Banker plants of Orius Insidiosus

Evaluation of seven plant species/cultivars for theirsuitability as banker plants for Orius insidiosus (Say)

M. O. Waite C. D. Scott-Dupree

M. Brownbridge R. Buitenhuis G. Murphy

Received: 8 May 2013 / Accepted: 17 October 2013 / Published online: 26 October 2013

International Organization for Biological Control (IOBC) 2013

Abstract Marigold (cv. Lemon Gem), castor bean,

ornamental pepper (cv. Black Pearl and Purple Flash),

gerbera daisy (cv. Festival), feverfew, and sunflower

(cv. Choco Sun) were evaluated for their suitability as

banker plants (BP) for Orius insidiosus (Hemiptera:

Anthocoridae) in commercial greenhouses. Oviposi-

tion, egg hatch, nymphal development to adulthood,

and population increase were quantified in laboratory

trials. Assessments of oviposition and egg hatch

indicated that all plants tested were equally accepted

by O. insidiosus. Nymphal development to adulthood

and survival tests indicated that gerbera may be a

suitable BP as survival was the highest (58.1 %),

whereas marigold would not be an acceptable BP as

only 10.7 % of nymphs survived to adulthood. Nym-

phal development time differed by only one day

among all plants. In greenhouse cage experiments,

Purple Flash pepper supported the greatest population

growth over a ten week period. Based on the com-

bined results from all tests, Purple Flash pepper

appears to have the greatest potential as a BP species

for O. insidiosus.

Keywords Orius insidiosus Hemiptera Anthocoridae Frankliniella occidentalis Banker plant Biological control

Introduction

In greenhouse ornamental crops, western flower thrips

(WFT), Frankliniella occidentalis Pergande (Thysa-

noptera: Thripidae), is one of the most economically

important and challenging pests to control, causing

aesthetic feeding damage to plants and vectoring

tospoviruses (German et al. 1992; Tommasini and

Maini 1995; Daughtrey et al. 1997; Brdsgaard 2004;

Bosco et al. 2008). Insecticide resistance, worker health

and safety considerations, and a lack of efficacious

insecticides have provided incentives to increase the use

of biological control agents to manage WFT globally.

However, lack of access to effective chemical control

options has driven an accelerated use of biological

control in Canadian floriculture greenhouses.

Handling Editor: Patrick De Clercq.

M. O. Waite (&)Monsanto Canada Inc., Guelph, ON N1G 0B4, Canada

e-mail: [email protected]

C. D. Scott-Dupree

School of Environmental Sciences, University of Guelph,

Guelph, ON N1G 2W1, Canada

M. Brownbridge R. BuitenhuisHorticultural Production Systems, Vineland Research and

Innovation Centre, Vineland, ON L0R 2E0, Canada

G. Murphy

Ontario Ministry of Agriculture, Food and Rural Affairs,

Vineland, ON L0R 2E0, Canada

123

BioControl (2014) 59:7987

DOI 10.1007/s10526-013-9549-4

The biological control agent, Orius insidiosus Say

(Hemiptera: Anthocoridae), is an omnivore and has

been documented as feeding upon a variety of arthropod

pests in addition to pollen and plant sap (Almer et al.

1998; Deligeorgidis 2002; Osborne et al. 2004).

Successful control of WFT using augmentative releases

of O. insidiosus has been achieved in greenhouse

vegetable crops such as sweet peppers, where the pollen

in the flowers provides a supplemental source of food

that aids predator survival and establishment (Chambers

et al. 1993). Populations of O. insidiosus can persist for

an extended period in the absence of prey providing they

are able to access alternative food sources. For example,

populations were maintained for six months on flower-

ing sweet peppers with low to absent populations of

WFT (van den Meiracker and Ramakers 1991; van

Lenteren and Loomans 1999). This suggests that

inoculative releases of O. insidiosus may be sufficient

to control thrips over an entire growing season if the

predator is released on pollen-producing plants.

The use of O. insidiosus to control WFT in

greenhouse ornamental crops, such as chrysanthe-

mums, has been limited to date as the predatory bug can

be slow to establish and exert controla critical factor

in short-term crops. Relatively poor establishment of

O. insidiosus is achieved in ornamentals as a result of

several factors. First, a lack of prey: as a result of the

low tolerance for thrips and the preference of WFT for

flowers, there are often few WFT in the vegetative

stages of plant development. Secondly, a lack of

alternative food sources as ornamentals typically are

not flowering in the production area of greenhouses

until just before they are shipped so pollen is not readily

available. Lastly, eggs of O. insidiosus are removed

from the greenhouse when the plants are shipped,

severely limiting population growth in production

areas. Repeated releases of O. insidiosus purchased

from commercial insectaries are thus necessary to

maintain an effective O. insidiosus population in the

greenhouse, a strategy that is not economically viable.

Determining a suitable flowering banker plant (BP)

system for O. insidiosus could improve opportunities to

use the predator to control WFT by providing a source of

supplementary food in the form of pollen (Frank 2010;

Huang et al. 2011). Establishing such a system in the

greenhouse would allow O. insidiosus to establish and

increase its population, offering growers the option of

preventative introductions. An effective BP should

provide a location for feeding and reproduction, as well

as allowing nymphs to reach the adult stage quickly,

ensuring a high survival rate, and supporting population

growth. The objective of this study was to evaluate the

potential of marigold (cv. Lemon Gem), castor bean,

ornamental pepper (cv. Black Pearl and Purple Flash),

gerbera daisy (cv. Festival), feverfew, and sunflower

(cv. Choco Sun) plants to support a population of Orius

insidiosus in commercial greenhouses. The plant spe-

cies/cultivars were selected based upon growers obser-

vations of wild O. insidiosus specimens within and

adjacent to greenhouses and a literature review of plants

known to have favourable characteristics for supporting

O. insidiosus and similarities in their growth require-

ments as ornamental crops. The Black Pearl ornamental

pepper is currently used as a BP by some commercial

growers at a rate of 100 BPs per acre (pers. obs, G.M.) as

it has been shown to support O. insidiosus in the absence

of prey (Wong and Frank 2012, 2013). Studies by Wong

and Frank (2012, 2013) indicate that pollen from Black

Pearl peppers can result in larger populations of O.

insidiosus by increasing the longevity of the predator

when prey are absent, reduce development time and

increase likelihood of survival to adult. While it has been

shown that pollen from the Black Pearl pepper plants

provides a suitable source of nutrition for O. insidiosus,

growers using Black Pearl pepper BPs have had varying

degrees of success in establishing populations of O.

insidiosus. Other plant species or cultivars may be more

suitable as BPs. Three tests were conducted to assess

different attributes of the different plant species/culti-

vars with regard to their comparative suitability to serve

as BPs, namely:

(a) Acceptance by O. insidiosus for oviposition and

rate of egg hatch.

(b) Orius insidiosus development time and survival

from first instar to adult.

(c) Effect of host plant on O. insidiosus population

growth.

Methods

Plants

All plants (Table 1) were grown in greenhouses at the

Vineland Research and Innovation Centre in Vine-

land, ON Canada under growing conditions of

21 1 C, RH 70 5 %, 16: 8 h (L:D). Plant

80 M. O. Waite et al.

123

species used in the BP trials were grown from seed

with the exception of gerbera, which was purchased as

a flowering plant from commercial growers who did

not use chemical insecticides. Seeds were hand sown

two months prior to trial initiation into seeding trays

filled with ProMix potting medium (Premier Tech

Horticulture, Rivie`re-du-Loup QC Canada). One -

month later, seedlings were transferred to 15 cm diam

plastic pots containing the same growing mix. All

plants were watered once daily by hand using a water

and fertilizer (202020, NPK) mixture until sub-

strate was uniformly moist.

Insects

Orius insidiosus adults were obtained from Biobest

Biological Systems Canada Ltd. (Leamington ON

Canada). A colony was maintained in a growth cabinet

[25 1 C, 70 5 % R.H., 16:8 h (L:D)] at theVineland Research and Innovation Centre. Adults

were transferred to cages which were constructed from

plastic containers (750 ml disposable Ziploc Glad-

Ware container) in which two holes (2 cm diameter)

had been cut into opposite sides of the container that

were covered with mesh screen (180 lm) to provideventilation. A handful of buckwheat hulls was placed

into each container to serve as a refuge for the insects.

Two green bean pods (Phaseolus vulgaris L.) were

placed into each cage as an oviposition substrate

(Richards and Schmidt 1996), along with a kidney

bean leaf to provide moisture. Frozen Ephestia

kuehniella Zeller eggs (Beneficial Insectary, Redding

CA) adhered to a (4 9 2 cm) Post-it note were also

provided as a food source. Adults were allowed to feed

ad libidum throughout. Every three days, the green

beans were transferred to a new cage to produce

discrete even-aged cohorts and egg strips, beans and

leaves were replaced as needed. Only adult cages

received green beans for oviposition.

Bioassays

Evaluation of plant species/cultivars as oviposition

substrate for Orius insidiosus

Adults were removed from the rearing colony using an

aspirator and their sex determined by observing the

abdomen (209, Olympus SZ61) which is symmetrical

for females and asymmetrical for males as their

genitalia are sickle-shape (Slater 2005). Five adult

females, which were 7 1 days old to ensure that

they were sexually mature and had mated, were

collected, placed in containers and starved for 24 h.

The females were placed into cages containing one

stem from an individual test plant species/cultivar.

Each plant stem carried multiple flowers, with the

exception of gerbera and sunflower in which each cup

contained one flower. The base of each stem was

wrapped in cotton batting and fed through a hole in the

lid of a 2 oz Solo cup. The cup was filled with water

to prevent the plant from desiccating. The cotton

batting placed around the stem of plants served to

prevent adults from entering the water-filled cup. The

entire set up was then placed into an 8 oz Solo dish

and a bottle cage positioned on top of each dish. A

bottle cage was constructed from the bottom portion of

a 2 l plastic bottle. To provide ventilation and prevent

build-up of condensation in the cages, 2 9 5 cm

diameter holes were made in the sides of the bottle

using a punch that was heated over a Bunsen burner.

Mesh-screening was glued over the holes using a hot

glue gun. The cages were held in a growth chamber

[25 1 C, 70 5 % R.H., 16:8 h (L:D)]. After48 h, the cages were removed from the chamber and

the adults were removed from the cages. The number

Table 1 Plant species/cultivars evaluated as potential bankerplants for Orius insidiosus

Common name Species Source

Marigold, cv.

Lemon Gem

Tagetes

patula

Veseys Seeds Ltd,

Charlottetown, PE

Castor Bean Ricinus

communis

Richters Herbs,

Goodwood, ON

Ornamental Pepper,

cv. Black Pearl

Capsicum

annuum

Stokes Seeds Ltd.,

Thorold, ON

Ornamental Pepper,

cv. Purple Flash

Capsicum

annuum

Stokes Seeds Ltd.,

Thorold, ON

Gerbera Daisy, cv.

Festival

Gerbera

jamesonii

Orchard Park Growers,

St. Catharines, ON

Lakeshore Inc., Jordan

Station, ON

Feverfew Tanacetum

parthenium

Richters Herbs,

Goodwood, ON

Sunflower, cv.

Choco Sun

Helianthus

annuus

Stokes Seeds Ltd.,

Thorold, ON

All source locations are within Canada

Evaluation of seven plant species/cultivars 81

123

of eggs laid on each stem and the oviposition sites

were recorded. Stems were returned to their respective

cages and returned to the growth chamber.

Egg viability was assessed by counting the number

of nymphs as a proportion of eggs laid on each stem

using a plant washing technique. Stems were removed

from the bottle cages on Day 6 (five days after the

females were introduced into the cages) and placed

into 100 ml plastic jars with lids containing an E.

kuehniella egg strip (2 9 2 cm) as a food source for

emerging nymphs. Jars were then returned to the

growth chamber. On Day 8, the egg strips were

removed from the jars and 40 ml of 70 % ethanol was

added. Parafilm was placed onto the top of the jar,

and the jars shaken for 60 s. The jars were emptied

into a funnel lined with a Whatman no. 4 filter paper,

which was placed on top of a vacuum flask and the

ethanol was withdrawn. The filter paper was trans-

ferred to a Petri dish and observed under a microscope

(209, Olympus SZ61) to count the numbers of

nymphs. The stem was also examined under a

microscope to locate any nymphs which did not

transfer to the filter paper during the plant washing

process. The oviposition assays were conducted in

three blocks and replicated eight times per plant

species/cultivar.

Development of first instar Orius insidiosus nymphs

to the adult stage on selected plant species/cultivars

Orius insidiosus adults (7 1 days old) were

removed from the rearing colony using an aspirator

and their sex was determined as described above.

Twenty females were collected and transferred for

24 h to a plastic cage containing four green bean pods

for oviposition. The eggs laid on the green beans in the

plastic cages were observed daily for hatching to

ensure nymphs used in the development assays were

\24 h old. Nymphs hatched from these eggs wereused in this study to ensure that all individuals had the

same nutritional starting point. These first instars were

transferred to development cages using a moistened

paint brush. Development cages were constructed by

cutting a small hole in the centre of the bottom of a

60 ml Solo cup (Kaumeyer Paper Ltd., St. Catha-

rines, ON). The Solo cup was then placed inside a

250 ml plastic DART Conex Classic cup. To

provide ventilation, two 2 cm diameter holes were

cut into the sides of the 250 ml DART cup and mesh

screening was glued over the holes. A stem from an

individual test plant species/cultivar was inserted

through the hole cut into the Solo cup and wrapped

in cotton to prevent nymphs from escaping. The

bottom of the DART cup was filled with water and the

Solo cup containing an individual plant cutting from

each plant species/cultivar was placed inside. A

nymph was placed on the plant and the lid was placed

on the cup. Cages were placed in a growth chamber

[25 1 C, 70 5 % R.H., 16:8 h (L:D)] andnymphs were monitored daily for development,

recorded as the number of days to adulthood and

survival. Observations were continued until the adult

stage was reached or the nymph died. The experiment

was repeated until at least 15 nymphs had reached the

adult stage on each BP species.

The effect of host plant on Orius insidiosus population

growth

The suitability of plant species/cultivars as host plants

was evaluated based upon the ability of an Orius

population to increase in cage bioassays conducted in a

greenhouse at the Vineland Research and Innovation

Centre. Eight individual potted flowering plants, one of

each species/cultivar, were randomly assigned to a

dome cage (60 cm960 cm960 cm; Model 2120F,

MegaView Science Co. Ltd; Taichung, Taiwan).

Plants were watered twice daily for 2 min using a drip

irrigation system (2 l h-1 flow rate) and fruit and dead

flowers removed weekly (ensuring no O. insidiosus

were removed on plant matter). Each treatment

received ten female and five male adults (7 1 days

old) which had been collected from the rearing colony.

Populations of O. insidiosus on each plant were

sampled bi-weekly for ten weeks. Sampling was

conducted by placing a white tray inside the dome

cage and tapping the plant vigorously over the tray to

dislodge nymphs and adults. Dislodged individuals

were collected using an aspirator. The seams and

ceiling of the cage were inspected for additional adults

which may not have landed on the white tray, and were

also collected using the aspirator. The collected

nymphs and adults were counted, the number recorded,

and insects returned to the appropriate cage. The

greenhouse bioassays were conducted in three blocks

with eight replicates for each plant species/cultivar.


123

Data analysis

Oviposition and number of hatched nymphs (as a

proportion of eggs laid) data were subjected to an

analysis of variance (ANOVA) using PROC GLM in

SAS v. 9.2 (SAS Institute, Cary, NC, USA). Means for

the number of eggs laid and the numbers of hatched

nymphs were analyzed independently and were sep-

arated using Tukeys multiple means comparison. The

mean of the residuals was equal to zero and a Shapiro

Wilk test confirmed that the residuals were approxi-

mately normally distributed. A Type I error rate (a) of0.05 was used to test for significance.

Nymphal development data was subjected to an

analysis of variance (ANOVA) using PROC GLM in

SAS v. 9.2 (SAS Institute, Cary, NC, USA). Means

were separated using Tukeys multiple means com-

parison. A Type I error rate (a) of 0.05 was used to testfor significance.

A repeated measures ANOVA using the Mixed

procedure, SAS v. 9.2 (SAS Institute, Cary, NC, USA),

with variance partitioned into the fixed effect treatment

and the random effect block, was used to test the effect

of host plant on population growth. The total number of

O. insidiosus individuals counted every two weeks

was analyzed to determine population growth over

time (ten week sampling period). The ShapiroWilk

test confirmed that the residuals were approximately

normally distributed. Differences between means were

determined using Tukeys multiple means comparison

using a significance level of a = 0.05.

Results

Plant species had an effect on the oviposition of O.

insidiosus (F = 2.50; df = 6, 46; P = 0.035) (Fig. 1).

Significantly fewer eggs (mean SE) were found on

sunflowers (14.9 7.1 eggs plant-1; P = 0.042)

than marigold (49.9 6.4; P \ 0.0001). Differencesin the number of eggs laid by O. insidiosus on

marigold, gerbera, Black Pearl pepper, Purple Flash

pepper, feverfew, and castor bean, were not signifi-

cant. Plant species/cultivar did not have an effect on

the emergence of nymphs (F = 1.17; df = 6, 38;

P = 0.34) (Fig. 1). The mean number of nymphs as a

proportion of emergence from eggs laid did not

significantly differ on sunflowers from the other six

potential BP species.

Nymphs reared on gerbera had the highest survival

rate at 58.1 %. In contrast, only 10.7 % of nymphs

reared on marigold reached the adult stage (Table 2).

No nymphs developed to adulthood on sunflowers.

Nymphal development time from first instar to adult

was affected by plant species (F = 3.47; df = 5, 77;

P = 0.007) (Fig. 2). Development time for nymphs

reared on gerbera (8.3 0.13 days) was significantly

shorter than for those reared on marigold (9.2 0.16

days) and Black Pearl pepper (9.2 0.23 days) and

Purple Flash (9.1 0.21 days). There was no signif-

icant difference in development times on feverfew,

castor bean, Black Pearl pepper and Purple Flash

pepper (Fig. 2).

There were significant differences in the size of an

O. insidiosus population developing on the different

plant species/cultivars (F = 23.35; df = 5, 201;

P \ 0.0001; Fig 3). Population size was significantlyaffected by plant species (F = 25.64; df = 5, 201;

P \ 0.0001), week (F = 26.10; df = 4, 201; P \

0

10

20

30

40

50

60

Plant species/cultivar

Mean number of eggsMean number of nymphs

a

a

a

a

a

b

ab

Mea

n #

of e

ggs

or n

ymph

s/ p

lant

A A

AA A

A

A

Fig. 1 Mean number (SE) of Orius insidiosus eggs laid byfive females in 48 h and subsequent hatched nymphs on seven

potential banker plant species/cultivars in no-choice tests in a

growth chamber at 25 1 C, RH 70 5 %, 16:8 h L:D(n = 8). Means for the number of eggs laid and the numbers of

hatched nymphs were analyzed independently and are indicated

by lower case (eggs) or upper case (nymphs) letters. Means

indicated by the same upper or lower case are not significantly

different according to Tukeys test (P [ 0.05)


123

0.0001), and the plant 9 week interaction (F = 5.00;

df = 20, 201; P \ 0.0001). In each assessment week,the population of O. insidiosus on Purple Flash pepper

plants was significantly higher (P \ 0.0001) than onany other plant species (Fig. 3). Marigold supported

significantly lower populations of O. insidiosus

throughout (P \ 0.0001).

Discussion

Based on the results from the current study, Purple

Flash ornamental pepper is the best candidate for use

as a BP for O. insidiosus, having characteristics that

were superior to all other species/cultivars tested. It

appears that the Purple Flash pepper is highly suitable

as a banker plant for O. insidiosus, promoting

oviposition, nymphal development and survival, and

supporting population development to levels that were

greater than on any other species/cultivar.

The first stage of the evaluation was done to

determine the suitability of host plants for oviposition

by O. insidiosus as a measurement of both the quality

of plants as oviposition substrate and by their quality

as food. Oviposition preferences are based upon

physical characteristics of a plant, such as trichome

density and epidermal thickness (Coll 1996; Lundgren

and Fergen 2006; Seagraves and Lundgren 2010).

Oviposition was equivalent on Lemon Gem marigold,

castor bean, feverfew, Black Pearl pepper, Purple

Flash pepper and gerbera daisy. The number of eggs

laid on Choco Sun sunflowers was significantly lower

than on plants other than gerbera. The number of eggs

counted on the Choco Sun sunflowers, however, was

inaccurate as fewer eggs were counted than nymphs

recovered. Errors in egg counts were likely a result of

O. insidiosus oviposition habits: the insect lays eggs in

concealed locations (e.g., sepals) and consequently

many eggs were missed. This is supported by the fact

that there are no significant differences between the

numbers of emerged nymphs found on each plant

species.

In nymphal development and survival trials, no

nymphs reached the adult stage on the Choco Sun

sunflowers. This could be attributed to a severe powdery

mildew (Blumeria graminis) infection that occurred on

the sunflower plants during the experiment. Sunflowers

were selected as a BP candidate as large Orius

populations can be found in field sunflowers during

summer months. However, owing to their susceptibility

to powdery mildew, sunflower cannot be recommended

as a BP for O insidiosus in greenhouses. BPs, like crop

plants, are susceptible to pests and diseases, and this has

to be considered as a factor in the selection of

appropriate candidate species (Huang et al. 2011).

Several studies have determined that O. insidiosus

females select oviposition sites based upon plant

species, and specific locations on a plant favour

Table 2 Survival (%) of Orius insidiosus nymphs (\24 h old)reared on seven potential banker plant species at 25 1 C,R.H. 70 5 %, 16:8 h (L:D)

Banker plant na Survival (%)

Gerbera daisy 31 58.1

Black pearl pepper 32 50.0

Purple flash pepper 40 45.0

Feverfew 45 42.2

Castor bean 41 36.6

Lemon gem marigold 140 10.7

Choco sun sunflower 15 0.0

a Initial number of nymphs

bc c

ab c c

0

1

2

3

4

5

6

7

8

9

10

Mea

n de

velo

pmen

t tim

e (d

ays)

Plant species/cultivar

a

Fig. 2 Mean development time (days SE) of Orius insidio-sus nymphs (\24 h old) to reach the adult stage when reared onsix potential banker plant species/cultivars in a growth chamber

at 25 1 C, R.H. 70 5 %, 16:8 h L:D. Means followed bythe same letter are not significantly different from each other by

Tukeys test (P [ 0.05). No nymphs reached the adult stage onthe sunflowers (cv. Choco Sun) and these replicates were

excluded from statistical analysis


123

nymphal performance and survival (Coll 1996; Lund-

gren and Fergen 2006; Lundgren 2011). As nymphs do

not tend to move among plants and are thus restricted

to the resources available on the plant on which they

hatch, females must choose a plant that will support

their development and survival. Survival and devel-

opment time (from egg hatch to adult) are thus

important measures of BP suitability. While each plant

tested was equally suitable for oviposition, nymphal

survival and development varied according to the BP

species/cultivar tested. Nymphal development time

was significantly different among plants. The fastest

and slowest times differed by one day. Orius insidio-

sus nymphs requiring one day longer to reach adult-

hood is unlikely to be as biologically significant as

plant species/cultivar, which had a much greater effect

on the size of an O. insidiosus population, as observed

in the ten week greenhouse trial. Nymphal survival on

the test BP species/cultivars varied widely. Only

10.7 % of nymphs reached the adult stage on marigold

plants. Marigolds have been suggested as a potential

banker plant for Orius sp., based on their observed

abundance on the plants. However, the high numbers

of Orius sp. observed in these trials may have been due

to feeding upon thrips rather than pollen (Baggen et al.

1999; Silveira et al. 2009). Buergi (2007) concluded

that the nutritional profile of marigold pollen is not

sufficient to support O. insidiosus reproduction.

Marigold would be an excellent choice for female O.

insidiosus to lay eggs if the plant was infested with

prey and hence the suitability of the pollen would not

be an important factor. However, among the criteria

for selection of a BP for O. insidiosus is that it must

provide an alternative source of food when prey is

limited or absent. This renders marigold a poor

candidate (Huang et al. 2011).

The final research component evaluated the plant

species/cultivars for their ability to support O. insid-

iosus population growth over a ten week period. This

provided more practical information on the potential

of BPs in a commercial ornamental greenhouse as O.

insidiosus were reared for multiple generations under

greenhouse conditions. From the results of the labo-

ratory bioassays, it might have been expected that

gerbera daisy would be a good choice as a BP. Orius

insidiosus nymphs reared on gerbera daisy had a

survival rate of 58.1 % and development time

(8.3 0.21 days) was significantly shorter than

nymphs reared on the other plants. However, the

nymphal development bioassays were carried out in

ideal conditions with one pollen-producing gerbera

flower per nymph. In contrast, the greenhouse bioas-

say was conducted over a ten week period and the

limited number of large flowers which are normally

produced per gerbera plant (2.7 flowers plant-1

observed, n = 8) was probably insufficient to support

0

5

10

15

20

25

30

35

40

45

50

55

60

65

May 12 May 26 June 9 June 23 July 7Mea

n N

umbe

r of O

rius

insi

dios

us N

ymph

s &

Adul

ts

Purple Flash Black Pearl

Castor Bean Feverfew

Gerbera Marigold

bb bc

c

d

b

b

a

d

c c

b b

a

c d d

b bb

a

d d

a

bc c

d d

a

Fig. 3 Mean number (SE) of Orius insidiosus nymphs andadults reared on six different host plants in a greenhouse

bioassay (n = 8) conducted in Vineland ON, Canada, May 6th

to July 7th, 2011. Means followed by the same letter within the

same sampling period do not differ significantly from each other

by Tukeys test (P \ 0.05)


123

O. insidiosus population growth over the trial period.

Weekly maintenance and pruning were conducted to

encourage new growth and re-flowering, but over

ten weeks, no new flowers were produced on the

gerbera plants from weeks 7 through 10. In compar-

ison, feverfew and marigold plants produce many

small flowers (22.9 and 31.8 flowers plant-1

observed, respectively). However, in both plants the

number of O. insidiosus also declined despite the

increased availability of pollen. The decline of O.

insidiosus populations on feverfew and marigold may

be attributed to the pollen having insufficient nutri-

tional value (e.g., amino acid and lipids content) to

sustain development of O. insidiosus rather than it

simply being a factor of the quantity of pollen

available (Buergi 2007; Schuel 1992). Future studies

should address the quantity of pollen of the plant

species/cultivars being tested in addition to pollen

quality. Many flowers were consistently present on

Purple Flash peppers (23.3 flowers plant-1, n = 8)

and the number of O. insidiosus on this plant was

significantly higher than on any other plants, including

the Black Pearl pepper (7.9 flowers plant-1, n = 8),

over the ten week observation period. Defensive

properties of pollen also influence the ability of O.

insidiosus to utilize pollen from different plant

species/cultivars. Sporopollenin, which is a compo-

nent of the outer wall of a pollen grain, is highly

resistant to acids and enzymatic degradation (Schuel

1992). Pollen containing higher levels of sporopol-

lenin are, thus, likely to provide little nutritive value

and will not promote survival and development. Orius

insidiosus feeds on pollen in a similar manner to the

way it feeds on prey, i.e. it inserts its rostral tip into the

grain and extracts the inner contents as opposed to

ingesting the entire grain (Fauvel 1974). While certain

pollen may have a high intrinsic nutritive value, the

thickness of the pollen wall and the sporopollenin

content of the wall may prevent O. insidiosus access-

ing these nutrients. So, while certain pollen sources

may have high nutritive value, O. insidiosus may be

unable to access these nutrients rendering the pollen

unacceptable as a supplemental food.

The key attribute measured for a suitable BP is its

ability to support long term population growth of the

biological control agents. Results of the current study

suggest that the Purple Flash pepper has the greatest

potential for use as a BP for O. insidiosus as it has

superior characteristics for population growth

compared with other species/cultivars tested. The

Purple Flash ornamental pepper provided equally

acceptable oviposition locations in comparison to all

other plants tested, predator development time was

equivalent to all other plants tested (9.1 0.21 days)

with the exception of gerbera, and it supports popu-

lation growth over multiple generations. Populations

were consistently higher on Purple Flash than on any

of the other plants tested in the greenhouse bioassays.

In addition, the Purple Flash cultivar is a smaller, more

compact plant that is better suited to placement on

benches in ornamental greenhouses than the Black

Pearl. Future studies should investigate the suitability

of other ornamental pepper cultivars in addition to

Purple Flash and Black Pearl, and it is important to

assess their performance in a commercial greenhouse.

When evaluating potential benefits of placing Black

Pearl pepper BPs in commercial hoop houses follow-

ing augmentative releases of O. insidiosus, Wong and

Frank (2012) found that addition of the BPs did not

improve the level of pest control obtained. Spiders

colonized the BPs and reduced O. insidiosus access to

pollen in the flowers. They concluded that BPs might

be best suited for indoor greenhouse crops.

In commercial greenhouse ornamental crops, Pur-

ple Flash BPs supported constant populations of O.

insidiosus (pers. obs, R.B.). Additional studies are now

required to determine the dispersal of O. insidiosus

through the greenhouse from the BPs, as well as

determining effects on their searching behaviour when

prey is scarce. The Purple Flash ornamental pepper is a

promising BP for O. insidiosus that could enhance

utilization of the predator to control WFT in green-

house ornamental crops.

Acknowledgments This work was conducted at the VinelandResearch and Innovation Centre, a not for profit organization

dedicated to horticultural science and innovation, located in

Canadas Niagara Region. We thank Biobest Canada Ltd. for

supply of O. insidiosus, Angela Brommit, Rebecca Eerkes, Erik

Glemser, and Andrew McFarlane for technical support. This

research was funded through the OMAFRA-University of

Guelph Research Program and a MITACS grant sponsored by

Eco Habitat Agri-Services to M.O.W.

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Author Biographies

M. O. Waite This research is part of the M.Sc. project ofMeghann Waite which focuses on identifying new strategies to

increase the control and cost efficiency of the biological control

agent, Orius insidiosus Say, in greenhouse ornamentals.

C. D. Scott-Dupree Her research focuses on the integratedmanagement of insect pests as well as the impact of

agroecosystems on non-target beneficial arthropods.

M. Brownbridge His research projects include the develop-ment and integration of microbial biocontrol strategies for

insect pests and weeds.

R. Buitenhuis She studies the use of predators, parasitoids,entomopathogenic nematodes, trap plants, and banker plants

for the control of insect and mite pests.

G. Murphy He provides technical support to growers in theNiagara region, specializing in integrated pest management

solutions for greenhouse floriculture crops.


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Evaluation of seven plant species/cultivars for their suitability as banker plants for Orius insidiosus (Say)AbstractIntroductionMethodsPlantsInsectsBioassaysEvaluation of plant species/cultivars as oviposition substrate for Orius insidiosusDevelopment of first instar Orius insidiosus nymphs to the adult stage on selected plant species/cultivarsThe effect of host plant on Orius insidiosus population growth

Data analysis

ResultsDiscussionAcknowledgmentsReferences

Documents

Banker plants of Orius Insidiosus