B. Nontechnical Summary
Spring flower crops in the northeastern United States contribute about 0.5 billion
dollars annually to the economy, as bedding plants or hanging pots. Pests include
whiteflies, thrips, aphids and mites. We have developed effective, cost competitive
biological controls for whiteflies in flower crops and are mid way toward doing
the same for thrips. Aphids commonly appear in crops under biological control
management. Non chemical controls for aphids are needed if growers are to be
able to employ whitefly and thrips biological control. Aphids make flowers unsightly
and unsaleable. Aphid biological control options in greenhouse vegetables are
well understood and in use. Application to flower crops has lagged. Greenhouse
production in the northeastern US is over 90% flower production. One approach
to aphid biological control is to place “banker plants” in greenhouses.
These consist of some form of monocot (like rye), with a grain aphid (a species
unable to feed on dicot flower crops) on which a commonly used aphid parasitoid
(such as Aphidius colemani) can reproduce. This allows the parasitoid to develop
its population at the earliest moment when pest aphids appear in the crop. This
is important as aphid reproduction is very rapid and early stages of aphid infestation
are often missed by growers. To adapt the banker plant technology currently
in use in Europe and Canada on vegetable crops to flowers we need to run greenhouse
trials in flowers crops to see how well it works and at what cost. The dominant
aphids in flower crops are likely to cotton aphid (Aphis gossypii) and greenpeach
aphid (Myzus persicae). We will run the needed trials in University greenhouses
in MA and then in commercial greenhouses in both MA and NY. Controls that work
in these states will work for the whole NE region. Ancillary activities needed
in support of these trials include an initial aphid survey in the crop and screening
potentially selective aphicides to find a compound to use for spot treating
infestations of less common aphids, of species not susceptible to A. colemani.
C. Introduction
Regional importance of spring flower crops. Nationwide, in 1998 sales of flats,
pots and hanging baskets of such plants as marigolds, impatiens, geranium, petunias,
and cyclamen were approximately 2.5 billion dollars, which was 64% of all greenhouse
floriculture sales (National Agricultural Statistical Service, 1999). The majority
of these sales are concentrated in the spring crop. In 1998 in MA, CT, NY, NJ,
MD, PA, and VA combined, there were over a half a billion dollars in sales of
such floral crops, 20% of all U.S. production. Greenhouse businesses employ
a large labor force, averaging 16 employees per business. Thus the 446 greenhouse
operations in MA in 2001 (New England Agricultural Statistics Service, 2002)
and the ca. 965 operations in NY, likely generated over 20,000 jobs.
Regional importance of pest. Aphids (especially Aphis gossypii and Myzus persicae)
are a common problem on a wide variety of spring floral crops. In a survey of
MA flower growers in 1996, growers reported applying an average of three pesticide
applications per crop for aphids, second only to thrips (Smith, 1998). While
this survey has not been repeated recently, little has changed in this regard.
Failure to control aphids to low levels makes plants unsaleable. Use of pesticides
for control of aphids can disrupt biological control of thrips, mites and whiteflies.
For growers wishing to minimize pesticide use, aphid biological control options
are needed. Current practice is proceeding based on an inadequate research base,
largely guided by guesswork and insectary recommendations.
Risk reduction benefits of project. Reduction of pesticide use in greenhouses
will benefit greenhouse workers. Greenhouse workers are often minimum wage employees
who are the least sophisticated in protecting themselves from contact with potentially
damaging pesticides. Conversion to biological control will improve this situation.
Also, greenhouse growers want their products to be seen by their customers as
“green.” Use of biological control as much as possible will help
growers convey that image.
Reason for doing the study. This study is needed as a complement to our past
efforts to develop biological controls for other pests in greenhouse flower
crops (whiteflies and thrips). These programs would be less likely to be implemented
if pesticide controls for aphids were commonly used, disrupting biological control
of other pests.
D. Objectives
Obj. 1. Aphid/Crop Survey in MA and NY Greenhouses. The goal of this objective
is to determine which aphids, on which crops, are the dominant species found
in MA and NY on spring flower crops. While this information is known in superficial
terms, this survey will provide quantitative data, which are lacking.
Obj. 2. Assess the Efficacy of Banker Plants Systems for Biological Control of Aphids in Spring Flower Crops. We will assess the degree of aphid control provided by banker plants, examining the influences of aphid and plant species.
Obj. 3. Compatibility of Selective Aphicides and A. colemani. In the laboratory, we will measure the effect of pyretrozine and pyroproxifen on adults and mummies of Aphidius colemani.
Obj. 4. Efficacy under Commercial Greenhouse Conditions. After the previous work, we will examine the efficacy of A. colemani in commercial growers in MA and NY.
E. Approach
As a first activity, we will survey 40 greenhouses between NY and MA to determine
what aphids are the dominant species. We expect to find that these will be cotton
aphid and greenpeach aphid, but other species such as floxglove aphid may be
important. Following the surveys, technicians in both MA and NY will go to Florida
to be trained in aphid identification to work up the material found in the survey
The trial to measure efficacy of our banker plant system will be run in greenhouses
at UMASS. Each test greenhouse will contain 60 flats (= 90 sq ft or 8.6 m2)
of crop plants, of 1 or 2 plant species as called for in the design. The number
of parasitoids released (A. colemani) will be chosen so that the treatment will
be roughly cost-competitive with pesticides. A. colemani is sold by Koppert
for $22.50 per package of 500 parasitoids, or $0.045 each. Approximately 50
parasitoids will be placed on one open rearing unit per greenhouse (2.5 x 4.5
m). Using mixtures of cotton and greenpeach aphids on pansies and margarita
daisies, we determine the effects of (a) aphid species, (b) plant species, and
(c) mixing of aphid species within the crop affect the level of control provided
by A. colemani released via open rearing units (banker plants).
To assess the compatibility of potentially selective aphicides with A. colemani,
we will assess the mortality of A. colemani in two life stages (adults of mixed
sex or mummies) caused by contact with residues (for adult parasitoids) or direct
sprays (for mummies) of both pymetrozine and pyriproxyfen.
In year 2 (2006) we will simultaneously conduct a trial of our banker pant system
in commercial greenhouses in both MA and NY.
F. Progress
In the first year of the project, we have made the following progress.
1. Obj. 1 (aphid survey in commercial greenhouses). Forty greenhouses have been
surveyed. Technicians from MA and NY have been trained in aphid identification
by a specialist in Florida. Sorting of the species recovered is pending.
2. Obj. 2 (greenhouse trials at UMASS). Before the trial we needed to obtain
aphid cultures such that both of the target aphids would feed on both of the
intended test plant species. This was not possible for impatiens and geraniums.
We were able to find cultures of melon and greenpeach aphids that did both feed
on both pansies and margarita daisies. Using these aphids and test plants, the
first UMASS greenhouse trial was begun in April of 2005 and will conclude in
mid May. The second trial will follow immediately. Initial results show a strong
effect of the presence of parasitoids vs the untreated control.
3. No work has yet been attempted on Objs 3 or 4. Work on Obj. 3 is planned
for summer of 2005 and work on Obj 4 in commercial greenhouses will occur in
spring of 2006.
Sponsored by the Cooperative Extension and Land Grant University IPM programs of the Northeast (Connecticut, Delaware, Maine, Maryland, Massachusetts, New Hampshire, New Jersey, New York, Pennsylvania, Rhode Island, Vermont and West Virginia)