Bagrada hilaris
(painted bug)

Bagrada hilaris is a hemipteran insect with a host range of over 70 plant species in 23 families. A major pest of crucifers in its native land, many Asian and African countries, the pest’s geographical range of distribution has recently expanded to Europe and the Americas. It has been a serious pest in India since the early twentieth century. It is reported in localized areas in Italy and Malta. First detected in North America in 2008 in California (USA), this bug has spread to coastal production regions in California, several southern states of the USA, Hawaii and Mexico. The worldwide distribution of its host plants, the ability to reproduce quickly in a suitable environment and the absence of natural enemies in new habitats show the potential of B. hilaris to expand and establish in new areas, especially warmer regions of the western world.

B. hilaris is native to Africa and Asia. In Africa, it is reported in the eastern and southern parts of the continent (Infonet-Biovision, 2015). In Asia, it is present mainly in South Asia and the Middle East (Joseph, 2014). It has been a problematic pest of brassicaceous crops in India since the 1900s (Rakshpal,1949). In its non-native habitat, it has been reported in Europe on Pantelleria island, Italy as a pest on caper (Capparis spinosa) and in Malta (Infantino et al., 2007). It was first reported in the USA (California) in 2008, and has since spread to coastal regions of California and neighbouring states. It has recently been reported in Chile and Mexico (Sánchez-Peña, 2014; Faúndez et al., 2016).

B. hilaris has a broad host range and host plants are available worldwide. This bug can reproduce quickly in warmer climates and lacks natural enemies in new habitats. These features make B. hilaris a potentially risky pest for introduction to areas where it is not currently present, particularly in warmer regions of the western world. Though deliberate introductions are unlikely to occur because there is no explicit value of this insect, B. hilaris may be indirectly transported to new areas through the movement of produce (Matsunaga, 2014).

B. hilaris is primarily a pest of crucifers. In South Asian countries, oilseed Brassica crops such as oilseed rape (Brassica napus var. oleifera) are the most common hosts. On the island of Pantelleria in Italy (Colazza et al., 2004), host plants of B. hilaris include crops such as caper (Capparis spinosa). Hosts also include many non-Brassica crops such as maize (Zea mays), pearl millet (Pennisetum glaucum) and wheat (Triticum aestivum) during outbreak years. Thus, the primary habitat of this pest includes cultivated crop fields and the surrounding area where it can find non-cultivated wild hosts. Moreover, a recent report from Chile shows that B. hilaris may invade residential buildings and urban habitats (Faúndez, 2018).

Palumbo et al. (2016) lists 74 plant species in 23 families, including 56 crops, 13 weeds and five ornamentals, as hosts of B. hilaris. However, many of these plants are believed to be ‘bridging hosts’ that B. hilaris infests when Brassica host plants are absent between planting seasons (Palumbo et al., 2016). Reed et al. (2013) and Huang et al. (2014) reported that brassicaceous plants are the primary hosts of this insect. Among the brassicaceous plants, studies have shown that B. hilaris prefers plants such as radish (Raphanus sativus) to red cabbage (Brassica oleracea var. capitata). Other plant hosts such as sweet alyssum (Lobularia maritima), arugula (Eruca vesicaria) and broccoli (B. oleracea var. italica) are less attractive (Huang et al., 2014).

Reed et al. (2013) reported that plants such as Capsicum annuum, Chenopodium spp., Coriandrum sativum, Cucumis melo, C. sativus, Cucurbita foetidissima, C. pepo, Glycine max, Lactuca sativa, Lotus corniculatus, Nicotiana glauca, Senecio vulgaris, Solanum nigrum, S. lycopersicum, Sonchus spp., Spinacia oleracea and Vicia faba are not hosts of B. hilaris.

Several parasitic wasps have been identified as biocontrol agents of B. hilaris in India and Pakistan (Samuel, 1942; Chacko and Katiyar, 1961; Mani and Sharma, 1982; Ghosal, 2006; Mahmood et al., 2015). These include egg parasitoids, mostly in the family Platygastridae, and include several species of Telenomus (=Liophanurus), Paratelenomus, Gryon (= Hadrophanurus), Trissolcus and Ooencyrtus.

Egg parasitoids of B. hilaris in the family Scelionidae have been collected and identified in Mexico (Felipe-Victoriano et al., 2019). However, the rate of parasitism for these parasitoids appears to be low in the field. No natural enemies specific to B. hilaris have been reported in the USA (Reed et al., 2013). Dipteran parasitoids of adult B. hilaris (Crosskey, 1984) include sarcophagid and tachinid flies (Anwar Cheema et al., 1973). The efficacy of these natural enemies is unknown.

Chemical defence, emissions from the scent glands, makes B. hilaris less prone to predatory arthropod attack. However, there are reports of some predators that prey on painted bug. Many of these predators are thought to have significantly less impact on the regulation of painted bug populations. Some of those predators include the reduviid bug (Rhynocoris segmentarius) that feeds on nymphs and adults of B. hilaris (Gunn, 1918). Other predators observed to feed on painted bug nymphs or adults include spiders (Araneae), mantids, predatory heteroptera (Zelus sp.) (Palumbo et al., 2016) and a predatory mite (Bochartia sp.) (Thakar et al., 1969).

Human food and beverage

• Emergency (famine) food

There are currently no monitoring techniques specific to B. hilaris. However, Reed et al. (2013), from observation of B. hilaris activity on cole crop seedlings, suggested that sampling should be performed during mid-morning to late afternoon when painted bug activity is highest. Huang et al. (2014) reported that B. hilaris is most active between mid-morning (10.00 h) and late afternoon (16.00 h) when ambient temperatures are >29°C.

B. hilaris has been observed feeding on seedlings immediately after emergence. Therefore, sampling is recommended when seedlings begin to emerge (Reed et al., 2013). The young seedlings should be checked thoroughly for the presence of B. hilaris adults and feeding damage. Sampling of larger or transplanted seedlings (i.e., two- to three-leaf stage or larger) should involve thorough inspection of the undersides of leaves, the stem and the soil surface (Palumbo et al., 2016).

The colour pattern of B. hilaris adults and nymphs resembles some other stink bugs and ladybeetle adults in the USA (LeVeen and Hodges, 2015). The adults resemble and may be confused with, harlequin bug, Murgantia histrionica, another related stink bug, due to similarity in colouring pattern. However, painted bugs are smaller, about a quarter to a third of the size, and have smaller orange markings than harlequin bugs.

Due to the variable regulations around (de)registration of pesticides, your national list of registered pesticides or relevant authority should be consulted to determine which products are legally allowed for use in your country when considering chemical control. Pesticides should always be used in a lawful manner, consistent with the product's label.

Cultural Control and Sanitary Measures

Field sanitation is important in minimizing B. hilaris infestation in crops. Sanitation measures involve the removal of crop residues from the field after harvest and keeping the field and surrounding habitat free of wild hosts (Infantino et al., 2007; Sachan and Purwar, 2007; Hill, 2008; Nyabuga, 2008). Cultivation of vegetable beds to kill the eggs of B. hilaris in the soil has been recommended for control (Bok et al., 2006). Keeping the plant stand healthy by the application of fertilizer, especially nitrogen, and keeping the plants free of moisture stress may reduce damage to seedling crops (Parsana et al., 2001). Similarly, varying the planting times of Brassica crops has also been used to avoid pest damage (Parsana et al., 2001; Ahuja et al., 2008).

In the USA, many direct-seeded Brassicas are now transplanted to minimize the severity of damage by B. hilaris (Reed et al., 2013).

Literature from the early twentieth century has indicated that mustard was successfully used as a trap crop to divert painted bugs away from cabbage (Brassica oleracea var. capitata) fields (Howard, 1907). More recent studies have shown that the use of Indian mustard (Brassica juncea) to attract B. hilaris away from the main crop, followed by insecticide sprays, was effective in reducing damage by the pest (Reddy, 2013). Huang et al. (2014) found that B. hilaris preferred radish (Raphanus sativus) to other Brassica crops suggesting that it was a good candidate as a trap crop for painted bug.

Physical/Mechanical Control

Many small-scale growers have traditionally removed painted bugs by hand to manage the pest (Nyabuga, 2008). Other methods of physical control include the use of cloth cover or mosquito netting to keep B. hilaris from feeding on plants (Howard, 1907).

Biological Control

Several species of hymenopteran parasitoids have been found to parasitize the eggs of B. hilaris (Chacko and Katiyar, 1961; Mani and Sharma, 1982; Ghosal et al., 2005) in the Old World. Similarly, a species of tachinid parasitoid (Rakshpal, 1949) has been reported to attack the adults. In the New World, laboratory studies have indicated that some generalist parasitoids can attack the eggs of B. hilaris. However, the behaviour of B. hilaris, laying eggs individually or in small masses in the soil, makes attack by generalist predators more difficult. No native natural enemies that specifically target B. hilaris in the USA have been reported.

Chemical Control

The use of synthetic chemicals is a primary method of control for B. hilaris throughout the world. Various groups of insecticides (carbamates, organophosphates, pyrethroids and neonicotinoids) are used. Foliar application of organophosphates, pyrethroids and neonicotinoid insecticides can provide good knockdown control of B. hilaris; however, many of the old generation organophosphate insecticides, popular in countries such as India for control of B. hilaris, have been phased out in western countries.

Current pest management practices for B. hilaris involve multiple sprays of mostly broad-spectrum insecticides to provide effective control. In India, pyrethroids and other older organophosphate products such as chlorpyrifos, malathion and profenofos are the most widely used insecticides (Sachan and Purwar, 2007; Nagar et al., 2011). In the USA, where B. hilaris is relatively new, pyrethroids (e.g. bifenthrin and lambda-cyhalothrin) and neonicotinoids (imidacloprid, dinotefuran, clothianidin) provide effective knockdown control (Palumbo, 2011a). Many neonicotinoids that offer systemic control of some pests through soil applications have not been able to provide such protection of young seedlings from feeding damage by B. hilaris (Palumbo, 2011b). However, drench application of these insecticides during seedling establishment reduced damage by B. hilaris in broccoli fields in California (Joseph et al., 2016). Similarly, seed dressing with neonicotinoid insecticide provided acceptable control (Joseph, 2019).

Several reduced-risk insecticides have been evaluated against B. hilaris including diamides, sulfoxamines and ketoenols, which are generally effective against hemipteran and other pests that have piercing and sucking mouthparts. However, preliminary studies have shown that these new insecticides are ineffective against this bug on cole crops (Palumbo, 2011c).

In the USA, some studies have attempted to explore other options, such as the use of insect growth regulators (IGR). In the laboratory, IGRs such as novaluron were observed to affect nymph development of B. hilaris (Palumbo et al., 2013; Joseph, 2017), reducing the number of nymphs developing into adults. Other insecticides, such as azadirachtin, which is also found to act as an IGR, have been reported to reduce painted bug injuries to broccoli (Palumbo et al., 2013).

Though much is yet to be explored for management of B. hilaris in organic production systems, a couple of studies conducted in the USA have indicated that chemical insecticides approved for organic use are not very effective as stand-alone treatments. For example, Joseph (2018) found that spinosad, pyrethrins, azadirachtin and potassium salts applied as stand-alone or combined treatments were ineffective in providing consistent bug control.

11/09/20 Original text by:

Sudan Gyawaly, University of California Agriculture and Natural Resources, 3800 Cornucopia Way, Modesto, CA 95358, USA

Jhalendra Rijal, University of California Agriculture and Natural Resources, 3800 Cornucopia Way, Modesto, CA 95358, USA

Shimat V. Joseph, University of Georgia, Turf Science R and E Facility, 1109 Experiment Street, Griffin, GA 30223, USA