Crop protection

The toxic alkaloid nicotine, a natural component of tobacco, has been detected in many food crops, medicinal plants and plant food such as spices and teas, thus threatening food security. So far the origin of such nicotine contamination was unknown. Plant scientists Selmar et al. studied the possible contamination of peppermint by soils enriched in nicotine from cigarette residues. They also checked whether peppermint could take up nicotine from cigarette smoke. They found that peppermint take up nicotine from soil and from smoke. The tobacco industry and users are therefore responsible, at least partly, by the wide contamination of many crops and food by nicotine.  Selmar et al. also explain that the passive incorporation and metabolisation of nicotine by peppermint is surprising and unprecedented with respect to current knowledge in allelopathy.

Conventional crop protection with toxic pesticides has often led to issues such as pollution, faunal imbalance, and resistance of pests after adaptation to the pesticides.  Deguine et al. review safer, agroecological techniques to control Cucurbitaceae flies, a worldwide pest. Results show that farmers from the Reunion Island have reduced insecticide use with substantial cost savings using agroecological techniques. Such agroecological techniques  are currently being extended to other countries of the Indian Ocean.

The burrowing nematode, a worm, is damaging banana plantations worldwide. Actual control methods use toxic nematicides to kill the worm. Alternative control methods are therefore needed due to the high demand for safer and organic food.  Agronomists Jesus et al. found that an extract of sisal, a plant species growing in desert areas, is effective to contol nematodes.  This method is cheap  because the sisal extract is a byproduct of fiber and fabric production from the sisal plant.

Global warming is changing the geographical distribution of pests with, for instance, new insect pests appearing in previously uncontaminated areas. Scientists Lamichhane et al. propose seven recommendations to improve plant protection under a changing climate.

Agrochemicals such as pesticides are used to protect crops and ensure food production. However, conventional formulations of agrochemicals contaminate the environment due to a lack of efficiency. Alternatively, polymers such as polysaccharides can be used to coat the active substance, thus decreasing its toxicity and delaying its release over several days. Moreover, when added to the soil, polysaccharides form hydrogels that improve soil structure, and store water and plant nutrients. The use of polysaccharides are reviewed by Campos et al.

Sisal is a major economic crop in the Bahia state of Brazil. Sisal production is decreased by the infection of the red rot disease caused by Aspergillus niger (picture). Current control methods are not effective, and there is a need to invent sustainable treatments as alternatives to toxic pesticides. Gama et al. tested homeopathic drugs to control red rot. Homeopathic drugs are substances used at very low levels, similar to human disease treatments. Results show that homeopathic drugs reduced disease severity.

Food contamination is due to toxic pesticides that are used to control pests and diseases. Therefore safer treatments are need for better food security. Scientists Luvisi et al. show that soil steaming with addition of potassium hydroxide or calcium oxide decreased the infectivity of the Tobacco mosaic virus below 3.0 %.

Herbicides are widely used in agriculture to control weeds that decrease cereal production and economic profits. A new control method is based on cultivation of Clearfield® wheat cultivars that are resistant to the imazamox herbicide. Scientists Rojano-Delgado et al. have evidenced several mechanims involved in  imazamox resistance.

Current control of pests in agriculture is done mainly using mineral fertilizers and toxic pesticides. Alternative solutions are thus needed due to concerns for public health, environmental protection, and development of resistant pests. Chitosan, obtained from exoskeletons of crustaceans and insects, showing both antimicrobial and plant-immunity eliciting properties. Agronomists Xing et al. explain that chitosan, a material obtained from exoskeletons of crustaceans and insects, can be used to enhance natural plant defenses. Chitosan also displays antimicrobial properties.

Plant diseases cause major economic losses for farmers worldwide. The Food and Agriculture Organization (FAO) estimates indeed that pests and diseases are responsible for about 25% of crop loss. To solve this issue, new methods are needed to detect diseases and pests early. Agronomists Martinelli et al. review advanced detection methods such as novel sensors that detect plant odours, and spectroscopy and biophotonics that are able to diagnostic plant health and metabolism.