Management of the lepidopteran pest complex in cabbage: Augmentative biological control strategies in different landscape contexts

Management of the lepidopteran pest complex in cabbage: Augmentative biological control strategies in different landscape contexts

Summary

Cabbage is the most economically important vegetable crop grown in NYS. Lepidopteran pests such as Plutella xylostella, Pieris rapae, and Trichoplusia ni are a major constraint for the production of cabbage in NYS. Insecticides have been the primary means to manage these pests, but the rapid evolution of resistance makes this lepidopteran pest complex particularly challenging to control. A promising control alternative is to increase generalist predators that can potentially control several pest species simultaneously.

The spined soldier bug, Podisus maculiventris, is one of the most effective predators of lepidopteran pests in cabbage. This project will investigate how the effectiveness of augmentative biocontrol by the spined soldier bug could be influenced by the landscape context in which a farm is embedded.  Our general prediction is that augmentative releases will be more effective for suppressing lepidopteran pest in simple landscapes dominated by agricultural areas than in complex landscapes dominated by natural areas. In field trials we will determine the effects of augmentative releases on biocontrol levels and consequent plant damage and yield in different farms located along a landscape complexity gradient. We will also use sentinel preys and surveillance video cameras to identity the natural enemies that are attacking the pest in the field and to determine their efficiency rates. Understanding such interactions among natural enemies and landscape complexity will help us develop a sustainable management strategy based on augmentation of a generalist predator to control cabbage pests while maintaining high yields and profits.

Objectives/Performance Targets

Two objectives will be addressed using the proposed budget. The hypothesis, predictions and expected outcomes for each objective are described below.

1. 1. Determine the effects of landscape complexity mediated by natural enemy community on lepidopteran pests control and cabbage yield

Hypothesis: Natural Enemies Hypothesis- landscape complexity increases the resources for natural enemies and therefore the diversity of natural enemies (Tscharntke et al. 2005), which in turn positively affects the provision of ecosystem services such as biological pest control and agricultural yield.

Predictions: Landscapes with greater amounts of non-crop habitat (i.e. complex landscapes) will support a higher diversity of natural enemies leading to reduced pest pressure. Therefore, increased biological control rates in more complex landscapes will reduce plant damage by lepidopteran pest, leading to increased cabbage yield.

Outcome: By the end of the study we will know whether increased natural enemy density or diversity associated with increased habitat complexity confers enhanced biological pest control services and productivity in cabbage fields. 

2. 2. Examine the role of landscape complexity on the effectiveness of augmentative releases of spined soldier bugs for biological control of lepidopteran pests.

Hypothesis: the effectiveness of augmentative biological control is influenced by landscape scale complexity.

Predictions: Augmentative releases of P. maculiventris will be more effective for suppressing lepidopteran pest in simple and in intermediate landscapes than in complex landscapes.

Outcome: By the end of the study we will know in which landscape context augmentative releases of spined soldier bugs are most effective. The results will allow farmers to estimate where augmentative releases of spined soldier bugs could compensate for the lack of efficiency of natural occurring enemies of lepidopteran pests.

Accomplishments/Milestones

The experiments will begin in May 2015 and will be conducted over one field season (may 2015-december 2015). The analysis of the experimental data will be performed during the spring semester. 

Impacts and Contributions/Outcomes

The experiments will begin in May 2015 and will be conducted over one field season (may 2015-december 2015). The analysis of the experimental data will be performed during the spring semester.

Collaborators: