Evaluation of the sea anemone Anthothoe albocincta as an augmentative biocontrol agent for biofouling on artificial structures

Augmentative biocontrol, defined as the use of indigenous natural enemies to control pest populations, has not been explored extensively in marine systems. This study tested the potential of the anemone Anthothoe albocincta as a biocontrol agent for biofouling on submerged artificial structures. Biofouling biomass was negatively related to anemone cover. Treatments with high anemone cover (>35%) led to significant changes in biofouling assemblages compared to controls. Taxa that contributed to these changes differed among sites, but included reductions in cover of problematic fouling organisms, such as solitary ascidians and bryozoans. In laboratory trials, A. albocincta substantially prevented the settlement of larvae of the bryozoan Bugula neritina when exposed to three levels of larval dose, suggesting predation as an important biocontrol mechanism, in addition to space pre-emption. This study demonstrated that augmentative biocontrol using anemones has the potential to reduce biofouling on marine artificial structures, although considerable further work is required to refine this tool before its application.     

An experimental test of stationary lay-up periods and simulated transit on biofouling accumulation and transfer on ships

Abstract

Biofouling accumulation on ships’ submerged surfaces typically occurs during stationary periods that render surfaces more susceptible to colonization than when underway. As a result, stationary periods longer than typical port residence times (hours to days), often referred to as lay-ups, can have deleterious effects on hull maintenance strategies, which aim to minimize biofouling impacts on ship operations and the likelihood of invasive species transfers. This experimental study tested the effects of different lay-up durations on the magnitude of biofouling, before and after exposure to flow, using fouling panels with three coating treatments (antifouling, foul-release, and controls), at two sites, and a portable field flume to simulate voyage sheer forces. Control panels subjected to extended stationary durations (28-, 45- and 60-days) had significantly higher biofouling cover and there was a 13- to 25-fold difference in biofouling accumulation between 10-days and 28-days of static immersion. Prior to flume exposure, the antifouling coating prevented biofouling accumulation almost entirely at one site and kept it below 20% at the other. Foul-release coatings also proved effective, especially after flume exposure, which reduced biofouling at one site from >52% to <6% cover (on average). The experimental approach was beneficial for co-locating panel deployments and flume processing using a consistent (standardized) flow regime on large panels across sites of differing conditions and biofouling assemblages. While lay-ups of commercial vessels are relatively common, inevitable, and unavoidable, it is important to develop a better understanding of the magnitude of their effects on biofouling of ships’ submerged surfaces and to develop workable post-lay-up approaches to manage and respond to elevated biofouling accumulation that may result.     

Osmotic stress adaptation, compatible solutes accumulation and biocontrol efficacy of two potential biocontrol agents on Fusarium head blight in wheat

Fusarium head blight (FHB) caused by Gibberella zeae (anamorph = Fusarium graminearum) is a devastating disease that causes extensive yield and quality losses to wheat in humid and semi-humid regions of the world. Biological control has been demonstrated to be effective under laboratory conditions but a few biocontrol products have been effective under field conditions. The improvement in the physiological quality of biocontrol agents may improve survival under field conditions, and therefore, enhance biocontrol activity. Bacillus subtilis RC 218 and Brevibacillus sp. RC 263 were isolated from wheat anthers and showed significant effect on control of FHB under greenhouse assays. This study showed the effect of water availability measured as water activity (a_W) using a growth medium modified with NaCl, glycerol and glucose on: (i) osmotic stress tolerance, (ii) viability in modified liquid medium, (iii) quantitative intracellular accumulation of betaine and ectoine and (iv) the biocontrol efficacy of the physiologically improved agents. Viability of B. subtilis RC 218 in NaCl modified media was similar to the control. Brevibacillus sp. RC 263 showed a limited adaptation to growth in osmotic stress. Betaine was detected in high levels in modified cells but ectoine accumulation was similar to the control cells. Biocontrol activity was studied in greenhouse assays on wheat inoculated at anthesis period with F. graminearum RC 276. Treatments with modified bacteria reduced disease severity from 60% for the control to below 20%. The physiological improvement of biocontrol agents could be an effective strategy to enhance stress tolerance and biocontrol activity under fluctuating environmental conditions.     

Tamarisk biocontrol,endangered species risk and resolution of conflict through riparian restoration

A long-standing debate between wildlife agencies and biological control researchers and practitioners concerns Diorhabda carinulata Desbrochers (Coleoptera: Chrysomelidae) introduced to suppress invasive Tamarix spp. (Tamaricaceae), and potential impacts of Tamarix defoliation on endangered southwestern willow flycatchers using this non-native plant as nesting habitat in some western riparian ecosystems. The conflict and ensuing legal actions are currently centered on the presence of D. carinulata within the breeding range of the flycatcher in the Virgin River watershed, which has led to APHIS termination of permits supporting the biocontrol development program and has also affected other programs to develop biocontrol agents against environmental weeds. Central to concerns over wildlife is the lack of rehabilitation of native vegetation where biocontrol is expected, so there are current and planned efforts to promote restoration of native cottonwood-willow habitat to mitigate the anticipation decline in Tamarix cover. A strategic approach to riparian restoration is outlined which could facilitate sustainable, and scientifically documented recovery of this iconic habitat type. While the results of these efforts will not be known immediately, the process which is leading to riparian restoration has brought specialists from both sides of the debate together in search of resolution via collaboration, and if successful, may allow re-initiation of the Tamarix biocontrol program attendant with habitat enhancement for wildlife species of conservation concern.     

What makes a successful biocontrol agent? A meta-analysis of biological control agent performance

We qualitatively reviewed the biocontrol literature in two major journals, Biological Control and Environmental Entomology, over the past 10 years by scoring 878 studies into 11 biocontrol-oriented questions. Quantitative meta-analyses were then used on data from 145 studies to examine the effects of different types of biocontrol agents (parasitoids, predators, and pathogens) on several attributes of weed and pest populations. Results for our qualitative review showed that most biocontrol studies were focused on lepidopteran pests, and that parasitoids were the most common biocontrol agents used. Our quantitative review showed that, for weeds, biocontrol agents significantly reduced weed biomass (−82.0%), flower (−98.9%), and seed production (−89.4%). For pests, our quantitative review showed that biocontrol agents significantly reduced pest abundance by 130% compared to control groups, increased parasitism (+139.0%) and increased overall pest mortality (+159.0%) compared to targets not exposed to biocontrol agents. Effects on pest mortality tended to be stronger for parasitoids than predators, although reductions caused in pest abundance were much stronger when predators were used as biocontrol agents. Addition of two or more biocontrol agents increased mortality by 12.97% and decreased pest abundance by 27.17% compared to single releases. Separate sets of meta-analyses demonstrated that the negative impacts of biocontrol on non-target species were much smaller than those for target species, although adverse effects of biocontrol on non-target organisms are based on small sample sizes and should be interpreted with caution. Our results also showed that biocontrol efficacy tended to be higher when agents were generalists than when they were specialists. Large fail–safe numbers found for most of the estimated effects indicate the robustness of the results found for the efficacy of biological control programs.     

Enhanced activity of introduced biocontrol agents in solarized soils and its implications on the integrated control of tomato damping-off caused by Pythium spp

Soil solarization in combination with introduction of biocontrol agents (BCA) was evaluated as a potential disease management strategy for tomato damping-off caused by Pythium spp. A rifampicin resistant Pseudomonas fluorescens strain (PfT-8) and a carbendazim resistant Trichoderma harzianum strain (ThM-1) were introduced into soil following solarization. Tomato seeds were planted into treated field plots. The influence of soil solarization and application of biocontrol agents on damping-off incidence, plant biomass, rhizosphere population of introduced antagonists, and native Pythium spp. was assessed by two consecutive field trials. Damping-off incidence was significantly reduced in solarized plots compared to control. Soil inoculation of biocontrol agents into solarized plots resulted in the highest suppression of damping-off incidence (PfT-8 up to 92%; ThM-1 up to 83%), and increase in plant biomass (PfT-8 up to 66%; ThM-1 up to 48%) when compared to un-solarized control plots. Rhizosphere population of introduced biocontrol agents gradually increased (PfT-8 up to 102% and ThM-1 up to 84%) in solarized soils when compared to unsolarized control. The population of Pythium spp in rhizosphere soil was reduced up to 55% in solarized plots; whereas, application of BCA to solarized soils reduced the rhizosphere population of Pythium spp. by 86 and 82% in P. fluorescens and T. harzianum applied plots respectively.     

The effect of vessel speed on the survivorship of biofouling organisms at different hull locations

This study used a specially designed MAGPLATE system to quantify the en route survivorship and post-voyage recovery of biofouling assemblages subjected to short voyages (<12 h) across a range of vessel speeds (slow, medium, fast; in the range 4.0–21.5 knots). The effect of hull location (bow, amidships and stern) was also examined. While no significant differences were evident in en route survivorship of biofouling organisms amongst hull locations, biofouling cover and richness were markedly reduced on faster vessels relative to slower craft. Therefore, the potential inoculum size of non-indigenous marine species and richness is likely to be reduced for vessels that travel at faster speeds (>14 knots), which is likely to also reduce the chances of successful introductions. Despite this, the magnitude of introductions from biofouling on fast vessels can be considered minor, especially for species richness where 90% of source-port species were recorded at destinations.     

Benthic assemblages,biodiversity and invasiveness in marinas and commercial harbours: an investigation using a bioindicator group

Fouling communities on artificial marine structures are generally different from benthic communities in natural rocky habitats. However, they may also differ among different types of artificial structures. Two artificial structures in direct contact with arriving vessels were compared: floating pontoons within recreational marinas, and sea-walls within commercial harbours. Natural rocky habitats were used as a reference, and the genus Eudendrium (Cnidaria, Hydrozoa) was chosen as a bioindicator. The assemblages were different among the three types of habitat studied, with different species characterising each habitat. The probability of finding an invasive Eudendrium species was significantly higher on pontoons. Diversity was the lowest on pontoons, but it was not significantly different between sea-walls and natural rocks. In general, a barrier to the spread of exotic species exists between harbours and natural rocky habitats. Floating pontoons seem to be a less suitable habitat for native fauna and a key element in marine biological invasions.     

The effect of manual defoliation and Macaria pallidata (Geometridae) herbivory on Mimosa pigra: Implications for biological control

Trials were conducted to test the effects of artificial defoliation and defoliation by Macaria pallidata (Warren) (Geometridae) larvae on the invasive weed Mimosa pigra L. Herbivory is generally thought to be detrimental to plant fitness but it is well documented that many plants can increase growth rates or reproduction to compensate for damage. The compensatory ability of an invasive plant has implications for the potential success of defoliating biocontrol agents. Mimosa compensated for 25% manual defoliation, but at 50% and 100% defoliation levels plants suffered a significant reduction in growth rate, height, stem diameter, and biomass. Defoliation by one cohort of macaria larvae, at densities of eight larvae per plant, significantly reduced growth rates and plant height after 1 week. There were no differences between the effects of macaria larvae and manually simulated defoliation. These results suggest that defoliating biocontrol agents can have a valuable role in mimosa control programs.     

Screening of antagonistic bacterial strains against Meloidogyne incognita using protease activity

Twenty-six bacterial strains that had demonstrated antagonism to some fungal and bacterial pathogens were evaluated for their ability to inhibit Meloidogyne incognita Kofoid & White. The inhibition rates of egg-hatching and second-stage juveniles (J2) mortality of M. incognita by these strains ranged from ?16.5 to 87.4% and from 1.3 to 77.8%, respectively. The 12 strains causing J2 mortality over 40% were chosen for greenhouse experiments in which their biocontrol efficacy reached 33.3–65.6%. On the other hand, among the 26 strains, 20 demonstrated in vitro protease activity and 14 revealed chitinase activity. Significantly, strains Bacillus sp. AR156 and GJ24 in greenhouse tests showed the strongest protease activities. The analyses of the relationships of the efficacy of the 12 strains with their protease and chitinase activities, respectively, indicated that biocontrol efficacy was highly correlated with protease activity (r=0.92, P<0.001) but barely correlated with chitinase activity. The strong positive correlation between protease activity and efficacy suggests that in vitro protease activity could be used as a parameter for selecting biological control agents (BCAs) against root-knot nematodes. Consistently, the biocontrol efficacy of AR156, GJ24, abamectin reached 74.3, 73.4, and 40.9% in the field in Huai-an, Jiangsu; and 71, 69.9, and 37% in Zao-zhuang, Shandong, respectively. The fact that the strains with high protease activities also had significantly higher biocontrol efficacy than abamectin in the field implies that in vitro protease activity may be adopted as a reliable new parameter for speeding up the process of screening the biological control agents (BCAs).     

Larval cannibalism in aphidophagous ladybirds: Influencing factors, benefits and costs

Spray retention on scentless chamomile and round-leaved mallow was characterized in relation to droplet size and travel speed. The effect of varying retention on biocontrol efficacy was studied using Colletotrichum truncatum and Colletotrichum gloeosporioides f. sp. malvae, the bioherbicide agents for the two weeds, respectively. In retention studies, a tracer dye solution was applied using a cabinet sprayer fitted with a fine, medium, or coarse nozzle at travel speeds of 0.5, 1.0, and 2.0 km/h that resulted in approximate application volumes of 500–2000 L/ha. Retention efficiency, a ratio between the volume retained on plants and actual volume applied, was calculated for each application. In general, finer sprays achieved higher retention efficiency on whole plants of both weeds. On an average, fine sprays resulted in 68% greater retention than coarse sprays on scentless chamomile and 22–59% on round-leaved mallow. Faster travel speeds increased spray retention only slightly. Applying the biocontrol agents at 500 L/ha with different droplet sizes showed different effects on weed control on scentless chamomile and round-leaved mallow. C. truncatum applied with fine droplets was more efficacious than treatments with coarser droplets on scentless chamomile. On round-leaved mallow, however, the efficacy of C. gloeosporioides f. sp. malvae did not appear to be substantially affected by the droplet size. This varying effect may be due to reduced retention on the vertical stems of round-leaved mallow, which is critical to biocontrol of this weed by C. gloeosporioides f.sp. malvae.     

Abundance and Spread of the Invasive Red Algae, <Emphasis Type="Italic">Kappaphycus</Emphasis> spp., in Kane’ohe Bay,Hawai’i and an Experimental Assessment of Management Options

Several species of Kappaphycus were intentionally introduced into Kane’ohe Bay, Hawai’i in the 1970s. Subsequent research has demonstrated that these algae have spread rapidly throughout the bay and can be found in a variety of reef habitats overgrowing and killing corals. This study was conducted to (a) quantify Kappaphycus spp. abundance both spatially and temporally, and (b) investigate control options including manual removal and the use of biocontrol agents. Kappaphycus spp. distribution has increased in the bay over the period between surveys conducted in 1999 and 2002, with variation among reefs. The biomass of Kappaphycus spp. removed, and the amount of time required to manually remove them from the reef varied with habitat type, but in all cases amounted to at least 10 kg/m² requiring almost 2 person-hours to clear 1 m². Re-growth of the algae following their removal was rapid at most sites, likely due to the experimentally demonstrated ability of the algae to re-grow from minute attachment points and the low palatability of the algae to native herbivorous fishes. The native sea urchin, Tripneustes gratilla, reduced the biomass of Kappaphycus spp. in small experimental enclosures and may be a useful biocontrol agent. Because Kappaphycus spp. are still spreading in Kane’ohe Bay and can overgrow over 50% cover on some reefs, we recommend that rapid management action be taken to prevent further damage and spread to other Hawaiian coral reefs.     

Feral horses dung piles as potential invasion windows for alien plant species in natural grasslands

Small scale disturbances could act as patches that provide sites for the colonization of competitively inferior species, promoting the establishment of non-native species in some cases. We analyzed the vegetation associated with feral horse dung piles in montane pampas grasslands in Mid-East Argentina and described the changes following their abandonment, evaluating whether dung piles act as invasion windows, allowing the entrance of alien plant species. We estimated the portion of the study area directly covered by horse manure and dung height was used to estimate the time elapsed after the abandonment of each pile. Vegetation replacement on dung piles of different ages was assessed and compared with grassland controls using discriminant analysis. We used regression analysis to look for changes in vegetation cover, species richness, species diversity and evenness in response to height (age) of the dung piles, and principal component analyses (PCA) to identify groups of plants associated with different successional stages. We compared cover of alien plant species on dung piles with grassland controls using one-way ANOVA. On average, 2.5% of the study area was covered by horse dung. Total vegetation cover, species richness, diversity and evenness increased after the piles were abandoned. Characteristic plant groups were associated with initial, middle and last phases of the studied succession. Vegetation on the dung piles significantly differed from that in grassland controls and two species were consistently associated with dung piles: the invasive Red Star Thistle, Centaurea calcitrapa, and a native grazing-intolerant grass, Nassella clarazii. Non-native species cover was also higher in dung piles than in control plots. Dung piles cover a significant portion of grassland area in our study site, produce significant changes in the vegetation and are associated with some invasive alien plants that could eventually colonize more pristine areas in the vicinity. On the other hand, they might represent refuges for palatable species, since horses seem to avoid them for grazing.     

Post-fire management targeting invasive annual grasses may have inadvertently released the exotic perennial forb Chondrilla juncea and suppressed its biocontrol agent

Top-down and bottom-up factors affecting invasive populations are rarely considered simultaneously, yet their interactive responses to disturbances and management interventions can be essential to understanding invasion patterns. We evaluated post-fire responses of the exotic perennial forb Chondrilla juncea (rush skeletonweed) and its biocontrol agents to landscape factors and a post-fire combined herbicide (imazapic) and bacteria (Pseudomonas fluorescens strain MB906) treatment that targeted invasive annual grasses in a sagebrush steppe ecosystem. Biocontrol agents released against C. juncea in previous decades included Cystiphora schmidti (gall midge), Aceria chondrillae (gall mite), and Puccinia chondrillina (rust fungus). C. juncea abundance was greater in sprayed than unsprayed plots, and where soils were coarser, slopes faced southwest, solar heat loads and topographic water accumulation were greater, and cover of deep-rooted native perennials was lower. Mite infestation was greater in unsprayed plots, midge infestation was greater at higher elevations on steeper slopes, and midges were more abundant while rust was less abundant on gravelly soils. Biocontrol infestation levels varied considerably between years and could not be predicted in 2019 from 2018 infestation levels. Multiple biocontrol species were often present at the same plots but were rarely present on the same C. juncea individuals. These results suggest that spatial patterns of invasion by C. juncea are related to deep-soil water availability, warmer conditions, and alleviation of competition. Treatments designed to reduce invasive annual grasses may inadvertently release C. juncea by both reducing plant competition for soil resources and affecting biocontrol agent (mite) abundance.

     

Successful biological control of mist flower (Ageratina riparia) in New Zealand: Agent establishment, impact and benefits to the native flora

The white smut fungus (Entyloma ageratinae) and the gall fly (Procecidochares alani) were released in New Zealand in 1998 and 2001 respectively to suppress mist flower (Ageratina riparia). The fungus established and spread rapidly, crossing 80 km of sea to Great Barrier Island within 2 years. The mean number of P. alani galls increased exponentially to 1.96/stem at release sites, but dispersal was slow. The impact of the biocontrol agents was monitored once annually from 1998/99 to 2003/04, at up to 51 sites in the North Island. The mean percentage of live leaves infected with fungus rapidly reached nearly 60%. Maximum plant height declined significantly. In heavy infestations, mean percentage cover of mist flower declined from 81 to 1.5%. Galls were only recorded towards the end of the impact study, and at low mean numbers. As mist flower declined, the species richness and mean percentage cover of native plants increased. In contrast, the species richness and mean percentage cover of exotic plants (excluding mist flower) did not change significantly. Many plant species colonizing the plots were important native mid- or late-successional shrubs or trees. With few exceptions, the exotic plant species common in the plots were not weeds that appeared to threaten native forest habitats. There was only a weak “replacement weed effect” from the potentially serious invader African club moss (Selaginella kraussiana). These data, together with reports of reduced threats to rare endemic plants from mist flower, suggest this rapid, well-monitored weed biocontrol program was very successful.     

Effects of biocontrol agents on Fusarium verticillioides count and fumonisin content in the maize agroecosystem: Impact on rhizospheric bacterial and fungal groups

The present study tested the ability of Bacillus amyloliquefaciens and Microbacterium oleovorans to reduce Fusarium verticillioides populations and fumonisin accumulation in the maize agroecosystem. The impact of releasing these biocontrol agents on rhizospheric bacterial and fungal groups was also evaluated through isolation and identification of culturable microorganisms. When applied as seed coatings at a concentration of 10⁷ CFU ml⁻¹ both agents were effective in reducing F. verticillioides counts and fumonisin B₁ and B₂ content from maize grains. Rhizospheric counts of the pathogen were also decreased by use of B. amyloliquefaciens at 10⁷ CFU ml⁻¹. Richness and diversity indexes calculated for bacteria and fungi inhabiting the rhizosphere of maize remained unchanged following the addition of both biocontrol agents to seeds. Our research is being continued to further characterize the bacterial and fungal isolates with additional field assays.     

复合微生物菌剂对水稻稻瘟病的生防效应

【背景】单一生防菌剂存在生防效果不够稳定、持效性差等不足,研究不同功能微生物的协同增效作用,开发复合微生物菌剂是控制植物病害的有效途径之一。【目的】探究不同功能微生物组合后对水稻稻瘟病的生防效应,开发高效生防水稻稻瘟病的复合微生物菌剂。【方法】将多株高效拮抗稻瘟病菌的链霉菌和细菌进行两两组合后与助剂复配,通过盆栽和大田试验,研究了复合微生物菌剂对水稻稻瘟病的生防效应。【结果】链霉菌Ahn75和解淀粉芽孢杆菌CWJ2菌株组合效果最好,与助剂复配后对水稻叶瘟和穗颈瘟的盆栽防效分别达到65.07%和63.00%,显著高于单一菌株Ahn75、CWJ2和其他菌剂组合的生物防效。同时,该复合菌剂能有效促进水稻植株生长,盆栽分蘖数和株高与对照相比分别提高93.33%和9.83%。而且,田间小区试验的结果也表明,该复合微生物菌剂的使用可以有效降低稻瘟病的发病,防效最高可达52.16%,与农药三环唑的防效(52.97%)相当。此外,菌株Ahn75和CWJ2分别对14种和16种稻瘟病病原菌生理小种的抑菌率超过50%,表明(Ahn75+CWJ2)复合菌剂对水稻稻瘟病具有广谱抗性。【结论】复合微生物菌剂(Ah...     

Development and application of tools for incursion response: Lessons learned from the management of the fouling pest Didemnum vexillum

In October 2001, an unidentified didemnid ascidian, was recorded for the first time in New Zealand, smothering wharf piles and moorings in a northern harbour. A heavily-fouled barge then translocated the ascidian to an international shipping port some 500 km south, near the heart of the New Zealand mussel industry. The species was subsequently identified as Didemnum vexillum, but its status as indigenous or non-indigenous was disputed. Nonetheless, its presence was regarded as a significant threat to the mussel industry because of its demonstrated invasiveness on artificial structures, and its ability to over-grow and smother mussels.From the barge's mooring area, D. vexillum subsequently spread to the seabed beneath, and to nearby vessels and artificial structures (i.e., barges, recreational vessels, moorings, salmon cages and wharf piles). Given the likelihood that infected vectors would spread the ascidian to mussel farms in the region, and in consideration of a benefit-cost analysis, an eradication program for D. vexillum was instigated. This paper provides a chronology of events surrounding the initial detection and spread of the ascidian, and describes the development of incursion response tools for the different substrata that were infected. The treatments included smothering soft-sediment habitats with uncontaminated dredge spoil, wrapping wharf piles with plastic, smothering rip-rap habitats using a geotextile fabric, and various other approaches based on water blasting, air drying or chlorine dosing. While many of the response methods were completely effective at eliminating D. vexillum from different substrata, the program overall failed to eradicate the organism from the region. The reasons for this failure are documented, and the important lessons learned are highlighted, as a contribution to the successful management of invasive species in the future.     

Biocontrol of Rhizoctonia solani damping-off of sugar beet with native Streptomyces strains under field conditions

A 3-year study was conducted to evaluate the effectiveness of two disease-suppressive Streptomyces spp. to control sugar beet Rhizoctonia solani damping off under field conditions. Streptomyces seed treatments reduced seedling damping off in naturally (2005) and artificially (2006 and 2007) infested soils. All biocontrol agents provided better efficacy than Vitavax to control seedling damping-off. There were no significant differences among Streptomyces isolates. Isolate C increased plant stand by 19.5, 50.5 and 53.75% in 2005, 2006 and 2007, respectively. Evaluation of final harvest revealed that the root yield of the biocontrol agents increased compared to untreated control in these years.     

Development of a mode of application of bioorganic fertilizer for improving the biocontrol efficacy to <Emphasis Type="Italic">Fusarium</Emphasis> wilt

More effective ways of applying biocontrol products should be developed based both on the characteristics of the biocontrol agents and the normal practices of the agricultural producer. A new system was developed to improve the biocontrol efficacy of Fusarium wilt for watermelon production, and this system was tested in pot and field experiments. Biocontrol was achieved by applying a novel bioorganic fertilizer product (BIO) to Fusarium-infested soil. The best biocontrol was obtained by application of a bioorganic fertilizer, BIO, into soil during the nursery phase of watermelon seedling followed by a second application to Fusarium-infested soil when watermelon seedlings were transplanted. In comparison with the controls, the incidence of the disease was reduced by 60–100% in the pot experiment and by 59–73% in the field experiment when the BIO was applied during the nursery stage. After application of BIO during the nursery stage, the number of colony-forming units of Fusarium oxysporum in rhizospheric soil was significantly (P < 0.05) inhibited compared to the controls. An in vitro experiment showed that the antagonist Paenibacillus polymyxa in the BIO could effectively colonize the rhizosphere of watermelon and proliferate along the extending plant roots. This inhibited growth of Fusarium oxysporum in the rhizosphere of watermelon and protected the watermelon roots from attack by the pathogens. The method used for biocontrol Fusarium wilt disease in watermelon should be a useful strategy to improve field efficacy of other biocontrol agents.