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Ministry of Agriculture, Food and Rural Affairs

Scouting for Weeds

What are Weeds? Weeds are plants growing in the wrong place. For crops, this usually means plants growing directly in or beside the rows. Some of the plants that are growing on the field edges are also considered weeds, especially those that are prone to spreading into cultivated fields.

Why are weeds a problem? Weeds are of concern because they compete with crops for moisture and nutrients. Some weeds may also be alternate hosts of diseases, nematodes or insects. Interference from weeds may also cause labour inefficiencies. (e.g., tall weeds at harvest, discomfort from allergies, or skin irritations from poison ivy, stinging nettles, or thistles).

Why Scout for Weeds? Although weeds are present in every field, there are wide variations in the species growing and the density of each population. Just as scouting for insects and diseases is well-established in integrated pest management, the need to scout for weeds is the basis for Integrated Weed Management (IWM). The information gathered from weed scouting will allow the grower to:

How to Scout for Weeds: Scouting for weeds can be done while looking for insects and diseases, although a separate walk through the field may allow more detail observations and collections. Here are some basic first steps:

How to Record Weed Scouting: Recording this information on your scouting reports will allow the grower to make decisions in this season, and will provide a long-term record of weed emergence patterns and problems in the orchard. Here are some basic notes that should be written down:

Tools Needed for Weed Scouting: A field scout will need a few basic supplies to do a good job of weed scouting. Be sure to bring along:

Basic Biology of Weeds for Field Scouting
It is easy to distinguish between broadleaf and grassy weeds. Beyond this, it is important to learn the growth habit of the weed, and target management strategies at susceptible stages.

Weeds have one (or more) of the following life cycles:

Annual and biennial weeds compete for nutrients and water as they grow near crops. After they flower, they die; however, their seeds may cause recurring problems for several years by forming a soil seed bank.