Xanthomonas campestris pv. poannua has potential as a biological control agent for perennial ryegrass (Lolium perenne L.), and it is being evaluated as a commercial bioherbicide. Field experiments were conducted on dormant `Tifway' bermudagrass [Cynodon transvaalensis Burtt-Davy × C. dactylon (L.) Pers.] and `Tifway' bermudagrass overseeded with perennial ryegrass to determine the effects of two isolates of X. campestris pv. poannua on annual bluegrass (Poa annua L.) control. Annual bluegrass control was 82% on 27 Apr. 1992 after isolate MB 218 was applied to dormant bermudagrass at 109 cfu/ml in three applications on 11 and 28 Feb. and 12 Mar. When isolate MB 245 was applied at the same rate and dates, it controlled only 60% of the annual bluegrass. The response from isolate MB 245 at the same rate and number of applications on 28 Apr. 1993 was similar to that in Apr. 1992, with 64% control on dormant turf and 52% control on overseeded turf. There was no significant advantage in annual bluegrass control when isolate MB 245 was applied at 109 cfu/ml in more than three applications during the fall and winter, compared to three applications on 15 Feb. and 1 and 11 Mar. when ratings were made on 28 Apr. 1993. The control of annual bluegrass in late Apr. 1992 and 1993 from X. campestris applied in three applications (11 and 28 Feb. and 12 Mar. 1992 and 15 Feb. and 1 and 11 Mar. 1993) at 109 cfu/ml was greater than when l08 cfu/ml was applied on the same dates.
While much research has been conducted in organic farming, little has focused on tropical systems. Tropical, versus temperate, systems present additional challenges for organic producers, including differences in soils, temperature, daylength, rainfall, and humidity. Pest management in tropical organic systems can be particularly demanding due to the year-round pest pressure and optimal environment for pest proliferation. Weed management is essential for the production of high-quality watermelons, but can be difficult when herbicides are not permitted. Weeds also serve as a source of inoculum for disease organisms and a habitat for insects, both beneficial and detrimental. Many products have been advertised for pest control in organic farming systems, most of which have not been adequately evaluated in independent, replicated trials. Here we investigated alternatives to pesticides for the control of weeds, insects, and diseases in `Crimson Sweet' watermelons. A split plot on a RCBD with four replications per treatment was used, with weed treatment (± paper-grass mulch) as the main plot and 12 insect and disease control alternatives as subplots. The alternatives for insect and disease control included traditional copper-based fungicides, biological control agents, potassium bicarbonate, hydrogen dioxide, milk, and commercial formulations of essential oils. Weed abundance (percentage cover), disease severity (percentage disease), and insect damage (percentage foliar damage) were evaluated weekly using a modified Horsfall-Barratt scale. Yield and quality were measured at harvest on five plants from each replication. While none of the products should be relied upon as the sole means of managing pests, those with efficacy could be integrated into organic management programs.
Several biological control agents for the control of fungal diseases have recently been commercialized. Do the claims of pest control meet the expectations of the growers? Do the biocontrol agents perform consistently? How do they compare to chemicals? These questions have yet to be answered but recent trials indicate mixed results. In Massachusetts, Mycostop worked well against fusarium stem rot but not against fusarium wilt. Deny (Burkholderia cepacia) did not perform well against Rhizoctonia or Pythium root rot of poinsettia. The following information was taken from the 1997 and 1998 Biological and Cultural Tests for Control of Plant Diseases. In Maryland, zinnia damping-off was controlled by both SoilGard (Gliocladium virens) and Bio-Trek (Trichoderma harzianum). The biocontrols performed as well as the conventional fungicide. In North Carolina, GlioGard (Gliocladium virens) and SoilGard gave only partial control against Pythium and Rhizoctonia damping-off of bedding plants. In Pennsylvania, Greygold (mixture of four microorganisms) did not provide adequate control of Botrytis on geranium. In Georgia, Pythium and Rhizoctonia diseases of a variety of plants were evaluated with SoilGard and RootShield (Trichoderma harzianum). Disease pressure was low and the results varied from inconclusive to both positive and negative. In addition, SoilGard apparently reduced fresh weight of several plant species. RootShield was reported to both increase root weight in one case and decrease root weight in another. In Connecticut, Rhizoctonia root rot of poinsettia was not significantly suppressed with SoilGard, RootShield, or Earthgro, a suppressive growing medium. However, the authors stated that the results indicated that the biocontrols had promise. Results of additional trials will be presented.
Powdery mildew (Sphaerotheca mors-uvae) severely infects young leaves and stems of gooseberry (Ribes uva-crispa) throughout the world. Environmentally friendly control measures are being sought as alternatives to sulfur or demethylation inhibiting fungicides. This study examined the effect of a mineral oil spray, the biological control agent Trichoderma harzianum Rifai strain T-22 (Trichoderma), a combination mineral oil + Tricoderma, and the chemical fungicide thiophanate, on powdery mildew severity in `Industry,' a susceptible gooseberry. Mineral oil at 8 mL·L-1 (1.0 fl oz/gal), Tricoderma at 4 g·L-1 (0.5 oz/gal) and thiophanate at 1.45 mL·L-1 (0.186 fl oz/gal), and mineral oil + Tricoderma mix was applied to plants until runoff at 2-week intervals from February 2002 through April 2002, on potted `Industry' plants growing in a greenhouse in U. S. Department of Agriculture, Agricultural Research Service, National Clonal Germplasm Repository (NCGR), Corvallis, Ore. The percent of infected leaves per plant were calculated and the percent of infected stem surface areas were visually rated in mid-April. The fungicide, mineral oil, and mineral oil + Tricoderma treatment applications significantly reduced powdery mildew severity inboth leaves and stems as compared with those of the unsprayed plants. The stem powdery mildew reduction levels of the mineral oil or a combination of mineral oil + Trichoderma treatments, were not statistically different than that of thiophanate, which is reported as commercially acceptable. We recommend mineral oil spray, or mineral oil + Tricoderma, as alternatives to fungicide control of powdery mildew on leaves and stems of young gooseberry plants.
Application of entomopathogenic fungi by inundative releases has been attempted for control of a wide range of insect pests, with generally poor results. This is largely because entomopathogens are often treated as direct substitutes for chemical insecticides and applied without an adequate knowledge of their interactions with the local environment. Humidity of greater than 90% RH has long been regarded as the a critical condition for germination and infection by the spores. With both temperature and humidity controlled, greenhouse crops offer an excellent potential for pest control using entomopathogens. The long-term maintenance of >90% RH, however, is not standard practice in greenhouse production. This study explored the possibility of improving the efficacy of the fungi by temporarily changing greenhouse humidity without adversely affecting crop growth. The study included laboratory and greenhouse trials. In laboratory trials, four humidity levels of 75%, 80%, 89%, and 97.5% RH were evaluated over a 48-h period. Three commercial products of Beauveria bassiana were evaluated (Naturalis-O, Botanigard 22 WP, and Botanigard ES). Greenhouse pests of green peach aphid, melon aphid, western flower thrips, whitefly, and two-spotted spider mite were used as target insects. The infection rate of B. bassiana was found to increase when the sprayed adult insects were exposed to higher humidity levels with the maximum infection obtained at 97.5% RH. Percent infection and difference between humidity levels, however, were formulation- and host-dependent. The highest overall control efficacy was obtained by using Botanigard ES. Botanigard ES was highly effective to adult green peach aphid, melon aphid, and greenhouse whitefly at high humidities. Effects of B. bassiana against biological control agents for greenhouse vegetable crops were also evaluated. Greenhouse trials were conducted in two adjacent greenhouse compartment with high and low humidity conditions for 48 h, respectively, for selected pest insects to valid laboratory results.
chemical control options including oils, soaps, synthetic organic insecticides, growth regulators, and pheromones and discuss scale resistance to insecticides. The authors also provide a detailed description of the biological control agents or natural
control, or the use of natural enemies, affords greenhouse producers an alternative plant-protection strategy to regulate fungus gnat populations in greenhouse production systems. The common biological control agents used against fungus gnat larvae in
Trichoderma is one of the most studied genera and includes plant growth–promoting fungi and biological control agents that are used against phytopathogenic fungi. Commercial formulations of Trichoderma have been developed worldwide because of
phytotoxicity, and both chemicals may face increased regulation as a result of environmental and health concerns. Additional means to suppress bacterial diseases use systemic acquired resistance (SAR) inducers, biological control agents, novel compounds, and
the increase in plant greenness and chlorophyll content ( Table 4 , Fig. 6 ). Although more studies are needed first to identify the VOCs emitted by the selected biological control agents (BCAs), our study results have shown that the selected