pheasant's eye

 Weeds represent a significant and ongoing constraint to horticultural production. 

This report

1. reviews the known effects of herbicides on weed populations within horticultural crops and the consequent indirect effects on fauna;

2. summarises the impact of weeds on horticultural crops;

3. Assesses perceived beneficial effects of weeds on the biodiversity of horticulturally based agro-ecosystems

 

This work was completed in 2003 but it still remains relevant today. The crops covered include potatoes, cauliflower, vining peas, onions, carrots and parsnips, lettuce, narcissi, strawberries and top fruit. A wide range of grass and broadleaved non-target (weed) species were included. 

Chapter 2 Crop/Weed interactions - covers the effects of time of sowing and soil type, rotations, impacts on crop harvesting, impacts on yield (including critical periods), avoiding weed competition, interactions between crops, weeds and other pests.

Chapter 3 crop areas and weed management strategies - a little dated but some is still topical.

Chapter 4 Herbicides in horticulture - still many relevant herbicides with weed susceptibility tables  for 46 species.

Chapter 5 Relationship between weed species and birds - how birds use horticultural crops, nesting, role of weeds in their diets.

Chapter 6 Relationship between weeds and invertebrates - how invertebrates use horticultural crops, benefits/disbenefits, role of weeds in their diets.

chapter 7 Weed seedbank of horticultural systems - importance of weed seedbank for horticulture, emergence periods of weeds in crops, reasons for changes in the weed seedbank.

chapter 8 - Assurance schemes and audits -  a liitle dated but relevant. 

The full report of the project5.33 MB

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Weeds

A weed can have many definitions, one being, any plant growing in a place it is not wanted. This topic focuses mainly on weeds affecting agriculture. Generally weeds are classified into two groups: grass-weeds (e.g Black-grass, Italian ryegrass, Bromes) and broad-leaved weeds (e.g Mayweed, Chickweed, Poppy, Cleavers). 

The impact of herbicides on weed abundance and biodiversity - PN0940

Weeds have been a constraint on crop yield since agriculture evolved. Technical advances in herbicides and arable crop management, particularly since the 1940s, have improved the efficiency of weed control. Today, we are aware that major changes in common flora and fauna of the arable ecosystem are occurring, with population size and range contractions. From a statutory regulatory viewpoint, it is necessary to know what risks are posed to users and the environment by the use of pesticides. The observed effects in the environment indicate that risks caused by indirect effects of pesticides also need to be evaluated, to augment the traditional assessment of direct risk using toxicity and exposure. Current draft risk assessments for non-target plants address effects outside the crop. However, the indirect effects within crops must also be addressed, as they may be of greater significance. 

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