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
Thomas Bjorkman, Gary E. Harman, and Lisa Blanchard
Production of shrunken-2 sweet corn is often limited by poor establishment. Good root development is necessary for establishment, and it can be limited by stress or disease. Trichoderma harzianum strain 1295-22 was developed as a biocontrol fungus with particularly strong root-colonizing ability. In addition to acting as a biocontrol agent, it stimulates root growth. In greenhouse experiments using field soil, root dry weight 21 days after planting was 500 mg, greater compared with 320 mg in uninoculated controls, an average increase of >50%. The thoroughness of soil exploration more than doubled, from 31% (control) to 70% (Trichoderma) of the soil being within 1 cm of a root. The difference in performance was not attributable to disease: no disease symptoms were evident, the occurrence of disease organisms was low, it was the same in both treatments, and it was not associated with smaller plants. Furthermore, the greatest differences were noted in steam-sterilized soil. Colonization of the roots by Trichoderma was related to the age of the root. The oldest part of the radicle had 106 cfu/g root DW. Branched seminal roots had 105.5 cfu/g. Even the rapidly growing tips of the first-whorl roots were well-colonized (104.7 cfu/g). The mechanism of increased root growth has not been identified, but colonized roots acidify about 0.1 pH units more than control roots, which could cause both faster acid-growth and increased ion uptake. Ion leakage into distilled water is about 25% lower in colonized roots.
C. Stevens, V.A. Khan, J.Y. Lu, C.L. Wilson, P.L. Pusey, M.K. Kabwel, Y. Mafolo, J. Liul, E. Chalutz, and S. Droby
Applying low doses of ultraviolet light (254 nm, W-C) reduces the incidence of brown rot of (Monilinia fructicola) peaches, green mold (Penicillium digitatum) of tangerines, and Rhizopus soft rot (Rhizopus stolonifer) of tomatoes and sweetpotatoes resulting from field infection and artificial inoculation. In most studies, applying postharvest fungicide (PF) was better than W-C treatment. In this study, the effectiveness of combining a biocontrol agent, Debaryomyces hansenii (BC), with low UV-C dose for postharvest disease control was investigated. When these commodities were treated with BC 3 days after W-C treatment, the reduction of storage rots was more effective than when UV-C was used alone. For example, the percent brown rot infection of artificially inoculated Elberta peaches 36 hours after inoculation of the nontreated control, peaches treated with UV-C, BC, W-C + BC, and benlate were 100%, 55%, 67%, 12%, and 12%, respectively. The efficacy of W-C + BC was similar to when PF was used alone, indicating that an integration of UV-C treatment and BC can reduce storage rot to the levels of commercial PF treatment.
Neil S. Mattson, Elizabeth M. Lamb, Brian Eshenaur, and John Sanderson
methods of managing it, with an emphasis on biological control (often including live specimens of biocontrols). Disease topics included botrytis ( Botrytis cinerea ) (9), foliar fungi (8), nematodes (2), and viruses (1). Each disease topic included
Leonor F.S. Leandro, Lisa M. Ferguson, Frank J. Louws, and Gina E. Fernandez
naturally introducing beneficial microbial populations, or by amendment with commercial biocontrol strains ( De Ceuster and Hoitink, 1999 ; Hoitink et al., 1997 ). The fungus Trichoderma , for example, is well known for its ability to stimulate plant
Michael Brownbridge, Bruce L. Parker, and Margaret Skinner
Western flower thrips (WFT), green peach aphid (GPA) and sweet potato whitefly (SPWF) are major pests of the greenhouse industry. Chemical control of these pests is not desirable. Alternative approaches to pest management need to be developed.
Entomopathogenic fungi hold great promise as sustainable biological control options. A broad range of indigenous fungal isolates have been screened for activity vs. WFT and GPA. Strains of Metarhizium anisopliae, Beauveria bassiana and Verticillium lecanii have been shown to be particularly effective. Plant and soil trials vs. WFT are now underway to permit selection of the best strains for further development. To date, assays vs. SPWF indicate that strains of Paecilomyces farinosus and B. bassiana are the most pathogenic.
William C. Olien
Benefits of nimblewill (Ms = Muhlenbergia schreberi), a warm-season, perennial grass, as an orchard ground cover are: 1) it is not competitive with tree growth and 2) it reduces ring nematode (Cx = Criconemella xenoplax) soil population, even in the presence of a tree fruit host. Ms is difficult to establish in orchards in warm fruit-growing regions. In field studies, we found that Ms establishment was decreased by chemical mowing relative to seeding only. Successive years of reseeding at 22 kg seed/ha per year, mechanical mowing, and control of winter annuals gave best establishment of Ms in peach orchards. An orchard microplot study was established to evaluate effects of five Ms densities and two Ms sources on Cx population and on growth of `Redhaven'–Lovell trees (10 replications). Cx numbers were reduced hyperbolically in response to Ms density. Ms cover of 5 g dw/m2 (planted at 9 kg seed/ha) reduced Cx from 200 (control) to the accepted threshold of 50 Cx/100 cc soil. Maximum Cx reduction to 26 Cx/100 cc was obtained at 34 g dw/m2 Ms (planted at 40 kg seed/ha). Cx response to Ms density was not affected by Ms source.
J.E. Flaherty, B.K. Harbaugh, J.B. Jones, G.C. Somodi, and L.E. Jackson
Bacteriophages specific to Xanthomonas campestris pv. pelargonii (Xcp), the causal agent of bacterial blight of geranium, Pelargonium ×hortorum L.H. Bailey, were isolated from soil and sludge samples from Florida, California, Minnesota, and Utah. Sixteen phages were evaluated for their potential to lyse 21 Xcp strains collected from around the world. The Xcp strains varied in their susceptibility to the phage isolates with 4 to 14 phages producing a lytic or highly virulent reaction. A mixture of five h-mutants was developed from phages that exhibited the broadest host-ranges and tested against the same Xcp strains. The h-mutant phage mixture lysed all 21 Xcp strains. Three experiments were designed to determine the efficacy of using a mixture of four h-mutant phages to control the spread of the bacterial blight pathogen on potted and seedling geraniums under greenhouse conditions. Plants surrounding diseased inoculated plants were treated with a phage mixture at 5 × 108 pfu/mL daily, biweekly, or triweekly, or treated with Phyton-27®, at 2.0 mL·L-1 every 10 or 14 days. In potted geraniums, daily foliar sprays of the phage mixture had reduced disease incidence and severity by 50% and 75%, respectively, relative to control plants after 6 weeks. In two plug experiments, the phage mixture applied daily also had reduced disease incidence and severity by 69% and 86%, and 85% and 92%, respectively, when compared with controls after 5 weeks. In all three experiments, disease incidence and severity were less for plants treated daily with phages than for those treated less frequently with phages or with Phyton-27®. Chemical name used: copper sulfate pentahydrate (Phyton-27®).
Philip A. Stack, Francis A. Drummond, and Lois Berg Stack
The application of supplemental blue light in greenhouse chrysanthemum production is part of a biological control strategy to enhance reproduction of Orius insidiosus Say, a natural predator of the western flower thrips, Frankliniella occidentalis Pergande. Two greenhouse experiments were conducted to determine the influence of a blue light—supplemented long day on flowering and vegetative growth in three cultivars of the short-day plant Dendranthema ×grandiflora (Ramat.) Kitamura. In Expt. 1, two cut chrysanthemum cultivars (`Manatee Iceberg' and `Naples') were exposed to: a) 9-hour ambient light and 15-hour artificial blue-biased (400-500 nm) light at two blue light intensities (3.6 or 7.0 μmol·m-2·s-1); b) 9-hour ambient light and 15-hour artificial broad spectrum light at a broad spectrum intensity of 3.6 μmol·m-2·s-1; c) 9-hour ambient light maintained with black cloth; or d) an ambient short day. Under a continuous photoperiod, flower initiation in both cultivars in the lower intensity blue light was not significantly different from that in short-day regimes. However, in both blue light intensities, flower size and dry mass were significantly less than in the short-day regimes. Increasing the dose of blue light decreased flower dry mass in `Naples' by 60% and in `Manatee Iceberg' by 72%. Plants were shorter with less vegetative mass in the short-day regimes. In Expt. 2, `Naples' and the pot chrysanthemum `Boaldi' were exposed to a) 9-hour ambient light and 6-hour artificial blue-biased (400-500 nm) light at four blue light intensities (0.4, 0.7, 1.6, or 3.5 μmol·m-2·s-1); b) 9-h ambient light maintained with black cloth; or c) an ambient long day. For both cultivars, in all blue light regimes, neither flower dry mass nor vegetative dry mass differed significantly from those in the short-day regime. The results indicate that exposing D. grandiflora to a blue light—supplemented long day at blue light intensities <3.5 μmol·m-2·s-1 does not adversely affect flower initiation and development.
Orapin Kerdchoechuen, Natta Laohakunjit, Sasathorn Singkornard, and Frank B. Matta
Essential oils from sweet basil (Ocimum basilicum L.), holy basil (O. americanum L.), hairy basil (O. tenuiflorum L.), lime (Citrus aurantifolia Swingle), kaffir lime (C. hystrix DC.), and clove (Eugenia caryophyllus L.) were isolated by simultaneous distillation extraction. Toxicity assays against the maize weevil (Sitophilus zeamais Motschulsky) using 30 to 120 μL oil extract from the six plants on 70-mm-diameter filter paper discs resulted in 100% weevil mortality within the 5-h assay period. On rice samples, sweet basil oil extract was the most effective, resulting in 96% to 100% mortality regardless of oil extract volume on the first day during the 5-day assay period. Probit analysis showed that sweet basil oil extract applied on grains had four to five times lower LD50 (lethal dose to kill 50% of the weevils) and two to three times lower LD99 values than the remaining oil extracts. Repellency assay using 1 to 8 μL oil extract showed a different trend, because hairy basil was the most effective among treatments. Based on the effective control of the maize weevil by the oil extracted from herbal plants, such oil extracts could be useful in stored agricultural products and plant protection and reduce the risk associated with synthetic insecticides.