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Lack of a conclusive evidence of ingestion of plastid components by plant-parasitic nematodes cautions the use of plastid transformation technology for nematode resistance. Nematode-resistant effector proteins generally require ingestion by the nematode to be effective. Transgene-encoded proteins produced in plastids are not known to be exported into the cytoplasm. Disintegration of plant cell organelles after nematode feeding suggests that nematodes possibly ingest plastid components. Proof of ingestion will validate the development of plastid transformation for nematode resistance. Small subunit ribulose-1,5-bisphosphate carboxylase/oxygenase (SSRubisco) protein is prevalent in chloroplasts and thus chosen as a study molecule. The migratory endoparasitic nematodes Pratylenchus penetrans and Radopholus similis were cultured on green carrot callus containing chloroplasts. Total nematode proteins were extracted and subjected to western blot analysis using cross-reactive polyclonal antibody raised against spinach SSRubisco. Positive detection of SSRubisco occurred in protein extracts from nematodes fed on green carrot callus, but not in extracts from nematodes cultured on non-green alfalfa root callus as negative control. These results confirm the ingestion of plastid components of MW 14 kDA by migratory endoparasitic nematodes.

Radopholus similis distribution in Anthurium plant tissue was determined in a greenhouse experiment. Two thousand mixed life stages of R. similis per plant were inoculated onto Anthurium cultivars `Alii' and `Midori'. Nine months later, nematodes per gram of tissue were determined from stem sections (0-3, 3-6, and above 6 cm from the base), the lowest leaf petiole, and root tissue. R. similis occurred in all stem sections, leaf petioles, and roots in both `Alii' and `Midori'. Nematode distribution differed between the two cultivars. `Midori' had higher numbers of nematode in the roots whereas `Alii' had higher numbers of nematode in the stem sections and first leaf petiole. Anthurium apical stem cuttings could be contaminated with R. similis and may not be a nematode-free propagation material.

To determine the potential to suppress root-knot nematode Meloidogyne javanica, 10 genotypes of seven green manure species were evaluated in a greenhouse study. These species were: black hollyhock (Alcea rosea L.); canola (Brassica napus L.); cabbage (B. oleracea L.); French marigold (Tagetes patula L.), sorghum–sudangrass [Sorghum bicolor (L.) Moench nothosubsp. drummondii (Steud.) de Wet ex Davidse]; sunn hemp (Crotalaria juncea L.); and yellow mustard (Sinapis alba L.). Plants were inoculated with eggs of M. javanica and after 6 weeks, nematode eggs and reproduction factor (Rf = final egg population density/initial egg population density) were determined. Marigolds were non-hosts to M. javanica; other crop species that were poor hosts to M. javanica included canola cv. Dwarf Essex, sorghum–sudangrass cvs. Piper and Sordan 79, black hollyhock cv. Nigra, and sunn hemp. Based on low Rf, four groups of species were selected for further evaluation in the greenhouse to determine the response to both M. javanica and another crop pathogen, Pythium aphanidermatum. These four groups of green manure crops were: 1) seven marigold genotypes; 2) four Brassicaceae genotypes; 3) seven sorghum–sudangrass hybrids; and 4) four other species [black hollyhock, sunn hemp, elecampane (Inula helenium L.), and black-eyed Susan (Rudbeckia hirta L.)]. Plants were inoculated with a factorial combination of M. javanica and P. aphanidermatum (none, each alone, and in combination) and repeated four times in a split-plot experimental design (whole plots were factorial treatments and subplots were green manure crop genotypes). Six weeks after inoculation, plants were harvested and measured for fresh and dry weights of shoots and roots and Rf of M. javanica. Adverse effects of P. aphanidermatum were characterized by dead or dying roots and measured by reduced plant biomass. Negative synergistic effects were observed in several marigold and Brassicaceae genotypes, in which the combined effects of M. javanica and P. aphanidermatum reduced shoot and root growth more severely than either treatment alone. Marigold T. erecta cv. Orangeade, sorghum–sudangrass cvs. Graze-All, Piper, and Sordan 79, and sunn hemp appeared to be resistant to M. javanica and P. aphanidermatum, either alone or in combination. Based on results of greenhouse trials, eight green manure crops (yellow mustard cv. Ida Gold, French marigolds cvs. Nema-gone and Golden Guardian, sorghum–sudangrass cvs. Sordan 79 and Tastemaker, sunn hemp, unplanted plot, and a control plot with weed mat) were selected and grown for 3 months in a field trial in Pepeekeo, HI. Each treatment was replicated four times in a randomized complete block design. Shoot biomass was sampled at 1, 2, and 3 months after planting. Plant–parasitic nematodes were counted before planting and at 4 months after planting. Dry weight biomass averaged across three sampling dates was greatest for the two sorghum–sudangrass hybrids followed by those of two marigold cultivars that did not differ from them. No significant differences in populations of root-knot nematodes were found. Based on this field trial as well as greenhouse trials, marigold cultivars, sorghum–sudangrass hybrids, and sunn hemp appeared to be non-hosts or poor hosts to reniform (Rotylenchulus reniformis) as well as root-knot nematodes and well adapted to the environmental conditions found along the Hamakua Coast of the Hawaii Island.

Burrowing nematode (Radopholus similis) causes severe stunting and yield reduction in anthurium (Anthurium andraeanum) cut flower production. Two field trials were conducted at commercial grower farms to test the efficacy of fluopyram or fluopyram + trifloxystrobin for managing burrowing nematodes. Nematode population densities in roots and cinder media were evaluated during the trial in addition to cut flower yield and canopy cover. In the first trial, the nematode population in roots was reduced by 57% after two applications of fluopyram 3 months apart. As plant health improved, the increasing anthurium root weight supported higher nematode populations. After 14 months, fluopyram-treated plots had 43% more green canopy cover and a 53% increase in flower production compared with the untreated control plots. At a second location, population densities of burrowing nematode were reduced in roots after one application of fluopyram + trifloxystrobin and remained low with quarterly applications. Nematode populations were initially reduced in fluopyram-treated plots followed by a resurgence as demonstrated in the other trial. Ten months after the initial treatment, flower yield was greater in fluopyram + trifloxystrobin-treated plots with more large and extra-large flowers produced. Canopy cover was 45% and 22% greater with fluopyram + trifloxystrobin and fluopyram applications, respectively. Fluopyram shows potential for management of burrowing nematodes in anthurium by improving plant vigor and cut flower production.

Reducing grower reliance on off-island inputs to promote plant nutrition was identified by industry as a high priority in efforts to improve agricultural sustainability in Hawai’i. A variety of knowledge gaps exist that prevent producers from using locally produced amendments in the fertility program. This study will focus on recent transdisciplinary efforts at the University of Hawai’i to improve understanding of factors that affect variability in the quality, application, efficacy, and cost-effectiveness of locally produced composts, vermicomposts, rendered animal products, and algae in Hawai’i. A series of greenhouse, experiment station, and on-farm trials have supported several conclusions, including 1) aqueous extracts of vermicomposts and high-quality, farmer-produced thermophilic composts can effectively improve crop growth and reduce costs associated with the use of these inputs; 2) replacement of peat and other imports with local materials in vegetable seedling production have the potential to improve seedling vigor and reduce costs in the long term; 3) commercially produced rendered meat products, alone and in combination with commercial composts, are a valuable local source of nitrogen (N); and 4) invasive algae from coral reef remediation may provide a significant source of potassium (K) in the near term, but K content of algae is highly dependent on species and location of growth.