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• Approved 2 hours of continuing education units for CURES (nitrogen management plan self-certification)
• Approved 2 hours of continuing education units for CCA (crop management)
• Requested 1 hour of continuing education units for PCA

Bagrada Bug, Bagrada hilaris:

Organic Management in Yolo County

Margaret Lloyd^a and Ian Grettenberger^b

^aUCCE Small Farms Advisor in Yolo Solano and Sacramento Counties

^bUC Cooperative Extension Specialist in Entomology

Bagrada bug, Bagrada hilaris, is an invasive stink bug first found in Southern California in 2008, but was found in Yolo County in 2014. Fall 2018 has been dry and warm, with days in the low to mid-80°F, favoring significant build up of bagrada bug populations and preventing tail-off of populations. With extended favorable conditions multiple generations and rapid population increase has led to severe damage. Organic management is challenging and no complete control has been identified. However, a multi-pronged IPM approach has potential to reduce populations and crop damage.

Bagrada bug, adult

Bagrada bug (circled in green) on harlequin bug.

Bagrada bug nymph (upper left) and ladybug larvae (center right) on a broccoli stem.

IDENTIFICATION

Adults are black with orange and white markings, nymphs range from solid red-orange (instar) to red bodies with black stripes and a black head. Adult harlequin bugs look most similar to adult Bagrada bug, however, an adult bagrada bug averages 0.25” in length, at least a third smaller in size than the Harlequin bug. Adults are commonly moving in the copulating position, but all stages can be seen crawling on soil and climbing on plants and leaves. While often seen walking, Bagrada bugs readily fly when temperatures reach the mid-80's°F. When approached by equipment or other, adults tend to hide under leaves or even fly.

Bagrada bugs are highly temperature sensitive, emerging as the day warms, with peak activity at the warmest part of the day, and seeking cover as temperatures cool.

LIFECYCLE

Bagrada bug life cycle lasts 3-4 weeks. Eggs are barrel-shaped and deposited singly or in small clusters of about six on leaves but especially in the soil, hatching in 4 -10 days. Eggs are initially white, but turn orange or red prior to hatching. Depending on conditions, a female bug can lay up to 150 eggs within 2-3 weeks.

HOST RANGE

Bagrada bug preferentially feeds on cruciferous crops (family Brassicaceae), including broccoli, cauliflower, cabbage, radish, turnip, mizuna, arugula, kale, bok choy, and collards, among others. This includes cruciferous weeds such as short pod mustard, pepperweed, wild radish, London rocket, and shepherd's purse, as well as the insectary plant, sweet alyssum. It reportedly also feeds, but to a much lesser extent, on strawberries, melons, and members of the nightshade (potatoes, peppers, tomatoes), mallow (okra, cotton), legume, and grain families (wheat, corn, sudangrass, millet). Populations of bagrada bug are unlikely to build to levels seen in cruciferous crops, since it requires cruciferous plants to complete its lifecycle. Lettuce and spinach are NOT a suitable host for bagrada bug.

SYMPTOMS and DAMAGE

Using needle-like mouthparts, bagrada bugs pierce plant tissue and “lacerate and flush”, sucking up the liquid plant material. Feeding on leaves produces white stippling and starburst/fan-shaped leaf lesions. Feeding on the apical meristem (growing tip) can lead to blind plants (no head) or multiple heads. Damage to growth nodes can lead to multiple secondary shoots, resulting in stunted or deformed plants.

Young crops, For young plants (just germinating up to several leaves), heavy feeding can completely kill seedlings. Bagrada bugs can detect just-germinating seeds, resulting in newly emerged seedlings with bagrada bug feeding injury or new emergence. In Salinas, some growers who find noticeably high mortality of cotyledons skip thinning to maintain a decent crop stand.

Bagrada bug damage on broccoli cotyledon

Feeding damage on mizuna

Multiple shoots caused by feeding damage

Feeding damage on leaf edge

MANAGEMENT

1. Scouting of weeds, prior to a brassica planting, or managing weeds.

Look for the characteristic starburst/fan shaped lesion on weedy hosts, as well as for the insects themselves. Damage can be easier to find than the insects at low populations. On the Central Coast, where commercially grown cruciferous crops are available nearly year-round, shortpod mustard (Hirschfeldia incana), and perennial pepperweed (Lepidium latifolium) appear to be the two most important weeds for buildup of bagrada bug populations. Most mustards can be hosts, but these, along with wild radish, are probably key weeds for bagrada bug in Yolo Co. as well. When these growing populations of bagrada bugs run out of food in the patches of weeds, they migrate into crop fields in search of food.

For shortpod mustard (pepperweed is more challenging), if it is possible to successfully manage weeds when they are still small, you may prevent buildup of bagrada populations from happening. Thinking of bagrada bug as a landscape-scale pest, as opposed to field scale, is a good way to approach population management. With that in mind, managing both hosts that function as reservoir (e.g. brassica weeds) and hosts that aid to sustain their populations in fields (brassica crops), will be more effective.

Shortpod mustard is one of the most important weeds for buildup of bagrada bug populations

2. Row cover can protect direct-seeded and transplanted brassica crops.

Protecting any type of seedling helps reduce overall damage and prevents extreme damage to a new seed line. By protecting cole crops such as broccoli until >4-5 mature leaves, the apical meristem, or growing tip, will become more protected as the plant grows, reducing the number of blind or multiple heads. Keep in mind this only works if you don't trap bagrada bugs inside the row cover and also that row cover can cause issues with other pests (e.g., aphids).

3. Trap cropping, coupled with crop arrangement, could reduce populations in your focal crop.

Trap cropping can be effective at targeting populations as they move from the weedy edges into a field. The goal of trap cropping is to provide an attractive food source for bagrada bug. When the trap crop is infested, management, with chemistry, vacuums or incorporation (when populations are high) may still be important to prevent movement into the main crop. Using insecticides only in the trap crop could help reduce costs. Turnip is worth considering since it is highly attractive to bagrada bug, seed is inexpensive, and germination is quick. The trap crop should be on the edges of fields to intercept bagrada bugs as they move. If possible, order plantings or beds as follows, moving towards the center of a field: field edge -> trap crop -> non-host (e.g. lettuce) -> susceptible host.

Turnip trap crop is worth considering since it is highly attractive to bagrada bug, seed is inexpensive, and germination is quick.

4. Monitor the field edges adjacent to ditches and weedy edges early and focus early treatment on this area.  

Bagrada bug has a strong edge effect, and damage is more severe adjacent to farm edges.

5. Use transplants for cole crops, especially when bagrada bug populations are high

If possible, use transplants. Older plants are much more resistant to damage. Transplants also narrow the window where damage is likely to occur. The same idea applies for other brassicas, but where cosmetic damage is important, significant damage can still occur later in the season.

6. Best efficacy has been found with mixtures containing pyrethrins and/or spinosad, in combination with kaolinite clay, azadirachtin, and/or insecticidal soap.

In conventional management, pyrethroid chemistry has the most effective knockdown and residual control. However, options for organic systems have much lower efficacies and shorter residuals, making management more challenging. In multiple studies, stand-alone applications of pyrethrins, spinosad, and azadirachtin have been significantly less effective then in combination with other materials. Significant damage could still occur with high populations. As contact herbicide, application is best during warm days when bugs are active.

The following are combinations with promising efficacy. Consider multiple applications in shorter time intervals (4-7 days).

• Entrust+ Pyganic^a (17 fl oz) + Azadirect (32 fl oz ) optional: M Pede^b (2%)
• Pyganic^a + Azadirect
• Azadirect (32 fl oz/ac) + Surround^c (10 lb/ac)
• Pyganic^a (17 fl oz)+ Surround^c (10 lb/ac)**
• Pyganic^a (17 fl oz) + M Pede^b (2%)
• Entrust + M-pede^b
• Azadirect (highest labeled rate) + Mycotrol^d

 ^a Adjust pH for Pyganic (5.5-7 recommended)

^bThe rate of M-pede used in the study was 2% of the water volume. Typically, 2% of M-pede is considered as a high rate and increasing the rate (> 2%) may cause phytotoxicity (burning of leaves).

^cBecause Surround could clog the spray tanks, it requires rigorous agitation before application. Also, because Surround easily comes off from the leaf surface with sprinkler irrigation, reapplications are warranted if irrigated at closer intervals especially during the early stages of the crop.

^dConsider applying in the evening to encourage fungal germination to minimize reduce spore desiccation from a warm day.

7. Essential oils did not deter bagrada bug, except geraniol may have potential to suppress Bagrada bug activity.

In a controlled study evaluating bagrada bug response to essential oils, geraniol was the only oil that elicited a behavioral response by adult bagrada. This study was not a field trial, but rather a test of concept to screen for a response in activity. Essential oils tested included citronellal, lemongrass oil, peppermint oil, thyme oil, rosemary oil, pine needle oil, limonene oil and vetiver acetate (Joseph, 2017).

8. Traps do attract bagrada bug, but will not significantly reduce populations

Black traps are most effective, however, a pheromone lure or other lure that is much more attractive than cruciferous crops has not been identified. At this time, sweet alyssum is a good choice as a lure and 100-1000 bugs can be trapped to a single trap, but this is often not enough to reduce damage and will occur when populations are already very high. Traps may be useful as an early detection tool, although scouting weeds and your crops has a better chance of success.

REFERENCE

Grettenberger, Ian, Jhalendra Rijal, Richard Smith, Larry Godfrey, and Shimat Joseph. Bagrada Bug Update: Organic Management. Presentation February 2016.

 Joseph, Shimat V.. 2018. Lethal and Sublethal Effects of Organically-Approved Insecticides against Bagrada hilaris. Journal of Entomological Science, 53(3):307-324.

Joseph, S.V., I.M. Grettenberger, L.D. Godfrey and N. Zavala. 2017. Susceptibility of germinating cruciferous seeds to Bagrada hilaris (Hemiptera: Pentatomidae) feeding injury. Arthropod-Plant Interact. 11: 577–590.

Joseph, Shimat V.. 2017. Repellent Effects of Essential Oils on Adult Bagrada hilaris by Using an Olfactometer. Southwester Entomologist: 42, 3: 719-724.

Joseph, Shimat V.. 2014. Bagrada bug monitoring: Does trap color influence bug captures? Salinas Valley Agriculture blog. August 7, 3014.

Joseph, Shimat V. and Richard Smith. Occurrence and abundance of Bagrada bug on brassica crops and weeds Salinas Valley Agriculture blog September 30, 2013

Photo credits (See attachment)

Successful Cover Cropping on

Organic Farms

 

Thursday, November 15th, 2018

3-5 pm  Followed by a potluck

Norton Hall  70 Cottonwood St.

Woodland, CA

No charge, but please RSVP here

 

e v e n t  o v e r v i e w

 

Join Jim Durst (Durst Organic Growers) and Eric Brennan (USDA) for an afternoon of conversation on the ins and  outs of successful on-farm production and management of cover crops.

 

Bringing decades of science and experience to the table, we will explore a range of topics including:

 

•The benefits

•Impacts on soil health

•Scheduling

•Yield effects

•Weed management

•Economics

•Selecting seed

•Irrigation

•Microbes

•Challenges

 

 

The learning lab will be discussion-based  and potluck style, and will be facilitated by Margaret Lloyd (UCCE Small Farms Advisor). Please bring a dish to share or simply join us.

 

about the farmer spotlight series

This is the first of four learning labs that will explore a variety of farm management topics related to soil health through conversation with a farmer and a researcher. Future topics: Soil organic matter; reducing tillage, beneficial soil microbes, and water. Stay tuned for the next spotlight series in January 2019.

 

Contact Margaret with question: mglloyd@ucanr.edu 530-564-8642

2 hours CCA, Crop Management

1 hours DPR credits requested

2 hours CEU for CURES 

(Nitrogen management plan self certification)

 

 

The University of California prohibits discrimination or harassment of any person in any of its programs or activities. (Complete nondiscrimination policy statement can be found at http://ucanr.org/sites/anrstaff/files/107734.doc)

Inquiries regarding the University's equal employment opportunity policies may be directed to Affirmative Action Contact and Title IX Officer, University of California, Davis, Agriculture and Natural Resources, 2801 2nd Street, Davis, CA 95618, (530) 750-1397; titleixdiscrimination@ucanr.edu.

 

Bacterial Wilt and Canker in Field-Grown Tomatoes in California

Clavibacter michiganensis subspecies michiganensis (Cmm)

Bacterial canker has periodic outbreaks that can cause significant damage in a single season from primary and secondary spread. It is a vascular disease of tomato that spreads easily during the season by superficial movement of the bacterium via workers and equipment. This disease causes loss of photosynthetic surface, wilting, premature death and unmarketable fruit. Control and management relies primarily on clean seed, healthy transplant practices, sanitation, and crop rotation.

SYMPTOMS

All plant stages are susceptible, though initial infection typically starts at the seedling stage. As seedlings, small, white raised spots may occur on the leaves,   wilting and possibly death. However, disease may not develop in infected seedlings until conditions are more optimal, resulting in asymptomatic infected seedlings that get planted.

Early symptoms in-field include wilting, curling of leaflets and browning of leaves. Due to the vascular location of the organism, symptoms are often limited to one side of the plant.   Early infection can be difficult to diagnose based on symptoms alone, but vigilance is important to minimize spread. Therefore, diagnosis of suspect plant material by a lab or a highly sensitive and effective in-field diagnosis kit is suggested.

Leaf symptoms are often called ‘firing' due to the scorched appearance and rapid development. Initial appearance is yellow to tan patches between veins, ¼ inch diameter on the upper leaf surface of mature leaves. The leaf margin turns brown with a yellow border. As the leaves die, the petioles remain green and firmly attached to the stem.

Fruit symptoms are small (⅛ inch), creamy white spots with tan/brown centers found on the upper, exposed parts of the fruit. These characteristic ‘Bird's-eye spots' may eventually become brown, necrotic and merge with other spots. Fruit symptoms can be observed at any stage, but are usually seen on green fruit ½ to 2” diameter.

Vascular discoloration, initially yellow, then light brown to reddish, can also be seen in the stem and petiole. Pith appears dry and mealy, as well as discolored. Yellow sticky fluid may emerge from cut stem when squeezed. Stems can split open, forming cankers that facilitate secondary spread.

Whole plant wilting begins with the lower leaves but travels up the stem. Infection tends to be more severe in plants infected early, as seedlings, versus late in their growth cycle due to secondary spread.

"Bird's-eye spots" is a classic symptom, but can be hard to find

Sunken stem cankers are often abundant as the disease advances

Unilateral (left) and vascular symptoms (right)

BIOLOGY and EPIDEMIOLOGY

Disease development is favored by warm (75-90°F), moist conditions. Greenhouse operations are highly susceptible to disease development.

Initial inoculum can come from several sources, including infected plant debris in soil, infected weed hosts, infected volunteer tomato plants, diseased transplants, contaminated wood stakes, and infested seed. Clean seed is very important, for disease can develop and spread rapidly under greenhouse conditions, and a 1% seed transmission rate is sufficient to give 100% disease. In-field spread occurs easily by workers' hands, equipment, during vine pruning, particularly when plants are moist with dew or irrigation water. Bacteria present in and on the plant can be transmitted to adjacent plants by pruning or abrasion wounds, or simply contact with infected leaves, entering through pores on the leaf margin (hydathodes) which links directly to the plant xylem vasculature.

Cmm can survive as free-living bacteria in soil for short periods, in non-decomposed tomato plant debris, on weed hosts (nightshade) and volunteer tomato/pepper plants, on contaminated stakes or equipment and in association with seed. Volunteer plants from a previous infection or susceptible weeds can maintain low levels of the pathogen. It survives better in cool, dry conditions than in hot, moist conditions.

CONTROL

Bacterial canker can be challenging to control because of challenges with early detection, the highly infectious nature of the disease, and the number of inoculum sources. Sanitation and preventative measures must be enforced.

• Use certified, disease-free seed from canker-free plants. The standard hydrochloric acid method or fermentation process should produce clean seed. However, these methods will not treat embryonic infection. Centrifuge extraction can lead to high levels of seed contamination.

• Certified disease-free transplants. It is not usually possible to identify infected seedlings at the time of transplanting.

• Remove disease plants as soon as possible. If infection occurs early in the season, infected areas should be plowed down to prevent spread to nearby healthy fields. Several healthy plants adjacent to symptomatic plants should also be removed.
• Hands, tools, shoes and crop support materials should all be disinfected. Hypochlorite (bleach) is not satisfactory as a disinfectant. Quartenary ammonium compounds are recommended.

• Copper-fungicide compounds in foliar sprays are not highly effective for bacterial canker control because they only act at the tissue surface while many of the bacteria are internal to the plant. Sprays should not be applied at high pressure as this may damage the plant (causing many micro-wounds) and lead to more disease. Fixed copper field sprays may help in protecting healthy plants, especially if only superficial symptoms are present.

• When leaves are moist with irrigation water or dew, do not allow movement through the field by workers or equipment

• Remove or plow in infected plants as soon as possible after harvest in order to ensure good decomposition. The bacterium cannot survive in soil for long, but can survive in the field in complex with plant material.

• Discard wooden stakes and strings from infected areas. The porous condition of wood makes sanitation imperfect.

• Rotate out of tomato, peppers, eggplant and related crops for 2-3 years

• Control Solanaceous weeds and volunteer tomatoes and peppers.

• There are currently no resistant tomato varieties for bacterial canker

REFERENCES
Koike, S., P. Gladders, and A. Paulus. (2007) Vegetable Diseases: A Colour Handbook. Boca Raton, FL: CRC Press.

http://vegetablemdonline.ppath.cornell.edu/factsheets/Tomato_Bacterial.htm#Click

https://extension.umn.edu/plant-diseases/bacterial-canker-tomato

Dr. Sally Miller, Dr. Ruguo Huang Bacterial canker of tomato, Asta: A commercial growers guide.

Jones, J. B., T. Zitter, M. T. Momol, and S. A. Miller. 2014. Compendium of Tomato Diseases and Pests, Second Edition. St. Paul, Minnesota: The American Phytopathological Society.

Special thanks to input from Dr. Gitta Coaker and Dr. Cassandra Swett.