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Brad Geary, Corey Ransom, Brad Brown, Dennis Atkinson and Saad Hafez

Onions (Allium cepa) are a high-value crop in the Treasure Valley of eastern Oregon and western Idaho. To grow quality bulbs, growers use fumigants and pesticides to control weed, pathogen, and nematode pests. Metam sodium and other commonly used pesticides are considered effective in controlling onion pests but also pose a wide range of problematic issues related to the environment, human health, and economic profitability. Biofumigant crops ‘Idagold’ mustard (Sinapis alba) and ‘Colonel’ oil seed radish (Raphanus sativus) were evaluated as substitutes for commercial fumigants in controlling soil-borne pests. During some years of this study, there was limited control of a few weed species based on visual and biomass data for metam sodium and biofumigant treatments, but the weed control was not consistent or acceptable. The severity of pink root (Phoma terrestris), a major fungal onion root pathogen, was significantly lower with metam sodium in most comparisons with other treatments. Biofumigants showed limited effects on pink root severity and are not a viable option for pink root control. Nematode damage or populations were not high enough to determine if the biofumigant and metam sodium treatments influenced their control. In some years, biofumigants reduced onion yield. The influence of these biofumigants on onion pest control was limited and their use in onion production is not warranted without significant nutrient recycling or soil quality benefits.

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Charles E. Barrett, Xin Zhao and Alan W. Hodges

Growers are looking for sustainable alternatives to methyl bromide as a soil fumigant that are effective and economical. Increased demand for organically produced fruits and vegetables has also contributed to the need for environmentally friendly soil-borne disease control methods. Grafting may be a valuable tool for vegetable growers to cope with pest management challenges in production of cucurbits and solanaceous crops; however, there are concerns regarding the higher costs associated with the use of grafted plants in the United States. The main objective of this 2-year study was to determine if grafting with a resistant rootstock could be cost-effective to overcome root-knot nematodes (RKN) (Meloidogyne sp.) and maintain fruit yield in organic heirloom tomato (Solanum lycopersicum) production in Florida's sandy soils. The heirloom tomato cultivar Brandywine was grafted onto the rootstock ‘Multifort’. Nongrafted and grafted ‘Brandywine’ plants were grown organically in two fields that exhibited different levels of RKN infestations. Grafted and nongrafted transplants were estimated to cost $0.78 and $0.17 per plant, respectively. The cost of rootstock seeds accounted for 36% ($0.28/plant) of the total cost of the grafted transplants and 46% of the cost difference between grafted and nongrafted plants. Sensitivity analyses were conducted using these estimated transplant production costs and crop yield data from the field trials as well as price information for heirloom tomato. Results showed that under severe RKN pressure, grafting may be an economically feasible pest control measure to help maintain a profitable production given that the risk of economic crop losses due to RKN outweighed the higher cost of grafted transplants.

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Susan L.F. Meyer, Dilip K. Lakshman, Inga A. Zasada, Bryan T. Vinyard and David J. Chitwood

Clove oil derived from the clove plant [Syzygium aromaticum (=Eugenia caryophyllata)] is active against various soil-borne plant pathogens and therefore has potential for use as a bio-based pesticide. A clove oil formulation previously found to be toxic to the southern root-knot nematode (Meloidogyne incognita) in laboratory assays was investigated in greenhouse studies for nematode suppression and phytotoxicity on vegetable crops. Phytotoxicity studies were conducted with 0.1%, 0.2%, and 0.3% clove oil applied to soil 0, 2, 5, and 7 days before transplant of cucumber (Cucumis sativus), muskmelon (Cucumis melo), pepper (Capsicum annuum), and tomato (Solanum lycopersicum) seedlings. Tomato seedlings were the most sensitive to clove oil. The 0.2% and 0.3% clove oil concentrations applied as drenches at transplant (0 day) were the most phytotoxic to seedlings of all the tested vegetable species, with only 0% to 50% seedling survival. Most of the clove oil concentrations applied as drenches at transplant decreased shoot heights and fresh shoot weights of all seedlings. Some applications of clove oil at 0.2% and 0.3%, applied 2, 5, or 7 days before transplant also significantly reduced shoot growth, especially of pepper and tomato. Greenhouse experiments evaluating suppression of nematode populations on cucumber were conducted with 0.10%, 0.15%, and 0.20% clove oil applied 7 days before transplant. Overall, plants inoculated with nematodes tended to have smaller shoots and heavier roots than plants without nematodes. Effects of clove oil treatments on nematode population densities were inconsistent between the two trials. In Trial 1, 0.10% and 0.15% clove oil decreased population densities compared with the carrier control. In Trial 2, nematode population densities were lowest in the water and carrier control treatments. The results indicate that, with the tested clove oil formulation and application times, southern root-knot nematode populations would not be consistently reduced with clove oil concentrations that were not phytotoxic to one or more of the tested vegetable crops.

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Hector R. Valenzuela and Joseph DeFrank

Living mulches offer a low-input alternative to achieve weed control while minimizing herbicide applications, decreased fertilizer leaching, insect and nematode management. and improved soil texture. A study was conducted to evaluate the effect of a Rhodes Grass (Chloris gayana cv. Katambora) living mulch on the growth and productivity of ten eggplant. Solanum melongena, cultivars grown under fertigation. The living sod was established at the Univ. Hawaii Waimanalo Experiment Station in June 1992. Soil analysis was taken before experiment initiation. Ten eggplant cultivars were transplanted on both living-mulch and control (woven-polyethelene mulch) plots on 4 March 1993. Weekly or bi-weekly harvests were conducted for six months. beginning on 19 May 1993. In addition plant height and canopy dimensions were determined on 16 April. and 10 Nov. Plant growth was monitored throughout the experiment. Soil samples were taken from the eggplant rhizosphere, hare-ground and in Rhodes grass monoculture, for nematode count determinations. Soil samples were also taken for nutrient determination after completion of the experiment. Overall yields were greater in the polyethelene mulch than in the living mulch plots. A differential response was observed on the response of cultivars to cropping system. However the most vigorous cultivars performed well in both systems. The living mulch system showed potential for nematode management in eggplant agroecosystems.

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J.A. Thies, J.D. Mueller and R.L. Fery

The southern root-knot nematode [Meloidogyne incognita (Kofoid & White) Chitwood] is a serious pest of pepper (Capsicum annuum L.). Currently, methyl bromide is used for nematode control, but the pending withdrawal of this fumigant from the United States market has resulted in a need for effective alternative root-knot nematode management measures. We evaluated the effectiveness of resistance of `Carolina Cayenne' relative to the susceptible genotypes `Early Calwonder' and PA-136 in greenhouse, microplot, and field studies. In all tests, `Carolina Cayenne' exhibited exceptionally high resistance (minimal galling, minimal nematode reproduction, and no yield reduction) to M. incognita; `Early Calwonder' and PA-136 were highly susceptible. In a test conducted in a heavily infested field, `Carolina Cayenne' outyielded PA-136 by 339%. The exceptionally high resistance exhibited by `Carolina Cayenne' provides an alternative to methyl bromide and other fumigant nematicides for managing root-knot nematodes in pepper.

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J. Farías-Larios, J.G. López-Aguirre, J.L. Miranda and L.A. Bayardo-Vizcaino

Acerola (Malpighia glabra L.) is a small, red fruit that is native to the West Indies, but is also grown in South and Central America. In western Mexico, this crop is very important because acerola is the richest known natural source of vitamin C, with a content of 1000 to 4500 mg/100 g of fruit. In nursery and field conditions, acerola growth is severely affected by root-knot nematode. The objective of this study was to evaluate the use of commercial formulations of Bacillus spp. on root-knot nematode management. This study was carried out in the Farm Santa Clara Maria in Colima State. Acerola plants, 60 days old were used. They were grown in 3-L pots with soil, compost, and pumice stone mixture as substrate. Treatments evaluated were: 5, 10, 15 and 30 mL/pot of Activate 2001, Tri-Mat (5 mL/pot) and control, without application. Activate 2001® is a concentrated liquid in water suspension of Bacillus chitinosporus, B. laterosporus, and B. licheniformis. Initial nematode population was of 3,305 in 50 g of roots. Acerola plants were harvested at 30, 60, and 90 days after application. Results show that Activate 2001 at 10 and 30 mL rates reduce significantly root-knot populations in acerola plants 60 days after application with 135 and 178 nematodes/50 g of roots, respectively. Diameter stem, shoot fresh and dry weight and root production were also increased by rhizobacteria application. These results are promising and confirmed the potential of Bacillus as a biological agent for nematode management.

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Alan W. McKeown, John W. Potter, Mary Gartshore and Peter Carson

Root lesion nematodes (Pratylenchus penetrans Cobb) are well-adapted to sandy soils and have a host range including most agronomic, horticultural, and wild species grown in Ontario. As native climax sand-prairie species have coexisted with the nematode for millennia, resistance or tolerance may have developed. We have screened using the Baermann pan technique, soil samples taken from a private collection of sand-prairie species collected from local prairie remnants. Several species [Liatris cylindracea Michx., Monarda punctata L., Pycnanthemum virginianum L., Echinacea purpurea (L.) Moench] proved to be excellent hosts (>500/kg of soil) of root lesion nematode, confirming the presence of this nematode in the soil. Over two seasons, we determined that 10 plant species belonging to the families Asclepiadaceae, Compositae, Graminae, and Leguminosae to support very low numbers of P. penetrans. Brown-eyed susan (Rudbeckia hirta L.) had no root lesion nematodes throughout both seasons, Butterfly weed (Asclepias tuberosa L.) very low counts, while Switch grass (Panicum virgatum L.) and Indian grass [Sorghastrum nutans (L.) Nash] had detectable root lesion nematodes on only one sampling date each year. Big Bluestem (Andropogon gerardii Vitman), Little Bluestem [Schizachyrium scoparium (Michx) Nash], Sand Dropseed [Sporobolus cryptandrus (Torr.) Gray], Side-oats Grama [Bouteloua curtipendula (Michx.)) Torr], Broomsedge (Andropogon virginicus L.), Bush clover [Lespedeza capitata (Michx] also are poor hosts. These species have potential as cover or rotation crops useful for nematode management.

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A.W. McKeown, J.W. Potter, M. Gartshore and P. Carson

Because of the need to find plants that suppress root lesion nematodes for use in rotation or cover-crops, 16 native sand-prairie species were evaluated for host status for 6 years. Plants were grown on a Fox sand soil at a local prairie plant nursery. Soil cores were taken in the spring, summer, and fall and assayed for plant parasitic nematodes. Five species supported very low numbers (less than 100/kg soil) of root lesion nematodes. Brown-eyed Susan (Rudbeckia hirta) had no detectable nematodes for the duration. Switchgrass (Panicum virgatum L.) and Indiangrass (Sorghastrum nutans L., Nash) samples produced detectable nematodes on only two sampling dates over the 6 years and were statistically not different from brown-eyed Susan. Butterfly weed (Asclepias tuberosa L.) also had very low detectable nematodes as did sand dropseed [Sporobolus cryptandrus (Torr.) Gray.]. New Jersey tea (Ceanothus americanus L.), little bluestem [Schizachyrium scoparium (Michx.) Nash], and big bluestem (Andropogon gerardi Vitman) were poor hosts with <200 nematodes/kg soil. Mountain mint (Pycnanthemum virginianum L), wild bergamont (Monarda fistulosa L), horsemint (Monarda punctata L), and dwarf blazing star (Liatris cylindracea L) all had root lesion populations over 3000/kg soil. Horsemint and wild bergamont plants died out, possibly as a result of nematode infestation. Root lesion nematodes have an extremely wide host range in current agronomic and horticultural crops, and weeds and are difficult to manage using nonchemical means. Indiangrass, switchgrass, big bluestem, and little bluestem have all been used agriculturally for pastures and consequently have potential as beneficial long-term rotation crops for nematode management and soil building.

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Wenjing Pang, John E. Luc, William T. Crow, Kevin E. Kenworthy, Robert McSorley and Robin M. Giblin-Davis

courses as well as athletic fields and lawns ( Crow and Han, 2005 ). With the cancellation of fenamiphos (Nemacur; Bayer CropScience, Research Triangle Park, NC), turfgrass managers are in need of new nematode management strategies. Use of resistant or

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James P. Gilreath, Bielinski M. Santos and Timothy N. Motis

methyl bromide alternatives, 2002 7 Nov. 2006 < http://mbao.org/2002proc/018chellemid%20large%20scale%20field%20evaluation-mbao2002.pdf >. Noling, J.W. Nematode management in strawberries 2005 Inst. Food Agr. Sci. Publ. ENY-031. Univ. of Florida