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Discoveries in Agriculture and Food Sciences - Vol. 11, No. 4
Publication Date: August 25, 2023
DOI:10.14738/dafs.114.14934.
Mbemba, K. F., Rwegasira, G. M., & Tryphone, G. M. (2023). Studies on the Influence of Altitude on Abundance of Fall Armyworm
(Spodoptera Frugiperda (Je Smith)) (Lepidoptera: Noctuidae) in Tanzania. Discoveries in Agriculture and Food Sciences, 11(4). 43-
54.
Services for Science and Education – United Kingdom
Studies on the Influence of Altitude on Abundance of Fall
Armyworm (Spodoptera Frugiperda (Je Smith)) (Lepidoptera:
Noctuidae) in Tanzania
Kiva F. Mbemba
Department of Crop Science and Horticulture, Sokoine
University of Agriculture, P. O. Box 3005 Chuo Kikuu, Morogoro, Tanzania
Gration M. Rwegasira
Department of Crop Science and Horticulture, Sokoine
University of Agriculture, P. O. Box 3005 Chuo Kikuu, Morogoro, Tanzania
George M. Tryphone
Department of Crop Science and Horticulture, Sokoine
University of Agriculture, P. O. Box 3005 Chuo Kikuu, Morogoro, Tanzania
ABSTRACT
Fall armyworm (FAW) (Spodoptera frugiperda) is one of the most devastating
polyphagous field crop pests in many parts of the world, including Tanzania.
Influence of altitude on the abundance of S. frugiperda was studies by using
Pheromone (Frugilure S. frugiperda, Chemtica international, S.A) embedded cup
traps. The study was conducted along sites of Mt. Uluguru slopes including; SUA
(525 masl), Mlali (579 masl), Mgeta (1050 masl) and Nyandira (1691 masl) located
in Morogoro Region, Tanzania. A total of 16 cup traps (four at each site equidistantly
arranged at 100 m apart) were used. Weather data were recorded using Hygrocron
i-button hung on a tree at equidistant from the four traps. Data on S. frugiperda
counts and weather variables were recorded weekly for duration of six months
from January to June 2020. Results showed that S. frugiperda was abundantly
recorded across he tested altitude albeit at varied abundance. There was significant
difference (p < 0.001) among altitude on S. frugiperda abundance, whereby at low
altitude, S. frugiperda abundance was high compared to medium and high altitude.
Rainfall had positive correlation on S. frugiperda abundance (r = 0.16, r = 0.04) for
SUA and Mlali and negative correlation (r = -0.44) and (r = -0.03) for Mgeta and
Nyandira. Temperature had positive correlation (r = 0.21) on S. frugiperda
abundance at Nyandira while SUA (r = -0.03), Mlali (r = -0.35) and Mgeta (r = -0.28)
had negative correlation. Relative humidity for all four locations showed negative
correlation with S. frugiperda abundance. Thus, appropriate and effective
management practices of S. frugiperda should be considered throughout maize
production areas and across crop production seasons regardless of the altitude.
Keywords: Abundance, Altitude, Maize, Pheromone traps, Spodoptera frugiperda
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Discoveries in Agriculture and Food Sciences (DAFS) Vol 11, Issue 4, August- 2023
Services for Science and Education – United Kingdom
INTRODUCTION
Fall Armyworm (FAW) (Spodoptera frugiperda JE Smith) (Lepidoptera: Noctuidae) is a
devastating pest of maize which is native to America [1]. The pest was reported for the first
time in the African continent in early 2016 [2]. According to Day et al.[1], yield losses due to S.
frugiperda in Africa range from 8.3 to 20.6 million metric tonnes per year in the absence of any
control methods. Under farmer level, the insect can cause up to 100% yield loss if no control
measures are imposed [3].
Weather parameters play an important role in regulating the population of S. frugiperda under
agro-ecosystems [4]. Positive or negative correlation of weather factors with S. frugiperda
abundance have been reported [5]. Outbreaks and resurgence of the insect pest is linked to
environmental factors including elevation (Low, Medium and High altitude) weather such as
temperature (high or low), abundance or scarcity of rainfall and the use of susceptible varieties
in ecosystems [4]. Altitude is inversely related to temperature given the fact that the increase
of the former leads to the decrease of the later.
Weather condition affects physiological and behavioural characteristics of insects leading to
temporal and spatial dynamics [6]. Temperature is a single most important factor controlling
insects' development and hence population outbreak. Rainfall on the other hand can be the only
reason for insect epidemic. Similarly, relative humidity above or below a certain limit can
augment or lessen development of pests under certain conditions [4]. Pheromone lures have
long been used in monitoring, mass trapping and mating disruption of a great diversity of insect
pests [7].
Traps help to detect the invasions by novel pest species, the onset of seasonal pest activity,
determine the range and intensity of pest infestation and track changes in pest populations all
which help to inform decision making on pest management [8]. Once the chemical composition
of naturally occurring pheromone has been determined, the similar synthetic pheromone can
be manufactured and used as a lure in a trap to monitor the moth population [3]. Frugilure, the
pheromone lures specific to S. frugiperda has been manufactured by Chemtica International S.A.
and recommended by FAO for monitoring the pest. The only major challenge with pheromone
traps is that some predators have evolved to detect these pheromones and may use them to
locate prey [8]. Trap uses may sometimes results into undesired outcome when non target
insects including natural enemies are lured [9, 8]. Thus, traps and accompanying lures are
expected to be as specific as possible.
Maize crop in Tanzania is grown across a wide range of altitude from sea level to as high as
about 2000 m above sea level. There has been assumption that the population and abundance
of S. frugiperda could be affected by the altitude suggesting the possibility of higher altitude to
be less infested with the pest as the case would be with low to medium altitude. Data on the
altitudinal influence on abundance and distribution of S. frugiperda are scanty. Whether the
pest abundance varied through the crop growing season has not been established in Tanzania.
Understanding these parameters will guide informed decision making on where maize can be
grown without much worry about S. frugiperda and locations that requires intensive
management of the pest. Timing of maize crop planting with season of low pest abundance
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Mbemba, K. F., Rwegasira, G. M., & Tryphone, G. M. (2023). Studies on the Influence of Altitude on Abundance of Fall Armyworm (Spodoptera
Frugiperda (Je Smith)) (Lepidoptera: Noctuidae) in Tanzania. Discoveries in Agriculture and Food Sciences, 11(4). 43-54.
URL: http://dx.doi.org/10.14738/dafs.114.14934
could also help in reducing pest management costs. The objectives of the current study were; i)
to determine the abundance of S. frugiperda across varied range of altitude, and ii) to establish
the relationship between selected weather parameters and S. frugiperda abundance.
MATERIALS AND METHODS
Study Location
The study was conducted in Morogoro at four locations along the Uluguru maountain ranges
which included; Sokoine University of Agriculture (SUA) Horticultural Unit located at 525 m
above sea level (masl), Mlali located at 579 masl, Mgeta located at 1050 masl, and Nyandira
located at 1691 masl. Experimental locations coordinate for each location were collected using
the Geographical Positioning System (GPS) and used to map the experimental sites using Google
map (ArcGIS software version 10.4) (Fig. 1). Variation in altitude (from low to high) has been
clearly shown using colours with SUA site being the lowest and Nyandira the highest.
Experimental Design
The experiment was laid out in Randomized Complete Block Design (RCBD) with four locations
(as blocks). Treatments were the altitude (low, medium and high) and the four traps at each
site represented four replications. A commercially available S. frugiperda lure (Frugilure S.
frugiperda manufactured by Chemtica international, S.A batch number P061-Lure) and moth
catcher bucket traps were used for the study. Four traps embedded with pheromone lures were
equidistantly set (100 m apart) at each location as per protocol [10]. Each trap comprised of a
rubber septum impregnated with S. frugiperda female sex pheromone hanged in a cage at the
top of the moth catcher bucket and a single strip of Dimethyl 2, 2-DichloroVinyl Phosphate
(DDVP) placed at the bottom of the bucket to serve as a killing agent. Male moths and other
insects entering through vents on the sides of the bucket were knocked down by the DDVP into
the bucket. A single trap was hanged on a pole at each of four sides (100 meters apart) of the
selected maize farms at a height of 1.5 m above the ground (Fig 2).
The experimental sites were approximately about 15 km apart. Grease was applied to the pole
and the strings that held the trap to the pole to prevent the catches from being preyed on by
predatory arthropods such as Big-headed ants, Pheidole megacephala. Traps were deployed in
January 2020 and they remained in the field for 6 months. Trap deployment was planned to be
available throughout six months regardless whether maize was available or not. This study was
conducted for a total of 26 weeks. The lures and the DDVP were replaced after every two weeks.
Monitoring of S. frugiperda dynamics was done throughout the crop establishment stage to
harvesting then extended for three more months post crop maturity. Please note that in the
study area maize crop takes three months from establishment to maturity.