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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