Chapter 14

Weed Management for Organic Crops

Weed Monitoring

Monitoring of weed populations allows organic farmers to make decisions about crop rotations and weed control practices that will be most effective in specific fields. Monitoring fields is a key component of an integrated weed management system. The systematic collection of data on the distribution of weed species is useful in the short term for making immediate weed management decisions to avoid crop losses. In the long term these records provide a basis for evaluating the effectiveness of weed control programs and help managers make sound decisions in the future.

How to Scout for Weeds

Scouting for weeds can be done while looking for insects and diseases, although a separate walk through the orchard allows for more-detailed observations and collections. Basic first steps are:

Unmanned Aerial Vehicles (UAVs) for Monitoring Weeds

Unmanned aerial vehicles (UAVs), commonly known as drones, are emerging as a cost effective way to collect data with many advantages over the traditional forms. UAVs are as the name suggests an unmanned vehicle, which flies over the field to collect data. When compared with satellites or manned planes/helicopters, low cost drones are cheaper and can be deployed every day, even in a cloudy day.

Maintaining Accurate Weed Records

Maintaining accurate, up-to-date records of weed infestations are important to track the progress of weeds in the field and to assist in selecting the most appropriate method(s) of control. Over time, the records become a timeline of changes in the weed flora over the seasons and in response to crop rotations, cover crops, cultivations, and other weed control practices.

Crops' Minimum Weed-free Periods

Weeds that emerge after a crop’s minimum weed-free period will have little direct impact on its yield. A general guideline is to keep crops weed free during the first one-third to one-half of their life cycle. Weeds that emerge after a crop’s minimum weed-free period will have little direct impact on its yield. A general guideline is to keep crops weed free during the first one-third to one-half of their life cycle. In practice, the minimum weed-free period for a given crop varies widely with the weed species composition, weed density, soil conditions, weather, climate, and the vigor of the crop itself.

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