Eradication of Clavibacter michiganensis subsp. michiganensis by incorporating fresh crop debris into soil: Preliminary evaluations under controlled conditions

A method for the eradication of Clavibacter michiganensis subsp. michiganensis was tested for its efficacy in three experiments carried out in the laboratory and greenhouse. In the first experiment, peat moss and sand mix in pots was amended with fresh tomato debris which was either artificially infected with the pathogen, or was not amended. Pots were enclosed in plastic bags or left open. Two temperatures (25 °C and 45 °C) were tested over a 6-week period. The pathogen was not detected in the amended soil after 4 weeks treatment at 45 °C, but was not eradicated after treatments in open pots at 25 °C.In the second experiment, the survival of C.m. michiganensis in either artificially infested soil or in artificially infected tomato plants was studied to determine the behaviour of the pathogen under these conditions. Strains of saprophytic bacteria in the genera Bacillus, Paenibacillus and Brevibacillus were identified under the experimental conditions. In vitro antagonism between Bacillus subtilis and C.m. michiganensis was observed. Finally, the recovery of C.m. michiganensis introduced into disinfected substrate was determined. Survival of C.m. michiganensis in plates artificially inoculated with substrate was greatly reduced after a 4-week treatment at 25 °C, or after 1 week at 45 °C.C.m. michiganensis remained pathogenic on plant tissue after 4 weeks of either thermal treatment.It is important to take these results into account with regard the effect of different soil disinfection techniques or ecological alternatives such as biofumigation, solarization, and the addition of organic matter, as well as for integrated pest management systems.     

Soil suppressiveness to Meloidogyne javanica as induced by organic amendments and solarization in greenhouse crops

We assessed soil suppressiveness against root-knot caused by Meloidogyne javanica, following the incorporation of crop residues (organic amendments [OA]) and soil solarization, under agricultural conditions. Two field experiments were established in tomato greenhouses and a third in a nethouse for growing Antirrhinums, all infested with M. javanica. Dried residues of wild rocket (WR) were incorporated into the soil and then it was solarized to moderate temperatures to partially effect the pathogen population. Root galling on the roots of the successive tomato crop was significantly reduced to different levels by WR, solarization or their combination, in two experiments. Solarization, alone or combined with WR amendment, significantly reduced root knot incidence in the roots of snapdragon, but suppression of root galling in the roots of snapdragon in the following crop was not evident. We further assessed the potential of various herb residues, incorporated in small plots, and solarization to induce soil suppressiveness against root-knot caused by M. javanica. Amending soil with residues of WR, tarragon, peppermint or sage induced soil suppressiveness to root knot even when M. javanica was introduced into the soil after the termination of the treatment, and reduced the galling index in subsequently grown tomato plants, compared with non-amended soil. Our findings further validate the potential role of OA and solarization in inducing soil suppressiveness, which contributes to sustainable management of soilborne pathogens.     

Mature watermelon vine decline: Suppression with fumigants of a soil-borne problem and association with Rhizopycnis vagum

Mature watermelon vine decline (MWVD) is a late-season disease of unknown etiology, characterized by vine collapse and discolored, much reduced root systems. While several new disorders in watermelon have been reported recently, this problem appears specific to the Midwest. To test for a biological cause and methods to suppress this disorder, soil was collected from two southern Indiana fields with histories of MWVD for microplot and greenhouse experiments. Watermelons grew best in microplots treated with methyl bromide or methyl iodide. Roots of plants growing in the untreated MWVD soil were severely necrotic; those from the fumigation treatments appeared healthy. In heating experiments, watermelon seedlings were grown in autoclaved soil mixed with 10% MWVD soil that was either untreated or heated at 40, 50, 60, 70 or 80 °C for 30 min. Watermelon plants in the untreated controls and the 40 and 50 °C treatments had reduced top dry weights with decreased fibrous roots and associated discoloration in contrast to treatments of equal to and greater than 60 °C. Representative cultures from necrotic roots were identified as Rhizopycnis vagum by morphological analysis and sequencing the ITS region of the ribosomal DNA. PCR analysis with specific primers confirmed that R. vagum was present in roots from untreated MWVD soil but not in symptomless roots. This is the first report of R. vagum associated with plants suffering from MWVD in Indiana and indicates that this fungus occurs much farther north in the U.S. than known previously.     

Impacts of biocontrol products on Rhizoctonia disease of potato and soil microbial communities,and their persistence in soil

Four commercial biocontrol formulations (Bacillus subtilis GB03, Burkholderia ambifaria type Wisconsin isolate J82, Trichoderma virens Gl-21, and Trichoderma harzianum strain T-22), a chemical seed treatment (thiophanate-methyl, mancozeb, and cymoxanil mixture, TMC), and a combination chemical/biological treatment, were compared with no-pathogen and pathogen-treated controls, and monitored in two field seasons in Maine for their effects on the development of Rhizoctonia disease of potato and soil microbial community characteristics. All treatments reduced the incidence and severity of stem canker (37–75% reduction) relative to the pathogen control over both years, with the best control provided by B. subtilis and the combination chemical/biological treatment (TMC/Bamb). Both bacterial treatments (B. subtilis and Bu. ambifaria) reduced severity of black scurf in both years, and T. virens reduced scurf in one year, with reductions of 11–20% relative to the pathogen control. Over both years, the B. subtilis, T. virens, and TMC/Bamb treatments increased total and marketable yield, and Bu. ambifaria increased marketable yield, by 11–15% relative to the pathogen control. Substantial populations of the added fungal agents, but not the bacteria, were detected in bulk soil at the end of the growing season. Biocontrol treatments also significantly (P < 0.05) affected soil microbial community characteristics, as assessed by single carbon source substrate utilization (SU) and whole soil fatty acid methyl ester (FAME) profiles. Bacterial biocontrol treatments generally resulted in higher microbial activity and substrate utilization. Some effects on soil microbial communities were also observed the following spring (1 yr after application). This research indicates that biocontrol treatments can assist in the control of Rhizoctonia disease of potato, persist in soil to some degree, and have significant effects on soil microbial communities long after application.     

In vitro starch digestibility and pasting properties of germinated brown rice after hydrothermal treatments

Germinated brown rice (GBR) recently has received renewed attention due to its enhanced nutritional value. Pasting properties and in vitro starch digestibility of GBR were examined before and after hydrothermal treatments. Steeping in water (30 °C, 24 h) raised the moisture content and germination percentage of brown rice. Pasting viscosity was substantially decreased but gelatinization temperatures and enthalpy were decreased only marginally by germination (30 °C, 48 h). However, annealing (50 °C, 24 h) and heat-moisture treatment (100 °C, 1 h at 30% moisture) after germination resulted in increased pasting viscosity and gelatinization temperatures. The hydrothermal treatments, however, induced browning reactions to darken the flour of GBR. The digestibility of starch in brown rice was increased by germination. The contents of rapidly digestible starch (RDS), slowly digestible starch (SDS) and resistant starch (RS) in the cooked brown rice were 47.3%, 40.8%, and 11.9%, respectively, but changed to 57.7%, 39.1%, and 3.2%, respectively upon germination. The hydrothermal treatments, however, decreased the digestibility of starch in GBR. The heat-moisture treatment decreased the RDS content in GBR near to that of native brown rice. The digestibility and physical properties of brown rice can be controlled by germination and hydrothermal treatments.     

Latent infection of potato tubers byPseudomonas solanacearum

Strains ofPseudomonas solanacearum differed in their ability to infect tubers of different resistant potato clones grown in infested soil. When eight resistant clones (Solanum phureja orS.phureja ×S. tuberosum hybrids) were grown at 24–28°C in soil infested with a race 1 or a race 3 strain of the bacterium, relatively few plants had wilt symptoms at harvest, but 26.7% and 9.2% of the tubers harvested from plants infected with the race 1 and race 3 strains, respectively, carried latent infections. Some infected clones never yielded diseased tubers, however. The development of symptoms above ground was not correlated with the incidence of tuber infection in any particular clone. No tuber infection occurred in tolerant or resistant clones grown in infested soil at cool (12–22°C) temperatures. Tubers were inoculated directly in an attempt to evaluate the ability of bacteria to multiply in these tissues at different temperatures. Highly virulent strains ofP. solanacearum survived in susceptible tubers in higher numbers and for longer periods than in resistant ones. Low temperature (4°C) had a deleterious effect on survival of the bacterium in tubers, but did not completely eliminate the pathogen even after 40 days.     

Two Bacillus amyloliquefaciens strains isolated using the competitive tomato root enrichment method and their effects on suppressing Ralstonia solanacearum and promoting tomato plant growth

Two tomato root colonizing strains, Bacillus amyloliquefacien CM-2 and T-5, were isolated after the enrichment procedure on the roots of tomato seedlings, and evaluated for their antagonistic activities against pathogenic Ralstonia solanacearum (RS) in vitro. Three inoculation methods were used to test their biocontrol efficacy and growth promotion effects in greenhouse based on their colonization ability in rhizosphere soil. Both CM-2 and T-5 strains showed strong biocontrol and growth promotion effects on tomato seedlings. The best biocontrol efficacy was obtained by treating both seedlings and soils with the biocontrol agents. In comparison to the control, the disease incidence was reduced by 70.1 and 79.4% for CM-2 and T-5, respectively. The numbers of colony-forming units of RS in rhizosphere soil were significantly (P < 0.05) decreased as compared to the control. The density of both strains in the rhizosphere soils remained at a high level (≥10⁷ CFU/g) during a five-week period. Both strains were recovered from the interior of the stems and roots of plants. They showed positive reactions for ammoina, indole acetic acid and siderophores production, and phosphate solubilizing activity. Our data proved the potential of isolated strains for the biocontrol of tomato bacterial wilt.     

Integrated effect of Glomus mosseae and selected plant oils on the control of bacterial wilt disease of tomato

This study investigated the efficacy of Glomus mosseae and thyme and peppermint oils in controlling bacterial wilt disease (BW) of tomato caused by Ralstonia solanacearum under in vitro conditions and under greenhouse and field conditions. In an in vitro study, we tested nine plant oils against R. solanacearum, and the results demonstrate that only caraway, thyme, peppermint and marjoram oils inhibited the growth of the BW pathogen with differing degrees, thyme oil caused the highest reduction of the growth of the pathogen followed by peppermint and the lowest was caraway and marjoram. We evaluated the effect of thyme and peppermint under greenhouse and field conditions. Under greenhouse conditions, the thyme treatment exhibited the highest disease reduction percentage followed by the thyme + peppermint treatment, while G. mosseae caused the least disease reduction percentage. Under field experiments, thyme oil treatment exhibited the highest ability to reduce the disease by 94.8 and 97.1% in the 2011 and 2012 growing seasons, respectively, followed by the treatment of thyme oil + peppermint oil with the reduction of 89.5 and 82.4%, respectively. G. mosseae exhibited the lowest percentage of disease reduction; however, it caused a greater yield increase percentage during both of the tested seasons.     

Antifungal activity of Vitex agnus-castus extract against Pythium ultimum in tomato

Vitex agnus-castus methanolic extract showed strong antifungal activity against Pythium ultimum in tomato under both in vitro and in vivo conditions. The 0.2% extract delayed the mycelial growth of the fungus and showed significant antifungal activity against P. ultimum on tomato seedlings with an efficacy comparable to that of the synthetic fungicide. To determine the involvement both of plant extract and pathogenic fungus in PR gene induction, tomato plants were treated with V. agnus-castus extract and/or inoculated with P. ultimum. The expression of four PR genes (PR-1, PR-2, PR-5, PR-6) was monitored at five time points within 48 h of the extract treatment and fungal inoculation. The PR-1 and PR-4 genes were activated directly by V. agnus-castus extract up to 12 h after treatments; at 24 h, the direct activation by plant extract disappeared and a synergistic inducing effect of extract and pathogen applied simultaneously on the plant was observed. The PR-6 gene was not activated directly by the V. agnus-castus extract but only when applied together with the pathogen; activation of the PR-6 gene occurred 24 h after treatments and the gene expression increased at 48 h. There was no activation of PR-5 gene by the plant extract. The ability of V. agnus-castus extract to enhance plant defence responses upon pathogen inoculation might be further investigated. The activation of various PR genes suggests that induction of defence responses by V. agnus-castus extract in tomato may be regulated by more than one signalling pathway.     

Thermal tolerance of propagative anthurium stem cuttings to disinfestation by heat treatment for burrowing nematodes and bacterial blight

Hot water and hot air treatments were evaluated for disinfesting anthurium, Anthurium andraeanum Lind., stem cuttings of the bacterial blight pathogen, Xanthomonas axonopodis pathovar dieffenbachiae (Xa pv. dieffenbachiae), and burrowing nematodes, Radopholus similis, and their effect on viability of the cuttings. Xa pv. dieffenbachiae suspended in distilled water in 1.5 ml microcentrifuge tubes, lost at least 6 logs of viability when exposed to hot water at 50 °C for 12 min or hot air at 50 °C, 60% RH for 35 min administered in commercial-sized heat treatment facilities. Stem cuttings exposed to hot air at 50 °C, 60% RH were disinfested of R. similis when their core temperatures attained 50 °C. Plant response to heat treatments varied among cultivars; however, all evaluated cultivars exhibited high tolerance to hot water at 50 °C for up to 24 min with equal or enhanced sprouting rates as compared to untreated checks. Sprouting rates of three of the four cultivars treated with hot air at 50 °C, 60% RH for up to 125 min were equal to or higher than untreated checks, while cuttings from the less tolerant cultivar ‘Tropic Fire’ registered lower sprouting rates for all hot air treatment durations as compared to untreated checks, Flower quality parameters, including average spathe size, stem diameter and number of flowers harvested from plants heat-treated as cuttings, were comparable to or higher than untreated checks for all treatments and cultivars. Disinfestation of anthurium stem cuttings for bacterial blight and the burrowing nematode can be achieved in hot water at 50 °C for 24 min without loss of sprouting rate or flower quality.     

Management of bacterial wilt in tomatoes with thymol and acibenzolar-S-methyl

The combination of thymol, a monoterpene phenol compound originating from thyme, and acibenzolar-S-methyl (ASM; Actigard 50 WG), a systemic acquired resistance (SAR) inducer, was applied to tomato plants in field conditions to evaluate the effectiveness of both chemicals to control bacterial wilt. Thymol was applied as a soil fumigant at 9.43 kg per ha 24 h after soil infestation and seven days before transplanting. ASM was applied as a foliar spray at 3.59-8.98 ml per ha, once in the greenhouse and five times in the field. The field was inoculated by applying 50 ml of pathogen suspension (10⁷ cfu/ml) into each transplanting hole eight days prior to transplanting. The experiment was performed in 2006 and repeated in 2008 at the North Florida Research and Education Center in Quincy, FL. In 2006, the combination of ASM and thymol significantly reduced disease in the bacterial wilt tolerant genotype 7514 compared to thymol alone. In 2008, the combination of ASM and thymol significantly reduced disease and increased yield compared to the control, whereas ASM or thymol alone did not significantly reduce disease or increase yield compared to the control. This is the first report of the use of both thymol and ASM to control bacterial wilt on moderately resistant tomato cultivars. Based on this study, control of the pathogen can be achieved by using both chemicals and moderately resistant cultivars.     

Temporal progress and control of tomato spotted wilt virus in flue-cured tobacco

Tomato spotted wilt virus causes tomato spotted wilt (TSW), a disease that results in economic losses on several crops including tobacco in the southeastern United States. The effect of imidacloprid (IMD) applied as a pre-transplant soil drench alone, in combination with acibenzolar-S-methyl (ASM), or followed by a foliar application of ASM immediately after transplanting on TSW incidence and severity on tobacco was quantified in studies conducted in North Carolina from 2006 to 2008. Pre-transplant IMD application in combination with ASM provided the greatest reduction in TSW incidence and severity; however other treatments provided economically efficacious controls when TSW incidence was <30% in a field. From these results, TSW incidence was classified as Low (<10%), Moderate (11-20%), High (21-30%), or Very High (>30%), classes corresponding to different control recommendations, and subsequently used for modeling temporal TSW progress in a field. The temporal progress of TSW was modeled with data collected from 23 tobacco fields in North Carolina from 2006 to 2008. Cumulative degree-days (DD) and the average class of TSW incidence observed in a field for 5 seasons before the one that data were collected were significant variables (P < 0.05) for explaining the temporal progress of TSW incidence. DD based on four temperature thresholds (10.5, 18.0, 20.0, and 26.0 °C) were investigated, resulting in four models. Models were validated with data collected in 2009 and the model in which DD were calculated based on the threshold of 10.5 °C had a higher predictability (R² = 0.70) than the other three models. The 26 °C DD model had the poorest predictability (R² = 0.33). These models are currently being validated in North Carolina and the other flue-cured production states of the southeast United States as a tool for implementing disease control recommendations.     

Evaluation of non-fumigant alternatives to methyl bromide for weed control and crop yield in California strawberries (Fragaria ananassa L.)

In California, USA, agricultural fumigant use regulations hinder the complete transition from methyl bromide (MB) to alternative fumigants. Alternative fumigants such as 1,3-dichloropropene (1,3-D) and chloropicrin (Pic) are being used on approximately half of California conventional strawberry production fields. Geographic use limits and buffer zones set by the California Department of Pesticide Regulation for 1,3-D + Pic restrict a more complete replacement of MB. Due to the regulatory constraints and public resistance to fumigant use, it is necessary to develop fumigant-free strawberry production systems. Trials were conducted during the 2007/2008 and 2008/2009 strawberry growing seasons at Salinas and Watsonville, California. Non-fumigant treatments including steam, mustard seed meal (MSM), Muscodor albus, and furfural, fertilizers including Mustard Products & Technologies fertilizer and stabilised urea, and fungicide treatments including AG3(NP), fludioxonil + mefenoxam (mfx), and mfx + thiophanate-methyl were evaluated for weed control and strawberry fruit yield, and compared to MB + Pic (MBPic) standard soil fumigation and an untreated control. Steam treatment applied pre-plant to achieve soil temperature of ≥70 °C for 20 min up to 25 cm soil depth consistently provided weed control similar to the MBPic standard soil fumigation. Use of oxyfluorfen herbicide prior to fungicide applications in 2008/2009 also controlled weeds similar to the MBPic standard soil fumigation. Strawberry yields in steam-treated plots with the exception of steam alone in 2007/2008 at Salinas, were comparable to MBPic. At Watsonville in 2008/2009, treatment effect on strawberry yields was insignificant. Yields in furfural and MSM treatments were comparable to MBPic only in some years or sites. With the exception of steam, none of the treatments can be considered viable replacement to MB.     

Effect of temperature on lutein esterification and lutein stability in wheat grain

The creamy colour of many wheat-based end-products is conferred by endogenous lutein. During post-harvest storage of grain, free lutein may be converted in part to potentially more stable lutein mono- and di-fatty acid esters. This study investigates the synthesis of lutein esters and stability of free lutein and lutein esters over a wide range of temperatures in grain of a high lutein bread wheat, Triticum aestivum L. line DM5685*B12 and a durum, Triticum durum L cv Kamilaroi. Disappearance of free lutein and lutein esterification followed first order reaction rates. The maximum rate of lutein esterification was at ≈80 °C, however, the optimum temperature for maximum synthesis with minimum degradation was between 30 °C and 60 °C. No ester synthesis was observed at temperatures higher than 120 °C. The data are consistent with an enzyme participating in the esterification reaction. Lutein esters were found to be more stable than free lutein with a longer shelf life at 60 °C whilst at temperatures ≤40 °C, lutein degradation was minimal. This study provides new information on lutein ester formation and lutein stability that should be useful to grain handlers and food manufacturers seeking to optimise retention of lutein for the benefit of consumers.     

Influence of temperature on the fermentation of bambara groundnut (Vigna subterranea) to produce a dawadawa-type product

Bambara groundnut (Vigna subterranea) was fermented to produce a dawadawa-type product using a starter culture of Bacillus licheniformis isolated from naturally fermenting bambara groundnut beans. Fermentation was carried out at 30 and 37 °C for four days and at 45 °C for two days. The pH of the substrate decreased after 24 hours and then rose at 30 and 37 °C but remained constant at 45 °C after the initial drop. Total titratable acidity of the fermenting beans mimicked the pH values. Proximate analyses for moisture, protein and fat of the cotyledons showed an increase in all three constituent at each of the three fermentation temperatures. At the end of fermentation, total available carbohydrate was 55%, 59% and 62% of the original value at 30, 37 and 45 °C, respectively. Fermentation of bambara groundnut at 45 °C for two days is recommended as the ideal fermentation temperature and time.     

Evaluation of bacterial biological control agents for control of root-knot nematode disease on tomato

Among 19 bacterial strains isolated in Yunnan from rhizosphere soils and plant tissues, Bacillus methylotrophicus strain R2-2 and Lysobacter antibioticus strain 13-6 exhibited the highest antagonistic activity against the tomato root-knot nematode Meloidogyne incognita in plate and greenhouse pot experiments. The two strains, when applied as soil drenches or seed treatments in greenhouse experiments, reduced root-knot severity and incidence on tomato compared to no-bacteria controls. In tomato field trials conducted in separate years, soil drench treatment with either strain reduced root-knot disease levels and increased yields compared to the control. Levels of disease control and yield enhancement provided by the strains were higher than those using the chemicals abamectin and carbofuran. This is the first report of B. methylotrophicus being used as a biocontrol agent against a plant parasitic nematode and the first demonstration that B. methylotrophicus and L. antibioticus can suppress disease caused by root-knot nematodes in the field.     

Effects of 1,3-dichloropropene on nematode,weed seed viability and soil-borne pathogen

1,3-dichloropropene (1,3-D, C₃H₄Cl₂) is one of the potential candidates as soil disinfectant since the restriction of methyl bromide (MeBr) in soil fumigation due to its ecological risk. Its nematode, soil-borne pathogen and weed control efficacies were evaluated in a laboratory dose-response study and in two commercial tomato fields. Laboratory studies found that the seeds of Digitaria chinensis Hornem. were the most sensitive to soil fumigation with 1,3-D, followed by Eleusina indica (Linn.) Gaertn., Echinochloa crusgalli (L.) Beauv. and Amaranthus retroflexus L. with the LC₉₀ values between 14.23 and 73.59 mg kg⁻¹ soil. Among the pathogens, Phytophthora capsici Leonian was the most sensitive and Fusarium oxysporum f. sp. fragariae was the least sensitive to 1,3-D fumigation with the LC₅₀ values were 0.24 and 1.55 g m⁻². Rhizoctonia solani Kühn., Phytophthora nicotianae var. nicotianae and Botrytis cinerea Persoon exhibited intermediate susceptibility. Field trials revealed that 1,3-D applied to the field at 180, 120 and 80 L ha⁻¹ could suppress Meloidogyne incognita root galling while maintaining high tomato marketable yields, better than Dazomet at the concentration of 400 kg ha⁻¹. Our results indicated that 1,3-D was an excellent nematicide and could provide good to moderate weed and pathogen control. Based on our results, 1,3-D, in combination with other alternatives to MeBr is recommended to reach an integrated pest management.     

Control of brown rot of stone fruits by brief heated water immersion treatments

The effectiveness of brief (30 or 60 s) immersion in water at 24, 50, 55, 60, 65, or 70 °C was evaluated for the control of brown rot, caused by Monilinia fructicola, on California-grown peaches, nectarines, and plums. Inoculated fruits were treated and either stored at 20 °C for 5 days or at 0 °C and 95% RH for 30 days followed by 5 days at 20 °C to simulate commercial marketing conditions. Immersion in water at 55 °C for 60 s or at 60 °C for 30 or 60 s significantly reduced both decay incidence and severity among the remaining wounds that developed the disease. Water temperatures of 65 °C or higher were phytotoxic and caused moderate to severe surface injuries. Immersion in water at 60 °C for 60 s was effective for plums and it reduced the incidence of brown rot from more than 80% among control fruit to less than 2%. In nectarines, this treatment reduced decay incidence from 100 to less than 5% on fruit stored at 20 °C and from 73 to 28% on cold-stored fruit. Therefore, brief immersion in heated water can be an effective approach to manage postharvest brown rot of stone fruits, especially for the organic fruit industry.     

Biorational versus conventional insecticides – Comparative field study for managing red spider mite and fruit borer on tomato

Tomato, Lycopersicum esculentum L. (Solanaceae), is an important crop worldwide that is grown both outdoors and under protected structures, for fresh market consumption and for processing. In the Mariana Islands, tomato is grown as an outdoor crop throughout the year. Tomatoes are attacked by a variety of pests, including the tomato fruitworm, Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae), and, in Pacific islands, the red spider mite Tetranychus marianae McGregor. These pests cause scarring, tissue damage, and aberrations in fruit shape or color, making the tomatoes undesirable for fresh market. Also, insect bodies, excretia or parts in fruits reduce their market suitability. Field trials aimed at improving management of these pests were undertaken at two locations in Guam (Yigo and Inarajan), USA in 2012 and 2013, assessing the efficacy of different biorational and conventional insecticides against T. marianae and H. armigera on tomato. At both locations, the mean percentage of mite-infested leaves and the population density of T. marianae were higher in control than in treated plots. An integrated pest management (IPM) program comprising sprays of selective insecticides (Petroleum spray oil, Beauveria bassiana, azadirachtin, and Bacillus thuringiensis), evaluated at 15, 30, 45 and 60 days after transplantation of tomato seedlings, significantly reduced the number of T. marianae-infested leaves and the density of T. marianae over plots treated with carbaryl, malathion, six applications of B. bassiana or B. thuringiensis and over both controls at both locations. Similarly, significantly lower fruit damage by H. armigera was recorded in the plots treated with the IPM program than in plots treated with carbaryl, malathion, or the control treatments at both locations. Marketable tomato yields from the plots which received with the IPM program were significantly greater at both locations than were those in the other treatments.     

Effects of 1,3-dichloropropene plus chloropicrin on weed seed germination

Telone C-35, a commercial formulation of 1,3-dichloropropene (1,3-D) and chloropicrin (CP), is one of the potential replacements to methyl bromide (MB) for soil fumigation. A laboratory dose–response study and two field trials in tomato were conducted to evaluate their weed control efficacy and their effect on tomato yield. Laboratory studies found that the seeds of Digitaria chinensis were the most sensitive to soil fumigation with Telone C-35, followed by Eleusina indica, Portulaca oleracea and Stellaria media with the LC₅₀ values between 3.35 and 11.68 mg kg⁻¹ soil. Field trials revealed that Telone C-35 applied to the field at 327, 243 and 164 L ha⁻¹ could suppress the percentage of germination weed seeds while maintaining high tomato marketable yields, with no significant differences between MB + CP and the higher two Telone C-35 rates. The yield data from both seasons indicated that all Telone C-35 treatments had a positive effect on tomato yield; there was a 32%–62% increase the mean marketable tomato yield. Our results indicated that Telone C-35 was an excellent MB alternative and could provide acceptable weed control efficacy. Based on our results, Telone C-35, in combination with other alternatives to MB, is recommended to achieve integrated pest management.