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  • Author or Editor: B.R. Smith x
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Verticle gradients of moisture, salinity, specific fertilizer ions, and pH in the root zone in the closed, insulated pallet system (CIPS) are relatively stable compared with those in the open container system (OCS). Establishment of the VA mycorrhizal fungus Glomus intraradices and maintenance of the biocontrol fungus Trichoderma harzianum and the entomopathogenic nematode Steinernema carpocapsae were greater in CIPS than in control OCS. In CIPS, percent corn root length colonized by G. intraradices was greatest in roots in the top stratum of the root medium. Colonization was significantly greater in copper-coated root-containment pouches. Population maintenance in CIPS of T. harzianum, initially uniformly inoculated throughout the root medium, was highest in the top stratum of the root medium where K+ and NO 3 concentrations were highest. Efficacy of S. carpocapsae in parasitizing Galleria mellonella larvae, while greater in CIPS, was significantly related to host plant in CIPS but not in OCS. Inoculation with bacterial antagonists Bacillus cereus, Enterobacter aerogenes, and Serratia plymuthica significantly increased plant growth in CIPS, but not in OCS. Phytophthora cinnomomi root rot infection readily occurred in inoculated plants, but did not spread to noninoculated plants in CIPS when roots were contained within plant pouches. Because of the stability of the root zone parameters and the lack of leaching-dilution of exudates, volatiles, and other materials from the root zone, CIPS is an excellent system for evaluating effects of microorganism and other factors on root growth and development.

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Polyphenols were analyzed in expanding buds and developing leaves of pecan [Carya illinoensis (Wangenh.) C. Koch] cultivars with varying responses to Cladosporium caryigenum (Ell. et Lang. Gottwald), the organism causing scab. Plant tissue extracts were examined by high-performance liquid chromatography using a water: methanol gradient to separate polyphenolic components on a C-18 reversed phase column. A diode-array detector was used to identify profile components by retention times and computer matching of ultraviolet spectra to standard compounds in a library. Concentrations of these polyphenols were compared throughout the growing season in leaves of pecan cultivars with low (`Elliott'), intermediate (`Stuart'), and high (`Wichita') susceptibility to scab; during susceptibility to infection by Cladosporium caryigenum from 16 cultivars; and in `Wichita' leaf discs with and without scab lesions. The major polyphenolic constituent of tissues for all cultivars was identified as hydrojuglone glucoside, which was detected in intact buds and leaves throughout the growing season. Hydrojuglone glucoside concentration increased concomitantly with leaf expansion and then declined slowly. Juglone was barely, if at all, detectable, regardless of leaf age. No correlation was found between cultivar susceptibility to pecan scab and the levels of either juglone or hydrojuglone glucoside in the healthy leaves of 16 cultivars. Leaf tissue with scab lesions had significantly higher juglone and hydrojuglone glucoside levels than leaf discs without scab lesions. Chemical names used: 4-8-dihydroxy-1-naphthyl b-d-glucopyranoside (hydrojuglone glucoside); 1,5-hydroxy-naphthoquinone (juglone).

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Legume ground covers were evaluated in pecan orchards to reduce nitrogen inputs and increase beneficial insects. Treatments were established at two sites in Oklahoma, each with 5 ha of a `Dixie' crimson clover/hairy vetch mixture and 5 ha of grass sod. Nitrogen was applied at 0-200 kg·ha-1 to the sod plots, but legume plots were not fertilized. Aphids and selected arthropods were monitored on ground covers and in the pecan canopies. Data indicated that a mixture of crimson clover/hairy vetch supplied up to 186 kg·ha-1 N to the trees. Beneficial arthropods monitored were Coccinellidae, Chrysopidae, Nabid, Syrphid, and spiders. Lady beetles, primarily Hippodamia and Coleomegilla, were the most important aphid predator in the spring, and green lacewing was the most important fall predator. There were fewer aphids infesting pecans using a crimson clover/hairy vetch ground cover than a grass sod.

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Annual legume ground covers were evaluated in pecan (Carya illinoinensis) orchards to supply nitrogen and increase beneficial arthropods. Treatments were established at two sites, each with 5 ha of a `Dixie' crimson clover (Trifolium incarnatum) /hairy, vetch (Vicia villosa) mixture and 5 ha of grass sod. Data indicated that the legume mixture supplied over 100 kg·ha-1 N to the pecan trees. Beneficial arthropods were greater in orchards with legume ground covers than in orchards with a grass groundcover. Lady beetles and green lacewings were the most important spring predators, and green lacewings were the most important fall predator. The Species distribution on the ground covers differed from that in the canopy. Coleomegilla maculata lengi, Hippodamia convergens and Coccinella septempunctata were the most abundant lady beetle species in the legume ground covers, and Olla v-nigrum, Cycloneda munda, and Hippodamia convergens were the most abundant species in the pecan canopies. Beneficial arthropods appeared to suppress injurious pecan aphids.

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In the mid-1980s, a statewide educational program was initiated to help improve productivity in replanted apple orchards. This effort began with a study of the background of the problem in Washington and an assessment of the problems growers faced when replanting orchards. An array of potential limiting factors were identified-most important, specific apple replant disease (SARD)-but also low soil pH, poor irrigation practices, arsenic (As) spray residues in the soil, soil compaction, nematodes, nutrient deficiencies, and selection of the appropriate orchard system. The educational program was delivered using a variety of methods to reach audience members with different learning styles and to provide various levels of technical information, focusing on ways to correct all limiting factors in replant situations. Results have been: Acceptance of soil fumigation as a management tool: increased recognition of soil physical, chemical, and moisture problems; reduced reliance on seedling rootstock, and an increase in the use of dwarfing, precocious understocks; and better apple tree growth and production in old apple orchard soils.

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