Trap crops, indicator plants and banker plants: Tools for IPM in Greenhouse Production

1. Trap crops, indicator plants and banker plants:Tools for IPM in Greenhouse Production Elizabeth Lamb New York State IPM Program Coordinator for Ornamentals eml38@cornell.edu www.nysipm.cornell.edu All photos by E. Lamb except where otherwise noted

2. Indicator plants, trap crops and banker plants provide additional tools for managing pests in greenhouses

3. Indicator plants • Indicator plants are usually species or varieties that are particularly susceptible to, or tolerant of, certain conditions • Environment • Ground ivy in shady lawns • Salt tolerant species • Phenology for insect development • Gypsy moth egg hatch corresponds to the first bloom of Eastern dogwood in Ohio • Disease and insect presence • Indicators are more attractive to insects than crop

4. Potato chunks as indicator for fungus gnat larvae

5. Virus Indicator Plants • Diseases indicated • Impatiens Necrotic Spot Virus (INSV) • Tomato Spotted Wilt Virus (TSWV) • Vectored by • Western flower thrips • Petunia • cultivars Summer Madness, Super Blue Magic, Calypso, Red Cloud • Fava beans • cultivar Aquadulce

6. Virus Indicator Plants • Characteristics • Very attractive to western flower thrips • Feeding scars show up quickly and infected lesions form quickly (2-3 days) • Petunias do not serve as a source of virus • Not true of fava beans but seed may be less expensive • Therefore must remove infected fava beans as soon as possible • Remove infected petunia leaves but plants can stay

7. Blue attracts the thrips but the plates aren’t sticky so the thrips feed on the indicator plants rather than getting stuck. Photos: Tina Smith, UMass Extension

8. Tomato plant Photo: Graeme Murphy Tomatoes as indicator plants for whitefly in poinsettia

9. Trap crops • Trap crops are most often used for insect pest control • Perimeter trap cropping in field vegetables • Trap crops interspersed in greenhouse ornamentals • Characteristics • Species or cultivar used needs to be more attractive to pest than crop is

10. Perimeter trap cropping of collards for cabbage - diamondback moth Photo: T.J. Boucher, University of Connecticut • Other vegetable trap crop systems: • Hubbard squash for other Cucurbita - cucumber beetles • Cherry peppers for bell peppers - pepper maggots

11. Methodology • Trap crop must encircle other crop • Control pest on trap crop as soon as it is seen • Advantages • Lower use of pesticide • Maintains populations of indigenous natural enemies • Attractiveness as a problem? • Will the trap crop plants attract more insects than would have been there anyway?

12. While perimeter trap cropping can be used in the greenhouse, it is more common to see the trap crop interspersed among the crop plants

13. Some examples • Whitefly in poinsettia • Tomato • Eggplant • Thrips in chrysanthemum • Gerbera • Verbena • Chrysanthemum - more susceptible cultivar

14. For attracting western flower thrips, the trap crop is in flower before the saleable crop

15. At all 3 distances from the release point, the chrysanthemum plants with open flowers were more attractive to the thrips than plants with foliage, buds or buds showing color (crack buds). Table from Buitenhuis, Shipp, Jandricic and Short, Greenhouse Canada, September 2006, pp 10, 12

16. What factors do you need to consider when using trap crops? • Placement • Near vents for pests moving in from outside • Throughout crop • Number • How far does pest move? • Stage of crop plant • Flowering vs. vegetative • Control on trap crop or not • Chrysanthemum example - systemic control on trap plants

17. Eggplant in gerbera crop

18. Banker plants • Banker plants serve as a site for rearing biocontrol agents in the greenhouse by providing them with an alternative food source. • The banker plants can consist of the same crop/crop pest as that you are trying to control, or can be an alternate host and prey • Bird cherry aphid on wheat for green peach aphid control • Greenhouse whitefly on eggplant for greenhouse whitefly control

19. Banker plants for aphid control • Bird cherry aphid does not infest plants other than grasses but the parasitoid (Aphidius, commonly) can easily more throughout the greenhouse to parasitize other aphids • Need a continuous supply of infested wheat (or barley or oat) plants to provide an alternate host when aphid numbers in crop decrease • This system is being sold as a unit by biocontrol companies or can be a do-it-yourself operation

20. Parasitized aphids on wheat banker plants

21. Grower with new pots of wheat in greenhouse and with aphid infested wheat in cooler before placing pots in greenhouse

22. Banker plants dispersed in greenhouse

23. Note irrigation - this system saves bench space for crop and allows best maintenance of banker plant Old plants are left in the greenhouse for parasitoid to emerge from parasitized aphids

24. Eggplant trap crop/banker plant for whitefly on poinsettia • New system not yet commercially available • Eggplant is more attractive to white fly than poinsettia • Eggplant acts as an indicator plant, a trap crop and a ‘nursery’ for biological control agents • Pest populations on eggplant are inoculated with parasitoids to provide beneficials for crop

25. Note whiteflies on undersides of leaves

26. Eggplants inoculated with Encarsia formosa for control of greenhouse whitefly and Eretmocerus mundus for control of Bemisia whitefly

27. Eggplants interspersed in poinsettia crop

28. While this system is used less commonly, there are indications that it can aid in the control of whitefly in poinsettia Table from Osborne and Barrett, 2005, You Can Bank On It, Ornamental Outlook, September, pp 26-27

29. Supporting information • Lance Osborne, University of Florida • http://mrec.ifas.ufl.edu/lso/banker/banker.htm • You Can Bank on It, Ornamental Outlook, September 2005, pp 26-27 • Graeme Murphy, OMAFRA • http://www.omafra.gov.on.ca/english/crops/hort/news/grower/2004/07gn04a1.htm • Trap Crops and Banker Plants - thinking outside the pest management tool box • Leanne Pundt, University of Connecticut • http://www.hort.uconn.edu/ipm/greenhs/htms/tospov.htm • Using Indicator Plants to Detect Tospoviruses