Assessing CPB Control Options and N Fertility in Organic Potato Production

Organic potato producers have access to a limited number of options to control the populations of Colorado potato beetles in their crop. The bacterial insecticide Novador has been a key product over recent years but was being eliminated from approved organic input lists when this project was undertaken. It was necessary to assess the efficacy of a replacement insecticide, Entrust.

In potato production in general but especially in organic production, it is also important to understand potential interactions between N fertility, plant development, insect population dynamics with their potential consequences for the use of insect control products.

The project, undertaken in 2004 on a transitional organic site at AAFC Fredericton, had three objectives:

1. Compare the efficacy of a potential organic insecticide (Entrust) to a bacterial insecticide (Novador) and to no insecticide,
   
2. Test the hypothesis that healthy, vigorous (well fertilized) plants have a better tolerance of insect pests such as the CPB
   
3. Compare the effect of three levels (0, 150, 300 kg total N ha-1) of organic fertilization (Nutriwave 4-1-2, Envirem Tecnologies, Fredericton, NB) on potato yield and plant biomass.

The high rate of organic fertilizer was required to produce significant marketable yields.

The efficacy of the insecticide Entrust at controlling a low density population of Colorado potato beetle in an organic production setting was shown to be similar to or better than Novador. It was possible to produce three levels of potato crop/plant health (measured as plant height and plant canopy) by manipulating fertilization levels.

The hypothesis that healthy, vigorous plants have a greater tolerance to insect pests such as the Colorado potato beetle was not fully assessed because of the unusually late colonization and very low beetle density. Insect control treatment (Entrust applied at 1.5 oz/acre and Novador at 6 L/ha) were not required until July 20th. However, data from weekly counts (taken from June 29th -August 21st) of abundance of CPB adults, egg masses, and larvae suggested that plant health affects the timing of the different potato beetle life stages and therefore the timing for the application of the insect control measures.

It is hoped to repeat this study in 2005, under conditions of greater beetle abundance.

Researchers
Gilles Boiteau, Agriculture and Agri-Food Canada, Fredericton, NB
Derek Lynch, OACC, Department of Plant and Animal Sciences, NSAC
Claude Berthélémé, NB Department of Agriculture, Fisheries and Aquaculture

Funding Sources
Funding for this project was provided by the NB Department of Agriculture, Fisheries and Aquaculture, with additional project support provided by Envirem Technologies Inc., Fredericton, NB.

For more details, please see preliminary report prepared by Dr. Gilles Boiteau