College of Agriculture

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As the foundation of the land grant mission at Montana State University, the College of Agriculture and the Montana Agricultural Experiment Station provide instruction in traditional and innovative degree programs and conduct research on old and new challenges for Montana’s agricultural community. This integration creates opportunities for students and faculty to excel through hands-on learning, to serve through campus and community engagement, to explore unique solutions to distinct and interesting questions and to connect Montanans with the global community through research discoveries and outreach.

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Evaluation of the effectiveness of entomopathogens for the management of wireworms (Coleoptera: Elateridae) on spring wheat
(2014-07) Reddy, Gadi V. P.; Tangtrakulwanich, Khanobporn; Wu, Shaohui; Miller, John H.; Ophus, Victoria L.; Prewett, Julie; Jaronski, Stefan T.
Wireworms, the larval stage of click beetles (Coleoptera: Elateridae), are serious soil dwelling pests of small grains, corn, sugar beets, and potatoes. Limonius californicus and Hypnoidus bicolor are the predominant wireworm species infesting wheat in Montana, particularly in the ‘Golden Triangle’ area of north-central Montana. Wireworm populations in field crops are increasing, but currently available insecticides provide only partial control, and no alternative management tools exist. In our study, three entomopathogenic fungi were tested for their efficacy against wireworms in spring wheat at two field locations (Ledger and Conrad, Montana, USA) in 2013. The three fungi (Metarhizium brunneum F52, Beauveria bassiana GHA, and Metarhizium robertsii DWR 346) were evaluated as seed-coat, in-furrow granular, and soil band-over-row drench applications in addition to imidacloprid (Gaucho® 600) seed treatment (as a chemical check), the approach currently being used by growers. Wireworm damage in these treatments was evaluated as standing plant counts, wireworm population surveys, and yield. The three fungi, applied as formulated granules or soil drenches, and the imidacloprid seed treatment all resulted in significantly higher plant stand counts and yields at both locations than the fungus-coated seed treatments or the untreated control. Significant differences were detected among the application methods but not among the species of fungi within each application method. All three fungi, when applied as granules in furrow or as soil drenches, were more effective than when used as seed-coating treatments for wireworm control, and provided an efficacy comparable or superior to imidacloprid. The fungi used in this study provided significant plant and yield protection under moderate wireworm pressure, supporting their value in the management of this pest.
Developing nominal threshold levels for Phyllotreta cruciferae (Coleoptera: Chrysomelidae) damage on canola in Montana, USA
(2014-12) Tangtrakulwanich, Khanobporn; Reddy, Gadi V. P.; Wu, Shaohui; Miller, John H.; Ophus, Victoria L.; Prewett, Julie
The flea beetles Phyllotreta cruciferae (Goeze) and Phyllotreta striolata (F.) (Coleoptera: Chrysomelidae) are serious pests infesting canola (Brassica napus L.; Brassicales: Brassicaceae) in the Northern Great Plains of the United States. In Montana, P. cruciferae is the only flea beetle species that attacks canola during the crop growing stage. Management of P. cruciferae is usually focused on treating adults feeding on canola seedlings, which is the stage most vulnerable to flea beetle damage. In the Golden Triangle area in Montana, canola growers traditionally use seed treatments or calendar based spraying to control P. cruciferae. Here, we compared calendar-based spraying with seed treatment and threshold-based treatment. The experiment treatments included threshold levels (15–20, 25, 45% of leaf area damaged), calendar based sprays (15, 30 and 45 day intervals after plant emergence), seed treatments (imidacloprid), and untreated controls. The trials were done at two locations (Conrad and Western Triangle Agricultural Research Center). We found that calendar-based spraying at a 15-day interval did not differ significantly in yields from threshold-based treatment at 15–20% leaf damage. Also, the seed treatment did not give significantly higher yields compared to calendar-based sprays. A negative correlation was detected between leaf damage and yield in each treatment. Overall, calendar-based and threshold-based treatments were most effective in improving yields. However, treatment made at the threshold of 15–20% leaf area damage is recommended in order to reduce the number of chemical applications and also to reduce the possibility of selecting for resistance in flea beetles.
Impact of species identity and phylogenetic relatedness on biologically-mediated plant-soil feedbacks in a low and a high intensity agroecosystem
(2014-12) Miller, Zachariah J.; Menalled, Fabian D.
Aims: Plant species-specific effects on soil biota and their impacts on subsequent plant growth, i.e. plant-soil feedbacks (PSFs, henceforth), are major drivers in natural systems but little is known about their role in agroecosystems. We investigated the presence and magnitude of PSFs in two contrasting agricultural settings and tested the importance of species identity and phylogenetic relationships in determining PSFs. Methods: We compared PSFs that developed from an intensified agricultural site and a nearby non-cultivated pasture. Four weed and seven crop species were grown in soil inoculated with either biologically active or sterilized soils from each system. Four crop response species were grown to estimate PSFs. Results: PSFs were species-specific. The identity of currently- and previously-planted species and their interactions explained over 80 % of the variation in feedbacks. Biota from the intensified agricultural site produced negative feedbacks in three of the four response species. Phylogenetic relationships partially explained PSFs. Conclusions: PSFs can alter crop growth and may be altered by agricultural practices. The species-specific effect to soil biota should be taken into account when assessing the extent to which crop and weed species could influence subsequent plant growth.
Enhanced Rice Growth is Conferred by Increased Leaf ADP-Glucose Pyrophosphorylase Activity
(2014-10) Schlosser, Alanna J.; Martin, John M.; Beecher, Brian S.; Giroux, Michael J.
Modification of leaf starch levels may be employed in attempts to increase cereal yield. Few studies have examined leaf starch as a plant biomass limiting factor. Here we test the hypothesis that rice plant productivity may be increased by increasing leaf starch. Starch biosynthesis is controlled by the heterotetrameric rate-limiting enzyme ADP-glucose pyrophosphorylase (AGPase). Rice variety Nipponbare was transformed with a modified form of the maize endosperm AGPase large subunit gene, Sh2r6hs, as well as with the small subunit gene, Bt2, under control of a rice RuBisCO small subunit promoter. RNA sequencing results indicated that Sh2r6hs and Bt2 transcript levels were each greater than 20 times that of the native genes. Increased total AGPase activity was correlated with higher leaf starch accumulation at the end of the day. Yield trials of T1 derived homozygous plants indicate that increased leaf AGPase leads to a 29% increase in plant biomass under the conditions tested without changing the rate of photosynthesis while significantly reducing leaf transpiration and conductance. Additionally, functional annotation clustering of significantly up and down regulated transcripts reveals areas of protein metabolism, specifically protein biosynthesis, transport, and localization, that were altered in response to increased leaf starch. Together, these findings indicate plant growth is limited by native levels of leaf starch and that it is possible to increase plant yield via the starch biosynthesis pathway.
Bromus tectorum Response to Fire Varies with Climate Conditions
(2014-09) Taylor, Kimberley T.; Brummer, Tyler J.; Rew, Lisa J.; Maxwell, Bruce D.
The invasive annual grass Bromus tectorum (cheatgrass) forms a positive feedback with fire in some areas of western North America’s sagebrush biome by increasing fire frequency and size, which then increases B. tectorum abundance post-fire and dramatically alters ecosystem structure and processes. However, this positive response to fire is not consistent across the sagebrush steppe. Here, we ask whether different climate conditions across the sagebrush biome can explain B. tectorum’s variable response to fire. We found that climate variables differed significantly between 18 sites where B. tectorum does and does not respond positively to fire. A positive response was most likely in areas with higher annual temperatures and lower summer precipitation. We then chose a climatically intermediate site, with intact sage-brush vegetation, to evaluate whether a positive feedback had formed between B. tectorum and fire. A chronosequence of recent fires (1–15 years) at the site created a natural replicated experiment to assess abundance of B. tectorum and native plants. B. tectorum cover did not differ between burned and unburned plots but native grass cover was higher in recently burned plots. Therefore, we found no evidence for a positive feedback between B. tectorum and fire at the study site. Our results suggest that formation of a positive B. tectorum-fire feedback depends on climate; however, other drivers such as disturbance and native plant cover are likely to further influence local responses of B. tectorum. The dependence of B. tectorum’s response to fire on climate suggests that climate change may expand B. tectorum’s role as a transformative invasive species within the sage-brush biome.
Laboratory Host Range Assessment of a Predatory Pentatomid, Podisus maculiventris(Hemiptera: Pentatomidae) for Field Release on Guam
(2011-12) Reddy, Gadi V. P.; Kikuchi, R.
Predation by Podisus maculiventris (Say) (Hemiptera: Pentatomidae) was evaluated with Erionota thrax (L.) (Lepidoptera: Hesperidae), Pericyma cruegeri (Butler) (Lepidoptera: Noctuidae), Pareuchaetes pseudoinsulata Rego Barros (Lepidoptera: Arctiidae), Papilio polytes (L.) (Lepidoptera: Papilionidae) and Eudocima phalonia (L.) comb. nov. (Lepidoptera: Noctuidae). Both free-choice and no-choice experiments indicated that the P. maculiventris attacked and consumed all the larvae of the 5 species included in the tests. Although the larvae died at different intervals, most of them were dead within 24–120 h of the introduction of the predatory species. Since the P. maculiventris is polyphagous in nature and the present findings indicate that these predators will feed on the introduced biocontrol moth, P. pseudoinsulata, it is recommended not to take the predators out of the quarantine laboratory for the field release on Guam. Additionally, P. maculiventris will feed on some native species as they become available.
Bioactivity of Selected Eco-Friendly Pesticides Against Cylas formicarius (Coleoptera:Brentidae)
(2012-12) Leng, P. H.; Reddy, Gadi V. P.
Seven low risk pesticides including 1.2% azadirachtin (Azadirachta indica), extracts from Morinda citrifolia, petroleum oil 97%, Beauveria bassiana strain GHA, mixed essential oils (rosemary oil: 0.25%, peppermint oil: 0.25%, thyme oil: 0.25%, clove oil: 0.25% and other ingredients: 99.00%), spinosad and malathion, were evaluated against adults of the sweetpotato weevil, Cylas formicarius (Fabricius) (Coleoptera: Brentidae) to determine potential insecticidal, repellent and feeding deterrence effects. Among the pesticides tested, A. indica and spinosad showed high insecticidal, repellent and feeding deterrence activity against C. formicarius. Spinosad, A. indica and malathion showed significantly higher insecticidal activity against C. formicarius. Similarly, these pesticides showed high repellency activity against adults, particularly 3–4 h after the treatment. The lowest food consumption was observed with the A. indica (0.8 g/adult/192 h), and the highest (9.9 g/adult/192 h) was with the petroleum oil spray. The other tested pesticides showed comparable activities. The chemicals we tested—particularly neem and spinosad—are therefore promising candidates as ecofriendly chemicals that could potentially replace broad-spectrum synthetic neurotoxins for control of C. formicarius.
Action Threshold Treatment Regimens for Red Spider Mite (Acari: Tetranychidae) and Tomato Fruitworm (Lepidoptera: Noctuidae) on Tomato
(2013-09) Reddy, Gadi V. P.; Tangtrakulwanich, Khanobporn
The tomato fruitworm, Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae), is the foremost pest of tomato in the Mariana Islands. Similarly, the red spider mite, Tetranychus marianae McGregor (Acari: Tetranychidae), is a chief pest of vegetables particularly on tomato, Solanum lycopersicum L. (Solanaceae). However, the infestations by T. marianae are heavy during the early stages of crop growth, while infestations of H. armigera become prominent at later stages. Because no threshold levels are available for these pests, many growers apply up to 15 chemical applications per tomato cropping period. To reduce the regular spray schedules chemical applications and to prevent damage to foliage and fruit quality, the present study was undertaken for the development of action threshold levels for the timing of chemical applications for T. marianae and H. armigera on tomato in the Mariana Islands. Therefore, different threshold levels were evaluated for timing applications of Sun-spray 6E® horticultural oil against T. marianae and Aza-Direct®, neem against H. armigera on tomato in the wet and dry seasons at 2 locations, Dededo and Inaranjan, in Guam, USA during 2011 and 2012. Based on T. marianae infested leaves, incidence of T. marianae and yield levels, the plots sprayed at 8–12 mites/leaf in the dry season and 8–14 mites/leaf during the wet season had significantly lower leaf damage and T. marianae densities compared to a greater number of mites/leaf, regular based sprays and control plots. Likewise, an initial spray scheduled when 2 eggs of H. armigera were detected on 10 of the samples, followed by an added spray only if 2 damaged fruit or H. armigera larvae were detected per 50 immature fruit resulted in lower percent fruit damage and higher marketable yield compared to other threshold levels or a regular spray schedule.
Registration of ‘Egan’ Wheat with Resistance to Orange Wheat Blossom Midge
(2014-08) Blake, Nancy K.; Stougaard, Robert N.; Bohannon, B.; Weaver, David K.; Heo, Hwa-Young; Lamb, Peggy F.; Nash, Deanna L.; Wichman, David M.; Kephart, Ken D.; Miller, John H.; Eckhoff, Joyce L.; Grey, William E.; Reddy, Gadi V. P.; Lanning, Susan P.; Sherman, Jamie D.; Talbert, Luther E.
Egan' hard red spring wheat (Triticum aestivum L.) (Reg. No. 1102, PI 671855) was developed by the Montana Agricultural Experiment Station and released in 2014. Egan is intended for production in areas of Montana infested with the orange wheat blossom midge (OWBM) (Sitodiplosis mosellana Géhin). Egan is resistant to OWBM due to antibiosis conferred by resistance gene Sm1. Egan also contains a chromosome segment originally introgressed into wheat from T. turgidum ssp. dicoccoides containing a gene for high protein (Gpc-B1) and a gene for stripe rust (caused by Puccinia striiformis Westend. f. sp. tritici) resistance (Yr36). Egan has shown high yield potential and high grain protein in nurseries grown under OWBM pressure in the Flathead Valley of Montana. Egan is the first hard red spring wheat cultivar with resistance to OWBM developed for Montana.
Field Evaluation of Petroleum Spray Oil and Carbaryl Against Tetranychus marianae (Acari: Tetranichidae) on Eggplant
(2014-03) Reddy, Gadi V. P.; Miller, R. H.
Tetranychus marianae McGregor (Acari: Tetranychidae) is a pest of several perennial crops and is widespread in the Pacific Basin, including the Mariana Islands where it was first reported. The mite is also present in the West Indies, Bahamas, southern USA, Nicaragua, Argentina, Brazil and Southeast Asia. Eggplant growers apply carbaryl 10 to 15 times against this pest during each cropping period. Some growers no longer cultivate eggplant and tomato because of uncontrollable mite infestations. Previous indoor studies have shown petroleum spray oil (PSO) to be effective against T. marianae. We therefore examined the comparative effectiveness of PSO (Sun-spray 6E®) at the rate of 5mL/liter, and carbaryl at the rate of 1.5 mL/liter, against T. marianae on eggplant at 2 locations in Guam. The mean percentages of mite infested leaves and the population densities of T. marianae at both the locations were significantly higher in control plots than in treatment plots. PSO treatments with 6 and 15 sprays more effectively reduced the number of T. marianae-infested leaves and populations of T. marianae than carbaryl treatments. Marketable yields of eggplant from PSO treated plots were significantly higher than from the other plots. We recommend 6 applications of PSO at 15, 25, 35, 45, 55 and 65 days of after transplanting for managing T. marianae on eggplant.

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