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Funded Project

Funding Program: IPM Partnership Grants

Project Title: Guardian Plant Systems for Greenhouse IPM (Year 2)

Project Director (PD):

Carol S. Glenister [1]

Lead State: NY

Lead Organization: IPM Laboratories, Inc.

Undesignated Funding: $39,982

Start Date: Apr-01-2008

End Date: Mar-31-2009

No-Cost Extension Date: Mar-14-2011

Pests Involved: whitefly, whiteflies

Site/Commodity: greenhouse, ornamentals

Area of Emphasis: trap crops

Summary: An innovative pest management system using eggplants as crop guardians has evolved over the last decade in Holland and Canada in peppers, tomatoes, fuchsias, and poinsettias. For whitefly control, the eggplants pull whitefly out of the crops, the growers apply natural enemies directly to the eggplants, and in some crops, the eggplants supply reproduction sites for the natural enemies. The eggplants have also assisted in determining if pesticide action thresholds have been reached by offering the grower an efficient snapshot of the natural enemy impact on pest populations within the greenhouse. Thus, the eggplants have been serving as indicator, trap and banker plants in a technique that we refer to as Guardian Plant Systems (GPS). These GPS have substantially enhanced grower confidence in biological control, reduced monitoring time, and reduced the purchases of natural enemies, thereby reducing the cost of biological control and IPM. In our 2007 NEIPM study, we demonstrated that eggplants reduce monitoring time for detecting both greenhouse and sweet potato whiteflies and the whiteflies' mortality. Importantly, the eggplants strongly attracted both the normal and the Q biotype strains of sweet potato whitefly adults. We also created guidelines for the best way to deploy eggplants in a crop. However, we need a second year of observations to refine and fully analyze the eggplant/crop/whitefly relationship.

Three experienced pest management groups from two northeastern states -- one from a university research laboratory (VT), and two from private industry (NY) -- will each demonstrate one of the following two Guardian Plant/crop combinations for the second year: eggplants in poinsettias or eggplants in specialty annuals. All of the demonstrations will occur at commercial greenhouses. Each cooperator will gather and compare data on whitefly and natural enemy incidence in the crop with data on whitefly and natural enemy incidence on the GPS. They will also compare costs, depending on available data, between conventional chemical treatments and biological control, or between biological control with and without GPS. Participants will share information by meeting for the purposes of comparing data, results and styles of observation and analysis.

All cooperators will actively share the project information with many grower groups and with the GO IPM Working Group of NE IPM. This project will encourage rapid innovation by timely sharing of methods to seed rapid implementation by greenhouse growers. This project addresses the working group priority to develop practical, user friendly methods of less toxic methods of pest management implementation

Objectives: 1. Evaluate use of eggplant Guardian Plant Systems (GPS) in two greenhouse crop systems: bedding plants and poinsettias.

2. Compare costs of GPS with those of standard parasitoid release strategies and conventional chemical control.

3. Disseminate information about GPS and trial results regionally via fact sheets, web pages and presentations at grower meetings.

Proposal

Interim Report: Jan-04-2010

Outcomes
We observed crop/whitefly/natural enemy dynamics in a 2-year study using eggplant as Guardian Plants at three poinsettia greenhouses and one annual bedding plant greenhouses, respectively. The sweet potato whitefly, Bemisia tabaci, and the greenhouse whitefly, Trialeuodes vaporariorum, were the predominant whitefly species present in the poinsettia and annual greenhouses, respectively. The eggplant Guardian Plants was found to serve three functions: indicator plant, whitefly trap plant, and a site for whitefly parasite reproduction.

The scouting time to detect whitefly on the Guardian Plant was less than half of the time required on the poinsettias and less than one quarter of the time required to find whiteflies on the sweet potato vine, flowering maple, Duranta, and Salvia (Table 2, Fig. 1). Lantana and the Garten Mister fuchsia in 2008 were more attractive to the whitefly than the other crops with the Fuchsia requiring just a little more time than the eggplant and the Lantana requiring twice the time. The Guardian Plants also served as sites for quicker detection of successful parasitism in the greenhouse, given that they hosted a higher concentration of whiteflies to host parasites (not shown).

Whiteflies were highly concentrated on the eggplants (Figure 2). 2007 data showed that whitefly numbers were not any higher on the adjacent crops than they were on crops spaced further away from the eggplants.

We tested the level of synchrony of the whitefly development on the eggplants with the crop data available. In 20 out of 22 cases, the developmental stage of the whiteflies was ahead of or at the same stage as the crop (Table 3). In 2 cases, the development lagged by one week behind 2 species that appear to be stiff competitors for whitefly: Lantana and Fuchsia.

The eggplants hosted much more Encarsia reproduction than Eretmocerus reproduction as evidenced by the highest number of parasitized nymphs found per leaf on the eggplants in the New York crops in 2007 and 2008 (Table 4). Nearly 10 or more times as many parasitized nymphs could be found with the Encarsia/greenhouse whitefly combination than with the Eretmocerus/sweet potato whitefly combination.

In 75% of the trials, the number of pesticide treatments declined in comparison with the controls (Table 1). At one Vermont site, the grower, who formerly used one or more insecticides per year to control whitefly on his crop, did not use any insecticide treatments at all in 2007 and 2008.

At the New York poinsettia site, the suspicious lack of control led us to bioassay the upper (new) poinsettia leaves versus the lower (purchased with cuttings 6+ weeks prior) leaves. On the older leaves 68 % of the Encarsia died within 48 hours versus 19% died on the younger leaves. We concluded that the parasites were perishing from pesticide residue. The grower resorted to pesticides to keep the whiteflies at acceptable levels.

The trap plant character of the Guardian Plants was evidenced in 2 ways: by the mortality of the whitefly nymphs on the eggplants, and at New York Site 2 in 2008, the physical bagging and removal of the eggplants from the greenhouse before abundant large nymphs hatched. Additionally, at least two other growers squashed all the adult whiteflies that they found on their eggplant Guardian Plants to supplement the control by the Eretmocerus.

Conclusions
1) Eggplant Guardian Plants can act as time-saving indicators of whitefly and natural enemy presence and growth stage in many ornamental crops. 2) Eggplants pull whitefly adults away from crop plants in greenhouses. 3) Eggplant Guardian Plants serve as high level reproduction sites for Encarsia on greenhouse whitefly but not for Eretmocerus on sweet potato whitefly. 4) Other potential Guardian Plants like lantana can be evaluated by comparing parameters between the crop and the Guardian Plant candidate of seconds to first pest detection, pest growth stage, natural enemy reproduction and pest mortality.

New applications of Guardian Plants: This work generated strategies for analyzing Guardian Plants that we were able to apply to 3 more Guardian Plant species in 2009: Lantana for whitefly control, Black Pearl ornamental pepper for thrips control, and marigolds for thrips control. The Guardian Plant work has created interest from western New York vegetable grower, Mark Zittel, in setting up a Guardian Plant system for spider mite control in field grown eggplants in 2010.

Unexpected failure at one site resulted in the creation of a quick bioassay for pesticide residues. At one grower, we analyzed poinsettia leaf toxicity to whitefly parasites after the parasites failed to control whitefly in poinsettias failed for a second year in a row. The bioassay demonstrated that the older poinsettia leaves that had not been treated with pesticides for more than 6 weeks still killed 68% of the parasites and killed more than three times as many parasites as the younger untreated poinsettia leaves.

Enhancement of collaboration among stakeholders: This grant supported the collaboration between 4 greenhouse businesses and 2 research labs in Vermont and New York State, including one meeting where researchers and stakeholders summarized and discussed our results.

Several meetings (see below) were held in order to share the 2007-2009 information with grower groups. At these grower meetings, surveys were distributed to approximately 274 growers in order to measure the proportion of these growers that were using natural enemies in conjunction with GPS, what guardian plants they were using, what functions the guardian was performing (indicator, trap, habitat), and if they planned to incorporate eggplants into their pest management system in the next one to two years? A web site is planned to share the results of this GPS study and the grower surveys. The intent of the project is to encourage rapid innovation by timely sharing of methods to seed rapid implementation of GPS IPM by greenhouse growers. Lists of Presentations, Workshops, and Publications are included in the full report.

Impacts
Safeguarding human health and the environment: This project resulted in a reduction in pesticide use in 75% of the trials (Table 1). At one Vermont site, the grower, who formerly used one or more insecticides per year to control whitefly on his crop, did not use any insecticide treatments at all in 2007 and 2008.

Economic benefits: The Guardian Plants demonstrated major time savings in pest and natural enemy detection. The scouting time to detect whitefly on the Guardian Plant was less than half of the time required on the poinsettias and less than one quarter of the time required to find whiteflies on the sweet potato vine, flowering maple, Duranta, and Salvia (Table 2, Fig. 1).

Implementation of IPM: The project demonstrated whitefly parasites controlling pesticide-resistant Q biotype sweet potato whitefly as well as the older strain of sweet potato whitefly. The Vermont cooperators had struggled with Q biotype in the past, yet reduced pesticide use by 50-100% in the presence of Q biotype in our trial.

The project developed 4 ways to analyze Guardian Plant usefulness: 1) seconds to 1st detection of pests on Guardian Plant in comparison to crop plant (in future, we should do the same for natural enemies), 2) Presence/absence of natural enemies on Guardian Plant in comparison to crop plant, 3) Detection of evidence of natural enemy reproduction on Guardian Plants vs crop plants, and 4) Pest growth stage synchrony on Guardian Plants vs crop plants. These analysis tools were used to analyze 3 more Guardian Plant species in 2009: marigolds, ornamental peppers, and lantana.

The project demonstrated that the eggplants were excellent at drawing whitefly adults away from greenhouse crops.

An unexpected outcome was the need to devise a leaf bioassay for pesticide residue killing whitefly parasites on poinsettia.

Report Appendices

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