.8abA 22.2±5.7cB 13.4+1.9cB F4,22=17.58; P0.0001
Methly anthranilate 134.4±22.6abcA 120.5+20.4abA 108.6+17aAB 86.1±11.4abBC 69.6+12.9abC 1-4,22=8.4; P-0.0002
Phenyiethanol 102.9±25.7bcA 71.9±21.6bcAB 45.9±18.2bcBC 20.4±5.9cC 13.4+1.9cC F4,22=7.1; P-0.0007
Transcaryophyllene 179.3±49.1abA 112.9+34.1abB 81.0±2.1.6abBC 66.2±21.8abcBC 42.1+13.9bcC F4,22=9.9; P<0.0001
Lurem-TR 75.7±22.6bcA 20.6+6.1cB 13.6±3.3cB 15.4+7.9 cB 11.5±0.0cB 1-4,13=14.3; P-0.0001
Solvent (paraffin oil) 139.3±19.9abcA 107.9+21,4abB 87.7±19.0abBC 64.7±18.0abcBC 54.7±16.4abC F4,22=8.3; P-0.0003
ANOVA Fg,45=4.3;P=0.003 F9l45=6.7;P<0.0001 F9,45=6.9;P<0.0001 Fg,45=6.5; P0.0001 F9.45=5.6;P<0.0001

 

Within columi, m ns (: SE) folic ^ed by the same small letters £ re not significantly different by the Student- Newman-Keuls test (SNK); Within rows, means (±SE) followed by the same capital letters arc not significantly different by the Student-Newman-Keuls test (SNK).

Figure 1. Scattergram showing correlation between Metarhizium anisopliae conidial germination and germ tube length using the Pearson method.

 

Fig ire 2. Mean (± SE) number of M. sjostedti attracted to blue sticky card baited with Memyl anthranilate, Cis-jasmone, Lurem-TR and control. Means bearing the same small letters are not significantly different by the Student-Newman-Keuls test (SNK).

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

defense mechanism. ;i is a volatile (gas phase of Cis- jasmone) which is releasee during insect attack and controls the response to oamage (Menzei et ai., 2014).

Essential oil from Perovskia airiplicifolia Benth (Lamiales: Liamiaceae) containing 9.30% of trans­caryophyllene are reported to have antimicrobial activity against fungal strains (Erdemgil et al., 2007). The difference between these results and our results coula be explained oy the fact that attractants were used as volatiles in our study while they were used as oil supplements in culture media.

This study also confirmed previous findings on the antifungal effect of Lurem-TR on conidial germination (Niassy et al., 2012a). More recently, it was demonstrated that direct exposure of fungus without separation from Lurem-TR recorded the lowest conidial germination as compared with the other treatments where separation was made. However, fungal persistence increased with distance of separation of Lurem-TR (Mfuti et ai., 2015).

The strong correlation observed between conidial germination and germ tube length suggests tnat fungal inoculum wouid still cause infection in the insects. The role of germ tube formation in the oathogenesis is wei! established (Ortiz-Ribbing ano Williams, 2006). For instance, comparing foui different growth stages of isaria fumosorosea (Paecilomyces fumosoroseus) (Eurotiales: Trichocomaceae) (conidla, germinated conidia with either one or two germ tubes and hyphai bodies), -argues et ai. (1994) found tnat germinated conidia ana hyphai bodies were more aggressive man ungerminated conidia against first-instar larvae of Spodoptera frugiperda Smith (Lepidoptera: Noctuidae).

The catches of BFT were significantly higher on blue sticky cards baited with methyl anthranilate and Lurem- TR than the control and cis-jasmone baited cards. The increased attraction of BFT to Lurem-TR and blue sticky traps was reported by (Muvea et al., 2014). No difference in BFT attraction was found between the two compounds. Methyl anthrinalate has been reported to be attractive to four species of fiower thrips, Thrips hawaiiensis, Thrips coloratus, Thrips flavus, and Megalurothrips distal is, irrespective of sex (Murai et ai., 2000; Imai et al., 2001). However, this study is the first report on BFT response to methtyl antnranilate. This study has identified methyl anthranilate as an attractant effective for BFT and also compatible with conidia of M. anisopliae and hence can be considered for a ‘‘lure and kill” management strategy for BFT. The “lure and kill” strategy could be adopted either as an autoinoculation device or spot spray. Further studies need to be carried out to validate this proof of concept.

Conflict of interests

The authors have not declared any conflict of interests.

ACKNOWLEDGEMENTS

This study was funded by the African Union through the African Union Research Grant Contract no: AU RG/108/2012X We acknowledge icipe, Duduville, Nairobi, Kenya and /c/pe-ITOC, Mbita, Kenya for field facilities on tne campuses. We are grateful to Mrs. Barbara Obonyo, Messrs Pascal Oreng, Daniel Ouma, Eieisha Orima and Gregory Chebire for technical assistance. We are grateful to the German Academic

Exchange Services (DAAD) through the African Regional Postgraduate Program in insect Science (ARPP1S) of ICIPE and the African Union Project on Grain Legumes for financial support of the study.

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Contents lists available at SueneeDirect

Biological Control

journal homepage: www.elsevier.com/locate/ybcon

Lure and infect strategy for application of entomopathogenic fungus for the control of bean flower thrips in cowpea

David K. Mfuti ■ , Saîiou Niassy , Sevgan Subramanian , Hannalne du Plessis Sunday tkesia, Nguya K. Maniania •

 »International Cent re of Insect Physiology and Ecology (icipe), PO Box 30772-00100, Nairobi, Kenya

b Unit for Environmental Sciences and Management, North-West University, Private Bag X6001, Potchefstroom 2520, South Africa

HIGHLIGHTS » Spot and cover sprays of Metarhizium with attractant were compared for the control of Megalurothrips.

  • Spot spray was as effective as cover spray in reducing Megalurothrips populations on cowpea.
  • Both spot and cover application strategies resulted in yield increase as compared to the control.

» Spot spray application recorded the highest rates of benefit returns than cover spray.

ARTICLE INFO
ABSTRACT

 

The efficacy of spot spray and cover spray applications of Metarhizium anisopliae (Metsch.) Sorok. in com­bination with the thrips attractant Lurem-TR (methyl-isonicotinate) was compared in field experiments for the management of bean flower thrips (BFT), Megalurothrips sjostedti (Trybom), on a cowpea crop in two seasons (June-December 201 n). Treatments were applied five days after the placement of Lurem-TR in the field. During the first season, BFT densities per plant 5 days post-application were lower in spot spray (10.1 ±4.3) and cover spray (11.5±4.8) treatments than in the control treatment (41.8 + 15.2). In the second season, 5 days post-application, the spot spray treatment recorded the lowest BFT density of 32.5 ± 6.0, followed by cover spray with 40.9 + 7.0 thrips. The control treatment recorded the highest BFT density of 67.4 + 10.3 5 days post-application. Ccnidiai viability and thrips conidial acquisition did not differ between the two application methods. Grain yields of 1430.7 ± 114.2 kg and 1312.1 ± 87.7 kg were obtained in the cover and spot spray treatments, respectively, while 976.8 + 105.2 kg in the control during the second season. The cost benefit analysis indicated profits with the spot spray than cover spray application due to the reduction in labor and the quantity of inoculum used. Spot spray application of biopesticides could therefore be a viable option for small-scale farmers for the management of BFT on cowpea.

© 2017 Elsevier Inc. All rights reserved.

 

 

 

 

Î. Introduction

Cowpea, Vigna unguiciilata L. Walp. (Fabales: Fabaceae), is an important food and cash crop in different parts of the tropics ( i: 1997). It occupies a vital place in human nutrition as a source of protein, vitamins and minerals. In Kenya, cowpea is among the most consumed grain legumes. Its yield is, however, low and cannot satisfy the demand ( vlergor et ai.. 200′.). Annual

* Corresponding author.

E-mail addresses: tavinkupesa@gmail.com (D.K. Mfuti), saliou.niassy@up.ac.za (S. Niassy), ssnbramania@icipe.org (S. Subramanian), hannalene.duplessis@nwu.ac. i (H. du Plessis), M-l;csi@;ci>x’.-.:(S. Ekesi), nmariania@icipc.org (N.K. Maniania).

htipp/dx.doi.org/ id. 1016.’i.bioconirol. 2017,0! .011

1049-9644/© 20)7 Elsevier Inc. All rights reserved.

 

production of cowpea in Kenya declined from about 83,000 MT in 2007 to about 48,000 MT in 2008, despite an increase in area pianted from around 130,000 in 2007 to about 148,000 ha over the same period (Belmain et ai., 2013; «iprotich et al., 2015). Insect pests are the main factor responsible for the low grain legume pro­duction (Abate et al., 2012; Ajeigbe et aL, 2012), The bean flower thrips (BFT), Megalurothrips sjostedti (Trybom) (Thysanoptera: Thripidae), is considered as key pest that attacks the reproductive structures of cowpeas during plant development (Bzueh, 1381). BFT can cause yield losses ranging from 20 to 100% (Singh and Allen, 1980).

The control of BFT currently relies heavily on synthetic chemical insecticides (Abate and Ampofo, 1996; jackal and Daoust, 1986)

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