Management of Tuta absoluta (Lepidoptera, Gelechiidae) with Insecticides on Tomatoes

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15
Management of Tuta absoluta (Lepidoptera,
Gelechiidae) with Insecticides on Tomatoes
Mohamed Braham and Lobna Hajji
Centre régional de recherche en Horticulture et Agriculture Biologique;
Laboratoire d’Entomologie – Ecologie; Chott-Mariem,
Tunisia
1. Introduction
Tomato, Lycopersicon esculentum Mill is a vegetable crop of large importance throughout the
world. Its annual production accounts for 107 million metric tons with fresh market tomato
representing 72 % of the total (FAO, 2002). It is the first horticultural crop in Tunisia with a
production area of 25,000 hectares and a total harvest of 1.1 million metric tons (DGPA,
2009) of which nearly 70 % are processed (Tomatonews, 2011). Tomatoes are grown both
under plastic covered greenhouses and in open field.
The tomato leafminer, Tuta absoluta Meyrick, (Lepidoptera : Gelechiidae) is a serious pest of
both outdoor and greenhouse tomatoes. The insect deposits eggs usually on the underside
of leaves, stems and to a lesser extent on fruits (photo 1). After hatching, young larvae
penetrate into tomato fruits (photo 2), leaves (photo 3) on which they feed and develop
creating mines and galleries. On leaves, larvae feed only on mesophyll leaving the
epidermis intact (OEPP, 2005). Tomato plants can be attacked at any developmental stage,
from seedlings to mature stage.
Photo 1. T. absoluta egg Photo 2. Larvae on fruit Photo 3. Larva of T. absoluta
Originated from South America, T. absoluta was reported since the early 1980s from
Argentina, Brazil and Bolivia (Estay, 2000); the insect rapidly invaded many European and
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Insecticides – Pest Engineering
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Mediterranean countries. It was first recorded from eastern Spain in late 2006 (Urbaneja,
2007), then Morocco, Algeria, France, Greece, Malta, Egypt and other countries (for a
complete list see www.tutaabsoluta.com; Roditakis et al., 2010, Mohammed, 2010).
Chemical control using synthetic insecticides is the primary method to manage the pest, but
it has serious drawbacks, including reduced profits from high insecticide costs, destruction
of natural enemy populations (Campbell et al., 1991), build-up of insecticide residues on
tomato fruits (Walgenbach et al., 1991) and in the environment and fundamentally the rapid
development of insecticide resistance. For example, resistance development has been
reported against abamectin, cartap, methamidophos and permethrin in Brazil (Siqueira et al.,
2000a, Siqueira et al., 2000b) and against deltamethrin and abamectin in Argentina (Lietti et
al., 2005). Thus, in order to avoid selection of resistant biotypes, a careful management with
frequent changes of active ingredients is desirable. Furthermore, modern integrated pest
management recommends effective pesticides that have low mammalian toxicity, low
persistence in the environment and high degree of selectivity. Since insecticide control
currently remains an indispensable tool, the goal is to minimize the amount and impact of
pesticides through the diversification of active ingredients used.
In this paper, we present the data from insecticides trials conducted in 2009 and 2010 under
laboratory and field conditions, in which the efficacy of several hitherto untested
insecticides and natural products was compared with that the widely used insecticides to
manage T. absoluta in Tunisia such as spinosad, indoxacarb and pyrethroids compounds.
2. Material and methods
2.1 Laboratory trials
2.1.1 Laboratory assays in 2009
Tomato seeds (cv Topsun) were sown on 30 January 2009. Seeds were deposited in 110 cm3
cells in a rectangular polyester tray of 60 cm x 40 cm x 5 cm filled with peat (Potgrond H,
Germany). On March 3, 2009, seedlings were transplanted into 1 liter plastic flowerpot
(bottom diameter =8 cm, top diameter = 12 cm and height = 12 cm) filled with peat without
fertilization and watered as required. The tomato plants were maintained in the laboratory
until use. Three days before the assay, plants (having four to six true leaves) were deposited
in a tomato crop situated in the vicinity of the laboratory to permit T. absoluta egg-laying
then transferred to the laboratory. Leaves were examined under binocular microscope and
T. absoluta larvae were counted. Insecticides were sprayed using a hand sprayer (1 liter of
capacity). After drying, the treated plants were kept in an unsealed empty greenhouse
bordering the laboratory. There were four replications (plants) for each product and an
untreated plant was used as a check. The efficacies of the products were tested twice: 48
hours following sprays and 12 days later. The Insecticides and natural plant extracts used
are given in table 1.
2.1.2 Laboratory assays in 2010
A colony of T. absoluta was established from larvae and pupae collected from tomato
infested field in the Chott-Mariem region. The insect was reared and maintained in a small
greenhouse (10*6 m). From time to time, tomato leaves harboring T. absoluta pre-imaginal
stages collected in the field were introduced in the rearing greenhouse.
Tomato seeds (cultivar Riogrande) were sown on February 13, 2010 in a rectangular
polyester tray as mentioned before. Plants having four to six true leaves were transferred to
the rearing greenhouse and remained there for 2 to 3 days to allow egg-laying. Thereafter
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Management of Tuta absoluta (Lepidoptera, Gelechiidae) with Insecticides on Tomatoes
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Active
ingredients Trade name Companies Dose cc/ hl
water
deltamethrin Decis EC25 Bayer Crop
Science 100 cc/hl
bifenthrin Talstar FMC
Corporation 100 cc/hl
acetamiprid Mospilan 200
SL Basf 50 cc/hl
methomyl Lannate 25
Dupont de
Nemours 150 cc/hl
metamidophos Tamaron 40 Bayer Crop
Science 150 cc/hl
abamectin Vertimec Syngenta 30 cc/hl
Spinosad Tracer Dow-
Agroscience 60 cc/hl
Rotenone Rotargan
Atlantica
Agricola
(Spain)
300 cc/hl
Neem extract Oleargan Atlantica
Agricola 100 cc/hl
Table 1. Insecticides and natural plant extracts used in the laboratory trial in 2009.
returned to the laboratory and put in wooden cages for insecticide trials. Leaves were
examined under binocular microscope and T. absoluta larvae were counted just before
insecticide spray (April 3, 2010) and regularly after 2 to 3 days post-treatment. Dead larvae
following trial were recorded. The second insecticide spray was done on April 19, 2010 (two
weeks later). The Insecticides and natural plant extracts used are given in table 2.
Active ingredients Trade name Companies Dose cc/ hl water
diafenthiuron Pegasus Syngenta 125 cc/hl
triflumuron Alystin SC 480 Bayer Crop science 50cc/hl
emamectin
benzoate Proclaim® Syngenta 2500 grams/hl
Plant extracts Tutafort AltincoAgro (Spain) 125 cc/hl
Table 2. Insecticides and natural plant extracts used in the laboratory in 2010.
2.2 Field trials
2.2.1 Trials using natural products
Field experiments using botanical extracts, Spinosad and Kaolin Clay were conducted from
March 2010 to May 2010 in a half commercial tomato greenhouse (34 meters long x 8 meters
width) in Saheline region, Tunisia (35°42’ North, 10°40’East). Tomato seeds (cv Sahel) were
sown on 27 October 2009 in an expanded polyester tray under plastic protected nursery bed.
Four double rows of tomato were transplanted on 23 November 2009. The plot (greenhouse)
was prepared according to usual cropping practices in the region. Ploughing, tillage and
second tillage to incorporate manure, bed formation, irrigation device establishment and
drip irrigation.
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Active in
g
redients Trade name Com
p
anies Dose cc/ hl water
S
p
inosad Tracer 240 Dow- A
g
roscience 60 cc/hl
Neem extract Olear
g
a
n
Atlantica A
g
ricola
(
S
p
ain
)
100 cc/hl
Kaolin Clay Surround WPTM En
g
elhard Corporation
(
NJ.U.S.A
)
5 kg/hl
Orange extract Prev-amTM ORO A
g
ri International
Ltd 300 cc/hl
Botanical extracts Deffort AltincoA
g
ro
(
S
p
ain
)
350 cc/hl
Botanical extracts Armorex Soil Technolo
g
ies Corp
(
U.S.A
)
60 cc/hl
Botanical extracts
(
Quassia
amara and Neem
)
Conflic Atlantica Agricola (Spain) 250 cc/hl
Table 3. Natural products experimented in 2010.
Plots measured 4 m2 each (10 plants) arranged in a randomized block design with four
replications. The active ingredients, the trade name and doses of the natural products are
given in table 3. The products were diluted with tap water and applied at field rates based
on the recommended label dilutions without surfactants.
2.2.2 Trials using insecticides
Trials using insecticides were undertaken during the same period in the second half
greenhouse. Plot measured 8 square meters each (20 plants) arranged in a randomized block
design with four replications. Three chemical compounds were used (table 4).
Active
ingredients Trade name Companies Dose cc/ hl water
indoxacarb Avaunt 150EC Dupont 50 cc/hl
triflumuron Alsystin SC 480 Bayer Crop
science 50 cc/hl
diafenthiuron Pegasus 500SC Syngenta 125 cc/hl
Table 4. Insecticides compounds experimented under tomato greenhouse in 2010.
Insect monitoring
To assess the T. absoluta infestation prior to the trial, thirty leaf samples, taken from about 30
different plants were weekly collected (from January to March 2010) at random from the
entire greenhouse. The sample was placed in a plastic bag and taken to the laboratory.
Leaves were examined under binocular microscope (Leica MZ12.5); eggs, larvae pupae, of T.
absoluta live or dead as well as mines were recorded. However, only larvae (live or dead)
were presented in this study.
2.3 Statistical analysis
Data on the effectiveness of various insecticides were analyzed using the Minitab Software
for Windows (Minitab 13.0). The mean number of live larvae per plant or per leaf was tested
for Normality assumption by Kolmogorov-Smirnov test then the data were square root
transformed. General linear model procedures were used to perform the analysis of
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Management of Tuta absoluta (Lepidoptera, Gelechiidae) with Insecticides on Tomatoes
337
variance. Wherever significant difference occurred, Tukey’s multiple comparison test was
applied for mean separation.
In the laboratory trial of 2010, due to the low number of live larvae in the control, a one way-
ANOVA percentage of mortality was used instead of corrected mortality.
The percentages of efficacies of insecticides were evaluated either:
i. Abbott formula : the percentage of efficacy = (Ca-Ta)/Ca*100 where Ca is the average
live larvae in the control and Ta is the mean survival score in the treatment.
ii. The percentage of larval mortality = mean number of dead larvae/( mean number of
dead larvae + mean number of live larvae)*100.
3. Results
3.1 Laboratory trials
3.1.1 Assays in 2009
One day before the assay, the mean number of total live larvae (L1 to L4 instars) per plant
varied from 0.75 to 3. There is no significant difference between treatments (GLM-ANOVA.
F= 0.99, df= 9,30; P = 0.47, table 5). Three days after the first application, the mean number of
live larvae per plant decreases in all treatments except in the control (Table 5). All
insecticides significantly reduced T. absoluta larvae when compared with non treated control
(F= 4.24, df = 9,30; P= 0.001, Table 5). However, the level of suppression by acetamiprid and
bifenthrin did not differ significantly from the control (Table 5).
Mean number of larvae/plant on indicated days before treatment (DBF) and days after
treatment (DAT)
Insecticides ! 1DBT1!! 3DAT1 5DAT1 8DAT1 12DAT1
spinosad(1) 1.75a 0.5a(86.66)* 0.50a(85.71)* 0.5a (87.5)* 0.25a(93.75)*
neem extract(2) 1.5a 0.75a(80) 0.75a(78.50) 0.5a(87.5) 0.5a(87.5)
rotenone(3) 0.75a 0.25a(93.33) 0.25a(92.90) 0.5a(87.5) 0.75a(81.25)
deltamethrin(4) 0.5a 0a(100) 1a(71.42) 0.75a(81.25) 1.5ab(62.5)
acetamiprid(5) 2a 1.25ab(66.66) 1.25ab(64.28) 1.25ab(68.75) 0.50a(87.5)
methomyl(6) 3a 0.5a(87) 0.5a(86) 0.50a(88) 0.75a(81)
metamidophos(7) 2a 0.75a(80) 0.75a(79) 0.75a(81) 1.00a(75)
abamectin(8) 2.25a 0.75a(80) 0.75a(79) 0.5a(88) 0.25a(94)
bifenthrin(9) 2a 1.25ab(67) 2ab(43) 1.25ab(69) 1.00a(75)
Control 2.5a 3.75b 3.5b 4b 4b
Statistical analysis F= 0.99 F= 4.24 F= 3.69 F= 4.20 F= 4.66
ANOVA- df = 9,30 df = 9,30 df = 9,30 df = 9,30 df = 9,30
GLM P = 0.47 P= 0.001 P= 0.003 P= 0.001 P=0.003
! denote commercial compounds: (1): Tracer, (2): Oleargan, (3): Rotargan, (4): Decis, (5): Mospilan, (6):
Lannate (7): Tamaran, (8): Vertimec, (9): Talstar
!! Means followed by the same letter within a column are not significantly different at P= 0.05 (ANOVA-
GLM procedure) followed by Tukey multiple comparison
* Data in brackets denote percent Abbott mortality (Abbott, 1925)
Table 5. Mean number of T. absoluta total live larvae/plant on indicated days before
treatment (DBF) and days after treatment (DAT) (the first treatment was done on April 1,
2009).
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Five days following the first application, all the products performed well except acetamiprid
and bifenthrin which show no significant difference compared with the control (Table 5).
Eight days after the first application, the mean number of total live larvae per plant varied
from 0.5 to 4. All the tested products reduced significantly the density of live larvae per
plant compared with the control (F= 4.20; df = 9,30; P= 0.001). Still, acetamiprid and
bifenthrin showed mild efficacy (table 5). At 12 days following treatments, all the products
performed well (F= 4.66, df = 9,30 ; P= 0.003), yet the plants treated with deltamethrin show
increasing mean live larvae per plant (table 5).
Regarding the corrected mortality according to Abbott formula, Spinosad and rotenone gave
satisfactory results post-treatment (88.4 % and 88.7% respectively) followed by Lannate
(85%), Vertimec (85%), neem extract (83. 22), and Tamaran (79%). However, Decis (78.8%),
Mospilan (71.8) and Talstar (63%) showed mild efficacy. Though, Decis performed well till 8
days following the first application (84.2%).
Mean number of total live larvae/plant on indicated days after the second treatment
(DAT)
Insecticides 0DBT2!! 2DAT2 4DAT2 8DAT2
spinosad 0a 0a(100)* 0a(100)* 0.75a(83.33)*
neem extract 0.5a 0.5a(92.85) 0.75a(78.60) 1.75a(61.11)
rotenone 0.25a 0.5a(85.71) 0.5a(85.71) 1.25a(72.22)
deltamethrin 0.75a 0.75a(78.60) 1a(71.42) 1.25a(72.22)
acetamiprid 0.5a 0.5a(85.71) 0.75a(78.60) 1.5a(66.66)
methomyl 1.25a 0.75a(78.60) 0.75a(78.60) 2a(83.33)
metamidophos 0.75a 0.75a(78.60) 0.5a(85.71) 1a(77.71)
abamectin 0.5a 0.5a(85.71) 0.5a(85.71) 1.5a(66.66)
bifenthrin 1a 1a(64.28) 1.5ab(57.14) 2a(55.55)
Control 3.5b 3.5b 3.5b 4.5b
Statistical
analysis
F= 6.07 F= 7.24 F=5.84 F= 4.39
df = 9,30 df = 9,30 df = 9,30 df = 9,30
P = 0.00 P= 0.00 P= 0.00 P= 0.001
* Data in brackets denote percent Abbott mortality (Abbott, 1925)
!! : Means followed by the same letter within a column are not significantly different at P= 0.05
(ANOVA-GLM procedure) followed by Tukey multiple comparison
Table 6. Mean number of total T. absoluta live larvae/plant the day of the second treatment
and thereafter (DAT2) (the treatment was undertaken on April 21)
Just before the second application, the mean number of live larvae in treated plants
remained low compared with the control. It varied between zero (Tracer) and 3.5 (control)
(table 6). Two days following the second insecticide application, all tested compounds show
good efficacy compared with control (F=4.24; df = 9,30; P<0.001). Spinosad (Tracer)
performed well (100 % efficacy according to Abbott corrected mortality formula). However,
bifenthrin (Talstar) shows mild efficacy (table 6). The same conclusion can be formulated
four days following treatments (table 6). At eight days after trial, the insecticide spinosad
remains active and performed well (83.33 % efficacy) (table 6).
The overall efficacy according to Abbott formula (1925) shows the good performance of
spinosad (Tracer), rotenone (Rotargan), methomyl (Lannate), abamectin (Vertimec) (Fig. 1.).
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Management of Tuta absoluta (Lepidoptera, Gelechiidae) with Insecticides on Tomatoes
339
However, the percentage of larval mortality (number of dead larvae/sum of dead and live
larvae) following the first and second insecticide application shows the best performance of
spinosad (91 %), neem extract (71 %) and abamectin (71%).
Fig. 1. Overall percentage of efficacy according to Abbott formula (1925). DAT1 = days after
the first treatment, DAT2 = days after the second treatment (laboratory trial, 2009).
0
10
20
30
40
50
60
70
80
90
100
spinosad (Tracer)
neem extract
Rotenone
deltamethrin (Decis)
acetamiprid(Mospilan)
methomyl (Lannate)
metamidophos(Tamaran)
abamectin (Vertimec)
bifenthrin(Talst ar)
Control
% larval mortalit
y
% mortalityT1 % mortalityT2 Average
Fig. 2. Percentage of larval morality following the first (T1) and the second treatment (T2)
(mean number of four dates after the fist treatment and 3 dates after the second treatment).
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3.1.2 Assays in 2010
Just before the first spray (April 3, 2010), the mean number of live larvae (first to fourth
instars) per leaf varied from 0.12 (Control) to 0.52 (Proclaim®). Although there is no
significant difference between treatments (ANOVA-GLM F= 1.37, df = 4, 116; P=0.24), the
control plants harboured less live larvae (table 7). There is no larval mortality.
Two days following the first spray (April 5), there is no significant difference between
treatments regarding live larvae (GLM; F= 0.93, df = 4, 116; P= 0.46. Table 7). However, the
percentage of larval mortality did vary (ANOVA, 1 factor, F = 4.17; df = 4, 120; P= 0.003)
showing the best performance of Proclaim® (57.14 %; Table 7).
Nine days after the first insecticide application (April 12), the mean number of live larvae
per leaf did not significantly vary between treatments (ANOVA-GLM procedure Table 7).
However, the percentage of mortality significantly varies between treated and untreated
plants (ANOVA 1 factor, F= 3.07; df = 4, 120; P= 0.021). The maximum percentage of
mortality is given by Proclaim® (45.70%, table 7).
At 11 days after the first insecticide application (on April 14), the mean number of live
larvae did not significantly vary among treated and untreated plants (ANOVA - GLM
procedures Table 7). However, the percentage of mortality did vary according to treatments
(F = 3.16, df = 4, 120; P= 0.017) showing the good efficacy of Proclaim® (52.93 % Table 7).
Mean number of live larvae/leaf on indicated days before treatment (DBF) and days after
treatment (DAT)µ
Insecticides! 0DBT! ! 2DAT1 9DAT1 11DAT1 13DAT1
(1) 0.36(0)a 0.36(10)a 0.37(13.61)a 0.44(12.66)a 0.34(12.82)a
(2) 0.32(0)a 0.2(37.5)a 0.24(29.47)a 0.34(23.52)a
0.34(20.05)a
(3) 0.52(0)a 0.24(57.14)a 0.29(45.70)a 0.25(52.93)a
0.23(51.51)a
(4) 0.44(0)a 0.48(0)a 0.26(17.91)a 0.20(21.91)a 0.18(27.39)a
(5) 0.12(0)a 0.24(0)a 0.22(0)a 0.25(0)a 0.20(0)a
Statistical
analysis F= 1.37 F=0.90 F= 0.57 F=0.63 F=0.27
ANOVA df =4,116 df =4,116 df =4,116 df =4,116 df =4,116
-GLM P =0.24 P =0.46 P = 0.67 P=0.64 P= 0.89
! :(1):triflumuron(Alystin), (2) plant extract (Tutafort), (3) emamectin benzoate (Proclaim®) (4)
diafenthiuron (Pegasus ) and (5) Control.
µ: Data under brackets denote percentage of mortality
! ! : Means followed by the same letter within a column are not significantly different at P= 0.05
(ANOVA-GLM procedure) followed by Tukey multiple comparison
Table 7. Mean number of live T. absoluta larvae on indicated days before treatments and
days after treatments (laboratory trial, 2010)
At 13 days after the first application, the mean number of live larvae did not significantly
vary between treatments and control (Table 7). However, the percentage of mortality
significantly varies between treated and control plants (F = 3.53 df = 4, 120; P= 0.009)
showing the good efficacy of the compound Proclaim® (51.51 %, table 7).
At 16DAT1 and just before the second spray, the mean number of live larvae shows no
significant difference between treated and control plants (table 7. continued). However, the
percentage of mortality did significantly vary between treated and control plants (One way
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Management of Tuta absoluta (Lepidoptera, Gelechiidae) with Insecticides on Tomatoes
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ANOVA F= 4.95 df = 4, 120; P= 0.001). The compound Proclaim® shows the highest
mortality percentage (54.83 % table 7.Cont.).
At three days after the second insecticide application, there is no significant difference
regarding the mean number of live larvae per leaf (GLM-ANOVA). Nevertheless, plants
treated with the product Proclaim® harbour zero live larvae per leaf suggesting the good
efficacy of this insecticide. This is confirmed by the high percentage of mortality (100 %) as
well as the significant difference between treated and control plants (One way ANOVA, F=
4.51 df = 4, 120; P= 0.002).
Mean number of live larvae/leaf on indicated da
y
s before treatment (DBF) and da
y
s after
treatment
(
DAT
)(
µ
)
Insecticides 16DAT1! 3DAT2 5DAT2 8DAT2 10DAT2
(
1
)
0.33
(
12.55
)
a0.19
(
51.71
)
a0.16
(
59.91
)
ac 0.15
(
59.4
)
ac 0.15
(
59.14
)
ac
(2) 0.31(21.47)a 0.06(80.15)a 0.06(83.64)ac 0.06(83.35)ac 0.06(83.35)ac
(3) 0.20(54.83)a 0(100)a 0(100)bc 0(100)bc 0(100)bc
(4) 0.20(19.60)a 0.16(0)a 0.1(59.55)ac 0.09(59)ac 0.09(59)ac
(
5
)
0.20
(
0
)
a0.16
(
0
)
a0.16
(
0
)
a0.16
(
0
)
a0.06
(
0
)
a
Statistical
analysis
F= 0.27 F= 2.02 F= 1.85 F= 1.85 F= 1.56
df =4, 116 df =4, 116 df =4, 116 df =4, 116 df =4, 116
GLM- P= 0.89 P= 0.096 P= 0.123 P= 0.096 P=0.189
ANOVA
µ : Data under brackets denote percentage of mortality
! : Means followed by the same letter within a column are not significantly different at P= 0.05
(ANOVA-GLM procedure) followed by Tukey multiple comparison
Table 7. (continued). Mean number of live T. absoluta larvae on indicated days before
treatments and days after treatments (laboratory trial, 2010)
Five days after the second spray, the mean number of live larvae did not vary among treated
and untreated plants (table 7. Cont.). But the percentage of mortality significantly varies
(ANOVA one factor F= 3.98 df = 4, 120; P= 0.03) showing again the good performance of
Proclaim® (table 7.Cont.).
At eight days after the second spray, there is no significant difference between treated plants
and control regarding the mean number of live larvae (table 7.Cont.). However, the
percentage of mortality varies (ANOVA, one factor, F= 3.88 df = 4, 120; P= 0.005). The
compounds Proclaim® and Tutafort are the best (100 % and 83.35 respectively, table
7.Cont.).
At 10 days after the second insecticide application, there is no significant difference between
treated plants and control (GLM-ANOVA, Table 7.Cont.). Concerning the percentage of
mortality, there is a significant difference between treated and control plants (ANOVA, one
factor, F= 3.99 df = 4, 120; P= 0.006). Proclaim® followed by Tutafort performed well (100 %
and 83.35 respectively, table 7.Cont.).
3.2 Field trials
3.2.1 Natural products experimented in 2010 under greenhouse
The first spray was undertaken on March 26, 2010, then on April 8 and on April 19, 2010.
At three days following the first application, the mean live larvae (small and old larvae) per
leaf did not significantly vary between treated and control plots (GLM-ANOVA Procedure,
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P= 0.09). Although, plots treated with spinosad show the minimum live larvae as
demonstrated by 70% efficacy according to Abbott formula (Table 8). The details of larval
instars (small larvae: first and second instars and old larvae: three and fourth instars) show a
significant difference between insecticides tested. The compounds Tracer, Armorex and
Deffort performed well (table 9).
Mean number of total larvae/leaf on indicated da
y
s before treatment (DBF) and da
y
s after
treatment
(
DAT
)
Insecticides 1DBT! ! 3 DAT1* 10DAT1
(
µ
)
2DAT2 6DAT2
Armorex
(
1
)
0.30a 0.20
(
20
)
a0.1
(
69.23
)
a0
(
100
)
a 0.325
(
0
)
a
Deffort
(
1
)
0.30a 0.25
(
0
)
a0.45
(
0
)
a 0.475
(
0
)
b0.3
(
0
)
a
Olear
g
an
(
1
)
0.20a 0.32
(
0
)
a 0.225
(
30.76
)
a0.05
(
33.33
)
a0.25
(
0
)
a
Konflic
(
1
)
050a 0.57
(
0
)
a0.2
(
38.46
)
a 0.125
(
0
)
a 0.075
(
0
)
a
Prev-amTM
(
2
)
0.32a 0.37
(
0
)
a0.45
(
0
)
a0.1
(
0
)
a0.2
(
0
)
a
Surround
WPTM
(
3
)
0.30a 0.32(0)a 0.25(23.07)a 0.075(0)a 0.15(0)a
Tracer
(
4
)
0.1a 0.075
(
70
)
a0.05
(
84.61
)
a0
(
100
)
a 0.025
(
0
)
a
Control 0.20a 0.25a 0.325a 0.075a 0.025a
Statistical
Analysis
F= 1.42 F= 1.94 F= 1.61 F= 1.61 F= 1.92
df =3, 309 df =3, 309 df =3, 309 df =3, 309 df =3, 309
GLM- ANOVA P= 0.120 P= 0.09 P= 0.131 P=0.008 P=0.066
(1): Botanical extracts
(2): Orange extract
(3) : Kaolin
* Corrected mortality according to Abbott formula
µ = second spray
! ! : Means followed by the same letter within a column are not significantly different at P= 0.05
(ANOVA-GLM procedure) followed by Tukey multiple comparison
Table 8. Mean number of total live larvae following natural products applications under
tomato greenhouse (Saheline, Tunisia, 2010).
At 10 days after the first natural products applications, the ANOVA-GLM procedure shows
no significant difference between treatments regarding the mean number live larvae (Table
8). The Abbott’s percentages of efficacy show the performance of spinosad (84.61 %) and the
plant extract (Armorex; 69.23%).
At two days after the second spray, (April 10) there is a significant difference between
treated plots (AVOVA-GLM procedure, P= 0.008, table 8). The plots treated with Deffort
show the maximum density of mean live larvae per leaf (table 8). However, there is no
significant difference between the other products and control. The details of larval stages
confirm the low efficacy of Deffort compared with the other products and control (small
larvae : P= 0.026; Old larvae P= 0.019; table 9).
Six days following the second application (April 14), the mean number of live larvae shows
no significant difference between treated and untreated plots (Table 8).
At eleven days after the second spray, the mean number of live larvae per leaf is relatively
similar among treatments and did not significantly vary (ANOVA-GLM procedure P= 0.211)
varying from 0.1 to 0.9. Plots treated with Kaolin (Surround) harbour the minimum density.
Four days after the third spray (April 23, 2010), the treated plot differed significantly
showing the good performance of the compounds neem extract, Tracer and Konflic (table
8). This is confirmed by the analysis of detailed larval instars (table 9).
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At nine days after the third spray, the mean number of total larvae varied between 0.2 and
2.05. The ANOVA-GLM procedure showed a significant difference between treatments. The
products Tracer, Armorex and Deffort were effective in reducing T. absoluta larval densities
(table 8).
Mean number of total larvae/plant on indicated days before treatment (DBF) and days
after treatment (DAT)
Insecticides 11 DAT2! 4DAT3! ! 9DAT3 18DAT3
Armorex(1) 0.525(0)a 0.1(85.18)a 0.3(85.36)b 0.9(12.2)a
Deffort(1) 0 .925(0)a 0.3(55.55)a 0.2(90.24)b 0.65(36.85)a
Oleargan (1) 0.325(13.33)a 0.075(88.88)ab 0.55(73.17)b 0.375(63.4)a
Konflic(1) 0.475(0)a 0(100)ab 0.825(59.75)a 0.325(68.3)a
Prev-amTM (2) 0.225(40) a 0.175(74.07)a 1.675(18.30)a 0.7(31.7)a
Surround(3) (3)0.1(73.33)a 0.2(70.37)a 0.55(73.17)b 0.375(63.4)a
Tracer(4) 0.35(6.66)a 0.1(85.18)a 0.25(87.80)b 0.75(26.8)a
Control 0.375a 0.675a 2.05a 1.025a
Statistical
Analysis
F=1.41 F=2.49 F=2.49 F=1.36
df= 7,309 df= 7,309 df= 7,309 df= 7,309
GLM-ANOVA P=0.201 P=0.017 P=0.000 P=0.220
! : third spray
! ! : Means followed by the same letter within a column are not significantly different at P= 0.05
(ANOVA-GLM procedure) followed by Tukey multiple comparison
Table 8. (Continued) Mean number of total live larvae following natural products
applications under tomato greenhouse (Saheline, Tunisia, 2010).
Mean number of live larvae/leaf on indicated da
y
s before treatment (DBF) and da
y
s after
treatment
(
DAT
)
Insecticides 3DAT1! ! 10DAT1
SL* OL* SL* OL*
Armorex
(
1
)
0.075
(
40
)
a 0.125
(
0
)
a0.1
(
50
)
a0
(
100
)
a
Deffort
(
1
)
0.05
(
60
)
a0.2
(
0
)
a 0.225
(
0
)
a 0,225
(
0
)
a
Olear
g
an
(
1
)
0.2
(
0
)
a 0.125
(
0
)
a 0.175
(
12.5
)
a0.05(60
)
a
Konflic(1) 0.425(0)b 0.15(0)a 0.1(50)a 0.1(20)a
Prev-amTM
(
2
)
0.25
(
0
)
ab 0.125
(
0
)
a 0.275
(
0
)
a 0.175
(
0
)
a
Surround WPTM
(
3
)
0.3
(
0
)
a 0.025
(
80
)
a0
(
100
)
a0.25
(
0
)
a
Tracer
(
4
)
O
(
100
)
a 0.075
(
40
)
a0.05
(
75
)
a0
(
100
)
a
Control 0.125
(
0
)
ab 0.125
(
0
)
a0.2
(
0
)
a 0.125
(
0
)
a
Statistical Analysis F= 4.03 F= 0.77 F= 1.76 F= 1.53
df= 3,309 df= 3,309 df= 3,309 df= 3,309
GLM-ANOVA P= 0.00 P= 0.611 P= 0.096 P=0.157
*: SL : Small larvae (L1-L2), OL: Old larvae (L3-L4)
! ! : Means followed by the same letter within a column are not significantly different at P= 0.05
(ANOVA-GLM procedure) followed by Tukey multiple comparison.
Table 9. Mean number of live small and old larvae following natural products applications
under tomato greenhouse (Saheline, Tunisia, 2010).
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Mean number of larvae/plant on indicated days before treatment (DBF) and days after
treatment (DAT)
Insecticides 2 DAT2! ! 6DAT2
SL* OL* SL*µ OL*
Armorex(1) 0(100)a 0(100)b 0.1b 0.225(0)a
Deffort(1) 0.175(0)b 0.3(0)a 0.025a 0.275(0)a
Oleargan (1) 0.025(0)a 0.025(50) b 0.175b 0.075(0)a
Konflic(1) 0.05(0)a 0.075(0)b 0a 0.075(0)a
Prev-amTM (2) 0(100)a 0.1(0)b 0.125b 0.075(0)a
Surround(3) 0.025(0)a 0.05(0)b 0.1b 0.05(0)a
Tracer(4) 0(100)a 0(100)b 0a 0.025(0)a
Control 0.025a 0.05b 0a 0.025a
Statistical
analysis GLM-
ANOVA
F= 2.31 F= 2.44 F= 2.18 F= 1.34
df= 3,309 df= 3,309 df= 3,309 df= 3,309
P= 0.026 P=0.019 P=0.036 P=0.069
µ: undetermined Abbott percentage of efficacy (zero Small larvae in the control plot)
SL: Small larvae (L1-L2), OL: Old larvae (L3-L4).
! ! : Means followed by the same letter within a column are not significantly different at P= 0.05
(ANOVA-GLM procedure) followed by Tukey multiple comparison
Table 9. (Continued) Mean number of live small and old larvae following natural products
applications under tomato greenhouse (Saheline, Tunisia, 2010).
Mean number of larvae/plant on indicated days before treatment (DBF) and days after
treatment (DAT)
Insecticides 11 DAT2! ! 4DAT3
SL* OL* SL* OL*
Armorex(1) 0.375(0)a 0.15(0)a 0(100)a 0.1(84.61)ab
Deffort(1) 0.7(0)a 0.225(0)a 0.15(0)b 0.15(76.9)ab
Oleargan (1) 0.25(0)a 0.075(50)a 0.025(0) a 0.05(92.30)b
Konflic(1) 0.425(0)a 0.05(66.66)a 0(100)a 0(100)b
Prev-amTM (2) 0.075(66.66)a 0.15(0)a 0(100)a 0.175(73.0)b
Surround WPTM (3) 0.07(66.66)a 0.02(83.33)a 0.125(0)b 0.075(88.4)b
Tracer(4) 0.275(0)a 0.075(50)a 0.075(0)ab 0.02 (96.15)b
Control 0.225a 0.15a 0.025a 0.65a
Statistical Analysis F=1.31 F=1.10 F=2.75 F=2.82
df=3,309 df=3,309 df=3,309 df=3,309
GLM-ANOVA P=0.246 P=0.361 P=0.009 P=0.007
*: SL : Small larvae (L1-L2), OL: Old larvae (L3-L4)
! ! : Means followed by the same letter within a column are not significantly different at P= 0.005
(ANOVA-GLM procedure) followed by Tukey multiple comparison
Table 9. (Continued) Mean number of live small and old larvae following natural products
applications under tomato greenhouse (Saheline, Tunisia, 2010).
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345
Mean number of larvae/plant on indicated days before treatment (DBF) and days after
treatment (DAT)
Insecticides 9 DAT3! ! 18DAT3
SL* OL* SL* OL*
Armorex(1) 0.125(72.22)a 0.175(89.06)b 0.75(0)a 0.15(75) a
Deffort(1) 0.025(94.44)b 0.175(89.06)b 0.4(5.88)a 0.25(58.33)a
Oleargan (1) 0.225(50)a 0.325(79.68)b 0.075(82.35)a 0.3(50)a
Konflic(1) 0.275(38.88)a 0.55(65.62)a 0.175(58.82)a 0.15(75) a
Prev-amTM (2) 0.375(16.78)a 1.3(18.75)a 0.45(0)a 0.25(58.33)a
Surround WPTM (3) 0.1(77.77)a 0.45(71.87)a 0.2a 0.175(70.83)a
Tracer(4) 0.125(72.22)a 0.125(92.18)b 0.45(0)a 0.3(50)a
Control 0.45a 1.6a 0.425a 0.6a
Statistical Analysis F= 2.33 F=5.68 F=1.41 F= 1.97
df = 3,309 df = 3,309 df = 3,309 df = 3,309
ANOVA-GLM P= 0.00 P=0.000 P=0.201 P=0.06
* Data in brackets denote percent Abbott mortality (Abbott, 1925)
! !: Means followed by the same letter within a column are not significantly different at P= 0.05
(ANOVA-GLM procedure) followed by Tukey multiple comparison
Table 9. (Continued) Mean number of live small and old larvae following natural products
applications under tomato greenhouse (Saheline, Tunisia, 2010).
Three days following the first insecticide application, the mean number of live larvae (small
and large) did not vary significantly between treated and untreated plots (ANOVA-GLM
Procedure F= 1.94, df = 3, 309 P= 0.063). However, the plants treated with spinosad (Tracer)
harbor the minimal larval density (Table 9).
3.2.2 Insecticides compounds experimented under tomato greenhouse in 2010
Four days before the first insecticide application, the mean number of live larvae per leaf
varied between 0.6 and 0.97 showing no significant difference between treatments and
control (ANOVA. GLM, F= 0.82, df =3, 156; P=0.82).
Two days following the first treatment (March 24), the mean number of live larvae remains
relatively low and did not significantly vary between treatment and control (F = 0.34; df = 3,
153; P= 0.79). The corrected mortality according to Abbott formula shows slight efficacy of
tested products (Table 10).
At 12 days following the first application, the mean number of live larvae significantly
differed between treatments (GLM, F=2.90, df = 3, 156; P= 0.037). The Tukey multiple
comparisons showed the good performance of indoxacarb (Avaunt) (Table 10). There is no
significant difference between plot treated with triflumuron (Alystin), diafenthiuron
(Pegasus) and untreated plots.
Three days after the second treatment, there is a significant difference between treated plots
and control (GLM, F= 16.45 df = 3, 153; P= 0.000). The three compounds performed well
particularly Avaunt (92.30 % according to Abbott formula).
Nine days following the second spray, all insecticides performed well compared with the
control (F= 46.7 df =3,153; P=0.000) with the best performance of indoxacarb (Avaunt) (96.87
% efficacy according to Abbott formula, Table 10).
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Mean number of larvae/leaf on indicated days before treatment (DBF) and days after
treatment (DAT)µ
Insecticides 4DBT1! ! 2 DAT1 12DAT1 3DAT2 9DAT2
indoxacarb 0.87a 0.7(15. 15)a! 0.2(71.42) a! 0.05(92 .30)a 0.075(96.87)a
triflumuron 0.97a 0.6(27.27)a 0.52 (25)ab 0.1(84.61)a 0.4(83.33)a
diafenthiuron 0.6a 0. 72 (12.12)a 0.4(42.85)ab 0.125(80.76)a 0.30(87.5)a
Control 0.87a 0.85a 0.7 b 0.65b 2.4b
Statistical
analysis
F=0.82 F= 0.43 F=2.90 F= 16.45 F= 46.7
df =3, 153 df = 3, 153 df = 3, 153 df =3, 153 df =3, 153
GLM-ANOVA P=0.48 P=0.72 P=0.037 P=0.000 P=0.000
µ : the first treatment was undertaken on March 22, 2010.
! : data in brackets denote percentage of efficacy (Abbott Formula)
! ! : Means followed by the same letter within a column are not significantly different at P= 0.05
(ANOVA-GLM procedure) followed by Tukey multiple comparison
Table 10. Mean number of T. absoluta larvae/leaf on indicated days before treatment (DBF)
and days after treatment (DAT) (Saheline tomato greenhouse, 2010).
Mean number of larvae/leaf on indicated days before treatment (DBF) and days after
treatment (DAT)
Insecticides 18DAT2! ! 3DAT3 12DAT3
indoxacarb (Avaunt) 0.05(95.83)a 0.075(95.45)a 0.35(78.12)a
triflumuron (Alystin) 0.05((95.83)a 0.5(69.69)a 0.7(56.25)a
diafenthiuron
(Pegasus) 0.075(93.75)a 0.325(80.30)a 0.32(87.5)a
Control 1.2b 1.65b 1.6b
Statistical analysis F= 40.88 F= 20.91 F=10.87
df =3, 153 df =3, 153 df =3, 153
P = 0.00 P= 0.00 P= 0.000
! ! : Means followed by the same letter within a column are not significantly different at P= 0.05
(ANOVA-GLM procedure) followed by Tukey multiple comparison
Table 10 (continued). Mean number of T. absoluta larvae per leaf on indicated days before
treatment (DBF) and days after treatment (DAT) (Saheline tomato greenhouse, 2010).
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Management of Tuta absoluta (Lepidoptera, Gelechiidae) with Insecticides on Tomatoes
347
At 18 days following the second application, the mean number of live larvae significantly
varies between treated and control plots (GLM F= 40.88; df = 3, 153; P= 0.000). The efficacy
of tested insecticide remains high compared with the control.
At 3 and 12 days following the third insecticide application all tested insecticides continue to
be effective compared with the control (F= 20.91 df =3, 153; P= 0.00 ; F=10.87; df =3, 153; P=
0.00). Nevertheless, indoxacarb (Avaunt) tend to be a powerful suppressor of T. absoluta
larvae (table 10).
4. Discussion
In Argentina, the primary T. absoluta management tactic was chemical sprays (Lietti et al.,
2005). Organophosphates were initially used for T. absoluta control then were gradually
replaced by pyrethroids during the 1970s. During the early 1980s, cartap which alternates
with pyrethroids and thiocyclam were sprayed showing the good effectiveness of the
former. During the 1990s, insecticides with novel mode of actions were introduced such as
abamectin, acylurea, insect growth regulators, tenbufenozide and chlorfenapyr (Lietti et al.,
2005).
Our laboratory results demonstrate the efficacy of spinosad (Tracer), rotenone (Rotargan),
methomyl (Lannate) and abamectin (Vertimec). Methomyl was only tried due to its highly
used frequency in tomato production against Noctuid larvae in Tunisia.
Spinosad, a mixture of spinosyns A and D, is derived from the naturally occurring
actionomycete, Saccharopolyspora spinosa (Sparks et al., 1998). Because of its unique mode of
action, involving the postsynaptic nicotinic acetylcholine and Gamma-aminobutyric (GABA)
receptors, spinosad has strong insecticidal activity against insects (Salgado, 1998) especially
Lepidoptera (e.g. Helicoverpa armigera (Wang et al., 2009), Spodoptera frugiperda (Méndez et al.,
2002), Diptera (King and Hennesey 1996; Collier and Vanstynwyk , 2003 ; Bond et al., 2004),
some Coleoptera (Elliott et al., 2007) as well as stored grains (Hertlein et al, 2011).
To date, spinosad is considered a good alternative control of Lepidopteran pests due to its
high activity at low rates and its use in integrated pest management programs. The product
possesses advantages in term of safety for farm workers and consumers due to its low
mammalian toxicity and rapid breakdown in the environment (Sparks et al., 1998). The
compound is considered as a standard product for the control of T. absoluta in Brazil
(Maraus et al., 2008) showing, however low efficacy compared with the insecticide
novaluron.
Rotenone has been reported to be an excellent insecticide against a wide range of insect
pests. Davidson (1930) found that rotenone was a toxic and effective contact insecticide
against several species of whiteflies, aphids, caterpillars and mites. Also, Turner (1932)
reported a high toxicity of rotenone to larvae of the Colorado potato beetle Leptinotarsa
decemlineata (Say).
Azadirachtin, a tetranortriterpenoid isolated from the seeds of neem tree, Azadirachta indica
(Meliaceae), and the fruit of chinaberry, Melia azaderach (Meliaceae) acts as an antifeedant
and inhibits the growth and the development of several insects (Meisner et al., 1981, Raffa,
1987; McMillian et al., 1969). The antifeefant effects of azadirachtin are partly due to sensory
detection and avoidance by insects (Simmonds and Blaney 1984).
Acetamiprid (Mospilan) is a neonicotinoid insecticide that is formulated for both soil and
foliar application. It is a broad-spectrum insecticide effective against several groups of
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insects including Lepidopterans, Coleopterans, Hemipterans and Thysanopterans. The
insecticide has an ingestion and stomach action and has a strong osmotic and systemic
action (Takahashi et al., 1998). The compounds interact with Acetylcholine receptors
(AChRs) in a structure-activity relationship, resulting in excitation and paralysis followed
by death (Ishaaya et al., 2007).
Abamectin a mixture of avermectins is extracted by the fermentation of the soil bacterium
Streptomyces avermitilis (Strong & Brown 1987). The insecticide acts on the GABA receptor
activating the chloride channel (nerve and muscles) (Aliferis and Jabaji, 2011).
Throughout the assay, the product emamectin benzoate (Proclaim®) showed the best
efficacy strongly suppressed T. absoluta larval populations. Indeed, several authors reported
the performance of this product against several insects, for example, Seal (2005), reported
the efficacy of emamectin benzoate at various rates in reducing the densities of the melon
thrips, Thrips palmi adults and larvae. Stanley et al., (2005) reported the high acute toxicity of
emamectin benzoate to Helicoverpa armigera under laboratory conditions.
Cook et al., (2004) conducted field and laboratory trials on cotton and soybean for the
control of the beet armyworm Spodoptera exigua (Hübner) and the fall armyworm Spodoptera
frugiperda using indoxacarb, pyridalyl, spinosad methoxyfenozide and emamectin benzoate
demonstrated the good efficacy of tested products compared with the control. Plots treated
with indoxacarb, spinosad and emamectin benzoate had significantly fewer beet armyworm
larvae.
Avermectins are a family of 16-membered macrocyclic lactone natural product homologues
produced by the soil microorganisms, Streptomyces avermitilis. They act as agonists on GABA
and glutamate gated chloride channels. The chloride ion flux produced by the direct
opening of channels into neuronal cells results in loss cell function and disruption of nerve
impulses. Consequently, arthropods are paralyzed irreversibly and stop feeding. Maximum
mortality is achieved within four days (Jansson et al., 1997).
Emamectin benzoate (Proclaim) is a novel semi-synthetic derivative of the natural product
abamectin in the avermectin family. This insecticide has a high potency against a broad
spectrum of lepidopterous pests with an efficacy of about 1,500-fold more potent against
certain armyworm species (Jansson et al., 1996)
Insect growth regulators like triflumuron, lufenuron are claimed to be safe and have little
impact on beneficial arthropods compared with conventional insecticides and thus attracted
considerable attention for their inclusion in IPM programs (Ishaaya et al., 2007). In this
study, triflumuron showed low efficacy against T. absoluta larvae. These results are in
accordance with data reported by El-Sheikh and Aamir (2011) suggesting the greater
efficiency of lufenuron in controlling Spodoptera littoralis Boisd compared with triflumuron
or flufenoxuron. Similarly, low effectiveness of triflumuron (Alystin SC48) for the control of
Cactoblastis cactorum (Lepidoptera: Pyralidae) was reported in Argentina by Labos et al.,
(2002). Yet the concentration used was lower (30 cc/ hl). Regarding the control of the
Mediterranean fruitfly, Ceratitis capitata, triflumuron (Alystin 25) failed to give satisfactory
results (a concentration of 150 ppm did not kill adults, Zapata et al., (2006)).
Diafenthiuron (Pegasus) is a new type of thiourea derivative that affects respiration in
insects. It disrupts oxidative phosphorylation by inhibition of the mitochondrial ATP
synthase, an enzyme with essential role in cellular bioenergetics (Ishaaya, 2010). It is an
insecticide and acaricide which kills larvae, nymphs and adults by contact and/or stomach
action, showing also some ovicidal action (e-pesticide manual, 2005). In our laboratory trial,
diafenthiuron (Pegasus) shows little efficacy in T. absoluta larval suppression (table 10).
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Tutafort (plant extract) shows little efficacy after the first application but increases
effectiveness after the second application engendering about 80 % of larval mortality (table
7.Cont.). Yet according to manufacturer, (Altinco, 2011), the product has a preventive action
and should be applied against eggs and adults. The compound acts by contact penetrating
the insect cuticle and dissolves the cell membranes causing the insect dehydrate and its
death (Altinco, 2011).
Management of resistance to prevent or delay the development of resistance to an
insecticide and cross resistance to additional insecticides is necessary for increasing the
chance of chemical control of T. absoluta. Thus, the avoidance of resistance requires the
development of pest management programs in which efforts are made to take advantages of
natural enemies of pests, plant resistant cultivars, if available, appropriate cultural and
physical methods.
Accordingly, diversification of control tactics should be implemented with the minimum
use of chemicals. Insecticides should be applied only as needed basis and only used as the
last form of control. When insecticides are applied, the way that they are used should be
rationalized and optimized to exploit the full diversity of synthetic chemicals and natural
products mostly used at rotational basis.
Development of resistance in T. absoluta is an important problem in regions where the insect
is established. The expanding international trade of plant material not only spread the pest
but also spreads the resistance genes associated with the pest (Denholm and Jespersen,
1998). It is possible that the Mediterranean populations of T. absoluta already carried gene
resistance from South American counterpart populations and thus, may already express
high level of resistance to one or multiple insecticide. Indeed, Cifuentes et al., (2011),
demonstrated high genetic homogeneity of T. absoluta populations came from
Mediterranean basin and from South America countries using ribosomal and
mithochondrial markers.
Our field results (tomato greenhouse) suggest the good performance of the tested
compounds (indoxacarb, triflumuron and diafenthiuron). So far, the product indoxacarb
tend to be a powerful suppressor of T. absoluta larvae.
Indoxacarb is reported by several authors as a powerful insecticide in managing many
Lepidopteran pests. Wakil et al. (2009) in their study for the management of the pod borer,
Helicoverpa armigera Hubner (Lepidoptera : Noctuidae) in Pakistan showed the integration
of weeding, larvae hand picking and indoxacarb sprays was the most effective in reducing
the larval population, pod infestation and maximum grain yield. Also, in Cameroon,
Brévault et al., (2008) reported a good efficacy of indoxacarb as a larval insecticide of H.
armigera.
In the United Kingdom, three insecticides were registered for the control of T. absoluta under
protected tomato, pepper and aubergine: Bacillus thuringiensis var. kurstaki, indoxacarb and
spinosad (FERA, 2009).
Indoxacarb belongs to a novel class of insecticides, the oxadiazines. It a broad spectrum
non-systemic insecticide active especially against Lepidoptera. Indoxacarb affects insect
primarily through ingestion but also by contact with treated plant surface. It kills by
binding to a site of sodium channels and blocking the flow of sodium ions into nerve cells.
The result is impaired nerve function, feeding cessation, paralysis and death (Wing et al,
2000).
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5. Conclusions
T. absoluta has been a serious pest of tomatoes in Tunisia since the autumn 2008. Farmers
have gradually come to understand that conventional insecticides such as
organophosphates and carbamates are not effective against the insect. Even though more
expensive compared with other insecticides, spinosad (Tracer) is now the widely used bio-
insecticide to manage the insect.
It is not the intent in this study to advocate one insecticide over another but to enlarge the
array of effective insecticide and bio-insecticides with different modes of action. These
studies clearly demonstrated the efficacious of several chemicals such as spinosad,
abamectin, emamectin benzoate, triflumuron and diafenthiuron. Although, plant extracts
such as Armorex and Deffort show mild efficacy in controlling T. absoluta larvae, they can
be used in conjunction with chemical products and integrated in a whole program of
control.
The efficacies of sprayings using mixtures of natural products and synthetic chemicals for
the control of the pest are planned in our laboratory studies. Indeed, insecticides that work
in synergy when mixed together are an avenue to explore in T. absoluta control. It has been
proposed that pesticides mixtures with different modes of action may delay the onset of
resistance developing in pest populations (Bielza et al., 2009). However, some problems need
to be considered when two or more insecticides are mixed together especially phyto-
toxicity.
The use of insecticides to control T. absoluta must not divert attention from the
implementation of alternative pest management strategies including cultural, mass-trapping
and biological control that can reduce reliance to chemical products.
Chemical pesticides continue to be an important component of insect pest management
even with the development of other control methods (mass-trapping, plant resistance…).
The use of insecticides based on different chemistries and with varying modes of action is an
important component of an integrated pest management strategy. Hence, insecticides will
continue to be an integral component of pest management programs due mainly to their
effectiveness and simple use. However, the principal factor account for the possible
reluctance to shift to the newer insecticides is the high cost.
6. Acknowledgements
The financial support for this work was provided by the Institution of Agricultural Research
and Higher Education (IRESA. Ministry of Agriculture and Environment. Tunisia) through
the research project “Tuta absoluta”. We wish to thank the former President Pr Mougou A.
and the current President Pr Amamou H. for their help.
We thank Bensalem A., Benmaâti S., Hajjeji F., Ammar A. and Rhouma J. for technical
assistance in both laboratory and field.
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Insecticides - Pest Engineering
Edited by Dr. Farzana Perveen
ISBN 978-953-307-895-3
Hard cover, 538 pages
Publisher InTech
Published online 15, February, 2012
Published in print edition February, 2012
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This book is compiled of 24 Chapters divided into 4 Sections. Section A focuses on toxicity of organic and
inorganic insecticides, organophosphorus insecticides, toxicity of fenitrothion and permethrin, and
dichlorodiphenyltrichloroethane (DDT). Section B is dedicated to vector control using insecticides, biological
control of mosquito larvae by Bacillus thuringiensis, metabolism of pyrethroids by mosquito cytochrome P40
susceptibility status of Aedes aegypti, etc. Section C describes bioactive natural products from sapindacea,
management of potato pests, flower thrips, mango mealy bug, pear psylla, grapes pests, sm all fruit production,
boll weevil and tsetse fly using insecticides. Section D provides information on insecticide resistance in natural
population of malaria vector, role of Anopheles gambiae P450 cytochrome, genetic toxicological profile of
carbofuran and pirimicarp carbamic insecticides, etc. T he subject matter in this book should attract the
reader's concern to support rational decisions regarding the use of pesticides.
How to reference
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Insecticides on Tomatoes, Insecticides - Pest Engineering, Dr. Farzana Perveen (Ed.), ISBN: 978-953-307-
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