Re-greening control for pest and disease control

posted in: Research Updates
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By Gemma Carroll


(at Tim Pikes spray trial in Canterbury)

The Regreening Project is a Sustainable Farming Fund project, in which it is hoped protocols for spraying-off seed crops will be developed to prevent and/or control re-greening.

One of the greatest challenges is in the post-spray-off period, when there is the highest risk of Liberibacter infections and ongoing risk throughout the season. The project aims to provide growers with guidelines for optimum spray-off.

Re-growth plants act as a magnet to tomato potato psyllids and large populations can often be found inhabiting this foliage. Obtaining a rapid and efficient kill is a vital component in seed crop disease management.

On our Canterbury field walks, we visited Tim Pike’s farm and heard from Brian Leicester about the work being trialled in a paddock there, to limit regrowth and thereby control TP psyllid spread disease.

Chloropicrin soil fumigation

This project is investigating the use of soil fumigation to manage soil borne disease load.

Chloropicrin has a long track record of effectiveness on many soil-borne pathogens, including verticillium wilt, scab, colletotrichum (black dot), rhizoctonia, fusarium, and phytophthora.

Chloropicrin advocates in the U.S. and Canada say, because the product can be selectively injected into just the seedbeds, rather than throughout the whole field, that this reduces the environmental impact. Because fumigation can mean healthier crops, it can be argued that this also helps reduce the overall carbon footprint of potato farming. Once your plant is healthy then it may not need as many other inputs.

If growers promote the healthy growth of the potato crop, with a much healthier root system then the plant may be better able to scavenge and make use of applied water, nitrogen or fertilizer. All that translates into healthier growth, higher yields and higher quality.

In an article on proponents say this:

Regardless of what type of applicator is used, “it’s a closed system, moving right from the container that the product is delivered in, to the soil.”

The fumigant is in a liquid form until it’s injected underground, when it then changes from a liquid into a gas that moves throughout that soil profile.

“Chloropicrin is degraded in the soil by microbes, so over a very short period of time, less than three or four days, it is chewed up and degraded into some very safe products. One is carbon dioxide, others are nitrogen and a little bit of chlorine. Basically no residue is left behind.”

“A lot of people have a perception that soil fumigants sterilize the soil, and that’s simply not the case, in fact, they’re fairly specific on the types of organisms that they do suppress, and there are several ‘beneficial’ organisms that really rebound well, say in the case of chloropicrin. They come back in and re-inhabit the soil, you can see massive growth in these populations. We think that that provides some of the growth benefit that you see in the crop, the fact that after the application, you get rebound in populations of beneficials.”

PNZ hope to have a presentation at our August conference on this work.