Hi Eric,

Adding floral resources can improve natural enemy abundance where the landscape is not providing enough of this resource already. This is often the case in agricultural landscapes, as the crops themselves may not provide pollen and nectar at the right time, or which is not suitable for that particular insect, or insufficient to meet population demands (e.g. unsuitable mouth parts). However, floral resources are not the only resource that might be restricting the beneficial, and where their abundance is limited by another factor (e.g. alternative prey prior to pest aphid infestation) adding floral resources may have little impact (1). Furthermore, adding more resources may encourage predators and parasitoids of the beneficial, which can cause a leveling off of benefits (2 & 3).

Essentially you have to pick the right floral resources to target the natural enemies you desire at the right time, and which don't encourage other pests. You also need to identify and address any other resource bottlenecks, as floral resources is likely not the only one.

Feel free to contact me for more info

1) Ramsden et al (2014) Optimizing field margins for biocontrol services: The relative role of aphid abundance, annual floral resources, and overwinter habitat in enhancing aphid natural enemies. Agriculture, Ecosystems and Environment. 

2) Rand et al (2011) Landscape complexity differentially benefits generalized fourth, over specialized third, trophic level natural enemies. Ecography 34; 1-8

3) Wackers et al (2007) Nectar and pollen feeding by insect herbivores and implications for multitrophic interactions. Annual review of Entomology 52; 301-323

Also recommend reading this:

Chaplin-Kramer, R., Valpine, P. de, Mills, N.J. & Kremen, C. (2013) Detecting pest control services across spatial and temporal scales. Agriculture, Ecosystems and Environment, 181, 206–212.

Hi Eric,

Actually, I just submitted a review paper co-authored by my post-doc on the effects of increased crop diversity using trap crops, flowering plants, and living mulches on vegetable insect pests. It includes a section titled " Effects on floral diversity on parasitoids of Brassica lepidopterous pests". In that paper, references # 58-74 deal with flowering plants for vegetable insect pest management at the farm level from within and outside the US.

I will send you a copy privately so that you can even make comments / suggestions for improvement if you have some time.

I currently have a Ms student working with insectary plants and potential enhancement of biological control in Crucifers in organic sytems (our 280 acre organic research farm). She is also conducting cage studies with Hippodamia convergens, some insectary plants and cabbage pests.

Cheers, Jaime

To add Mark's post, the second reference is:

Rand et al. (2012), Landscape complexity differentially benefits generalized fourth, over specialized third, trophic level natural enemies. Ecography, 35: 97–104. doi: 10.1111/j.1600-0587.2011.07016.x

Thanks to Mark, Jaime and Peter for the suggestions above.  Below are a few other papers I found that show that flowering strips don't always increase biological control.

-Berndt, L.A., S.D. Wratten, and P.G. Hassan, 2002. Effects of buckwheat flowers on leafroller (Lepidoptera: Tortricidae) parasitoids in a New Zealand vineyard. Agric. For. Entomol. 4:39-45.

-Pfiffner, L., H. Luka, C. Schlatter, A. Juen, and M. Traugott, 2009. Impact of wildflower strips on biological control of cabbage lepidopterans. Agric. Ecosyst. Environ. 129:310-314.

-Vollhardt, I.M.G., F. Bianchi, F.L. Wackers, C. Thies, and T. Tscharntke, 2010. Spatial distribution of flower vs. honeydew resources in cereal fields may affect aphid parasitism. Biol. Control 53:204-213.

Hello Dear

I think that quality and quantity of source food for natural enemies propagation is one the important factors that affected biilogical control effeciency. Many other factors sunch as phisical environment of rearing, pathogen and ect maybe imprtant and they must be contoroled in rearing system. Best regards