Nematodes as Biocontrol Agents. P.S. Grewal, R. Ehlers, and D. I. Shapiro-Ilan (eds.). 2005. CAB International, Nosworthy Way, Wallingford, Oxfordshire OX10 8DE UK. 505 pages with 63 tables and 77 figures. $75.91 (£39.95), softcover, ISBN: 978
Raymond A. Cloyd
Gladis M. Zinati
The discovery of disease suppression in certain bark composts increased the interest in using compost as growing substrate to control root rot diseases caused by Phytophthora cinnamomi. Disease suppression mechanisms include antibiosis, competition, hyperparasitism, and induced systemic resistance. Although abiotic factors may influence disease suppression, the latter is often based on microbial interactions—the two common mechanisms being general for pythium (Pythium spp.) and phytophthora root rot (Phytophthora spp.) and specific for rhizoctonia (Rhizoctonia solani). The discovery of disease suppression agents in compost led to the development of biocontrol agent-fortified compost during the last decade of the 20th century. The suggested recommendations for future research and extension outreach may include 1) development of methods to manage bacterial and viral diseases through the use of compost; 2) exploration of the potential effects of fortified compost on insect pests suppression; 3) improvement of inoculation methods of composts with biocontrol agents to produce consistent levels of disease suppression at the commercial scale; 4) development of effective fortified compost teas for suppressing foliar diseases; 5) education of compost producers on methods of production of fortified compost that suppress specific diseases; and 6) education of end-users on uses of fortified compost and its by-products.
Guirong Zhang, Mohammad Babadoost, Alan De Young, Eric T. Johnson, and David A. Schisler
., 2001 ), reduce FHB and the deoxynivalenol content of grain in greenhouse and field settings ( Khan et al., 2004 ; Schisler et al., 2002 ) when assayed alone or in combination with other biocontrol agents ( Kolombet et al., 2005 ; Yuen et al., 2010
One of the main difficulties in controlling root diseases biologically has been the inability of biocontrol agents to establish and persist in the rhizosphere. The inability of biocontrol agents to establish and persist is often attributed to competition from indigenous microorganisms for space and nutrients and to fluctuations in environmental conditions. The use of biocontrol agents over the entire geographic range of a crop also has been limited by differences in environmental and edaphic conditions from field to field and region to region. An advantage of hydroponic crop production in greenhouses is that environmental conditions such as temperature, moisture, pH, and growth medium can be consistently controlled in a house and from site to site. An additional advantage of many hydroponic systems is that they are virtually sterile upon planting. This initial period of virtual sterility greatly reduces competition for an introduced biocontrol agent. In addition, these systems are usually pathogen-free upon planting allowing the establishment of a biocontrol agent prior to pathogen introduction. Last, the temperatures, high moisture levels, and pH ranges of hydroponic systems can be ideal for the proliferation of many biocontrol agents. With all of these advantages for the use of biocontrol agents in hydroponic systems, our company, and many labs around the world, have focused their attention on developing biological control agents for these systems. I will provide a review of research focused on controlling root diseases of vegetables grown in rockwool and other hydroponic systems.
Margaret T. Mmbaga, Lucas M. Mackasmiel, and Frank A. Mrema
-isolated from root lesions and thus confirmed the presence of M. phaseolina as a causal agent for the root rot. Fig. 1. ( A ) Effect of six biocontrol agents (BCA) (B17A, B17B, F13, F16, Y4, and Y14), compared with the fungicide thiophanate methyl (fungicide
H.A.J. Hoitink and A.G. Stone
Many factors affect the potential for composts to provide biological control of diseases caused by soilborne plant pathogens. Heat exposure during composting kills or inactivates pathogens and weed seeds if the process is monitored properly. Unfortunately, most beneficial microorganisms also are killed by this heat treatment. Conditions must be provided after peak heating that enhance natural recolonization of composts by biocontrol agents. The raw feedstock, the environment in which the compost is produced, as well as conditions during curing and utilization, determine the potential for recolonization by this microflora and the induction of disease suppression. Controlled inoculation of compost with biocontrol agents has proved necessary to induce consistent levels of suppression on a commercial scale. Compost stability is another important factor. Immature composts serve as food for pathogens and increase disease even when biocontrol agents are present. On the other hand, excessively stabilized organic amendments, such as highly decomposed peats, do not support the activity of biocontrol agents and disease therefore develops. Finally, salinity, C to N ratio, and other factors affect suppressiveness. Each of these factors will be discussed.
Harry A.J. Hoitink, Alex G. Stone, David Y. Han, Weidzheng Zhang, and Warren A. Dick
Compost offers the potential to suppress root rots and vascular wilts caused by soilborne plant pathogens, as well as plant diseases affecting aerial plant parts. Many factors affect the degree of control obtained. They include the decomposition level (stability) of the compost, the types of microorganisms colonizing the organic matter after peak heating of the compost, plant nutrients released by the compost (fertility), its salinity, loading rates, and other factors. Biocontrol agents in composts induce suppression through various mechanisms, including competition, antibiosis, hyperparasitism, and the induction of systemic resistance in the plant (roots as well as foliage) to pathogens. Examples of each of the effects are reviewed.
Adrian Hunsberger and Ruben Regalado
The red imported fire ant (Solenopsis invicta) has become a serious agricultural and animal pest in the southern U.S. since its accidental introduction in the 1930s. Traditionally, this pest ant has been under chemical control with very limited success and treatments must be repeated on a regular basis. One strategy to manage the red imported fire ant, which has been tried in parts of the southern U.S., is to use biocontrol agents to reduce fire ant populations. We released decapitating phorid flies (Pseudacteon tricuspis) as a self-sustaining biocontrol agent specific to S. invicta at two sites in South Florida during the spring of 2003 (site 1) and 2005 (site 2). Establishment of fly populations was monitored by disturbing 10 fire ant mounds and inspecting the number of hovering flies for 15 min. per mound. At site 1, within 1.5 years, 30% of mounds were positive for phorid flies and total estimated fire ant mounds decreased by 94%. At site 2, the number of mounds was recorded 1 day prerelease and 2 months postrelease. Ant mound density decreased by 71.4% with 73% of the remaining ant mounds positive for flies. This study confirms the successful establishment of the decapitating phorid fly in South Florida.
Emergence of snap beans (Phaseolus vulgaris L.) in field soil in 1993–95 was enhanced by the biocontrol agent Gliocladium virens J.H. Miller, J.E. Giddens, & A.A. Foster. The fungus was applied to each seed at planting as a wheat bran alginate pellet formulation in 1993–95. Preemergence and postemergence damping-off were reduced in plots treated with G. virens. Nodulation on the roots of treated plants was numerically increased in 1993 and 1994 compared to nontreated plots. Efficacy of G. virens was reduced in 1995, probably due to high ambient temperatures at the time of planting. In plots with reduced stand, leaf area was increased and yield on a per-plant basis was larger than in plots with a better stand. Total yield also was increased in plots with fewer plants, except in 1994. Fungi isolated from failed seedlings included Fusarium spp., Pythium spp., and Rhizoctonia solani Kühn.
Charles L. Wilson, Michael E. Wisniewski, and Bruce L. Upchurch
An apparatus was designed and built to deliver micronized dust particles to the foliage of mature orchard trees under a mobile canopy. The dust is propelled by compressed air (about 1120 kPa), which is pulsed through sand-blast guns using the Bernoulli effect. The canopy consists of steel pipes that support the cover and serve as a conduit for compressed air that flows to the guns. Quick-coupling fittings on the canopy pipes allow for easy attachment and removal of multiple guns at various, optional positions. The support structure for the canopy is attached to a mobile trailer, which transports it over mature orchard trees while the dust is being applied. The canopy reduces drift and enhances the coverage of dusts while they are being applied. This innovative apparatus can be used to apply pesticides, growth promoters and regulators, fertilizers, and biocontrol agents in powdered form. The distribution of corn starch on apple foliage is assessed using this invention.