Field and greenhouse studies were conducted during 2004 through 2006 at the Rodney R. Foil Plant Science Research Center, Starkville, MS. Six sorghum and soybean rotation treatments were tested to determine their effect on plant pathogen, insect, and nematode diversity and density levels. Treatments included 1) continuous sorghum, 2) continuous soybean, 3) sorghum-soybean-sorghum rotation, 4) soybean-sorghum-soybean rotation, 5) sorghum-soybean-soybean rotation, and 6) soybean-sorghum-sorghum rotation. Several nematode and insect species were identified during the study, but were always below economic thresholds. Six insect species were identified on soybean during each growing season and used as the indicator species for this study. The most prevalent were threecornered alfalfa hopper (Spissistilus festinus (Say) and bean leaf beetle (Cerotoma trifurcata (Forester). Sorghum webworm (Nola sorghiella Riley) and corn earworm (Helicoverpa zea (Boddie) were the most common insects on sorghum panicles. Rotations did not affect the diversity or density levels of the indicator soybean or sorghum insects during the three year study. Plant disease levels during the investigation showed variable results. Three foliar fungal pathogens including Diaporthe phaseolorum (Cooke & Ellis) Sacc. var. meridionalis, Septoria glycines Hemmi, and Cercospora sojina Hara on soybean, and Gloeocercospora sorghi D. Brain & Edgerton ex Deighton on sorghum were observed. The only virus disease on soybean was bean pod mottle, but levels were not affected by the rotations during the study. Zonate spot caused by G. sorghi was the most prevalent foliar sorghum disease, but was not affected by the rotations. Six frequently isolated fungal pathogens from either soybean or sorghum roots included Macrophomina phaseolina (Tassi) G. Goidanich, Rhizoctonia solani Kühn, D. phaseolorum, Aspergillus spp., Trichoderma spp and Fusarium spp. Aflatoxin contamination of sorghum seed was low (<20 ppb) the first two years of the study, but was high (790 ppb) in 2006. Significantly greater soybean and sorghum yields were obtained from rotated systems compared to monoculture systems in 2005. In a greenhouse test, M. phaseolina infection of soybean led to significantly greater root disease ratings, lower plant height and dry weight than the untreated control. Sorghum plant growth was not affected by M. phaseolina and R. solani.

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The species of biological control agents which affect soybean pests in the Tidewater area were investigated, and their relative values were determined. Two pentatomids, <u>Podisus Macu1iventris</u> Say and <u>Stiretrus anchorago</u> F., were the only significant bio-contro1 agents which attacked the Mexican bean beetle, <u>Epi1achna varivestis</u> Mulsant. Thesepredators were not able to hold the pest population in check. A parasitic fly, <u>Trichopoda pennipes</u> F. was the only important biological control agent which attacked the green stinkbug, <u>Acrosternum hilare</u> (Say). Host and habitdt preferences of the fly suggested the presence of two strains in Virginia. Distribution of the fly was very uneven. Fungal disease was found to be an important control agent of many (larval) Lepidoptera. It was the most important control agent of <u>Plachypena scabra</u> (F.). P. <u>scabra</u> was also controlled by predation and parasitism. Nine parasites attacked the larvae and pupae. No effective biological controls were found for the corn earworm, <u>Heliothis zea</u> (Boddie). The only significant control agent, fungal disease, acted too slowly to prevent economic damage by this insect. / Master of Science

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This item was digitized as part of the Million Books Project led by Carnegie Mellon University and supported by grants from the National Science Foundation (NSF). Cornell University coordinated the participation of land-grant and agricultural libraries in providing historical agricultural information for the digitization project; the University of Arizona Libraries, the College of Agriculture and Life Sciences, and the Office of Arid Lands Studies collaborated in the selection and provision of material for the digitization project.

Petrol and ethanolic extracts of six asteraceous weeds were added to artificial diet and screened for inhibition of larval growth on variegated cutworm, Peridroma saucia (Hbn.). Petrol and ethanolic extracts of Artemisia tridentata and Chamomilla suaveolens and ethanolic extracts of Chrysothamnus nauseosus and Centaurea diffusa were highly inhibitory at five times the naturally occurring concentrations. The two C. suaveolens extracts and the ethanol extract of A. tridentata were active at the natural concentration (100%) and were further examined at 20, 40, 60, and 80% of this level. Inhibition of larval growth was directly related to concentration for each of the three extracts tested. EC₅₀'S (effective concentration to inhibit growth by 50% relative to controls) for the three extracts were 36-42% of the naturally occurring level in the plants. Nutritional indices were calculated for second instar P. saucia feeding on the active ethanolic A. tridentata extract and the petrol extract from C. suaveolens. The relative growth rate (RGR) of P. saucia larvae fed the ethanolic extract of A. tridentata in artificial diet was significantly lower than that in larvae fed diet with the petrol extract of C. suaveolens and larvae on control diet. Dietary utilization was significantly lower for larvae fed the A. tridentata extract. Results of a field trial indicated that a single treatment of A. tridentata extract at the equivalent of 0.2 g/ml could protect cabbage significantly better than the carrier solvent (30% aq ethanol) or distilled water as measured by a visual damage estimate. An insecticide standard, deltamethrin (17.9 µg/1 with 0.4% Superspred TM ), suppressed pest damage significantly better than the A. tridentata-extract treatment. A residual oviposition deterrency to Pieris rapae was found in the field results. Caged experiments in the laboratory confirmed the contact oviposition deterrency of the A. tridentata extract at 0.2 g/ml. Offspring of field-collected P. saucia larvae grew 2.5-fold heavier than larvae from the laboratory colony. However, diet with the A. tridentata extract inhibited both field-collected and laboratory reared saucia larvae equally when compared to their respective controls fed untreated diet. In summary, these results indicate the potential benefit of using specific unrefined plant extracts for growth inhibitors and oviposition deterrents against insect pests. The contribution of individual phytochemicals in the A. tridentata ethanolic extract to growth inhibition or oviposition deterrency is currently speculative. / Land and Food Systems, Faculty of / Graduate

Call number: LD2668 .T4 1958 Y68

6 pp. / Low Desert Citrus Varieties; Irrigating Citrus Trees / Diagnosing Home Citrus Problems includes information on all the commonly encountered dooryard citrus problems encountered in Arizona. Problems/disorders are grouped into three catagories: problems with fruit, problems with leaves, and problems with stems, branches and entire tree. Symptoms, causes and control measures are given for each disorder.