2004 Research Summaries

Maximizing the use of soybean meal and soybeans in dairy rations.

Dr. Zhiguo Wu at Penn State advised the Soybean Board that “because of cow availability issues for conducting the experiment at Penn State”, that portion of research involving the animals would be directed by Dr. Jim Ferguson at the University of Pennsylvania, Ferguson obtained the necessary clearance from the University of Pennsylvania and was expecting to begin the research in the summer of 2005, Dr. Wu reported. The analysis of samples and data would remain at Penn State, he added.

Dr. Ferguson, Dr. Wu assured the board, “is a professor in the Department of Clinical Studies and has done many reputed dairy studies in metabolism and nutrient utilization. He will bring significant research experience to the project.”

Influence of soybean management on the incidence of white mold.

Dr, Erick DeWolf of Penn State filed this report: During the past year we have been working to remove the final obstacles to our white mold research here in Pennsylvania. More specifically, our objective was to evaluate procedures for inducing white mold in soybean field experiments. Once these procedures are optimized, we will establish experiments to investigate the role of row spacing and planting density on incidence of' white mold.

We have successfully produced the reproductive structures of the fungus. Sclerotinia sclerotiorrum, the fungus that causes white mold. This process requires a month long procedure involving freezing temperatures to condition the fungus for germination and production of reproductive structure (apothecia), These apothecia were then used as part of the inoculation field experiments outlined below.

2004 Field Experiments for Soybean White Mold

A white mold susceptible variety of soybean was planted in 7-inch rows on the Penn Slate Plant Pathology research farm located near State College. This planting was divided into replicated plots used to evaluate methods of inoculating field experiments. The plots were subdivided into mist-irrigated and non-irrigated sub-plots. Treatments established in the sub-plots included placing ungerminated, and germinated sclcrotia within the soybean canopy, and inoculating plants with mycelia of the fungus through a wound on the leaf petiole.

Results indicate the petiole inoculation treatment was the most effective way to induce disease in a field environment. Nearly 100 percent of the plants inoculated in this fashion developed severe white mold. Other inoculation methods resulted in only low levels of disease, or no disease development. In the near future we plan to use the petiole inoculation technique to investigate the questions about white mold management that producers are continuing to ask. Possible questions include: Given the amount of disease 1 see in my field, how much yield loss can I expect? Would increased row spacing and lower planting density be an effective means of reducing losses to disease? How can I best integrate white mold control with weed management?

Measurement of the protein and oil content of soybeans

The 2004 season was the first of a planned three year project to measure and report data on the total protein and oil contents of soybeans in the Penn State variety trials. A total of 171 soybean specimens were evaluated at the trials in Lancaster and Centre counties..

Mark Antle, Dr. Greg Roth and Dr. David Johnson conducted the trials and provided the sub-samples for analysis. The data was published in the Soybean Variety Tests section of the PSU “Corn and Soybean Management” web site…. see http://cornandsoybeans.psu.edu/soyvarietytests.cfm

The data is found in Excel tables numbered 1, 2, 5, 6, 9 and 10.

The yield responses at the two sites are very different but the average protein and oil contents are fairly similar to each other and to that obtained in other regions. It is not easy to compare varieties at the site or even in different years because seed suppliers tend to use different varieties at the sites and there is a large turnover in varieties submitted. However, there is clearly the potential to select varieties that have high yields of high quality beans., The data will be most useful to seed suppliers that seek to optimize their product offerings for the local conditions. Over time, growers will learn which companies tend to offer better varieties for these Pennsylvania sites.

Evaluation 0f Soybean Germplasm under Pennsylvania Conditions

Year 13 of this study was successfully completed in 2004 with the help of very favorable growing conditions for soybean production.

Four soybean tests were completed in Lancaster County and are summarized as follows: 67 entries averaging 79.8 bu/A in the full season glyphosate resistant trial, 12 entries averaging 73.0 bu/A in the full season non-glyphosate resistant trial, 19 entries averaging 57.0 bu/a in the glyphosate resistant soybean following small grain trial, and 8 entries averaging 48.9 bu/a in the non-glyphosate resistant soybean following small grain trial. Two soybean tests were completed in Centre County with 49 entries averaging 63.8 bu/a in the glyphosate resistant trial and 10 entries averaging 59.8 bu/a in the non-glyphosate resistant trial. Yields in trials at both Lancaster County and Centre County were up considerably compared to 2003 (i.e. seeds were large in 2004). Average seed quality for all Lancaster County trials and the glyphosate resistant trial in Centre County were better than 2003. Seed quality in the non-glyphosate resistant trial in Centre County was nearly identical to 2003.

Growing conditions in 2004 were characterized by above average rainfall and near normal temperatures during most of the season. The Lancaster County trials received in excess of 27 inches of rain during the months of June through August. The Centre County trials received approximately 18 inches of rain during the June through August period. The Centre County trials were hit with the remnants of twqo different hurricanes during September. These storms caused some minor lodging problems and in some varieties, earlier than anticipated defoliation.

By and large, we were pleased with the outcome of the 2004 trials. Our higher than normal yields in all trials were consistent with the record-breaking statewide yield of 46 bushels per acre Pennsylvania experienced in 2004.

The 2004 Pennsylvania Soybean Performance Report is on-line at http://cornandsoybeans.psu.edu/.

Establishing Economic Thresholds for Soybean Aphid and Developing a Model to Predict Timing and Intensity of Infestations

Development of an Integrated Pest Management (IPM) program to protect Pennsylvania farmers against significant economic losses from the soybean aphid, a new invasive species, is the primary goal of this research, reported Dr. Dennis Calvin. To accomplish this goal, studies were initiated in 2003 and 2004 at the Russell E. Larsen Agricultural Research Center near Rock Springs. In addition to this research, studies were also initiated to follow the population dynamics of the pest in Central Pennsylvania and evaluate the impact of natural enemies. Laboratory studies were begun to quantify the impact of temperature on aphid development and reproduction. When combined with research under way in the Midwest and surrounding states, a functional IPM program is materializing for Pennsylvania farmers.

In 2004, narrow-row soybeans were inoculated with four initial infestation levels (0, 40, 100, and 200) of aphids per plant at V6 to simulate the natural timing of soybean colonization by the aphid. The initial population levels were then tracked over the course of the summer to determine the total number of aphids per plant, their rate of buildup and peak aphid infestation. At the end of the growing season, yield was taken from individual plants. In contrast to the 2003 growing season results, significant yield reductions were observed with aphid infestations. These yield impacts match results of Midwestern studies, economic thresholds were established at 250 aphids per plant. With as few as 500 aphids per plant, the infested plants experienced an average of 32 percent yield reduction. It is unclear why we observed no yield impact in 2003, while we observed a significant impact on yield in 2004. Both years were very moist years. As in 2003, the aphid infestation in Pennsylvania began and peaked about two weeks later than areas in the Midwest. In a separate spray timing study, a 12.8 bushel per acre or 19 percent yield impact was observed between the plot sprayed one week after the economic threshold was reached and the untreated plot.

The development of soybean aphid populations in both narrow and wide row soybeans was tracked weekly in 2004 at Rock Spring. Unlike the 2003 data, there was a statistical difference in aphid and Harmonia axyridis populations between the narrow and wide row soybeans. Natural enemy densities tracked the populations of aphids, but again lagged slightly behind. It appears that predator numbers increase rapidly once aphid density peaks. The average ratio of aphids to predators over the growing season was around 142:1 in narrow row beans and 212:1 in wide row beans. In 2004, Harmonia axyridis was found to track the soybean aphid populations most closely.

Laboratory studies of aphid development under constant temperatures were conducted at 18,26, 31, and 34 degrees C. Using the developmental information a mathematical equation for soybean aphid development was constructed. The optimal temperature of development was estimated to be 29.2 degrees C and the base threshold of development was 14.0 degrees C. The optimal temperature for adult longevity and fecundity, however, was 26 degrees C. No individuals completed development at 18 degrees C. Unlike similar research conducted in Minnesota, soybean aphids survived and reproduced at 34 degrees C. Over the next few months, a soybean aphid population dynamics model will be constructed from this data.

Strategies for Sustaining Glyphosate Tolerant Soybeans: Managing Against Glyphosate Resistance

The project was initiated in the spring of 2003 with data collected for each of the last three summers. The work explored how weed populations are likely to behave in response to a glyphosate-dominated herbicide use program in soybean. This research involved two broad objectives. The first was to identify herbicide management programs that would provide acceptable levels of weed suppression of current and future weed problems in Pennsylvania grain crop production. The second objective centered on developing a spatially explicit way of assessing the impact of weed management programs on the spread of glyphosate-resistant horseweed. Much progress has been made in the research.

• Since writing this proposal we have had numerous reports of glyphosate resistance in horseweed in Pennsylvania, reports that have been substantiated in our greenhouse through support from this grant. In addition, in the last 2 1/2 years glyphosate-resistant biotypes of common ragweed and palmer amaranth have been confirmed, with suspected resistant population of waterhemp (a pigweed), common lambsquarters, and giant ragweed undergoing testing.

• The use of mid or late-applications of Roundup resulted in increased proportion of morningglory in the first year and densities of morningglory increased significantly in the second year of the study.

• The rate of spread of glyphosate-resistant horseweed is greater than previously observed, moving at a rate of least 1 1/2 miles a year. Both wind and the combine appear to play an important role in seed dispersal. The second important observation is that farmers will change herbicide use practices once resistance is perceived as a local threat.

• During the funding period from 2003 to 2005, the results of this Soybean Board-funded project have been presented at 46 meetings and workshops.