IOP Conference Series: Earth and Environmental Science
PAPER • OPEN ACCESS
Evaluation of botanical insecticides in controlling the population of fall
armyworms (Spodopterafrugiperda Smith) present on corn crops (Zea
mays) located in Santa Cruz, Guanacaste
To cite this article: J Mora and H Blanco-Metzler 2018 IOP Conf. Ser.: Earth Environ. Sci. 215 012013
 
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I COAT 2017 IOP Publishing
 
IOP Conf. Series: Earth and Environmental Sci1e2n3c4e 5261758 (9200 ‘1’8“)” 012013  doi :10.1088/1755-1315/215/1/012013
Evaluation of botanical insecticides in controlling the 
population of fall armyworms (Spodopterafrugiperda Smith) 
present on corn crops (Zea mays) located in Santa Cruz, 
Guanacaste 
1* 1 
J Mora , H Blanco-Metzler
1
University of Costa Rica, Sede Guanacaste 
*Email: jairomopre@gmail.com, helgablanco@gmail.com 
Abstract. Botanical insecticides manufactured under the name of spinetoram, Solaris 6 SC® 
(75 ml.ha-1) and Capsoil 9,82 EC® (Capsicumm annum + mustard (Sinapis alba) + garlic 
(Allium sativum) (2 l.ha-1) were evaluated by comparing them with two homemade extracts: 
garlic extract + neem (Azadirachtaindica) + detergent (20 ml.l-1 water) and garlic extract + 
oregano (Origanumvulgare) + juanilama (Lippia alba) + rosemary (Rosmarinusofficinalis) (20 
ml.l-1 water); and a control with the objective to evaluate the effectiveness of non-chemical 
alternatives to treat the Spodopterafrugiperda in the corn crops of the test field in Santa Cruz, 
Guanacaste which is owned by the University of Costa Rica. Results show that the best 
insecticide to control the immature fall armyworm is Solaris 6 SC®, followed by the 
insecticide made of garlic extract, neem, and detergent. Also, the natural parasitism of the S. 
frugiperda on the area not treated with pesticides reached values of 60% where the Chelonus 
sp. was the parasitoid that was present at all times. The performance of the areas treated with 
pesticides range from 153 and 180 quintals of fresh corn by hectare where the insecticide made 
of garlic extract, neem, and detergent (20 ml.l-1 water) reflected the higher production.  The 
areas treated with Solaris 6 SC® had the less quantity of corn damaged by S. frugiperda and 
Helicoverpazea while the area treated with garlic extract + oregano + juanilama + rosemary 
had the greatest loss during this evaluation. Thus, the insecticide made of garlic extract, neem, 
and detergent is recommended because of its high capacity to kill S. frugiperda and other pests 
that affect the corncob, its higher performance it is more cost efficient for small farmers. 
1.  Introduction 
Corn has long been a staple agricultural crop across the Americas thanks to its many beneficial uses. 
This grain has been established as the third most widely grown product in the world after wheat and 
rice [1]. The countries that have the highest production of corn are The United States, The People's 
Republic of China, and Brazil; those three countries hold 73% of the annual world production [2]. 
Corn, as well as many other crops, has a direct relationship with its natural predators that raise their 
population densities, when favorable environments are found, to the point they become pests of high 
agricultural importance [3]. Corn plants can be attacked by many different insects, which can damage 
their structures and directly interfere on the yield and quality of the grain, if they are not well 
controlled. 
The fall armyworm, Spodopterafrugiperda Smith (Lepidoptera: Noctuidae) is a pest with polyphagous 
habits that cause economicloss in many crops such as corn, sorghum, rice, and other grasses [4]. 
Despite being an insect that can reproduce in almost all grasses, it has an affinity for corn crops where 
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I COAT 2017 IOP Publishing
 
IOP Conf. Series: Earth and Environmental Sci1e2n3c4e 5261758 (9200 ‘1’8“)” 012013  doi :10.1088/1755-1315/215/1/012013
it is considered the most frequent pest due to the adapt ability this insect presents in a variety of 
climate conditions where corn is grown [5]. 
Most of the treatments that are used to control the fall armyworm are chemical products that can affect 
people's health and the environment [6]. Additionally, the constant use of chemicals causes a reduction 
of natural enemies in the field which in turn generates an imbalance in the agricultural ecosystem as 
well as the emergence of pest populations resistant to the applied pesticides [7].It is estimated the 
chemical pest control methods currently used in corn production account for 10% to 12% of the 
production direct costs [6]. Of these, 6% comes from the chemical control of S. frugiperda[8]. For this 
reason, pest control is considered one of the most expensive components of corn production in the area 
and in the world.In order to improve corn production systems, an initiative using natural pesticides to 
control S. frugiperda arose, to provide more alternatives in pest control for small and organic farmers. 
2.  Materials and Methods 
The research was carried out at the Test Field of the University of Costa Rica in Santa Cruz, 
Guanacaste, 10° 15'06" North latitude and 85° 41'07" West longitude. This canton is part of a dry 
tropical forest with an altitude of 54 m.a.s.l., annual rainfall of 1 834 mm, an average annual 
temperature of 27.9 °C and a relative humidity of 75%. 
2.1.  Experimental Material 
White corn seed (Hybrid HS5G) from Monsanto was used.  This hybrid is tolerant to drought and also 
to late lodging when it is not broken.  Additionally, this corn has a reputation as a hardy variety that 
provides good quality of grains for the industry. 
Table 1 shows the treatments used to controlS. frugiperda in corn, as well as the composition, and 
the application doses. 
 
Table 1. Description of the botanical pesticides used to controlS. frugiperda in a corn plantation 
located in Santa Cruz, Guanacaste. 
Treatment Treatment's Description Trade name Doses 
T1 Control treatment Not applicable Water 
garlic extract + neem + -1 
T2* Not applicable 20 ml.l water 
detergent 
garlic extract + oregano + -1
T3* Not applicable 20 ml.l  water 
juanilama + rosemary 
Hot chili extract + mustard + -1
T4 Capsoil 9.82EC® 2 l.ha  
garlic 
-1
T5 spinetoram Solaris 6SC® 75 ml.ha  
*T2 and T3 were artisanal formulations, while T4 and T5 were commercial formulations. 
 
2.2.  Extracts' Formulations 
In the formulation of each extract equal parts (meaning weights) of each component were used: 
oregano (Origanumvulgare), rosemary (Rosmarinusofficinalis), juanilama (Lippiaalba), neem 
(Azadirachtaindica), garlic (Allium sativum) (weight of the cloves in relation to the foliage), and 
detergent (1/8 of grated blue soap bar).  The materials were deposited in a 4 gallon plastic bucket and 
molasses was added in a 1:1 proportion. Once the solids and the liquid were mixed, the bucket was 
closed with a double water bag (with cover function that prevents the contact of the mixture with the 
spores of the environment) for 15 days. After that, the water seal was removed, and each of the 
extracts were filtered.The newly formulated pesticides were packed in dark plastic bottles, labeled, and 
stored in the refrigerator at 5°C. 
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IOP Conf. Series: Earth and Environmental Sci1e2n3c4e 5261758 (9200 ‘1’8“)” 012013  doi :10.1088/1755-1315/215/1/012013
2.3.  Experimental Design 
2
Fifty plots of 28 m  (3.5 m x 8 m) each were established, consisting of 5 grooves with 3 m spacing 
between them. A discretionary random design was used. The design consisted of 5 treatments and 10 
repetitions. Two seeds per hole were planted with a distance between rows of 0.7 m and 0.2 m 
-1
between plants, for a density of 71 428 plants per ha .  The three central furrows were considered 
useful for the experiment while the furrows located in the edge were considered useless as well as the 
plants that were at the beginning and at the end of the furrow. 
2.4.  Data Collection 
Initial and subsequent samplings were carried out to determine thedamage level of S. frugiperda as 
well as the effect of the treatments on the pest. Fifteen plants per plot were gathered and the affected 
leaf area was evaluated using the Peralta visual scale (2014) in which only the damage of the bud and 
the first fully expanded leaf of each plant were considered.Weekly samplings were carried out in all 
the plots in order to determine the incidence and development of the pest. In each sampling, 15 plants 
were randomly selected and the presence of larvae S. frugiperdaand larval instar were quantified. In 
addition, the presence of predators and natural enemies of the fall armyworm was recorded. 
Two treatment applications directed at the foliagewere carried out with a backpack sprayer having a 
16 lt capacity and a hollow-cone nozzle. The pesticides' applications were carried out in two periods. 
The first one, 15 days after the emergence (DAE) and the second one when the 60% of the plants were 
in bloom.After each application, the number of live and dead larvae of S. frugiperda was quantified. 
The live larvae were collected in the field and brought to the entomology laboratory for individual 
breeding.  The breeding process was carried out in plastic glasses of 120 ml with a cheese cloth cover 
to allow for good airing.  The feed of the larvae was based on corn leaves that were changed every day 
until the larvae had completed their life cycle or until the parasitoid emergence. 
The two times the larvae were raised in laboratories, the percentage of natural parasitism was 
determined by using the following equation: 
 Parasitaized Larvae 
%  of Parasitism :    *100 
 Total Larvae   
Total larvae are defined as the sum of immature S. frugiperda collected in each of the treatments. On 
the other hand, the parasitized larvae were quantified by the pupae of the parasitoids regardless of 
whether the adult emerged or not. 
With the aim of evaluating the damage of the fall armyworm in the corncob ears, in each experimental 
unit, 10 corncobs without husks were harvested and separated into two categories: healthy corncobs 
and corncobs damaged by the fall armyworm or any other pest. In this case, for both categories, fresh 
-1 
corncobs were weighed.  The yield in kg.ha was quantified by means of the total number of corncobs 
per plot and 10 fresh healthy corncobs per plot were harvested and weighed. In other words, the fresh 
weight of 50 healthy corncobs per treatment was quantified in order to extrapolate yield to one hectare 
of crop. 
3.  Data Analysis 
Data was analyzed by a Kruskal Wallis non-parametric test (p < 0.05) and a non-parametric multiple 
range test with the objective of determining statistical differences between the mean with a program 
called InfoStat [9]. 
  
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IOP Conf. Series: Earth and Environmental Sci1e2n3c4e 5261758 (9200 ‘1’8“)” 012013  doi :10.1088/1755-1315/215/1/012013
4.  Results and Discussion 
4.1.  First Application 
The intensity of the damage of S. frugiperdabefore the application of treatments was non-significant (p 
< 0.8822) for all plots. Subsequent to the application, Solaris®  significantly (p < 0.0001) reduced the 
damage of S. frugiperda in comparison to the control (Figure 1) with a reduction in plant damage from 
-1
32% to 1.3%. [10] found out that using a dose of 0.10 l ha  of spinetoram reduced the infestation of 
the fall armyworm in the corn plots by 6%. For the S. frugiperdadamage level to the crops receiving 
the remaining treatments, no significant differences were found between them, but the three of them 
significantly differed from the control by decreasingS. frugiperda damage by 50% when compared to 
the control. 
4.2.  Second Application 
The damage level increased as a result of five weeks in which there were no applications of any kind 
after the first application of pesticides.  There were no significant differences (p < 0.0537) between 
treatments due to the fact that the residual effect of the botanical pesticides was relatively short and the 
time period between applications was long. That allowed the new establishment of the pest in the 
plots. 
1,5 1
0,8
1
0,6
0,5 0,4
0,2
0
0
T1 T2 T3 T4 T5
-0,5 T1 T2 T3 T4 T5
Treatments  Treatments  
Figure 1. Damage level after treating the areas to Figure 2.Damage level after II 
killS. frugiperda in corn plantations, Santa Cruz,    treatmentapplication to killS. frugiperda in corn 
Guanacaste. plantations, Santa Cruz,Guanacaste. 
Explanation: 
Different letters show significant differences according to the Krusal Wallis Test (p < 0.05). 
T1 =control;  
T2 = garlic+neem+detergent; 
T3 =garlic+ oreganum+juanilama+romerum;  
T4 =Capsoil®;  
T5 =Solaris® 
 
The pattern of damage shown in Figure 1can be explained by the residual activity of the pesticide 
because there is a direct relationship between the persistence of the product in the field and the action 
it has on the pest. In the case of applying spinetoram, Its effect lasts for two weeks, which is reflected 
in a lower presence of S.frugiperda[11]. This is followed by the application of Capsoil® which lasts in 
the environment for about 10 days, and lastly, the protection of the pesticide made out of neem can last 
from 5 to 7 days.  However, that period of time can be shortened because ofclimate conditions like 
high humidity or ultraviolet rays, which can decompose the pesticide's active ingredient in the 
14hoursfollowing its application [12]. 
The second application showed significant differences (P < 0.0001) between the spinetoram, the 
control, and the other pesticides (Figure 2) which reinforces the results from the first application. So, 
this proves that the pesticide can be used during all the instars of the development of the crops with 
similar results. However, the best pest management was obtained when the larvae was found in its first 
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Degree of damage
Degree of damage
 
 
 
 
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IOP Conf. Series: Earth and Environmental Sci1e2n3c4e 5261758 (9200 ‘1’8“)” 012013  doi :10.1088/1755-1315/215/1/012013
instar, before it went into the bud of the plant, because once the insect is inside, the pesticide doesn't 
have direct contact with it, which most probably reduces the effect of the pesticide. 
Just as in the first application, the T2, T3, and T4 treatments did not show significant differences in 
the averages.Even so, a positive effect on reducing the damage level was found when compared to the 
control. Between these two, there were significant differences in the averages which lead one to infer 
that their use in the field is a feasible measure to fightS.frugiperda. 
4.3.  S.frugiperda and its natural enemies on the field 
Figure 3 shows larvae behaviour of S. frugiperda in the corn plots treated with botanical pesticides. 
There are two noticeable drops in the numbers of the pest (sampling 2 and 8) that coincide with the 
treatment application date.  This proves that natural pesticides used in this research do affect, in one 
way or another, the larvae's life cycle because they reduced the quantity of larvae on the crops both 
times they were used. In the beginning, applications had a similar effect on fall armyworms where the 
time to restore the insect population was what changed. Taking this into account, big differences 
among the T1, T2, T4 and T3 behaviour can be seen. These follow a pattern similar to the first 
application ones, which proves the significance among these pesticides. Moreover, Solaris® showed a 
separation between the lines under all the other treatments and it lasts even for 3 consecutive 
samplings, which equals three weeks. From the fifth sampling on, S.frugiperda populations were 
similar in all treatments, even for T1, which reduced populations notoriously maybe because of the 
rains. 
Seven natural enemies of S. frugiperda were found: predators like Zelusspp. 
(Hemiptera:Reduviidae), Podisusspp. (Hemiptera:Pentatomidae),HippodamiaconvergensGuérin-
MénevilleandCoccinellasanguinea L. (Coleoptera: Coccinellidae); and parasitoids like Sarcophagasp. 
(Diptera: Sarcophagidae), Chelonusspp. (Hymenoptera: Braconidae), 
Archytasmarmoratus(Townsend)(Diptera: Tachinidae). These were efficient enough to control 
immature fall armyworms by parasitism and predation. 
 
0,7
0,6
0,5
T1
0,4
0,3 T2
0,2 T3
0,1
0 T4
1 2 3 4 5 6 7 8 9 T5
Samplings
 
Figure 3.S. frugiperda's population dynamics during the life cycle of corn 
plantations,Santa Cruz, Guanacaste. 
 
4.4.  Natural Parasitism 
Natural parasitism of T1 reached 60% and showed that natural treatments could be an advantage in 
fighting S.frugiperda if a fighting methodology is designed based on botanical pesticides that will not 
kill natural enemies.  Other treatments did not show a negative effect on natural parasitism. 
Even though there are many other biological enemies of the fall armyworm, Chelonusspp. was the 
only one found in important numbers. Chelonusspp. is a parasitoid with a high reproductive rate, 
which parasitizes the S.frugiperda's eggs and continues to develop inside its host until the IV larval 
instar, where it kills its host to be able to complete its life cycle [13].  Being an endoparasite could 
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Larval average
 
 
 
 
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IOP Conf. Series: Earth and Environmental Sci1e2n3c4e 5261758 (9200 ‘1’8“)” 012013  doi :10.1088/1755-1315/215/1/012013
explain the increase of natural parasitism in the II sampling in relation with the I one, because in the II 
sampling the quantity and number of larvae instars of the fall armyworm favour the gathering of a 
higher number of parasitized larvae.This increase possibly happens due to the growth of weeds in the 
lots since the pollen and nectar are important factors in feeding and also in the life cycle of the target 
adults [14]. 
4.5.  Yield 
All treatments showed a high yield, in the range of 153qq to 180 qq ("quintal": 100 lbs) of fresh 
corncobs by hectare, which is similar to the one obtained at a national level (MAG 2010). T2 showed a 
higher yield by hectare, with significant differences with T4 (p < 0.0177) while the other treatments 
did not differ significantly among themselves (p < 0.1853). 
4.6.  Economic Analysis of Yield 
Lower economic losses were obtained by applying T5. The loss using this treatment was  ₡86 570.13, 
being an acceptable loss margin for farmers because even though the loss is somewhat high, it still 
allowed them to make a profit of ₡ 664 846.9 for selling healthy corncobs. The application cost was 
lowest for T2 (₡ 11571), followed by T3 (₡19 943), T5 (₡20 201) and T4 (₡37 949)(Table 2). 
 
Table 2.Economic analysis of yield while applying four botanical pesticides to kill S. 
frugiperda, Santa Cruz, Guanacaste. 
Treatment Total Yield High Quality Rejected Expected Loss (₡) Actual Profit 
(corncobs) Corncobs Corncobs Profits (₡) (₡) 
  
T3 7314.2 4411.4 2902.8 731 418.0 290 281.4 441 136.6 
T1 7555.4 4844.4 2711.1 755 544.0 271 107.0 484 437.0 
T4 7057.0 5034.2 2022.8 705 704.0 202 282.7 503 421.3 
T5 7514.2 6648.5 865.7 751 417.0 86 570.1 664 846.9 
T2 8285.6 6631.6 1653.9 828 559.0 165 394.3 663 164.7 
 
5.  Conclusion 
-1
Applying the pesticide Solaris 6 SC® with a dose of 0.075 l.ha showed the best results in killing fall 
armyworm in corn plantations.Corn plots treated with garlic + neem + detergent showed the highest 
yield in this research. In turn, this treatment showed a proper result in killing the pest during the 
vegetative and production phase since it reduced the loss of fresh corncobs to quantities close to the 
ones obtained with the best pesticide (Solaris 6 SC®.) Nevertheless, it is recommended to increase the 
application frequency so that the corncob loss is minimized. Capsoil 9.82 EC® provides an 
intermediate pest control but it is an expensive option to recommend for farmers.Garlic extract + 
oregano + juanilama + rosemary treatment showed the highest loss of all treatments, including the 
control treatment. This treatment does not provide any benefit to the farmers at this application rate; 
that is why it is recommended to reduce the time period between applications to compensate for its 
relatively short residual activity in the field.Natural parasitism byChelonus spp. reached values of 
60%, for this reason, the conservation of natural enemies plays an important role in killing S. 
frugiperda. 
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IOP Conf. Series: Earth and Environmental Sci1e2n3c4e 5261758 (9200 ‘1’8“)” 012013  doi :10.1088/1755-1315/215/1/012013
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