Recently, I received a call about a blackeye bean field in the San Joaquin Valley with a lot of bean pods that did not fill out at the tips (photo). I contacted the UC Riverside blackeye bean breeders Drs. Phil Roberts and Bao Lam Huynh and they shared that this problem is primarily caused by heat, which affects pollen viability and thus fertilization. Here's their response:
It [lack of pod fill] is the typical male-sterility symptom [lack of pollen viability] associated with extreme temperatures (heat or cold). Based on the planting date you gave, we just checked the temperature in Denair, CA [farm location] and noted that it was quite warm (~100) during the flowering time (40-50 days after planting) and recently during the pod filling stage, so heat must have been a main cause. The symptom could also be more severe if water is limiting.
Always be prepared with good irrigation management practices for all crops going into heatwaves, like the one we're having now. The minimum seasonal irrigation needed to produce a blackeye bean crop being managed for full yield from one pod set is 16 to 18 inches. This estimate includes a pre-irrigation of 4-inches, and irrigations of 4-inches when floral buds first appear, and 8 to 10 inches during 5 to 6 weeks of flowering and pod filling. If additional irrigations are needed during the vegetative stage, one could increase the total irrigation requirement to 20 or more inches. Irrigating for a second flush of pods could require an additional 8 to 12 inches of water. Irrigation requirements are further increased by any water required to leach salts or to compensate for an inefficient irrigation system.
Additional water may need to be applied during extreme heat events which drive plant transpiration rates to the limit. Make sure to check the soil moisture in the top 12 to 24 inches of the soil profile and apply additional water if the soil is dry. If in doubt about how much additional water is needed, check the reference evapotranspiration (ETo) and make sure to irrigate to replace at least 120% of your daily ETo in your area. The current (mid to late August) daily ETo in the San Joaquin Valley ranges from 0.25 to 0.30 in/day; make sure your applied irrigation replaces 120% of these values.
More information on growing blackeye beans can be found in the publication, UC ANR Blackeye bean production in California, http://beans.ucanr.edu/files/226601.pdf.
- Author: Michelle Leinfelder-Miles
My observations of the field were that there were patches of several nearby plants with symptoms, but across the three contiguous fields, the patches were widespread. I suspected a vascular disease because of what appeared to be a progression of the disease from yellowing to necrosis to eventually plant death. I submitted samples to the plant pathology lab at UC Davis, and they diagnosed Fusarium oxysporum f. sp. ciceris, which is the Fusarium wilt pathogen for garbanzos. Fusarium wilt (also called Fusarium yellows) has the external symptoms previously described, but in addition to these symptoms, splitting the stems may reveal reddish-brown streaking in the vascular system at the center of the stem (i.e. xylem). The roots won't show discoloration with Fusarium wilt like they will with Fusarium root rot. Fusarium wilt should not be confused with yellowing caused from virus, which will exhibit discoloration in the phloem. Fusarium wilt can reduce yield by reducing seed quantity and size.
In general, cultural practices are the only ways to manage this disease. Luckily, the Fusarium wilt pathogens are crop-specific, so this pathogen will only infect garbanzos. The pathogen, however, can survive for a long time in the soil (upwards of 6 years or more) because it can survive under wide temperature and pH ranges. Therefore, crop rotation is an important management practice. Crop rotation will help to slow the proliferation of the disease, but it generally won't eliminate it. Growers should plant certified disease-free seed. They should not save seed for planting because Fusarium wilt (and Ascochyta blight) can live externally on the seed. Growers should also consider planting UC-27, which has disease resistance and is adapted to the Central Valley. Disease management may also include cleaning soil from equipment when moving from an infected field to a non-infected field. In some studies, soil solarizaton has been shown to reduce Fusarium wilt in subsequent garbanzo crops, but to my knowledge, there hasn't been any work on soil solarization in California garbanzos.
Garbanzo beans are an important crop worldwide for human and animal nutrition. In California, they are grown during the winter months, like small grains, and provide growers with another crop choice that can be winter rain-fed. Because they are a legume, they can fix atmospheric nitrogen to fulfil some of their nitrogen needs. Garbanzos also are more tolerant of soil salinity than common beans and limas. In California, we annually grow approximately 10,000 acres of garbanzos. California garbanzos are generally a high-quality product grown for the canning industry. More information on garbanzo production in California can be found in the UC production manual.
The Insect and Mite sections of the UC IPM Pest Management Guidelines for Dry Beans have been recently revised and updated and are now available online at: UC IPM Dry Beans Pest Management Guidelines.
Authors include UCCE Farm Advisor Rachael Long and UC IPM Advisor Pete Goodell (emeritus). The guidelines include an updated photo page to help identify pests and the damage they cause to dry beans at: Photo Identification.
These guidelines can help with managing pests in your fields. Interested in Lygus bugs and how to control them? Take a look at the guidelines on lygus and see that the thresholds vary by bean class and type. For example, blackeye beans (cowpeas) have different tolerance levels to lygus than lima beans. Some lima bean varieties are more tolerant to lygus than others. Interested in biocontrol of aphids? See photos of natural enemies that prey on aphids at: Photos to identify natural enemies of aphids.
There is also a newly revised table on the relative toxicities of insecticides and miticides to natural enemies and honey bees in dry bean production, found at: Insecticide Toxicities.
This information and much more is available through the newly revised 2018 UC IPM Dry Bean guidelines! This follows the recent revision of diseases and abiotic disorders in dry beans. The weed management section is currently in review and will be available later this year.
- Author: Rachael Freeman Long
- Author: Sarah Light
UC Davis Agronomy Farm
Directions: In the field across from the UC Davis Bee Biology Lab (same place as previous years). From Hwy 113 in Davis, exit on Hutchison Dr. Go west, turn north at the first roundabout, then west at the second roundabout. Continue west on Hutchison Dr for about 1 mile. Turn south on Hopkins Lane (look for a row of olive trees), make your first left, and park under the trees. For questions, contact Rachael Long at 530-666-8143. No RSVP needed.
10:00 Sign in, introductions, updates, Antonia Palkovic, UCD Assistant Specialist
10:05 UC Dry Bean Blog and IPM update, Sarah Light, Farm Advisor, Sutter-Yuba Co.
10:15 Dry bean breeding program, pest and disease resistance, Dr. Paul Gepts, UCD
10:30 Cooperative dry bean nursery, MAGIC Beans, and interspecific crosses for drought tolerance, Dr. Jorge Berny, UCD Post-doc (with Santos Barrera Lemus)
10:55 Cowpea herbicide trial, Dr. Mariano Galla, Farm Advisor Glenn Co.
11:10 Bean seed moisture and quality at harvest, Rachael Long, Farm Advisor Yolo Co.
11:20 Diallel Crossing project, Kimberly Gibson, UCD PhD student
11:35 Lima RIL trial, Stephanie Smolenski Zullo, UCD PhD student
11:50 Caravan to field location 1, near sheep barn
12:05 Heirloom breeding and Mesoamerican Diversity Panel; Drones for high throughput phenotyping, Travis Parker, UCD PhD student
A baby lima bean field in the Sacramento Valley was recently found to be infected with southern blight (Sclerotium rolfsii), a fungal pathogen that's found in many crops. The field was double-cropped with barley and planted late June.
Symptoms and signs: Initial symptoms of southern blight include a yellowing of the foliage with a slight darkening of the stem, just above the soil line. Lesions rapidly develop, girdling the stem, causing sudden and permanent wilt of the plant. The fungus grows downward in the stem, causing rot. White mats of mycelium develop on the stem and nearby soil. In a few days, tan to brown spherical sclerotia (tiny compact masses of hardened fungal mycelium) may appear on the fungal mat. If present, these are a good diagnostic feature of this disease.
Comments on the disease: Southern blight is usually a minor disease of beans and other crops in California. However, high temperatures above 85°F together with high moisture favor the disease. High summertime temperatures combined with a later planting date likely stressed the young lima plants in this field, making them more susceptible to this disease. The best time to plant baby limas in the Sacramento Valley is around the third week in May; for large limas it's early May. Last year was a big year for southern blight in many crops, likely due to late plantings and high heat stressing the plants. This year the disease seems to be a little less common, but is still widely detected on many crops, from Kern to Sutter counties. Detections in the northern counties of the central valley have become more frequent in the last three weeks.
Disease Management: The fungus attacks a wide range of plants and survives for a long time in the soil as sclerotia. Rotations are not considered effective since this pathogen has over 500 hosts. However, it is thought that rotations to corn or small grains for at least 2 years may reduce inoculum; studies are underway to determine whether these rotations are effective. For most crops, southern blight resistant cultivars are not available. However, for vegetable crops such as tomatoes, there are some rootstocks reported to be resistant to southern blight, which are currently under study in field trials in California. Discing and burying plant refuse helps destroy sclerotia.