The biopesticide category includes innovative solutions for crop protection.
The number of biopesticides is rapidly expanding and various products have been developed to manage a variety of important agricultural pests and diseases. Applications include the use of natural enemies and antagonists of pests and pathogens. And biopesticides also include solutions that can be used to enhance desirable attributes of plants through natural physiological processes.
Included in the biopesticide category are solutions for:
Managing insect pests in ways that leave little or no toxic residues, have minimal impact on nontarget organisms, and are not prone to pest counter-adaptation (resistance) has always been challenge in modern agricultural systems.
Biopesticides can often fill these gaps, in some cases as stand-alone products. For example, some microbial biopesticides are used to kill mosquito larvae without contaminating the water in which they live. Such products have been proven to be a valuable and environmentally-friendly tool in public health programs to limit the spread of malaria, yellow fever, and other human diseases transmitted by mosquitoes. And, insect-parasitic nematodes (microscopic roundworms) are both highly specific and effective as a means for controlling soil-dwelling weevil larvae infesting citrus tee root systems.
Despite these prominent examples of stand-alone use, the more typical scenario involves the use of biopesticides as part of an overall integrated pest management (IPM) program. Typically such programs use microbial insecticides in rotations or tank mixes with traditional chemicals. Such programs focus more on maintaining insect pest populations below damaging levels than on providing quick fixes to pest outbreaks. Use of bioinsecticides also helps to extend the useful life of synthetic insecticides and to reduce the amount of unwanted pesticide residues in vegetable and fruit crops.
Biopesticides, key components of integrated pest management (IPM) programs, are receiving much practical attention as a means to reduce the load of synthetic chemical products being used to control plant diseases. In most cropping systems, biopesticides should not necessarily be viewed as wholesale replacements for chemical control of plant diseases, but rather as a growing category of efficacious supplements that can be used as rotation agents to retard the onset of resistance to chemical pesticides and improve sustainability. In organic cropping systems, biopesticides can represent valuable tools that further supplement the rich collection of cultural practices that ensure against crop loss to diseases.
Biopesticides for use against crop diseases have already established themselves on a variety of crops. For example, biopesticides already play an important role in controlling downy mildew diseases. Their benefits include: a 0-Day Pre-Harvest Interval, the ability to use under moderate to severe disease pressure, and the ability to use as a tank mix or in a rotational program with other registered fungicides. Because some market studies estimate that as much as 20% of global fungicide sales are directed at downy mildew diseases, the integration of biofungicides into grape production has substantial benefits in terms of extending the useful life of other fungicides, especially those in the reduced-risk category.
Weeds present a multifaceted problem in agriculture. Weeds are responsible for reducing crop yields by competing for space, sunlight, nutrients, and water. Weeds may also function as alternate hosts for pest insects and plant diseases that impact crop growth, yields, and quality.
Cost effective weed control is a major consideration for conventional growers and is consistently cited as the most difficult issue facing organic producers. Prior to the advent of chemical herbicides, weeds were controlled by cultural, physical and mechanical means. The introduction of chemical herbicides reduced the need for some low value rotations and mechanical cultivation, thereby saving growers time and money. At the same time, the widespread use of herbicides also led to new problems, including instances of groundwater contamination resistant weed populations.
The use of biopesticides for weed control presents a difficult challenge due to the physiological similarities between crop plants and weed species. In recent years, however, scientists have identified several disease causing organisms that specifically and effectively attack key weed species including Canada thistle and northern jointvetch. And, some plant extracts have also been identified that have broad spectrum herbicidal activity against numerous weed species. Biopesticides based on such active ingredients can be used to reduce our dependency on chemical herbicides.
As additional weed species develop resistance to chemical herbicides, there will be additional motivation to investigate biological sources for weed control.
Nematodes are unsegmented, mostly microscope roundworms that are ubiquitous in soils. More than 80,000 different nematodes have been described. Most species of nematodes rely on bacteria, fungi, or other microscopic organisms for food, and, therefore, are a key feature of healthy soil ecosystems. Additionally, some nematodes are beneficial to plant health by virtue of their ability to feed on plant pathogens or insect pests. Nonetheless, some nematodes parasitize plants, causing more than $50 billion in crop losses annually.
Plant parasitic nematodes have a stylet, or mouth-spear, similar to a hypodermic needle. The stylet is used to puncture plant cells and inject digestive enzymes and other fluids. The nematode then draws plant fluids through the stylets. The most problematic nematodes are the root knot nematode, which feeds on more than 2000 species of plants including most major crops, and the cyst nematode which is an important pest in soybeans and potatoes. More than 50% of all nematode control efforts are aimed at these two types of nematodes.
Historically, the most effective products for nematode control have been fumigants, particularly methyl bromide. With regulatory pressure to reduce or eliminate these fumigants, biopesticides have begun to emerge as alternative treatments to limit nematode damage.
Nematologists have identified several bacterial and fungal products for control of soil nematodes, as well as plant extracts that display nematoxicity or control the pest indirectly by boosting the natural defenses of crop plants. As fumigant nematicides continue to be phased out, biopesticides will play an ever-increasing role in control of these important pests.
Plant Physiology & Productivity
Plant physiology is highly responsive to the prevailing environmental conditions, and plays a critical role in crop productivity. Active management of plant physiology, therefore, plays an important role in crop production. A diverse group of biochemical compounds known as plant growth regulators (PGRs) includes both natural and synthetic versions of natural substances that affect plant physiology.
A few examples of management tactics where PGRs are utlitized include thinning fruit on fruit trees in order to reduce over-cropping, thereby increasing fruit size, and using PGRs to increase flower and fruit set. PGRs are also used to improve crop tolerance to a variety of abiotic stresses such as temperature and drought, and for managing fruit maturity during and after harvest to maintain a high level of fruit quality.