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Novel approaches to crop protection: synergistic manipulation of plant and insect defences - PS2110

Description
The development of insecticide resistance in a wide range of important insect pest species poses a serious challenge to effective crop protection, creating an urgent need for alternative control strategies. In the UK, the problem is exemplified by recent difficulties in controlling aphids. We propose to develop an alternative strategy that involves making full use of the plants' own defense mechansisms against insect attack.

A number of chemicals are able to 'turn on' plant defense pathways, maximising the production and release of chemicals within the plant that act against insect infestation. One such example is beta amino butyric acid (BABA). This chemical has been shown to enhance plant resistance to many insect pest species, including aphids, which show poor growth and survival on BABA-treated plants.

Pesticide resistance is often due to an enhancement of certain metabolic enzymes within the insect. These enzymes are able to break-down many toxic chemicals, including insecticides and the natural toxins found in the plants. Thus, although activating the plant defence mechanisms has been shown to have an effect on insect populations, this effect could be maximised if the enzymes within the insects were inhibited first. This concept has been utilised in overcoming insecticide-resistance by the use of synergists; chemicals (such as piperonyl butoxide) that inhibit the insects' enzyme systems resulting in greater potency from the insecticides. If such synergists are allowed sufficient time to fully inhibit these enzymes (temporal synergism) then the sensitivity of insect pests to pesticides can be increased by several orders of magnitude.

Since BABA-treated plants have an enhanced ability to produce defensive toxins, and temporal synergism leaves the insect defenceless, such a combined approach has the potential to enhance the potency of BABA as well as insecticides. Indeed, it is envisaged that with crops that have relatively toxic secondary metabolites (such as legumes, potatoes and brassicas), the use of temporal synergism in conjunction with BABA treatment will result in high mortality without the use of any pesticides.

The approach will be to optimise the toxins in the plants by using BABA whilst at the same time maximising the inhibition of the insects’ defensive enzymes by the use of a synergist. It may be that a mixture of these two components will suffice, but more likely that single applications at different times will give optimum results. If this is the case, a ‘smart’ formulation that delivers the two components at different times from a single spray will be composed. Finally, the concept will be tested under field conditions using brassicas and potatoes infested with the peach-potato aphid, Myzus persicae.
Objective
1. Optimise induction of plant secondary metabolites by BABA: laboratory studies to quantify levels of these compounds in the selected crop plants exposed to different concentrations of BABA and different densities of aphids.
2. Optimise the temporal parameters for maximal inhibition of aphid metabolic enzymes with the synergist piperonyl butoxide (PBO) in laboratory studies.
3. Determine optimal doses for combined application of PBO and BABA, with bioassays focussed on key crop-aphid combinations in laboratory and glasshouse conditions to compare combined and single treatments.
4. Assess effects of single (PBO, BABA, insecticide), dual and triple applications under glass, using plot-based trials and extending to a range of crop species including brassicas and potatoes. This approach is designed to test for synergistic interactions between PBO, BABA and insecticides, with a focus on Myzus persicae, a pest aphid species with extensive insecticide resistance.
5. Assess most effective application from Objective 4 (above) under field conditions, using plots of brassicas and potatoes artificially infested with standard susceptible and local resistant populations of Myzus persicae.

Project Documents
• Final Report : Novel approaches to crop protection: synergistic manipulation of plant and insect defences   (325k)
Time-Scale and Cost
From: 2007

To: 2008

Cost: £178,740
Contractor / Funded Organisations
Rothamsted Research (BBSRC)
Keywords
Biopesticide              
Chemicals              
Crop Pests              
Environment              
Insecticide use              
Pest and Weed Control              
Pesticide use              
Pesticides              
Plant              
Plants and Animals              
Resistance              
Fields of Study
Pesticide Safety