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Posts Tagged: Lygus bug
Emily Bick's AAUW Grant: Targeting the Lygus Bug
Watch out, lygus bugs! Agricultural entomologist Emily Bick is targeting you. Lygus hesperus, a serious pest of strawberries--as well as cotton, and seed crops such as...
Agricultural entomologist Emily Bick doing field work in Denmark before the lockdown due to the coronavirus pandemic precautions..
Emily Bick (right) in an engagement photo with her fiance, Nora Forbes. Bick is an agricultural entomologist and a postdoctoral fellow in the lab of Lene Sigsgaard at the University of Copenhagan and Forbes is a statistician at the Danish Medtronic office.
A Big Cheer for a Crab Spider
What happened in our pollinator garden on June 3 probably would have promoted a standing ovation from agriculturists who grow cotton, strawberries, sugarbeets, tomatoes,...
A crab spider nails an agricultural pest, a lygus bug. (Photo by Kathy Keatley Garvey)
Lygus bug management during and at the end of the strawberry production
Lygus bug (Lygus hesperus) adult (above) and young nymph (below). (Photos by Rodney Cooper, USDA-ARS and Surendra Dara)
Lygus bug or the western tarnished plant bug, Lygus hesperus is a major pest of strawberries in California (Zalom et al. 2014). Lygus bug has a wide host range that includes more than 100 species of cultivated crops and wild host plants (Scott, 1977; Fye, 1980 and 1982; Mueller et al., 2005) that include cultivated crops such as alfalfa, broccoli, celery, cauliflower, grapes, strawberries, and tomatoes on the California Central Coast. Additionally, ornamental and vegetable crops in greenhouses or home gardens along with weedy hosts from Chenopodiacae, Compositae, and Cruciferae in vast uncultivated landscapes offer a continuous food supply for lygus bug throughout the year. Warmer and dryer conditions as experienced in the recent years can also contribute to increased lygus bug problems. Milder winters fail to bring down overwintering populations and drought conditions dry out wild hosts early in spring forcing lygus bugs to migrate to cultivated crops. Under these circumstances, timely monitoring and implementation of appropriate management practices is necessary to limit damage and spread of lygus bugs to other crops. Vegetable crops such as celery are reported to have an increased risk of lygus bug damage in recent years (Dara, 2015a).
Damage
Lygus bugs primarily feed on inflorescence and developing seeds. They can also feed on foliage by sucking plant sap, but seeds which are rich in protein and lipids are important for the reproductive success of lygus bugs. Depending on the crop and crop stage, lygus damage can result in bud and flower loss, blemishes on seeds, necrotic spots on stems, or deformity of the fruit. In strawberries, fruit deformity caused by lygus bug renders fresh berries unmarketable. However, nearly 1/3 of the fruit deformity in strawberries is caused by factors other than lygus bug (Dara, 2015b).
Strawberry fruit deformity likely from lygus bug feeding (Photo by Surendra Dara)
Management
Lygus bugs typically move into strawberry or other cultivated crops from weedy hosts in the wild habitats in April. However, seasonal weather conditions can alter these typical patterns. In a typical fall planting of strawberries, three generations of lygus bugs can be seen. But summer-plantings, extended season for fall-plantings, or early planting of fall strawberries make the crop available almost throughout the year. Improper management of lygus or any pest can lead to increased problems in crops where the pest is not usually a problem.
While UC IPM guidelines provide details of lygus bug management in strawberries and celery, here are some important points for managing lygus bug in strawberries during and at the end of the fruit production season:
Biological control:
- Several species of predatory and parasitic arthropods provide natural control of lygus bug. Big-eyed bug (Geocoris spp.), damsel bug (Nabis spp.), minute pirate bug (Orius tristicolor), and multiple species of spiders are among the predacious arthropods. Parasitic wasps that attach eggs (Anaphes iole) and nymphs (Peristenus relictus) are commonly found in strawberries. Conserving natural enemies by providing flowering hosts as refuges and selecting chemicals that are less harmful can contribute to biological control.
Cultural control:
- Manage weeds near and around strawberry fields that serve as sources of lygus bug infestations.
- Some studies suggest growing strips of alfalfa or flowering hosts that attract lygus bugs and managing them with pesticides or vacuuming. This practice requires close monitoring to prevent dispersal of lygus bugs to strawberries.
Chemical control and biopesticides:
- A variety of chemicals that belong to different mode of action groups are registered for lygus bug in strawberries. Select appropriate label rates to obtain desired control. Using surfactants and proper application techniques can improve control efficacy.
- Rotate chemicals from different mode of action groups to reduce the risk of resistance development.
- Use appropriate materials for appropriate life stages of the pest. For example, an insect growth regulator like novaluron (Rimon) is effective against nymphal stages. To control a mixed population of nymphs and adults, novaluron can be used with other insecticides. Botanical insect growth regulator like azadirachtin (e.g., AzaGuard, Debug Turbo, Molt-X, and Neemix), which also has insecticidal properties, can be used with chemical pesticides. Microbial pesticides based on insect pathogenic fungi such as Beauveria bassiana (BotaniGard), Isaria fumosorosea (Pfr-97), and Metarhizium brunneum (Met52) in combination with azadirachtin or chemical pesticides can also be used as a part of the lygus IPM program.
Mechanical control:
- Bug vacuums can help remove lygus bugs from strawberry plants. They are typically run twice a week at a speed of 2 mph. Improved design and increased number of passes each time can enhance the control efficacy. Vacuums may not be effective in removing all life stages of lygus bugs and may also remove beneficial arthropods.
Control specific to end of the season:
- Do not neglect managing lygus until the end of the fruit production. Negligence can lead to the spread of the pest to neighboring fields requiring aggressive management practices. Such a situation that demands additional pesticide applications can lead to insecticide resistance in the long run.
- Some growers indicated that sulfuric acid applied as soil amendment at the end of the season helped in controlling lygus bugs. This practice is, however, not recommended for lygus management.
IPM strategies:
Several IPM studies in the Santa Maria area with a focus on lygus bug management provide information on effective chemical and non-chemical options.
- 2012: //ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=9595
- 2013: //ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=19290
- 2014: //ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=19294
- 2015: //ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=19641
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References
Dara, S. K. 2015a. Increasing risk of lygus bug damage to celery on the Central Coast. (//ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=19221)
Dara, S. K. 2015b. Role of lygus bug and other factors in strawberry fruit deformity. (//ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=19630)
Fye, R. E. 1980. Weed sources of lygus bugs in the Yakima Valley and Columbia Basin in Washington. J. Econ. Entomol. 73: 469-473.
Fye, R. E. 1982. Weed hosts of the lygus (Heteroptera: Miridae) bug complex in Central Washington. J. Econ. Entomol. 75: 724-727.
Mueller, S. C., C. G. Summers, and P. B. Goodell. 2005. Composition of Lygus species found in selected agronomic crops and weeds in the San Joaquin Valley, California. Southwest. Entomlo. 30: 121-127.
Scott, D. R. 1977. An annotated list of host plants for L. hesperus Knight. Bulletin of the Entomological Society of America 23: 19-22.
Zalom, F. G., M. P. Bolda, S.K. Dara, and S. Joseph., 2014. UC IPM pest management guidelines: strawberry. University of Californi a Statewide Integrated Pest Management Program. Oakland: UC ANR Publication 3468.
Role of lygus bug and other factors in strawberry fruit deformity
Lygus bug nymphal and adult stages
Lygus bug or western tarnished plant bug (Lygus hesperus) is a major pest in California strawberries and causes significant yield losses by contributing to the fruit deformity. Lygus bug is a hemipteran insect and has piercing and sucking mouthparts. They prefer plant parts rich in proteins and lipids. Developing berries and achenes offer as a good source of nutrition in strawberries and hence they are normally seen in the inflorescence. When lygus bug inserts its mouth parts and sucks the plant juices, the tissue at the site of feeding does not grow normally resulting in fruit deformity as berries develop. Deformed berries are not marketable for fresh market and growers adopt various control strategies to manage lygus bugs and limit damage. Chemical pesticides are the popular choice for managing lygus bugs and the use of bug vacuums is also increasing in the recent years.
While the treatment threshold is one lygus nymph/20 plants, infestations are generally very high above the threshold requiring aggressive management practices. Although treatment decisions are typically made based on lygus sampling, it is not uncommon (based on personal communication with some growers and PCAs) for fruit deformity to influence treatment decisions. In light of this scenario, it is important to determine the role of lygus bug in deformed strawberries among other causes such as poor pollination, genetic factors, and environmental conditions such as cold temperatures.
Literature suggests that fruit deformity due to lygus and other causes can be determined by the size of achenes (Zalom et al., 2014). Achenes in the deformed and normal areas of the fruit are more or less of the uniform size if the deformity is due to lygus bug. Achenes are of different sizes if the deformity is due to factors other than lygus damage.
A study was conducted in September, 2015 to evaluate the role of lygus bug and other factors in strawberry fruit deformity. Deformed berries were collected from 18 conventional and 10 organic strawberry fields. Conventional fields were sampled nine times and organic fields were sampled 5 times. On each sampling date a field block was divided into four quadrants and at least 100 deformed berries were collected from each quadrant. Each berry was examined categorized as lygus- and non-lygus-related based on the size of the achenes and shape of the berry. Data were subjected arcsine transformation and statistical analysis and significant means were separated using Tukey's HSD test.
In general, lygus bug damage was significantly higher (P = 0.0002) in organic fields than in conventional fields. When the causes for the deformity were compared, the proportion of deformed berries due to lygus bug damage was significantly higher (P < 0.00001) than those due to other causes in both conventional and organic fields. It is, however, important to note that 41% of the deformity in conventional fields and 33% in organic fields was due to factors other than lygus bug. These results are important in understanding the role of various lygus bug and other factors in causing fruit deformity and making appropriate treatment decisions. Sampling the fields for lygus bugs is always the right way to make a treatment decision rather than counting on deformed berries.
Information on lygus bug biology, sampling, and management can be found at the following resources:
Lygus bug biology and damage video: www.youtube.com/watch?v=7sZu9nirOPQ
Lygus bug monitoring and treatment threshold video: https://www.youtube.com/watch?v=Z7o7fafxuhE
Lygus bug management video: https://www.youtube.com/watch?v=5-4qcvceqmU
UC IPM Pest Management Guidelines: http://www.ipm.ucdavis.edu/PMG/r734300111.html
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Reference
Zalom, F. G., M. P. Bolda, S. K. Dara, and S. Joseph (Insects and Mites). 2014. UC IPM Pest Management Guidelines: Strawberry. University of California Statewide Integrated Pest Management Program. Oakland: UC ANR Publication 3468. June, 2014.
/span>Increasing risk of lygus bug damage to celery on the Central Coast
The western tarnished plant bug, Lygus hesperus has a wide host range and is an important pest of many crops. It is commonly referred to as lygus bug and is a major pest of strawberries on the California Central Coast. In the recent months, it has emerged as a major threat to celery causing significant yield losses which, in some cases, lead to a complete loss of the crop.
Lygus bug feeding causes fruit deformation in strawberry, but the damage is quite different in celery. Lygus bug punctures celery stalks with its piercing and sucking (needle-like) mouthparts to feed on plant juices. Damaged tissue results in brownish, sunken, elongated lesions. Such lesions are usually seen below the first node, but feeding of the nymphs (or adults) on the inner and developing parts can result in dark spots and twisted or distorted growth.
Nymphal instars and adult L. hesperus.
Lygus bug is a hemipteran pest (Family: Miridae) and prefers to feed on plant parts that are high in lipid and protein content such as developing seeds. Flowering weed hosts such as wild mustard and wild radish and cultivated crops such as alfalfa are among the favorite hosts of the lygus bug compared to strawberries or celery. However, when vegetation in the uncultivated areas dries out in late spring, lygus populations disperse in search of food and migrate to other crops. Intensive agriculture on the fertile and environmentally ideal Central Coast offers a never ending food source of a variety of crops to the lygus bug.
Drought and warmer conditions can dry up wild habitats and force the migration of lygus bug populations sooner than usual. Pests require less time to develop and complete their life cycle in warmer climate resulting in increased infestations. Cold temperatures during winter months typically reduce populations of several pests, but milder winters aided by an endless supply of food sources may also contribute to the carryover of lygus bug and other pests to the following season resulting in continuous and/or early infestations. Under these circumstances, using degree-day models or other such tools appear to be impractical in predicting lygus infestations.
Farms have boundaries, but pests do not have such limitations and freely move from one field to another. Effective pest management is thus necessary not only to limit damage to the infested fields, but also to limit the spread to other fields. In 2013, ineffective management of whiteflies on strawberries lead to their build up and resulted in the outbreak of an uncommon disease known as viral decline of strawberry (pallidosis-related decline). Increased outreach helped growers to take appropriate management decisions and reduce whitefly vector populations. Similarly, effective and timely management of lygus bug on strawberries or other hosts is very important to prevent their spread to other crops.
When a pest issue emerges, it is not uncommon to put an emphasis on chemical pesticides for bringing populations down to manageable levels. However, efficacy of various pesticides vary due to their modes of action and other factors and resistance of some populations make otherwise effective chemistries less efficacious. It is important to implement IPM strategies and use cultural, biological, botanical, chemical, microbial, and other options rather than relying on one or two options for managing lygus bug and other pests. When chemical pesticides are used, rotate among different modes of action groups to reduce the risk of resistance development.
According to the Santa Barbara County Ag Commissioner's office, failure to take timely actions to manage a pest that could become a major issue to the neighboring fields, can have legal implications.
Lygus bug management on strawberries and celery can be found at the following sources:
Strawberry:
- UC IPM: http://www.ipm.ucdavis.edu/PMG/r734300111.html
- 2012 Santa Maria Study: //ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=9595
- 2013 Santa Maria Study: http://capca.com/assets/magazine/February2014/index.html#/34/
- 2014 Santa Maria Study: http://capca.com/assets/magazine/February2015/index.html#/40/
Celery:
- UC IPM: http://www.ipm.ucdavis.edu/PMG/r104300411.html
To know more about lygus bug management and recent IPM studies, attend the Annual Santa Maria Strawberry Meeting on 10 November, 2015 at the Santa Maria Library. Register at http://ucanr.edu/2015strawberrymeeting.
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