Figure 1. Septoria leaf blotch leaf lesions.

I recently visited a wheat field with a crop consultant. The consultant was confident that the wheat had Septoria Leaf Blotch disease (Septoria tritici, Mycosphaerella graminicola); he was familiar with the leaf symptoms (Figure 1) and the region has a history of problems with Septoria. He was also noticing, however, some lesions on the glumes (Figure 2), and wondered if there was another disease present. It turns out that the lesions on the glumes are also a symptom of Septoria and can be seen if wet weather occurs after heading.

Septoria is a serious problem of wheat because, as lesions coalesce, particularly lesions on the flag leaf, it can reduce the photosynthetic capacity of the plant and reduce grain filling, thereby reducing yields. Septoria is most problematic in rainy years and in early-planted fields. Early-planted fields have a longer period of exposure if the disease is present on crop residues or volunteer plants. Crop rotation can help manage against Septoria in future plantings, but planting more tolerant varieties and properly-timed fungicide applications are also good management practices. Septoria ratings are not a regular part of the UC statewide variety testing program, but ratings are available from 2011 and 2012. (On the previous links, click on Table 3.) Fungicides, like Mancozeb and Propiconazole, should be applied between tillering and heading, with the purpose of protecting the flag leaf. Septoria only infects wheat, so other small grains like barley, oats, and rye are not affected by the disease. 

Figure 2. Septoria lesions on glumes.

The field that I visited was likely an early-planted field, and the disease seemed worse on the edges and on the south side of berms where the conditions were likely a little bit warmer and the plants advanced a little bit faster. The field is completely headed out, and the grain is in the milk stage, nearing the soft dough stage. The million dollar question is, with the forecast of rain later in the week, is it worthwhile to spray a fungicide? If it does rain, the disease may spread, showing more lesions on the flag leaf. With grain at the milk to soft dough stage, the grain may be able to mature even if the disease gets worse. Making the decision on whether to apply a fungicide at this time is a hard call to make for a farm advisor or consultant because it really comes down to dollars and cents. In this case, however, product labels say not to apply the product after 10.5 Feekes, or full heading, so this particular field is beyond the stage when a fungicide should be applied.

Information on products and practices is for educational purposes only and does not constitute an endorsement or recommendation by the University of California.

 

A grower recently called to ask about the minimum soil temperature for planting blackeye and large lima beans. The University of California, Division of Agriculture and Natural Resources has produced production manuals for both blackeyes and limas. A general guideline for blackeyes is to plant as soon as the weather warms and the soil temperature in the seed zone (about 2.5 inches deep) reaches at least 66⁰F for the three days following planting. Under these conditions, blackeyes will emerge about three to five days after planting. It is important to try to plant blackeyes early enough that they can set pods before the hottest temperatures of the summer. Planting when soil conditions are still cool, however, could result in a longer emergence time, around 10 days. This longer time to emergence means greater susceptibility to diseases, like Pythium or Rhizoctonia (Figure 1). Blackeyes can be grown on a range of soil types, both coarse and fine textured soils, provided that irrigation is adequately managed to keep the plants from being water-stressed or waterlogged. Blackeyes are moderately tolerant of salinity and can generally tolerate an average root zone salinity of 4.9 dS/m before yield declines are expected.

Similarly, large limas should also be planted when soil conditions have warmed, and a general guideline is when soils have reached 70⁰F in the seed zone (about 3 inches deep). At these warmer soil temperatures, wireworms will recede deeper in the soil and present less of a problem, and emergence will be quicker and more uniform. The effect of soil temperature on germination and days to emergence is shown in Figure 2. These data show that percent germination improved dramatically when soil temperature reached 68⁰F, but the average number of days to emergence was greatly shortened when the soil temperature reached 77⁰F. As with blackeyes, planting limas into warmer soil will help reduce fungal infection. Limas grow best in loamy soils. If grown on finer textured soils, irrigation must be properly managed to prevent waterlogging. Limas have low tolerance for saline soil conditions, and yield declines are expected when the average soil salinity reaches 1.5 dS/m.

In addition to the production manuals previously mentioned, I also consulted UC production manuals produced in the 1950's, including Dry Edible Bean Production in California (1954), Blackeyes: Costs of Production, Suggestions on Growing (1956), and Production of Dry Edible Lima Beans in California (~1951). 

The UC Davis Department of Plant Sciences has announced their field day for small grains and alfalfa. The event will take place on Wednesday, May 11, 2016 from 8:15am to 4:15pm. The small grains field day will take place in the morning, and the alfalfa field day will take place in the afternoon. Lunch will be provided, and there is no registration fee.

The field day is located on Hutchison Road, just west of the city of Davis.  Take Highway 113 north from Interstate 80, or take Highway 113 south from Woodland. Exit on Hutchison Road, and go west. Take a right at the first roundabout, left at the second roundabout, and the Agronomy Headquarters is about ¼ mile west in a clump of trees and buildings on your left. 

A tentative agenda is as follows:

 

8:15am – Noon: Small Grains Field Day

7:45  Registration (no charge)

8:15     Welcome and Introductions—Mark Lundy, UCCE/UCD Grain Specialist

8:20     Overview of wheat breeding—Jorge Dubcovsky, UCD wheat breeder

8:25     Introducing new California Wheat Commission Executive Director Deanna Fernandez

8:35     Depart for field

Field Tour:

8:50 – 10:50 Advances and directions in small grain breeding

8:50     Promising malting barley varieties —Alicia del Blanco, UC Davis

9:05     Durum Wheat Varieties: new genes for grain yield—Alicia del Blanco, UC Davis

9:15     Promising common wheat releases—Oswaldo Chicaiza, UC Davis

9:30     Evaluation of high resistant starch wheat lines—Andre Schönhofen, UC Davis

9:45     QTL for increased number of spikelets— Junli Zhang and Saarah Kuzay, UC Davis

10:00   Discovering genes for drought tolerance—Tyson Howell, UC Davis

10:15  Combining two stripe rust resistance genes in a single locus—Nicolas Cobo, UC Davis

10:30   Mutants for stripe rust resistance—Josh Hegarty, UC Davis

10:45   Travel to forage trial

10:55 – 11:55: Variety testing and agronomic management of small grain crops

10:55   Small grain forage variety evaluation—Cal Qualset & Lynn Gallagher, UC Davis

11:10   Statewide Variety Development and Evaluation – Wheat, Triticale, and Barley Yields, Performance and Pest Resistance—Mark Lundy & Phil Mayo, UC Davis

11:40   Demonstration of in-field N monitoring & quicktests for improved precision of N fertilization—Jessica Schweiger, UC Davis

11:50   Late-planted heirloom varieties at different seeding rates—Margaret Lloyd, UCCE

 

12:00 NOON – Barbeque Lunch – Many thanks to California Crop Improvement for the Complementary Lunch!

 

12:35pm - 4:15pm: Alfalfa/Forages Field Day

12:35  Introductions—Dan Putnam, UCCE/UCD Alfalfa Specialist

12:40   Welcome, Department of Plant Sciences—Chris Van Kessel, Chair

12:50   Welcome from the Dean-Changes at UC Davis in Agriculture—Dean Helene Dillard, Dean College of Agriculture and Environmental Sciences, UC Davis.

1:00     Depart for field

Field Tour:

1:05     Insect Management and Disappearing Options for Alfalfa—Larry Godfrey, UC Davis and Rachael Long, UCCE

1:20     Measuring Evapotranspiration (ET) in the Field – Ali Montazar, Project Scientist, UC Davis

1:35     Using ET to schedule irrigations – How to—Daniele Zaccharia, Irrigation Specialist, UC Davis.

1:50     Sorghum Field Studies for Grain and Forage Crops—Jeff Dalberg, Kearney Ag. Center, Fresno, CA

2:05     Field Studies with New Weed Management Options—Mick Canevari, UCCE, San Joaquin County

2:25     Kura Clover, an alternative Clover for Pastures—Dan Putnam, UC Davis

2:35     Subsurface Drip Irrigation Studies on Spacing—Dan Putnam, Daniele Zaccaria, UC Davis

2:50     Deficit Irrigation Strategies for Alfalfa—James Radavich, Dan Putnam, Ali Montazar, UC Davis

3:05     Controlling Gophers in Alfalfa Fields—Roger Baldwin, UC Davis

3:20     Understanding the Fertilizer Needs of Alfalfa—Steve Orloff, UCCE Farm Advisor, Siskiyou County

3:35     Variety Performance Data for Managing Diseases, Insects, and Nematodes, UC Davis—Dan Putnam, UC Davis

3:50     Breeding Alfalfa for California—Scott Newell, Gitanshu Munjal, Charlie Brummer, UC Davis 

4:15     Return to Base

A crop consultant brought in some alfalfa plants and asked if I could help identify the problem. In the field, he was observing stunted plants with shortened internodes and suspected stem nematode (Ditylenchus dipsaci). What seemed different this year is that he was seeing these stunted plants intermingled among healthy plants, and in the past, he was accustomed to seeing stunted plants in groups.

Figure 2. White flagging symptom of alfalfa stem nematode.

Nematodes are microscopic roundworms that use their stylet, or needle-like mouthpart, to puncture plant cells and suck out their contents. The alfalfa stem nematode lives and feeds in the stems and crown of the plant. Symptoms of infection include plant stunting, shortened internodes, and swollen buds (Figure 1), and white flagging where stems lack chlorophyll (Figure 2). Identification of stem nematode can be done under a dissecting microscope by cutting pieces of stems and the crown in a petri dish with water. I took this picture using my smartphone through the eyepiece of the microscope (Figure 3). The stem nematodes are indicated with the blue arrow; they are the almost-translucent wiggly lines emerging from the piece of stem.

Stem nematodes can be a perennial problem in California alfalfa. (See a previous article on the UC Alfalfa and Forage News blog.) They are a particular problem in the spring when the weather is cooler. As temperatures warm, the nematodes recede to the soil and go dormant until cool weather returns. They can cause complete plant die-back, leaving open areas in the field where weeds can become a problem. Unfortunately, management of this pest is challenging. Varieties have varying levels of resistance, but even with a highly-resistant variety, it can be typical to have susceptible plants next to healthy plants within a stand. For this reason, in an area where stem nematodes are a problem, a grower should plant nothing less than a highly-resistant variety. It is important to plant clean seed. Using proper sanitation methods is also advised and would include not moving equipment and wastewater from infected to clean fields, and also not applying manure from cattle fed with infected stem nematode hay to clean fields. Stem nematodes have a limited host range, so rotating out of alfalfa for at least 2 years can help to reduce the problem, but longer rotations (4 years) might be advised under severe infestations. Rotation crops could include small grains, corn, or dry beans. There are no registered nematicides for stem nematode.