This document provides information about the Journal of Entomology and Nematology (JEN), including its scope, peer-review process, author instructions, and editor/editorial board details. JEN is an open access journal that publishes articles in all areas of entomology and nematology. It accepts original research articles, short communications, and reviews. Manuscripts are peer-reviewed by members of the editorial board or outside reviewers. The journal aims to publish manuscripts within weeks of submission.

1. Journal of
Entomology and Nematology
Volume 7 Number 1, January, 2015
ISSN 2006-9855

2. ABOUT JEN
TheJournal of Entomology and Nematology (JEN) (ISSN: 2006-9855)is published monthly (one volume peryear) by
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Journal of Entomology and Nematology (JEN) is an open access journal that provides rapid publication (monthly)
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3. Editors
Dr. Mukesh K. Dhillon
ICRISAT
GT-Biotechnology, ICRISAT, Patancheru 502 324,
Andhra Pradesh,
India
Dr. Lotfalizadeh Hosseinali
Department of Insect Taxonomy
Iranian Research Institute of Plant Protection
Tehran, P. O. B. 19395-1454,
Iran
Prof. Liande Wang
Faculty of Plant Protection,
Fujian Agriculture and Forestry University
Fuzhou, 350002,
P.R. China
Dr. Raul Neghina
Victor Babes University of Medicine and Pharmacy
Timisoara,
Romania
Prof. Fukai Bao
Kunming Medical University
191 Western Renmin Road, Kunming, Yunnan,
PR of China
Dr. Anil Kumar Dubey
Department of Entomology,
National Taiwan University, Sec. 4, Lane 119, Taipei,
Taiwan 107
Dr. Mona Ahmed Hussein
National Research Centre, Centre of Excellence for
Advanced Sciences, El-Behooth Street, Dokki,
Cairo, Egypt
Associate Editors
Dr. Sam Manohar Das
Dept. of PG studies and Research Centre in Zoology,
Scott Christian College (Autonomous),
Nagercoil – 629 003,
Kanyakumari District,India
Dr. Leonardo Gomes
UNESP
Av. 24A, n 1515, Depto de Biologia, IB, Zip Code:
13506-900,
Rio Claro, SP,
Brazil.
Dr. J. Stanley
Vivekananda Institute of Hill Agriculture
Indian Council of Agricultural Research, Almora–
263601, Uttarakhand,
India
Dr. Ramesh Kumar Jain
Indian Council of Agricultural Research,
Division of Nematology, IARI
New Delhi-110012
India
Dr. Hasan Celal Akgul
Istanbul Plant Quarantine Service, Nematology
Laboratory
Halkali Merkez Mahallesi, Halkali Caddesi, No:2,
34140 Halkali, Kucukcekmece-Istanbul
Turkey
Dr. James E. Cilek
Florida A & M University
4000 Frankford Avenue, Panama City, Florida 32405
USA
Dr. Khan Matiyar Rahaman
Bidhan Chandra Krishi Viswavidyalaya
AICRP (Nematode), Directorate of Research,
BCKV, PO. Kalyani, Dist. Nadia, PIN-741235,
West Bengal,
India
Manas Sarkar
Defence Research Laboratory
(DRDO, Ministry of Defence, Govt. of India)
Post Bag No.2, Tezpur-784001, Assam,
India

4. Mehdi Esfandiari
Department of Plant Protection
College of Agriculture,
Shahid Chamran University of Ahvaz,
Ahvaz, Iran
Prof. Dr. Mahfouz M. M. Abd-Elgawad
Nematology Laboratory
Department of Phytopathology
National Research Center El-Tahrir St., Dokki
12622, Giza,
Egypt
Matthew S. Lehnert
Department of Entomology, Soils, & Plant Sciences
Clemson University,Clemson,
United States
Wenjing Pang
3318 SE 23rd Avenue
Gainesville, FL 32641
Agronomy and Biotechnological College,
China Agricultural University,Beijing,
China
Dr. G. Shyam Prasad
Directorate of Sorghum Research (DSR),
Rajendranagar, Hyderabad 500030, AP,
INDIA
Dr. Rashid Mumtaz
Date Palm Research
Plant Protection Department
Food & Agricultural Sciences
King Saud University, Riyadh
Kingdom of Saudi Arabia
Editorial Board
Godwin Fuseini
International SOS Ghana,
Newmont Ghana Gold,
Ahafo mine,
Ghana.
Dr. Waqas Wakil
Department of Agriculture Entomology,
University of Agriculture, Faisalabad,
Pakistan
Gilberto Santos Andrade
Universidade Federal de Viçosa
Avenida Peter Henry Rolfs, s/n Campus Universitário
36570-000
Viçosa - MG - Brazil
Ricardo Botero Trujillo
Calle 117 D # 58-50 apto. 515
Pontificia Universidad Javeriana, Bogotá,
Colombia
Dr. D. N. Kambrekar
Regional Agricultural Research Station,
UAS Campus, PB. No. 18,
Bijapur-586 101 Karnataka-INDIA
India
Dr. P. Pretheep Kumar
Department of Forest Biology
Forest College & Research Institute
Tamil Nadu Agricultural University
Mettupalayam – 641 301
Tamil Nadu, India
Dr. Raman Chandrasekar
College of Agriculture Entomology
S-225, Agriculture Science Center
University of Kentucky
Lexington, KY 40546-0091
USA.
Dr. Rajesh Kumar
Central Muga Eri Research and Training Institute
Lahdoigarh, Jorhat-785700, Assam,
India

5. Prof. Ding Yang
Department of Entomology,
China Agricultural University,
2 yuanmingyuan West Road, Haidian,
Beijing 100193, China
Dr. Harsimran Gill
University of Florida
970 Natural Area Drive, PO Box 110620,
Gainesville, Florida- 32611
Dr. Mehdi Gheibi
Department of Plant Protection,
College of Agriculture, Shiraz Islamic
Azad University, Shiraz, Iran
Dr. Nidhi KakKar
University College, Kurukshetra University,
Kurukshetra, Haryana, India
Dr. Marianna I. Zhukovskaya
Sechenov Institute of Evolutionary Physiology
and Biochemistry, Russian Academy of Sciences
44 Thorez Ave, 194223,
Saint-Petersburg, Russia
Gaurav Goyal
University of Florida
282#14 Corry village,
Gainesville, FL 32603, USA
Gilberto Santos Andrade
Universidade Federal de Viçosa
Avenida Peter Henry Rolfs,
s/n Campus Universitario
36570-000 Vicosa - MG -
Brazil
Joshi Yadav Prasad
Gyanashwor Kathmandu, Nepal
G P O Box: 8975 EPC:
5519, Kathmandu, Nepal
India
Baoli Qiu
Department of Entomology,
South China Agricultural University
No 483, Wushan Road, Tianhe, Guangzhou,
PR China 510640
T. Ramasubramanian
Central Research Institute for Jute and Allied Fibres
(Indian Council of Agricultural Research)
Barrackpore, Kolkata – 700 120,
India
Leonardo Gomes
UNESP Av. 24A, n 1515, Depto de Biologia,
IB, Zip Code: 13506-900, Rio Claro,
SP, Brazil.
Hasan Celal Akgul
Istanbul Plant Quarantine Service,
Nematology Laboratory
Halkali Merkez Mahallesi,
Halkali Caddesi, No:2, 34140 Halkali,
Kucukcekmece-Istanbul/Turkey
J. Stanley
Vivekananda Institute of Hill Agriculture
Indian Council of Agricultural Research,
Almora– 263601, Uttarakhand, India
Atef Sayed Abdel-Razek
National Research Centre,
Dept. of Plant Protection
El-Tahrir Street, Dokki, Cairo, Egypt

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9. InternationalJournalofMedicine and MedicalSciencesJournal of Entomology and Nematology
Table of Contents: Volume 7 Number 1, January, 2015
ARTICLES
Population dynamics and damages of onion thrips (Thripstabaci)
(Thysanoptera: Thripidae) on onion in Northeastern Ethiopia
Yeshitla Merene

10. Vol.7(1),pp.1-4, January, 2015
DOI: 10.5897/JEN2014.0112
Article Number: 713103550143
ISSN 2006-9855
Copyright © 2015
Author(s) retain the copyright of this article
http://www.academicjournals.org/JEN
Journal of Entomology and Nematology
Full Length Research Paper
Population dynamics and damages of onion thrips
(Thripstabaci) (Thysanoptera: Thripidae) on onion in
Northeastern Ethiopia
Yeshitla Merene
Amhara Agricultural Research Institute (ARARI).P.O.Box 527, Bahirdar, Ethiopia.
Received 11 November, 2014; Accepted 15 December, 2014
This study was conducted in kewet district of Amhara region, Ethiopia. The experiment on seasonal
thrips population dynamics and onion yield loss was conducted in 2003 and 2004. The treatments were
five transplanting dates of two month interval with and without spray of insecticide in five replications.
Thrips count per plant was low during the rainy and cool months of July to November and in April.
Thrips population started increasing in December and reached the pick value of 159 thrips per plant in
March. Thrips population on onion is high from six to ten leaves growth stages. Damage caused by
thrips on onion significantly varies with growing season. More yield loss was observed in onion
transplanted during dry seasons (October to February). The highest total bulb and marketable bulb yield
loss of 16.9 and 17.7 tons/ha occurred on December transplanted onion. Onion from six to ten leaves
growth stage is the most critical period for thrips control. These results are important for the
management of onion thrips by growers.
Key word: Onion thrips, population pick, bulb yield loss, insecticide, season.
INTRODUCTION
Onion is one of the most important vegetables grown in
Ethiopia. It is produced as a cash crop both under
irrigated and rainfed condition. In Amhara region of
Ethiopia area, under production of vegetable
cropsespecially onion is expanding with the expansion of
irrigation scheme. Onion yield in smallholder production
system is 15 tons/ha while the yield potentials are up to
30 tons/ha (Lemma and Shimeles, 2003). This yield gap
is because of lowadoption of improved production
practices by small holder farmers including disease and
pest management options.Onions and related allium
crops are subject to a variety of diseases and attack by
arthropod pests that can reduce cropyield and quality
(Workman and Martin, 2002).
Onion thrips, Thripstabaci (Lindemann) (Thysanoptera:
Thripidae), is the most damaging pest of onion in the rift
valley of Ethiopia (Tsedeke, 1986). Information on thrips
population dynamics and its damage level on onion in the
study area are lacking. Virtually all crops can tolerate a
certain amount of pest damage without appreciable
effects on vigor yieldand quality. For most of the key
pests, quantitative studies of the amountof damage
E-mail: merene73et@yahoo.ca. Tel: +251911902551
Author(s) agree that this article remain permanently open access under the terms of the Creative Commons Attribution License 4.0
International License

11. 2 J. Entomol. Nematol.
Figure 1.Seasonal thrips population dynamics in onion field at Shewarobit.
versus reduction in crop yield have established allowable
levels of damage or economic thresholds. However
Onion growers in the study area apply insecticide for the
control of thrips regardless of growing seasons and
without monitoring thrips population. Knowledge of
insect population dynamics can help to predict
where and when infestations will occur, how big
they will become, and how long they will stay.
This information is very helpful to apply the right
pest control measure at the right time. Therefore,
the objectives of the study was to assess changes in
seasonal fluctuation of thrips population and to determine
yield loss caused by thrips on onion transplanted at
different times of the year.
MATERIALS AND METHODS
The study was carried out in Kewet district of Amhara region
(Ethiopia) with longitude and latitude of 10°00′N 39°54′E and an
elevation of 1350 m above sea level. It is 230 km north east of
Addis Ababa.
Thrips population dynamics and yield loss on onion was studded
using five transplanting dates of two months interval with and
without spray of insecticide (Selecron 720 EC 720 EC) at the rate of
1 L ha-1
. The treatments were arranged in randomized complete
block design (RCBD) with five replications. Insecticide application
was done every two weeks throughout the growing period.
The plot size was 5 x 4 m containing six ridges of 100 plants per
ridge. Prior to planting, the plot was irrigated to settle the soil and
facilitate the planting operations. Healthy and vigorous seedlings of
two months old and 12- 15 cm height were carefully uprooted from
the seedbed and planted in two rows of 10 centimeter distance on
each ridge. The ridge and furrow space were 20 and 40 centimeter
respectively. Irrigation was done on weekly interval unless there
was rain. To protect the onion from the two common fungal
diseases (Powdery mildew and purple blotch) all the experimental
plots were sprayed with mancozeb 80 WP (2 L ha-1
).
Every 15 days five onion plants from 2nd
and 5th
ridge were
randomly taken on labeled polythene bag for thrips (adult and
nymph) counting in the lab with aid of 10 x magnifying hand lens. At
harvest, total and marketable bulb yields were collected from the 3rd
and 4th
ridges. Marketable bulb yield was obtained after discarding
unmarketable bulbs, which includes (undersized, diseased,
decayed and physiologically disordered bulbs) from the total bulb
yield. Daily records of rainfall and temperature (maximum and
minimum) for the study period were taken from Shewarobit
meteorological station. Daily relative humidity was recorded three
times a day using hygrometer. Yield loss for each transplanting
period was calculated using the formula indicated below:
% Yield loss = [(Yield of sprayed- Yield of unsprayed) / (Yield of
sprayed)] X100
Data on bulb yield and thrips count per plant for each treatment
were analyzed using SAS statistical software. Thrips counts per
plant were transformed using log transformation to reduce the
skewness of the parameter and fulfill the assumption of normality in
ANOVA. Correlation analysis was used to determine the
associations between mean monthly thrips count with mean
monthly rainfall, temperature and relative humidity.
RESULTS AND DISCUSSION
Thrips population was low during the months of July to
November 2003 and in April 2004. During these periods,
mean thrips count per plant was below ten. Thrips
population started increasing in December and reached
the pick value of 159 thrips per plant in March (Figure 1).
Very few thrips was first observed on newly transplanted
onion seedlings two weeks after transplanting. Thrips
population was low at early growth stage, started
increasing after six leaves growth stage and reached its
peak (50 thrips per plant) at 10 leaves growth stage and
decreased at crop maturity (Figures 1 and 2). Thrips
population on onion was high from six to ten leaves
0
2
4
6
8
10
12
14
Nov1,2003
Nov16,2003
Dec1,2003
Dec16,2003
Jan1,2004
Jan16,2004
Feb1,2004
Feb15,2004
Mar1,2004
Mar16,2004
Apr1,2004
Apr16,2004
May1,2004
May16,2004
Jun1,2004
Jun16,2004
Jul1,2004
Jul16,2004
Aug1,2004
Aug16,2004
Sep1,2004
Sep16,2004
Date
Meannumberofleavesfor
sampledplants
0
20
40
60
80
100
120
140
160
180
thripscountperplant
leaves/plant thrips/plant

12. Merene 3
Figure 2. Mean number of thrips per plant at different growth stage of onion.
Table 1. Mean total bulb yield, yield loss due to thrips and thrips infestation at different planting dates in 2003/2004 at Shewarobit.
Planting dates
Total bulb yield in qt ha
-1
SE Yield loss *Mean umber of thrips per plantSE
Un sprayed Sprayed P (value) In (qt ha
-1
) % loss Un sprayed Sprayed P (value)
Mid October 2003 166.610.9a 258.532.7a 0.035 91.9 35.6 22.33.2b 6.91.4c 0.001
Mid December 2003 108.718.4a 269.613.8a 0.003 160.9 59.7 74.98.3a 20.5 1.9a 0.01
Mid February 2004 95.812.7a 169.520.2b 0.049 73.7 43.5 18.3 6.6c 10.9 2.2b 0.37
Mid April 2004 107.114.8a 133.931.3b 0.44 ns ns 16.7 2.3c 21.22.5a 0.24
Mid June 2004 129.630.2a 149.714.5b 0.58 ns ns 2.70.82d 0.9 0.2d 0.096
Mean 121.5 9.2 196.315.1 0.001 74.8 38.1 26.9 5.5 12.1 1.8 0.01
*Means in the column followed by the same letters are not significantly different (P>0.05). Means with in the row are not significantly different when P
(value) >0.05. *Mean number of thrips per plant pooled from count taken at 30,45,60,75 and 90 DAP (N=125). SE=standard error of the mean.
growth stages because these succulent leaves are highly
preferred by the thrips and it also provides many crevices
into which the thrips can creep for protection. This thrips
population peak is the actively bulbing growth stage of
onion and it probably attributed to the highest bulb yield
loss. Thrips population reduces when the crop gets
maturity because the leaf nutritional value decline and
also become tougher and lignified and cannot be rasped
by thrips. During onion maturity stage adult thrips are
forced to move towards other hosts. This is in agreement
with the result of previous study on onion Workman and
Martin (2002).
There is an inverse relation between thrips population
and mean monthly rainfall (r= -0.93, p= 0.02). Sharp
decline in thrips population was observed during rainy
seasons. This is because of the fact that the rain washed
out the thrips from the plant. Similar results were also
reported by different authors (Tsedeke, 1986;
Dominicano et al. (1993). On the other hand, there is no
significant correlation between thrips count per plant and
maximum air temperature (r=0.09, P=0.7), minimum
temperature (r= -0.15, P=0.6) and relative humidity (r=-
0.33, P=0.3). Hence, changes in thrips abundance were
not attributed to seasonal variation of temperature and
relative humidity. Pearsall and Myers (2000) also found
that seasonal changes in temperature did not appear to
result in any consistent effect on western flower thrips
densities and damage level in British Columbia.
On insecticide sprayed onion, the effect of planting
dates on onion bulb yield is highly significant. The highest
total bulb yield of 258.5 and 269.6 Qt ha
-1
and marketable
bulb yield of 248.8 and 258.7 Qt ha
-1
were obtained from
October and December planted onions respectively
(Tables 1 and 2). The reason for high bulb yield at
0
2
4
6
8
10
12
14
15 DAT 30 DAT 45 DAT 60 DAT 75DAT 90 DAT
Crop growth stage
No. of leaves per plant
0
10
20
30
40
50
60
Thrips count per plant
No.of leaves per plant Thrips count per plant

13. 4 J. Entomol. Nematol.
Table 2. Mean marketable bulb yield and its loss due to thrips at different planting dates in 2003/2004 at Shewarobit.
Planting dates
Marketable bulb yield in qt ha
-1
SE Yield loss
Un sprayed Sprayed P (value) In ( qt ha
-1
) % loss
Mid October 2003 145.310.9a 248.832.2a 0.023 103.5 41.6
Mid December 2003 81.614.4a 258.713.5a 0.002 177.1 68.5
Mid February 2004 88.513.7a 158.823.8b 0.04 70.3 44.3
Mid April 2004 99.816.1a 128.732.7b 0.42 ns ns
Mid June 2004 12531.6a 146.815.5b 0.56 ns ns
Mean 1089.1 188.315.0 0.001 80.3 42.6
Means in the column followed by the same letters are not significantly different (P>0.05). Means within the row are not
significantly different when P (value) >0.05.
October and December plantings are the coincidence of
early growth stage with cool weather condition and warm
conditions during bulbing, bulb maturity and harvesting
stages, which are the optimal climatic condition favorable
for high yield and quality onion bulb production Tindall
(1983). Similar results of thrips population pick in March
and maximum onion yield on November and December
transplant has been reported on recent study conducted
in Sokoto, Nigeria by Ibrahim (2010).
Damage caused by thrips on onion varies depending
on time of transplanting. Significant yield loss was
observed in onion planted during dry seasons (October -
February) (Tables 1 and 2). In October transplanted
onion there were 41.6 % marketable and 35.6 % total
bulb yield loss because the population of thrips on the
different growth stages was on average 22.3 thrips/plant
in untreated plot. The maximum total bulb yield loss of
59.7% and marketable bulb yield loss of 68.5% occurred
on December planted onion with an average infestation
level of 75 thrips per plant on uncontrolled plots (Tables 1
and 2). On average, total and marketable bulb yield loss
of 38.1 and 42.6 % were recorded for the study period in
Shewarobit area (Tables 1 and 2). Previous study
conducted in Awash valley of Ethiopia (Tsedeke, 1983)
reported 33.5% onion bulb yield loss. Rueda and Shelton
(1955) have also stated up to 66% damage in tropical
countries.
Conclusion
Most of the farmers in the study area have the awareness
and use insecticide to control thrips, but it was not
effective as they do not apply the recommended rate and
miss monitoring thrips population before spray. In the
management of thrips, the most important conclusion of
this study is the requirement of an integrated thrips
management options to minimize insect population and
damage for onions transplanted from October to April.
Moreover six to ten leaves growth stage is the most
vulnerable stages for thrips. Hence, it is recommended to
properly monitor and apply integrated thrips management
options for onion production under irrigation for the study
area and other similar areas. Moreover for researchers
interested on the study of thrips population ecology it
would be advisable to adjust the sampling schedule at six
to ten leaves growth stages of onion.
Conflict of interests
The authorhas not declared any conflict of interest.
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14. Journal of Entomology and
Nematology
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