Effect of climatic factors, predators and plant

age on the

population dynamics of Empoasca decipiens and

Thrips tabaci on kidney bean plants

M. A. Mohamed, M. H. A. Soliman and H. B. HomamDep. Vegetable Pests, Plant Protection Research

Institute,

Dokki, Giza, 12618 Egypt

ABSTRACT

The present work was carried out to study the

effect of climatic factors (temperature and

relative humidity), associated predators

[Coccinella undecimpunctata L., Scymnus interruptus Coeze,

Chrysoperla carnea (Steph.) and Orius albidipennis

(Reut.)] and plant age on the population density

of Empoasca decipiens Paoli and Thrips tabaci Lind.

infesting bean plants during two successive

seasons. Plant age effect was considered as third

degree of polynomial.

The results indicated that, jassids

population were higher than thrips and had one

peak of abundance on May 28th and 27th and thrips

population had one peak of abundance on May 14th

and 20th during 2005 and 2006 seasons,

respectively. Concerning the total predators, two

peaks occurred during May and June in both

seasons.

The population of E. decipiens was affected

insignificantly by climatic factors in the two

seasons. While the predators had significant

positive effect on jassid population during two

seasons. The population of T. tabaci was affected

insignificantly by the climatic factors and

predators in the two seasons except for minimum

temperature which affected it significantly in

the first season. Plant age affected the

population significantly in the first and second

seasons. This mean that, the plant age had more

effect on Jassid and thrips population compared

with the role of climatic factors and predators.

The explained variance due to plant age was

(87.76 and 95.41%) for jassid, (92.08% and

76.94%) for thrips during two seasons. Plant age

is expected to reflect leaves content of

nutritional values according to plant phenology.

INTRODUCTION

2

Bean plant, Phaseolus vulgaris L. is an important

economic leguminous vegetables crops. It is

cultivated in Egypt for local consumption and

exportation. It contains high percentage of

protein, carbohydrates, vitamins and mineral

salts which are essential for human nutrition.

This crop is subject to be infested by many

pests which cause considerable damage in both

quantity and quality of the pods (El-Kifl et al.,

1974, Chang and Chen, 1993). Jassids and thrips

are considered as the main insect pests infecting

bean and cause partial or complete damage to the

infested leaves and also facilitate and encourage

the infestations with several pathogens.

Information about the interactions between

insects and their natural enemies, density may

become an important integrated part of the insect

management system (Kogan and Herzog, 1980 &

Riudavets 1995).

The present study aimed to evaluate the

effect of plant age, climatic factors (i.e.

temperature and relative humidity) and some

associated predators, on population density of E.

decipiens and T. tabaci on kidney bean.

3

MATERIALS AND METHODS

Field experiments were carried out during the

summer plantations (2005 and 2006 seasons) at

Kaha Agricultural Research Station, Qualubia

Governorate during two successive seasons. The

Kidney bean plant, P. vulgaris Fam. Leguminosae

(variety Giza 3) was planted.

The chosen area (4000 m2) was divided to four

equal replicates. Each replicate about 1000 m2

and planting in the last week of March in both

2005 and 2006. Normal agricultural practices were

followed without insecticides treatments.

To assess the population of jassids and

thrips and main associated predators, weekly

samples of 100 leaves were randomly collected

from the three plant levels (i.e. upper, middle

and lower). The collected samples were kept in a

paper bag and transferred to the laboratory for

investigation. The total number of E. decipiens and T.

tabaci (nymphs and adults) and predators were

counted and recorded. The considered predators

were Coccinella undecimpunctata L. (larvae and

adults), Scymnus interruptus Coeze (larvae and

4

adults), Chrysoperla carnea (Steph.) (larvae) and

Orius albidipennis (Reut.) (nymphs and adults).

The maximum and minimum daily temperatures

and relative humidity were recorded during the

period study and weekly numbers of predators in

relation to the age of bean plant were used for

calculating the simple correlation and multiple

regression values according to Fisher (1950).

Plant age was used as a factor affecting

studied pests population dynamics. The effect of

plant age was assumed to be polynomial of the

third degree (i.e. Y= a + b1x + b2X2 + b3X3). This

relation would indicate three stages of effect of

the plant age on pests population dynamics. The

first one would enhance the population, the

second one would reflect on stability and the

third stage would associate with population

decline. This effect can be evaluated using

multiple regression.

RESULTS AND DISCUSSION

5

1. Population density of E. decipiens and T. tabaci and

associated predators:

Data presented in Tables (1 and 2) show the

natural infestation of kidney bean with E. decipiens

and T. tabaci during two successive seasons of 2005

and 2006. The regular weekly inspections of

kidney bean leaves during two plantation seasons

revealed that the occurrence of E. decipiens and T.

tabaci (nymphs and adults) on this plant as

recorded during the whole two growing seasons

2005 and 2006. Monitor started on April, 23rd 2005

and 22nd 2006 by 1.40 and 2.22 jassids/leaf, 0.25

and 0.22 thrips/leaf, respectively.

During the first season, the population

density of E. decipiens increased up to the 28th of

May, as the highest peak of 13.28

individuals/leaf, while the population density of

T. tabaci increased gradually up to the 14th of May,

as the highest peak observed during this season

was 0.46 individuals/leaf and then decreased

gradually until the end of the season, as it

reached to 1.23 jassids/leaf, 0.05 thrips/leaf.

For the subsequent season 2006, the population of

E. decipiens and T. tabaci had the same trend of the

6

first season, where the highest peak observed was

14.55 jassids/leaf on the May 27th, 0.65

thrips/leaf on the May 20th, and then the

population decreased gradually reached 1.70

jassids/leaf, 0.09 thrips/leaf at the end of the

growing season.

Concerning the target (considered) predators,

Tables (1 and 2) show that all predators were

firstly observed in kidney bean nearly at the

same time as the first appearance of jassids and

thrips. It is apparent that Coccinella undecimpunctata

was the most common predator in kidney bean field

followed by Scymnus interruptus and Chrysoperla carnea

(Steph.) while Orius albidipennis came in the fourth

place.

Considering the total predators, two peaks

occurred, the first peak was in May, 14th and 20th

by 0.75 and 0.85 predators/leaf during two

growing seasons 2005 and 2006, respectively. The

second peak was in June, 4th and 3rd with mean of

1.00 and 1.13 predators/leaf, respectively.

It was clear that, the first peak of predators

occurred in association with the maximum

population of thrips during two growing seasons.

7

In general, the population of E. decipiens, T.

tabaci and associated predators were relatively

higher in the second season than in the first

one. This difference may be due to changes in the

environmental conditions prevailing in both

seasons and /or other factors. In addition, the

data in Tables (1 and 2) showed that the ratio of

jassids and thirps population to each one of

tested predators population (0.03, 0.02, 0.02,

0.007) and (0.03, 0.02, 0.01, 0.006), (0.88,

0.54, 0.54, 0.19) and (0.78, 0.63, 0.38, 0.16)

Coccinella, Scymnus, Chrysoperla and Orius during seasons

2005 and 2006, respectively, were explain the

highest role of the tested predator in decrease

the population of jassids. On the other hand, the

lowest role of the tested predator in decreases

the population of thirps.

These observations are almost obtained by Mundhe

(1982), Bachatly (1984), Metwally (1989) and

Awadalla et al. (1991) stated that, one peak was

recorded in the population density of T. tabaci on

soybean during the growing seasons. Also, Mowafy

(1988), Metwally (1989) and Ali (1993) found that

8

the population of E. decipiens on soybean and broad

bean plants had only one peak.

In the same field Daiber (1994) mentioned

that the pods of green bean sown in spring or in

summer were attacked by thrips, Megalurothrips

sjostedti. Devesthali and Saran (1998) in India,

stated that pea thrips, Caliothrips indicus infesting

green gram, reached peak population density in

the fourth and fifth weeks of August. Wnuk and

Pobozniak (2003) stated that the population of T.

tabaci initially were Table (1): Mean number of Empoasca decipiens Paoli and

Thrips tabaci Lind. individuals and associated

predators per kidney bean leaf during summer

plantation (2005).

predat

ors

/leaf

Mean No. of predators/leafThrip

s/

leaf

Jassi

ds/

leaf

Sampling

ScheduleO.

albidipenn

is

C.

carne

a

S.

interruptu

s

C.undecimpunctat

a

0.270.010.040.100.120.251.40April 230.470.030.090.130.220.335.61300.560.050.150.130.230.377.75May 70.750.090.200.150.310.469.36140.610.080.150.140.240.319.11210.620.050.130.180.260.2913.28281.000.110.250.260.380.228.57June 40.730.040.220.170.300.198.0011

9

0.420.010.110.110.190.144,50180.170.000.030.060.080.051.2325

0.560.050.140.140.230.266.88

Mean/

leaf/

season

-0.0070.020.020.03--

Predator

/

jassids

-0.190.540.540.88--Predator

/ thrips

Table (2): Mean number of Empoasca decipiens Paoli and

Thrips tabaci Lind. individuals and associated predators

per kidney bean leaf during summer plantation (2006).

Predators

/leaf

Mean No. of predators/leafThrips/leaf

Jassids/leaf

SamplingSchedule

O.albidipenn

is

C.carne

a

S.interruptu

s

C.undecimpunctat

a

0.160.000.010.000.150.222.22April 22

10

0.830.070.200.230.330.279.7529

0.550.030.110.190.220.3511.80May 6

0.630.050.130.220.230.4313.6113

0.850.070.090.240.310.6513.3120

0.710.090.150.270.340.4914.5527

1.130.110.230.380.410.309.50June 3

0.800.080.140.260.320.246.2210

0.400.030.100.120.150.205.1217

0.210.010.020.100.080.091.7024

0.630.050.120.200.250.328.78Mean/leaf/season

-0.0060.010.020.03--Predator/

jassids-0.160.380.630.78--Predator

/ thrips

11

found on the leaves of pea plants, Pisum sativum

and as the pea was growing on the flower buds and

flowers.

El-Defrawi et al. (2000) found that the

common predators observed in faba bean fields

were Coccinella undecimpunctata L., Chrysoperla carnea

Steph, Syrphus corollae F., Phaenobremia aphidivora

Rubs. and Scymnus interruptus coeze. The minor

predators were Coccinella septempunctata L., Labidura

riparia Pall., Paederus alfierii Koch, Orius spp. and

certain spiders.

2. Effect of some climatic factors associated

some predators and plant age on the population

of E. decipiens and T. tabaci:

Tables (3 and 4) show the correlation between

the population density of E. decipiens, T. tabaci and

maximum, minimum temperature and maximum, minimum

relative humidity and plant age as well as the

associated predators during the two seasons of

2005 and 2006.

Data in the Table (3) indicated that,

considered climatic factors affected

insignificantly jassids population in the two

seasons. This means that the considered climatic

12

factors were within the optimal range for

population activity of jassids. Also, the plant

age affected insignificant on jassids population

during two seasons. On the other hand, the

predators had significant positive effect on

jassids population during first and second

seasons(r = 0.71 and 0.69, respectively). While,

the combined effect of four considered factors

(plant age, temperature, RH% and predators) on

jassids population was given as percentage of

explained variance (EV%) was cleared that, the

previous factors were responsible for 98.61 and

99.87% of variability in the population of E.

decipiens during first and second seasons,

respectively. But the plant age was responsible

for 87.76 and 95.41% of variability in the

population of jassids during first and second

seasons, respectively.

This means that, the plant age and predators

considered responsible factors for the influence

ratio on jassids population and there are other

unconsidered environmental factors responsible

for the remained ratio on jassid population.

These results contrast with finding of Abd El-

13

Fatah (1991) who found good relationship and

large effect of temperature, relative humidity on

population activity of E. decipiens on bean under

Egyptian condition. Singh et al. (1990) and

Jayanthi et al. (1993) found that the

environmental factors (temperature, RH%,

rainfall, wind speed and sunshine) affected the

population build up of Empoasca kerri on ground nut.

Our results showed that, the tested factors

(plant age, temperature, RH% and predators)

responsible for explained variance recorded

(98.61, 99.87%) during the two seasons on bean.

Data in the Table (4) indicated that, there

highly significant negative correlation between

the plant age and the population density of T.

tabaci during the first plantation season of 2005.

Also the data indicated that, the three negative

values of (r) increased gradually with increasing

in plant age (r = -0.74, -0.85 and -0.88,

respectively). In addition the highest negative

values at the last age of plant, this may be mean

that, when the plant directed to conform pods the

plant saps becomes unsuitable to T. tabaci. In the

closely meaning, the low negative amount of (r= -

14

0.74) in the age 1 of plant, this may be mean

when the plant directed to form chlorophyll and

green leaves, this condition is suitable for T.

tabaci. From previous must be condense the control

of T. tabaci at the early stage of bean. While the

minimum temperature produced significant negative

correlation (r = -0.66). However, the maximum

temperature, maximum and minimum relative

humidity and predators had no significant effect

on thrips population during 2005 season. It may

be means that, the population density of this

pest affected by the plant age and minimum

temperature than other tested factors. Concerning

the changes occurred in the population of T. tabaci

due to the change in plant age, the calculated

explained variance was 92.08% and equal 99.48% in

case of the combined effect of the tested

climatic factors and plant age and associated

predators. These values reflected that the

combined role of the climatic factors and

predators in influencing of the activity and

abundance of T. tabaci on bean plant was lower than

the role of the plant age.

15

In the second season of 2006, the calculated

correlation indicated significant negative with

the first and second plant ages(r= - 0.31 and -

0.49, respectively). While the other factors, had

no significant effect on thrips population during

this season. The total explained variance

percentages due to the plant age measured 76.94%,

while the combined effect of the all tested

factors measured 88.87%. From previously

mentioned, the population density of this pest

was affected by the plant age. This means that

there are other unconsidered environmental

factors responsible for the remained influence

ratio on thirps population.

The present results are in agreement with the

finding of Agostini and Muruaga (1990) and

Jarosik et al. (1997) reported that the population

density of thrips increased with time age of

common bean and cucumber plants and reached to

peak during the vegetative period before

fruiting. Plants were damaged from emergence

until pod formation. Booij (2003) stated that the

population dynamics of thrips T. tabaci on seven

crops dose not only depend on the weather factors

16

and the presence of the most susceptible crop but

is significantly affected by the interplay of

different sources at small and large scale.

Generally, it could be concluded that the

population of jassids, thrips and associated

predators were relatively higher during 2006

season than in 2005 season. The associated

predators play a role on jassid abundance.

�ٍ Table (3): Simple correlation and multiple regression coefficient of four factors on the population

density of Empoasca decipiens Paoli individuals on

kidney bean plants during summer plantation seasons of2005 and 2006.

Multipleregression

Simplecorrelation

andregression

FactorSeason

EV%EV%bbr

98.61

56.6-3.31

-21.15

-0.12Max. Temp.2005

-2.96

13.76

-0.09Min. Temp.

0.352.420.02Max. RH

1.41-7.96

0.12Min.RH

2.71-0.71*Predators

17

0.85

87.76121.32--0.04Age1

-10.96

--0.24

Age2

-0.02

--0.38Age3

99.87

89.02-4.18

17.26

-0.11Max. Temp.2006

-7.01

-3.84

-0.18Min. Temp.

3.76-3.41

0.13Max. RH

-12.06

-2.49

-0.59Min. RH

2.60.140.69*Predators

95.41256.11

--0.27Age1

-38.95

--0.47Age2

1.54--0.57Age3

*=Significant P< 0.05 **= Highly significant P< 0.01

18

�ٍ Table(4): Simple correlation and multiple regression coefficient of four factors on the population

density of Thrips tabaci Lind. individuals on Kidney

bean plants during summer plantation seasons of 2005 and 2006.

Multipleregression

Simplecorrelation

andregression

FactorSeason

EV%EV%bbr

99.48

62.87-1.993.47-0.58Max. Temp.

2005

-2.81

1.49-0.66*Min. Temp.

0.450.550.23Max. RH

0.200.630.13Min. RH

0.210.240.42Predators

92.08918.71

-0.74**Age1

-3.50

-0.85**

Age2

0.16-0.88**Age3

88.87

77.6425.11

29.69

-0.31*Max. Temp.2006

-3.42

-5.26

0.49*Min. Temp.

0.10.21-0.58Max. RH

19

-0.97

0.83-0.18Min. RH

-0.35

3.86-0.06Predators

76.940.08--0.02Age1

-1.08

--0.38Age2

0.24-0.45Age3

*=Significant P< 0.05 **= Highly significant P< 0.01

The plant age is an effective factor more

than the climatic factors in the population

density of E. decipiens and T. tabaci in bean plants.

The obvious relation between plant age

(considered as third degree of polynomial) and

studied pests dynamics can be attributed to

nutritional factors. These pests invade the

leaves which assumed to be the plant nutrient

provides. These leaves content of nutrient

(epically nitrogen compounds) is expected to

increase during the first third of plant age,

flattened in the flowering stage and decrease by

20

fruiting stage. For sure this relation is in

harmony with other environmental factors, which

also affects the studied pest's activity. That

may explain the higher contribution of plant age

on studied pest's densities than plan

environmental factors, which simulate the leaves

content of nitrogen compounds.

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ة � ن6 ك ما اث ى� ك لأ ال موس مي� ل الي�رب �س ق� ى س ج� روة� واح دة� ق� د د� اس ي� و و 28ل لج� � دت� الkي�رب �س27 م أب kا احkم و ك � م أبى� دة� ق� kkروة� واح و و14د� � أب kkمى� 20 م kkوس لأل م � و ح � أب kkات�2006 و2005م kkي�رس ن6 ال مف� . ك مkkا ا والي� �kkت ع لى ال

وى� �kkعت ر م ي� �kkغ kًرا ي� ث�� أ � kkد ت ي� kkاس عkداد ال ج� � رk ت ي� ث�� أ � kkان6 ت kkوك . لأل م وس مى� ال دراسة� � و ح ت� � وي و وب�� � ى� م أب ن6 ق� ي� � روت ح دث �ت� د� اkرا ي� ث�� أ � kkد ت ي� kkاس عkkداد ال ج� � ات� ع لى ت kkي�رس رk ال مف� ي� ث�� أ � kkان6 ت kkا كkkم ي� ن¢ £ ن6 ت مي� kkموس ى� ال ات� ق� �kkي ة� و ع مkkر ال ن� � kkوث ل ال ج� kkعوام أل � ت

ن6 ى� ال موس مي� أ ق� � وت .م عت�

ة� ات� ال مصkاح ي�kي�رس ة� وال مف� � kوث ل ال ج� kعوام أل � وى� ت �kعت ر م ي� �kرًا غ ي� ث�� أ � kس ت� رة� الkي�رب عداد ح ش� � ر ت ي� ث�� أ � وك ان6 ت

ى� ًأ ق� � kkوت رًا م عت� ي� ث�� أ � kkس ت� رة� الkkي�رب �kkش عkkداد ح � رت� ع لى ت � kkت ات� ال حkkرارة� ال صkkغ�رى ا � kkدا درح kkا عkkم ي� � ن6 ق مي� kkموس ى� ال ق�

ن6 ع مkkkkر ى� ا �ي� ا ان� �kkkkي ول وال ى� ال موسkkkkم الأ أ ق� � kkkkوت رًا م عت� ي� ث�� أ � kkkkات� ت �kkkkي هkkkkر ع مkkkkر ال ن� ­ ظ مkkkkا ا ي� ن¢ £ ول. ت ال موسkkkkم الأ

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ة� � kkوث ل ال ج� kkعوام عض� ال ب� £ ة� ي � kkارث د والkkي�رب �س م ف� ي� kkاس رة� ال ج� �kkش عkkداد ح � ر ع لى ت ي� °kkك رk الأ ي� ث�� ا �kkي كkkون6 لkkة ال � ات� ت �kkي ال ن�ة� ) سkkي� ن� � عkkداد ت ى� ال ب� ر ق� � kkت د ا � kkات� ق �kkي ن6 ع مkkر ال ن� ج6 ا اب� �kkي هkkرت� ال ن� ­ ظ ت� ا ات� ح ي� kkي�رس 95.4 و 87.76وال مف�

راغة� 76.94 و92.8%( و) 1 لأل م وس مى� ال ر� � والي�2006 و2005%( ح ع لى ال ت�

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