Flower Crops.

Preface: Many of the past successes in biological control have

depended upon the identification and introduction of novel natural enemies

for a particular peg. The extremely low tolerances to arthropod damage

associated with floral crops grown for their aesthetic qualities suggest

that inundative releases of high rates of natural enemies are necessary

for successful biological Control of insect pests. Although releases of

natural enemies have produced excellent biological control of several insect

pests of greenhouse crops, this technique has not been widely embraced

by growers of ornamental plants due to the prohibitive costs associated

with maintaining post densities at extremely low levels, In response to

this problem, many researchers continue to search for natural enemies that

may be more effective than their present counterparts in hopes that a more

effective natural enemy will reduce costs. While this approach may eventually

be successful, it has not yet proven to be an effective approach to biological

control of insect pests of floral crops. My research takes another approach,

one that assumes that at least some of the many commercially available

natural enemies will be economical and effective if produced and utilized

in an optimal manner. The approach of my research funded by the American

Floral Endowment has been to develop efficient release strategies to bring

about economically feasible aphid biological control infesting chrysanthemums.

Project Objectives:

1. Assess how natural enemies locate and exploit patches of aphids

on chrysanthemums,

2. Determine natural enemy efficacy once they have located an aphid

infested plant.

3. Conduct Greenhouse trials to compare efficacy of each release strategy.

Summary of Results to Date: We have been able to Demonstrate

that so-called trivial movements of natural enemies may be used to improve

the efficacy of augmentative biological control of aphids infested potted

chrysanthemums based upon our results from several experiments. First,

we have studied how trivial movements of the green peach aphid, Myzuspersicae,

generate spa” heterogeneity within greenhouse cropping systems. Second,

we have documented how foraging patterns of the grow lacewing, Chrysoperla

carnea, and aphid parasitoid, Aphidius colemani, are influenced by the

spatial heterogeneity associated with their prey or hosts. These foraging

movements are of practical concern because they may influence the success

with which natural enemies regulate past populations. Chrysoperla carnea

is incapable of responding to changing spew patterns of aphid outbreaks

and is hence unable, to control aphids with weekly releases of the predator,

Aphidius colemani Is capable of locating and inflicting high rates of parasitism

on high and moderate density patches of aphids, but the parasitoid is unable

to locate low density patches. When wasps are released weekly, then low

aphid density patches develop into superabundant aphid patches between

parasitoid releases. Superabundant patches, which exhibit exponential population

growth, cannot be brought under biological control regardless of the wasp

release rates used. Currently we are conducting greenhouse trials to determine

whether we can prevent the formation of superabundant aphid patches using

one of two methods: (1) using an even greater number of wasp release points

within a greenhouse for a specified wasp release rate, and (2)

reducing the time period between wasp releases.

Future Plans Covered by the Endowment Grant: The information

obtained from this research yields a clear picture as to ways natural enemies

move through spatially and temporally heterogeneous greenhouse environments

and will form the bases for the development of optimal release strategies.

A next step of this research will be to generate these strategies and to

test their abilities to biologically control aphids in commercial chrysanthemum

production greenhouses.

Anticipated Benefits to the Floral Industry: The development

of non-chemical methods of arthropod pest control continually ranks as

a top research priority for the floral industry. In response to ties demand,

research on the use of parasitoids, predators and pathogens for arthropod

pest control has spurred tremendous growth in the commercial availability

of biological control agents. Unfortunately, scientific data necessary

to develop effective and economically feasible biological control programs

have not kept pace with the growth of the industry. Simply stated, the

research community is currently unable to provide scientifically based

recommendations to the floral industry as to the efficacious and cost effective

use of most, if not all, of the commercially available natural enemies

for use in floricultural crops. Biological control remains very much an

art form rather than a reliable technology. At the completion of my multiyear

project, I will have made significant advances in correcting this problem

for at log one major pest of floricultural crops. Current benefits already

include, (1) delineation of maximum aphid densities at which biological

control ran be expected to be effective, (2) quantification of parasitoid

release strategies that may lead to successful biological control, and

(3) comparison of the relative abilities of natural enemy species to bring

about successful biological control.

Presentations and Publications on Research Applicable to the Floral

Industry:

Heinz, K.M. 1996. A review of Liriomyza leafminers and a potential

new pest species, L. huidobrensis. Texas Greenhouse Bulletin. May, 1996.

pp. 8-9.

Heinz. K.M., L.M. Heinz, & M.P. Parrella. 1996. Natural enemies

of western flower thrips indigenous to California ornamentals. Integrated

Control in Glasshouses. IOBC/WPRS Bulletin (Vienna, Austria). 19(l): 51-54.

Heinz, K.M. 1996. Predators and parasitoids as biological control agents

of Bemisia in greenhouses. pp, 435-449.7 In (D. Gerling & R. Mayer,

eds,)Bemisia 1995: Taxonomy, biology, damage, control and management. Intercept,

Hants.

Heinz, K.M. 1996. ‘Movement and Foraging by Aphid Natural Enemies:

Oversimplification of the Functional Response” Pacific Branch of the Entomological

Society of America. Symposium on the Biorational/Biological Control Strategies

for Greenhouse Grown Crops N%ft-

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