Efficacy of Bacillus thuringiensis Strain 407 versus Synthetic Pesticides in Controlling Sugar Beet Pests under Open Field Conditions

概要

九州大学学術情報リポジトリ
Kyushu University Institutional Repository

Efficacy of Bacillus thuringiensis Strain 407
versus Synthetic Pesticides in Controlling
Sugar Beet Pests under Open Field Conditions
Mohsena Rizk MANSOUR
Field Crop Insect Pests Department, Plant Protection Research Institute, Agricultural Research
Center

UENO, Takatoshi
Laboratory of Insect Natural Enemies, Division of Biological Control, Department of Applied
Genetics and Pest Management, Faculty of Agriculture, Kyushu University

Kareem Mohamed MOUSA
Economic Entomology Department, Faculty of Agriculture, Kafrelsheikh University

https://doi.org/10.5109/6796257
出版情報：九州大学大学院農学研究院紀要. 68 (2), pp.143-150, 2023-09. 九州大学大学院農学研究院
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J. Fac. Agr., Kyushu Univ., 68 (2), 143–150 (2023)

Efficacy of Bacillus thuringiensis Strain 407 versus Synthetic Pesticides in Controlling
Sugar Beet Pests under Open Field Conditions
Mohsena Rizk MANSOUR1, Takatosh UENO* and Kareem Mohamed MOUSA2
Laboratory of Insect Natural Enemies, Division of Biological Control, Department of Applied Genetics and Pest Management,
Faculty of Agriculture, Kyushu University, Fukuoka 819–0395, Japan
(Received May 18, 2023 and accepted May 18, 2023)
In sugar beet fields of West Eurasia and North Africa, including Egypt, the beet moth Scrobipalpa
ocellatella, cotton leafworm Spodoptera littoralis and beet armyworm Spodoptera exigua are commonly
major and serious pests causing irreparable damage to beet plantation. However, frequent use of synthetic
pesticides can harm beneficial insects in the agroecosystem and should preferably be avoided in terms of
environmental protection and safety. This study aimed to evaluate the impact of Bacillus thuringiensis
(Bt) strain 407 in comparison to major chemical insecticides, chlorfenapyr (Pestpyr) and methomyl
(Goldben), on the populations of the above–mentioned pests and their associated natural enemies in the
field. Our results showed that the densities of S. ocellatella were remarkably higher than those of S. littoralis and S. exigua in two successive growing seasons. Within the first week of application with both chemical pesticides, numbers of pests were dropped and its population size reduced by 95 – 100% though reduction percentage tended to decline with time. Bt application was equally effective in reducing the three pest
species after 7 or 10 days of application though it had less effectiveness in the earlier days due to a time–
delayed impact. The major natural enemy predators, i.e., the green lacewing Chrysoperla carnea,
Coccinella septempunctata and C. undecimpunctata, disappeared completely three days after chemical
application and remained few during the study period. By contrast, reduction of the predators compared to
control plots was markedly small in study plots with Bt application, indicating use of Bt conserved the predator populations. Thus, multiple sprays of Bt may be useful in sugar beet production, which can solve the
dilemma between pest control and beneficial natural enemy conservation.
Key words: Bio-insecticides, conservation biological control, natural enemies, IPM

Egypt, resulting in serious economic loss (Al–Keridis,
2016; Amin et al., 2008; Shalaby and El–Samahy, 2010;
Talaee et al., 2016; Zheng et al., 2011). Pest management is thus a key practice for stable production of sugar
beet.
Although use of synthetic chemical pesticides is a
main pest control practice, the frequent use or overuse
often causes development of pesticide resistance, leading to the outbreak or resurgence of pests (El–Agamy et
al., 2021; Ishtiaq and Saleem, 2011; Su and Sun, 2014).
Also, the excessive use of pesticides has pernicious
impact on natural enemies or natural control and may
result in the environmental hazardousness (Mousa et al.,
2013; Ueno and Tran, 2015). Therefore, combination
and integration of other practices, such as use of resistant varieties, plant extracts, inter–cropping, natural
materials and entomopathogenic micro–organisms, etc.,
are favorable to suppress insect pest overrun and promote environmental protection (Elkhateeb et al., 2021;
Elsharkawy and Mousa, 2015; Talaee et al., 2016; Mousa
and Ueno, 2019; Mousa, 2020). Bacillus is a well–known
bio–insecticide widely used to control insect pests with a
high level of specificity against different lepidopteran
species (Daquila et al., 2021; Mousa et al., 2014; Mannu
et al., 2020). The advantage of such a bio–insecticide is
safety to non–targeted beneficial organisms, enhancing
conservation biological control of insect pests by reducing a negative impact on beneficial insects, i.e., parasitoids and predators, in agricultural ecosystems
(González–Zamora et al., 2007; Zhao et al., 2016). The
use of bio–insecticides is also supposed to contribute in

I N T RODUCTION
In Egypt, sugar beet, Beta vulgaris L., is one of the
most important cultivated crops. Beside it plays an
indispensable role in the crop rotation system, sugar
beet has long been utilized for sugar extraction to meet
the country’s need for sugar (Youssef et al., 2020).
Sugar beet is a modern sugar crop in the Egyptian fields,
and the industrial demand for sugar beets has been
steadily increasing. Therefore, the Egptian government
encourages farmers by offering a high price, thus incentivizing many farmers to plant more sugar beets.
Accordingly, the harvested area in 2021/22 showed an
increase of 10,000 hectares, compared to the previous
year with total cultivated area of 265,000 ha (USDA,
2021).
Like other crops, sugar beet is attacked by numerous insect pests throughout growth stages, which
directly or indirectly lead to yield and quality reduction
(Bassyouny, 1993; El–Dessouki et al., 2014; Evaristo,
1983; Youssef et al., 2020). Among the insect pests, cotton leaf worm Spodoptera littoralis (Boisd.), beet
armyworm Spodoptera exigua (Hübner) and sugar beet
moth Scrobipalpa ocellatella Boyd. are commonly
abundant and are destructive in sugar beet fields of
Field Crop Insect Pests Department, Plant Protection
Research Institute, Agricultural Research Center, Sakha, 33511
Egypt
2
Economic Entomology Department, Faculty of Agriculture,
Kafrelsheikh University, Kafr El–Sheikh, 33516 Egypt.
* Corresponding author (E–mail: ueno@grt.kyushu–u.ac.jp)
1

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MANSOUR et al.

Pesticides and bio–pesticides
Two commercial pesticides that have been widely
used in sugar beet fields were selected for use in this
study. Formulations of the pesticides were: Pestpyr SC
36% (4–Bromo–2–(4–chlorophenyl)–1–(ethoxymethyl)–5
–(trifluoromethyl)–1H–pyrrole–3 carbonitrile) (Shandong
Weifang Shuangxing Pesticide Co., Ltd., China) applied
at 357 ml/hectare (= 150 ml/feddan) and Goldben SP
90% (S–methyl n–(methylcarbamoyl oxy) thioacetamide) (Shoura Chemicals, Egypt) was dissolved in water
and was applied at 711 gm/hectare (= 300 gm/feddan,
600 liter) (Table 1). Spore suspension of Bacillus thuringiensis isolated from larvae of beet fly Pegomya
mixta (Diptera: Anthomyiidae) was also tested as bio–
pesticide. The isolation was identified by GATC Biotech
Company, Germany as Bt strain 407 (Table 1), was kept
at Sugar Crops Research Institute, Sakha, Kafer El–
Sheikh, Egypt and was used in the present study.

reducing production costs, ameliorates the product quality, and slowdown the development of pesticide resistance (De Bortoli et al., 2017). The genus Bacillus
includes multiple species and/or strains, which in turn
differ in their mode of action and efficacy to target insect
pests. For example, the endophytic bacterium Bacillus
aryabhattai can promote plant growth by inducing
important molecular pathways (Park et al., 2017) while
the bacterium Bacillus thuringiensis is infectious to
insects, including agricultural pests, and produces delta–
endotoxins (Bravo et al., 2007), which has been used to
control various insect pests including Lepidoptera
(Mousa et al., 2014).
From this perspective, we investigated the efficacy
of applying the bacterium Bacillus thuringiensis Bt
407 in suppressing three main lepidopteran sugar beet
pests. To compare its usefulness, the efficacies of two
commercial chemical insecticides were tested. We also
examined their impact on associated natural enemies to
evaluate the compatibility with natural enemies for conservational biological control or integrated pest management. Field studies were therefore designed, and foliar
spray of tested compounds were applied in sugar beet
fields. Based on the results, we discuss usefulness of Bt
for pest management in sugar beet fields.

Data collection
The first sampling was done before the spraying of
the test pesticides in order to calculate the percentage
of reduction of target insects (see below). Ten plants
from each plot were randomly chosen and inspected
directly in the field to count pest insects. Thus, forty
plants in all were sampled for each experimental group.
Sampling was made 1, 3, 7 and 10 days after spraying of
test pesticides. Because the Bt requires two or three
days to kill lepidopteran larvae (Nawrot–Esposito et al.,
2020), we did not count the numbers of pest insects in
Bt applied plots on the first day after application. The
numbers of S. ocellatella, S. littoralis and S. exigua and
the associated predators, Chrysoperla carnea (Steph.)
(Neuroptera: Chrysopidae), Coccinella septempunctata L. and C. undecimpunctata L. (Coleoptera:
Coccinellidae) were recorded. Percentage reduction of
the insect populations was calculated according to the
equation of formula given by Henderson and Tilton,1955
as follows:

M AT ER I A LS A N D M ET HODS
Experiment setup
The experiment was carried out in two successive
beet growing seasons in 2019–2020 and 2020–2021 at
the experimental farm of the Sugar Crops Research
Institute, Sakha, Kafr El–Sheikh, Egypt. Beet was
planted twice a year; first planting time was in the beginning of August to examine the presence of Spodoptera
littoralis (Boisd.) and S. ...

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