Hansjoerg Kraehmer

Herbicides as Weed Control Agents: State of the Art: I. Weed Control Research and Safener Technology: The Path to Modern Agriculture

The development of weed control and safeners and of screening tools to find them has evolved substantially over the past 100 years. The purpose of modern industrial herbicides is to control weeds. The species of weeds that plague crops today are a consequence of the historical past, being related to the history of the evolution of crops and farming practices. Chemical weed control began over a century ago with inorganic compounds and transitioned to the age of organic herbicides. Targeted herbicide research has created a steady stream of successful products. However, safeners have proven to be more difficult to find. Once found, the mode of action of the safener must be determined, partly to help in the discovery of further compounds within the same class. However, mounting regulatory and economic pressure has changed the industry completely, making it harder to find a successful herbicide. Herbicide resistance has also become a major problem, increasing the difficulty of controlling weeds. As a result, the development of new molecules has become a rare event today.

Herbicides as weed control agents – state of the art. II. Recent achievements

Herbicide discovery has faced significant challenges over the past few decades, and weed control innovations are urgently required. In response to changing market dynamics, the discovery of new herbicides has declined significantly over the past few decades and has only seen a modest upsurge in recent years. Nevertheless, the few introductions have proven to be interesting and have brought useful innovation to the market. In addition, herbicide-tolerant or herbicide-resistant crop technologies have allowed the use of existing nonselective herbicides to be extended into crops. An increasing and now major challenge is being posed by the inexorable increase in biotypes of weeds that are resistant to herbicides. This problem is now at a level that threatens future agricultural productivity and needs to be better understood. If herbicides are to remain sustainable, then it is a must that we adopt diversity in crop rotation and herbicide use as well as increase the use of nonchemical measures to control weeds. Nevertheless, despite the difficulties posed by resistant weeds and increased regulatory hurdles, new screening tools promise to provide an upsurge of potential herbicide leads. Our industry urgently needs to supply agriculture with new, effective resistance-breaking herbicides along with strategies to sustain their utility.

Rice Production in Europe

Rice cultivation in Europe is restricted to a few southern European countries. In 2015, the rice-growing acreage of Italy and Spain together comprised around 75 % of a total area of around half a million hectares. The milled rice equivalents in the EU amounted to 0.4 % of the global rice production. Japonica rice varieties are dominating in Europe. Rice is planted in spring and harvested in autumn. All rice fields in Europe are irrigated. Most rice seed is drilled. In some Spanish areas, pregerminated rice is sown by air. Average yields per hectare range between 4 and 8 tons. In some regions 10 tons can easily be achieved. Monocot weeds are prevailing with wild rice, Echinochloa, Cyperus and Heteranthera species being the most frequent representatives. Hydrellia griseola, Chilo suppressalis, Eysarcoris inconspicuus and Lissorhoptrus oryzophilus have to be regarded as the most serious insect problems. Magnaporthe grisea, Cochliobolus miyabeanus and Gibberella fujikuroi are the most widespread disease-causing organisms. A wide range of chemical and biological products is registered for rice protection. For some countries, however, costs for the registration of new products are too high compared with the low acreage so that lacking product innovation becomes a major problem. The acreage of Clearfield rice is continuously growing primarily due to wild rice as an increasing problem. Water shortage is a problem in a few areas in Spain primarily. Irrigated rice provides a habitat for a great number of organisms such as migratory birds and deserves special attention as far as biodiversity is concerned. Greenhouse gas emission and heavy metal concentration in rice fields have been a problem in some areas in the past. New cultivation methods with a reduced water consumption and new rice varieties should, however, contribute to the reduction of these problems.