MASS REARING IN BIOLOGICAL CONTROL: THE FORGOTTEN

FACTORS OF QUALITY

Damayanti Buchori Department of Plant Protection

Bogor Agricultural University

Biological Control: Emphasize on Parasitoid

Hawkins et al. (1997): parasitoids are the most important factor causing mortality of herbivores than do either predators or pathogens.

Why Parasitoid: • highly specialized, • have high searching capacity

under low density of hosts, • can introduce several species

together with little interference between the bioagents

ISSUES in BIOLOGICAL CONTROL

• Is bringing science into action

• Understanding the behaviour, ecology, evolution toward its capacity to suppress its hosts (pests)

• Field Collection

• Mass Rearing

• Field Release

• Effectiveness

• Non-Target Impact

Criteria for Success?

– reproductive potential

– temporal coincidences—synchronization

– host specificity

– search capacity

– dispersal capacity

– response to variations in host density (functional response)

– response to variations in host condition

– absence of hyperparasitism

What do we need to understand? Some Basic Facts

– Females are the “attacker of the pests”. Unlike predators which eats their prey, parasitoids are mainly searching their hosts for reproduction, i.e place to lay eggs. This means that in terms of producing the maximum effect of parasitoids on pests, females are more important than males

– Their haploid diploidy: the ability to produce offspring even when not mated. This means that all females can attack their hosts, regardless of their mating status.

BASIC FACTS – Fitness effect: fitness is

positively correlated with body size. These are characters that can be exploited for BC purposes

– Functional response : what and why is it important in Mass rearing (and in the field)

– Synovigenic vs proovigenic and the impact on the effectiveness of parasitoids as bioagent.

Body size and fitness

The relationship between a female’s body size (the

cube of hind tibia length (mm 3)) and: (a) the

number of eggs in her ovarioles after the

experimental pretreatment (see text for details); (b)

the number of offspring laid in the experimental

patch; (c) the number of eggs left in her ovarioles

after she left the experimental patch.

Flanagan et al

1998

BASIC FACTS

• Arrhenotoky

– The ability of females to make decisions on sex of offsprings

• Telytoky

• Deuterotoky

• Local mate competition (LMC)

– Female bias sex ratio

– Inbreeding depression should not be an issue

LOCAL MATE COMPETITION

• Gregarious parasitoid

• Sib mating (siblings mate)

• Female only mates once

• Males can have access to many females

• Imbalance Cost of females and of males

• To maximize fitness: Female bias population

What Does Those Basic Facts Imply?

• BC should be geared toward Female bias population

• Need Big size females

• Respond to variation in host density

• However: short lived (days) and thus may need Multiple introduction

MASS REARING

IMPORTANT ISSUES

Mass rearing: What we need to know?

• Effect of Host size • Effect of host type (preference,

encapsulation) • Effect of Food • Host deprivation • Effect of Foundress Numbers

• Sex ratio • Inbreeding depression

• Generation time and Host shift/preference and inbreeding depression

• Effect of Temperature

EFFECT OF HOST: SIZE

• Positive correlation between host size and body size of parasitoid

• Since body size is positively correlated with fecundity, larger host size results in bigger parasitoid

• Positive correlation between host size and clutch size

Larval development (days)

Pupa development time (days)

Host species

Host species affect the fitness of larval parasitoid Eriborus argenteopilosus

EFFECT OF HOST: QUALITY AND PREFERENCE

Proportion of survived parasitoid (%)

Host Type and Parasitoid Encapsulation

±Std. Dev.

±Std. Err.

Mean

Host stages of C pavonana

Host conta

inin

g e

ncapsula

ted p

ara

sitoid

(%

)

0

10

20

30

40

50

60

70

80

90

100

L1 L2 L3

AA

B

Older host has a higher capacity in encapsulating immature parasitoid

Effects of Temperature on Functional Response

Temperatures as well as egg densities contributed significantly to the number of eggs parasitized the number of eggs parasitized at 20°C did not differ significantly from that at 27°C, though both were significantly higher than at 17°C Temperature affect type of functional response.

Wang & Fero (1998), functional response of Trichogramma ostriniae

Effects of temperature on parasitoid development and activity

Cumulated percentage of female

Trichogramma turkestanica displaying

walking activity in relation to

temperature (n= 62).

Hansen LS (2000)

The speed of development ( s.d.) from

eggs to adult eclosion (both sexes

combined) in Trichogramma turkestanica

on Ephestia kuehniella at four constant

temperatures. The equation is based on

linear regression of the data (n =48–58 at

each temperature).

0.00

0.50

1.00

1.50

2.00

2.50

3.00

3.50

4.00

Control Moderat High

Lo

ng

evity (

da

ys)

0.00

10.00

20.00

30.00

40.00

50.00

60.00

Control Moderate High

Eg

g p

rod

uctio

n

Honey solution

Eevryday once

Effects of food on Trichogramma pretiosum Food was provided for parasitoid with different frequency and concentration Control: water Honey solution (50%--high) Honey solution (25%--moderate)

Effects of Food on Parasitoid

Effects Of Host Deprivation On E argenteopilosus

Deprivation days

Number of eggs laid increased after

deprived for one day, but decreased with

increasing deprivation day

Effects of Host Deprivation on Fecundity of Trichogramma japonicum

Deprivati

on

duration

Number of eggs

laid X±SD

The remaining

eggs inside ovary

X±SD

Produced eggs

X±SD

0 hour 44,50 10,96 ab 0,50 1,08 ab 45,00 ± 10,52 ab

1hour 48,90 9,97 a 1,10 1,10 a 50,00 ± 10,04 a

2 hours 34,10 7,25 c 0,70 1,06 ab 34,80 ± 7,29 c

3 hours 38,90 5,32 bc 1,00 1,05 a 39,90 ± 9,97 bc

6 hours 42,70 5,96 b 1,00 1,05 a 43,70 ± 6,13 ab

12 hours 41,70 4,37 b 0,80 0,92 ab 42,50 ± 4,91 b

24 hours 39,80 4,16 bc 1,00 1,05 a 40,80 ± 4,39 bc

48 hours 0,00 0,00 d 0,00 0,00 b 0,00 ± 0,00 d

FOUNDRESS NUMBERS

• The numbers of females that “found” a patch/initiated a population

– Has implication toward genetic variability

– Inbreeding depression due to recessive alleles increasing in frequence

Foundress effects on Sex Ratio

Debout et al 2002

Proportion of males among the progeny of foundress females as a function of foundress density (Curves reprsent predictions of Taylor and Bulmer’s model for three values of on-patch mating)

Generation Time and Inbreeding depression

0

2

4

6

8

10

12

14

16

18

Generation-5 generation 10th generation 15th generation 20th

Fe

cu

nd

ity

Generation

Inbreeding is expected to occur under mass rearing condition, that may have an effect on the fitness of parasitoid. Fecundity of Trichogramma pretiosum decreased with increasing generation time under laboratory condition

CLOSING

• The important factors to consider when mass rearing: – Temperatures

– Quality of hosts

– Ratio of foundress: to achieve female bias sex ratio

– Ratio of foundress to hosts and hosts size: to minimize multiparasitism and achieve bigger individuals

– Functional response: to achieve maximum parasitization

• Food for adults: to increase egg production

CLOSING

• But remember that Mass Rearing is only some part of Biological Control

• Field Release and Environmental Factor

• Effectiveness