Grower Notes and Pest News
Current status of the invasive Bagrada bug in California: geographic distribution and affected host plants
Bagrada bug [Bagrada hilaris (Burmeister)] is an invasive hemipteran insect (Family: Pentatomidae) that was first reported in Los Angeles County, California in 2008. It has now spread to several counties in California and is moving northwards.
Distribution: Citizen scientists have been instrumental in reporting the occurrence of Bagrada in various counties and are helping map its current distribution. As of September 2014, Bagrada bug is known to be present in Imperial, San Diego, Orange, Riverside, Los Angeles, San Bernardino, Kern, Kings, Inyso, Fresno, Ventura, Santa Barbara, Monterey, San Benito, Santa Cruz, San Mateo, Santa Clara, and Yolo Counties and is likely to be present in some other.
Distribution of Bagrada bug in various California counties as of September, 2014.
Bagrada bug is also spreading eastwards from California and is currently reported in Nevada, Arizona, Utah, New Mexico, and Texas.
Host plants affected: While Bagrada bugs are known to feed on a variety of host plants in addition to their preferred cruciferous hosts, serious damage to barley, corn, pepper, potato, tomato, and sunflower was recently reported by growers or gardeners. In a previous study where multiple food sources were offered, Bagrada bugs did not feed on tomatoes. They were also found on strawberries and reported to be present on other hosts, but damage has not been confirmed. Bagrada bugs might have been present on these plants as they move around in search of suitable food sources.
Backyard corn damaged by Bagrada bugs. (Photo by Larry Adcock, Arroyo Grande)
Pepper plant damaged by Bagrada bugs. (Photo by Rick Machado, Menifee)
Seriously damaged seed potato plants (above) and tubers (below). (Photo by Rick Machado, Menifee)
Bagrada bug damage to sepals on sunflower. (Photo by Larry Adcock, Arroyo Grande)
Bagrada bug feeding damage to tomatoes. (Photos by Rick Machado, Menifee, above and Jennifer Evangelista, San Luis Obispo, below)
Bagrada bugs on strawberry foliage. Not seen to cause any feeding damage. (Photo by Jennifer Evangelista, San Luis Obispo)
Management: Regular monitoring, mechanical exclusion or removal, destruction of weed hosts, and chemical, botanical, and microbial pesticides continue to be available management options. There have been several queries in the past two months from home owners, community garden operators, and organic growers about serious Bagrada bug infestations. Avoiding cruciferous and other hosts at risk should be a serious consideration for community and home gardens where using some of the currently available management options is difficult.
What to do: If you see Bagrada bug in an area or on a host that is not previously reported, please contact Surendra Dara at firstname.lastname@example.org or 805-781-5940. This information will be useful to track the distribution of this pest.
Biology, damage, and control video: www.youtube.com/watch?v=gSj3AZoJIRM
Biology, damage, and control: http://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=4047
Potential organic solutions: http://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=11031
Host preference: http://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=9611
General information: http://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=8438/span>
Adult tomato bug (Cyrtopeltis modesta) on backyard tomato plant. See its slender, greenish body and needle-like mouthparts. (Photo by Jessie Altstatt, Goleta)
A homeowner in Goleta recently reported severe infestation and damage of tomatoes by the tomato bug, Cyrtopeltis modesta (Distant) in their home garden. It also appears that they have become more frequent in recent years. This article provides an overview of the pest and some management options.
Tomato bug also known as tomato suck bug belongs to the family Miridae in the order Hemiptera. Lygus bug and other plant bugs also belong to the same family. There seems to be some confusion in the description of C. modesta (Engytatus modestus) and without a good key, identification of related species such as C. tenuis, C. geniculata, and Dicyphus spp. can be complicated.
Origin and distribution: Origin of C. modesta was not clear in literature, but Carvalho and Usinger (1960) referred to it as an American species while reporting a new species of Cyrtopeltis from Hawaii. Tomato bug is reported from Europe, South America, and North America and its related species from other parts of the world.
Biology and identification:
Adults are 7-8 mm or 0.25” long. Body is slender, pale and has a green or red tinge. Pronotum (shield like plate on the thorax) is narrow. Eyes are small. Wings are membranous, pale green or translucent. Nymphs look similar to adults, but without wings or with developing wing pads. There are four to five nymphal instars. Eggs are laid inside the petiole or the terminal shoots. Nymphs and adults actively feed.
Adult (above) and nymphal stages (below) of tomato bug. Nymphs can be seen with no wings or developing wing pads. (Photos by Jessie Altstatt, Goleta)
Nymphs and adults actively feed by inserting their piercing and sucking mouthparts in plant tissues and sucking the juices. Yellowish red rings develop around the stem as a result of feeding. These areas are corky and break easily leading to the dropping off of flowers or developing fruit. Tomato bugs are common in Central Valley and Southern California both in organic and conventional tomatoes. However, they are usually not a problem in large farms where pesticides are applied to manage major tomato pests. They can be a problem in home gardens and small farms where pesticide treatments are less common (Tom Turini, personal communication).
Damaged leaves and flower from tomato bug feeding. (Photo by Jessie Altstatt, Goleta)
There is no information available on natural enemies, pesticide treatments, or other management options specific to tomato bugs. Pesticides that are usually effective against lygus bugs (http://www.ipm.ucdavis.edu/PMG/r783301611.html) or stink bugs (http://www.ipm.ucdavis.edu/PMG/r783300211.html) in tomatoes can be effective against tomato bugs. Based on my research on other hemipterans, botanical insecticide/insect growth regulator – azadirachtin (especially against nymphal stages) and insect pathogenic fungi – Beauveria bassiana, Metarhizium brunneum (M. anisopliae), or Isaria fumosorosea (Paecilymyces fumosoroseus) can also be effective against tomato bugs. These could be good alternatives to chemical pesticides for home gardens.
Carvalho, J.C.M. and R. L. Usinger. 1960.New Species of Cyrtopeltis from the Hawaiian Islands with a Revised Key (Hemiptera: Miridae). Proc. Hawaiian Entomol. Soc. 17: 249-254.
Goula, M. and O. Alomar. 1994. Míridos (Heteroptera Miridae) de interés en el control integrado de plagas en el tomate. Guía para su identificación. Bol. San. Veg. Plagas 20: 131-143.
Letourneau, D. K. and B. Goldstein. 2001. Pest damage and arthropod community structure in organic vs. conventional tomato production in California. J. Appl. Ecol. 38: 557-570.
Swezey, O. H. 1925. Notes and Exhibitions (Sept. 4, 1924). Proc. Haw. Ent. Soc, 6:18.
University of Arizona http://ag.arizona.edu/ceac/sites/ag.arizona.edu.ceac/files/pls217nbCH4_3.pdf.
Spider mites are an important arthropod pest of strawberries in California. Plants are especially sensitive to damage early during the season. While the Oxnard area strawberries were hit by early and heavy infestations of spider mites, especially the twospotted spider mite, Tetranychus urticae, several growers in the Santa Maria area reported achieving good control by releasing predatory mites and timely applications of miticides. Predatory mites continue to play a major role in managing spider mites in strawberries and it is important to understand the impact of miticide applications on these beneficial arthropods.
Miticides vary in their impact on natural enemies and their safety to predatory mites is usually determined based on laboratory assays. This information is critical in making treatment decisions when predatory mites are also used for spider mite management. This article presents predatory mite (Phytoseiulus persimilis and Neoseiulus spp.) data from miticide evaluation studies conducted on commercial strawberry fields in 2011, 2012, and 2013 in Santa Maria.
2011: A small study was conducted to evaluate the efficacy of abamectin (Agri-Mek 0.15 EC, 16 fl oz/ac) and cyflumetofen (Nealta SC, 13.7 fl oz/ac) where treatments were applied twice using a backpack sprayer. A 100 gal/ac of spray volume was used. The second treatment was made 21 days after the first. Ten mid-tier leaflets from each plot were randomly collected and mites were counted using a mite brushing machine. Predatory mite numbers were available only from observations made 27 days after the second treatment. The average number of predatory mite adults was 2.5, 0.5, and 0.75/leaflet for untreated control, abamectin, and cyflumetofen, respectively.
2012: A small plot study was conducted using abamecting (Agri-Mek 0.15 EC, 16 fl oz/ac), bifenazate (Acramite 50WS, 1 lb/ac), entomopathogenic fungus, Beauveria bassiana (BotaniGard 22WP, 4 lb/ac), B. bassiana (BotaniGard 22WP, 4 lb/ac) + fenpyroximate (Fujimite 5EC, 2 pt/ac), cyflumetofen (Nealta SC, 13.7 fl oz/ac), fenpyroximate (Fujimite 5EC, 2 pt/ac), and spirotetramat (Movento, 5 fl oz/ac). Treatments were applied only once using a backpack sprayer (200 gal/ac for all and 150 gal/ac for B. bassiana treatments) and mite counts were made 0, 3, 7, 14, 21, and 28 days after treatment (DAT). Four days after the treatment, Microthiol Disperss was applied as a fungicidal treatment across the entire field and that could have had an impact on spider mite and predatory mite populations. Average number of predatory mite egg and mobile stages varied across different observation dates, but the differences were not statistically significant (Tukey's HSD P > 0.05).
Number of predatory mite eggs and mobile stages at different time intervals before and after a single application of various miticides in a field study in 2012.
Pre-treatment numbers and post-treatment average for eggs and mobile stages of predatory mites, 2012.
Percent change in eggs and mobile stages of predatory mites after treatment (average for post-treatment counts), 2012.
It was not clear why there were fewer predatory mite eggs and mobile stages in untreated control than some of the treatments throughout the observation period. When the percent change in post-treatment average was compared to the pre-treatment average, there was a 50-480% increase in predatory mite eggs and 7-280% increase in mobile stages in various treatments except for bifenazate where there was a 37% decrease in the number of eggs and no change in mobile stages.
2013: In a small plot trial, the efficacy of bifenazate (Acramite 50WS, 1 lb/ac), abamecting (Agri-Mek SC, 4.29 fl oz/ac), B. bassiana (BotaniGard ES, 1 qrt/ac) + bifenazate (Acramite 50WS, 0.75 lb/ac), Eco-Mite (rosemary and cotton seed oil, 1%), fenpyroximate (Fujimite 5EC, 2 pt/ac), fenpyroximate (Fujimite XLO, 2 pt/ac), Chromobacterium subtsugae strain PRAA4-1 (Grandevo, 2 lb/ac), Burkholderia spp. strain A396 (Venerate XC, 2 gal/ac), and cyflumetofen (Nealta SC, 13.7 fl oz/ac) was compared. Treatments were applied twice at weekly intervals using a backpack sprayer at 150 gal/ac rate. Mites were sampled 3 and 7 days after each application.
There was some variation in predatory mite populations in treated and untreated plots throughout the observation period. Significant differences were seen only on observations made 3 days after the first spray in eggs and 7 days after the first spray in mobile stages (Tukey's HSD P < 0.05).
Number of eggs and mobile stages of predatory mites on 3 and 7 days after first and second applications of various miticides, 2013.
Average number of eggs and mobile stages of predatory mites from four observation dates following two miticide applications, 2013.
Although the number of predatory mites or their eggs was not statistically different, average for four observation dates indicates their response to chemical, botanical, and microbial miticides.
These results may not correspond with those from laboratory studies conducted under controlled conditions, but they show the relative abundance of predatory mites in response to various miticides under field conditions./span>
Natural enemies play an important role in managing pest populations. Using predatory mites in strawberries against spider mites is a good example where growers take advantage of the potential of the natural enemies. Multiple species of predatory mites are commercially available and several California strawberry growers use biological control as a complementary tool to chemical control.
Predatory mites belong to four categories – Type I, Type II, Type III, and Type IV.
Type I: These predatory mites are specialists feeding exclusively on spider mites (family Tetranychidae) that produce considerable webbing. They require feeding on spider mites for their survival and reproduction. Type I predators are aggressive and voraciously feed on pest mites. Because of their dependence on spider mites, Type I specialists rapidly decline and cannibalize when pest mite populations decline.
Type II: These are also specialist predators, but they feed on spider mites and other species of mites. They also feed on pollen and in some cases on thrips and other species of predatory mites. Having more food choices for survival and reproduction, Type II specialists continue to be present in the absence of spider mites and are less likely to cannibalize.
Type III: These are generalist predators that feed on multiple species of mites that include spider mites, eriophyid mites, and tarsonemid mites and insects such as thrips and whiteflies. They also feed on pollen, honeydew, and plant juices. Type III generalists are also known to cannibalize and feed on other species of predatory mites in the absence of pest mites or other food sources.
Type IV: These mites primarily feed on pollen and can also feed on pest mites.
There are five species of predatory phytoseiid mites (Acari: Phytoseiidae) that are commercially available for spider mite control.
Phytoseiulus persimilis Athias-Henriot is a Type I specialist that exclusively feeds on spider mites. It is bright orange, teardrop-shaped and moves rapidly. It prefers cooler temperatures and is sensitive to hot and dry conditions. So, it is more effective during earlier parts of the production season before temperatures increase.
Egg and adult of Phytoseiulus persimilis. Egg is slightly oval and larger than twospotted spider mite eggs, which are round. Being able to identify predatory mites and their eggs is important during pest monitoring (Photo by Surendra Dara).
Neoseiulus fallacis (Garman) is a Type II specialist that primarily feeds on spider mites. It is translucent to peach or orange and appears to have a flatter body compared to spider mites or P. persimilis. It is also sensitive to hot and dry conditions.
Neoseiulus californicus (McGregor) is a Type II specialist that primarily feeds on spider mites, but also has Type III generalist characters. It appears similar to N. fallacis. It can withstand warmer conditions better than P. persimilis and N. fallacis. It can withstand cold temperatures for short periods and tolerates relative humidity range from 40-80%.
Egg and adult of Neoseiulus sp. Similar to the P. persimilis egg, this is also large and oval (Photo by Surendra Dara).
Galendromus occidentalis (Nesbitt) also known as western predatory mite is a Type II specialist that primarily feeds on spider mites. It prefers warm temperatures and tolerates dry conditions as low as below 30% relative humidity. It is sensitive to cooler temperatures.
Egg and adult of Galendromus occidetalis along with spider mite egg in the middle. Photo by Jack Kelly Clark, UC IPM.
Amblyseius andersoni (Chant) is a Type III generalist predator. It can tolerate high temperatures when relative humidity is high.
Among these predatory mites, P. persimilis, N. fallacis, and N. californicus are the most commonly used species in strawberries. Using the right species depending on the environmental conditions is important for the success of biological control. Timing insecticide and acaricide applications in a manner that is least disruptive to the predatory mites is essential. When chemical pesticides are necessary, softer materials should be selected.
In addition to the predatory mites, several species of natural enemies feed on spider mites. They include big-eyed bug (Geocoris spp.), black lady beetle (Stethorus sp.), black rove beetle (Oligota oviformis), brown lacewing (Hemerobius spp.), damsel bug (Nabis spp.), green lacewing (Chrysopa spp.), minute pirate bug (Orius tristicolor), predatory midge (Feltiella acarivora), and the predatory sixspotted thrips (Scolothrips sexmaculatus).
Top row: Big-eyed bug, black lady beetle, black rove beetle, brown (upper), and green lacewing (lower)
Bottom row: Damsel bug, predatory midge larva, minute pirate bug, and sixspotted thrips.
Photos by Jack Kelly Clark, UC IPM.
Croft, B. A., L. N. Monetti, and P. D. Pratt. 1998. Comparative life histories and predation types: are Neoseiulus californicus and N. fallacis (Acari: Phytoseiidae) similar type II selective predators of spider mites? Econ. Entomol. 27: 531-538.
Çakmak, I. A. Janssen, and M. W. Sabelis. 2006. Intraguild interactions between the predatory mites Neoseiulus californicus and Phytoseiulus persimilis. Exp. Appl. Acarol. 38: 33-46.
Rincon-Vitova. 2009. Catalog of beneficials. Rincon-Vitova Insectaries, Inc. (http://www.rinconvitova.com/CATALOG%202009%20screen.pdf)
Comparing lygus bug and natural enemy populations in organic and conventional strawberry fields in Santa Maria
Integrated pest management recommends using multiple approaches such as selection of resistant varieties, manipulation of habitat and modifying cultural practices in a manner that is not beneficial to the pest, and conserving natural enemies before using pesticides. In certain production systems that have well established agronomic practices with limited scope for modifying the habitat or cultural practices, pest management is primarily dependent on pesticide applications. There are several options for conventional strawberry production where pesticides from different classes (based on their mode of action) can be used against one or more pests. However, these options are limited in organic strawberries. As a result, some growers put a major emphasis on conserving natural enemies and timing the application of organic oils, pyrethrins, and other products in a manner that is least disruptive to natural enemies.
In a 2009 study, seasonal average for lygus bug (Lygus hesperus) numbers did not show a specific trend between organic and conventional strawberry fields. The average number of nymphal and adult stages of lygus bugs, from mid-May to the end of August, was 12.6 from 20 plants in an organic field. This average was 15.6 (between mid-May and mid-July) in a conventional field and 7.7 (between mid-May and mid-August) in another conventional field. Conventional fields received several pesticide applications while the organic field received only two during the study suggesting that pesticide applications did not really help to bring lygus populations below threshold levels (1 lygus bug nymph per 20 plants). As the natural enemy populations were not monitored during this study, the impact of pesticide applications on their numbers or their role in managing lygus populations was not clear.
To understand the lygus bug and their natural enemy interactions more, another study was conducted in 2013 on a commercial organic and a conventional strawberry field in Santa Maria. Observations were made at weekly intervals from June 24 to July 15 where 10 randomly selected plants from each of the four quadrants of an acre area were sampled using a beating tray. The number of young (1st-3rd instar) and mature nymphs (4th to 5th instar) and adults of lygus along with their natural enemies – big-eyed bugs (Geocoris spp.), minute pirate bugs (Orius spp.), green lacewings (unknown), damsel bugs (Nabis spp.), parasitic wasps (unknown), lady beetles (multiple species), and spiders (multiple species) was recorded.
Among various materials that were applied in the conventional field, abamectin (Epi-Mek 0.15 EC applied once), sodium tetraborohydrate decahydrate (Prev-Am, applied thrice), and sulfur (Microthiol Dispress applied once) were primarily used as acaricides. Novaluron (Rimon 0.83EC) was applied on May 22, about one month prior to the first sampling. Aadjuvant, pinene (polyterpenes) polymers (Miller Nu Film P) was also applied thrice between May 7 and June 22. In the organic field, neem oil (Trilogy) and alcohol ethoxylate (OROBOOST) were each applied thrice between May 1 and July 11.
A higher number of lygus bugs were seen in the organic field than in the conventional field throughout the observation period. While the older nymphs and adults stayed at or below the treatment threshold, younger nymphs were consistently above the threshold (2.5 to 4 per 20 plants) in the conventional field. In the organic field, they were consistently above the treatment thresholds during the observation period.
Occurrence of lygus bug nymphs and adults in a conventional and an organic strawberry field in Santa Maria from Jue 24 to July 15, 2013.
When the average number of natural enemies for the observation period was considered, the organic field had more big-eyed bugs than the conventional field. The organic field also had slightly higher numbers of minute pirate bug and lady beetles. Very low numbers of lacewings or parasitic wasps were present only in the organic field. In general, damsel bug numbers were also very low, but they were slightly higher in the conventional field. A higher number of spiders were seen in the conventional field compared to the organic field.
Although some key species of natural enemies were present at higher numbers in the organic field, they were not able to keep the lygus populations under control. On average, there were 10 natural enemies of all species per 20 plants in the conventional field and 12 in the organic field during the observation period. Applying novaluron at the right time appeared to control lygus bug nymphs and prevented population build up there after in the conventional field. While natural enemies generally play a significant role, this study suggests the importance of other options such as pesticides for managing lygus bugs.
Acknowledgements: Thanks to Dave Peck (Manzanita Berry Farms and Eraud Farms, Santa Maria) for his collaboration and Chris Martinez for technical assistance.