Trap Cropping Systems and a Physical Barrier for Suppression of Stink Bugs (Hemiptera: Pentatomidae) in Cotton

Euschistus servus (Say), Nezara viridula (L.), and Chinavia hilaris (Say) (Hemiptera: Pentatomidae) are economic pests of cotton in the coastal plain of the southeastern United States. The objective of this 2-yr study was to determine the ability of trap cropping systems, pheromone-baited stink bug traps, and a synthetic physical barrier at the peanut-to-cotton interface to manage stink bugs in cotton. The physical barrier was the most effective management tactic. Stink bug density in cotton was lowest for this treatment. In 2010, boll injury was lower for the physical barrier compared to the other treatments except for soybean with stink bug traps. In 2011, boll injury was lower for this treatment compared to the control. Soybean was an effective trap crop, reducing both stink bug density in cotton and boll injury regardless if used alone or in combination with either stink bug traps or buckwheat. Incorporation of buckwheat in soybean enhanced parasitism of E. servus egg masses by Telenomus podisi Ashmead in cotton. The insertion of eyelets in the lid of the insect-collecting device of a stink bug trap allowed adult stink bug parasitoids, but not E. servus, to escape. Stand-alone stink bug traps were not very effective in deterring colonization of cotton by stink bugs or reducing boll injury. The paucity of effective alternative control measures available for stink bug management justifies further full-scale evaluations into these management tactics for control of these pests in crops.

Predation of the newly invasive pest Megacopta cribraria (Hemiptera: Plataspidae) in soybean habitats adjacent to cotton by a complex of predators

The kudzu bug, Megacopta cribraria (F.) (Hemiptera: Plataspidae),is a newly invasive exotic insect found primarily on kudzu, but also on soybean, in the southeastern United States. We used molecular gut-content analysis to document predation on this pest by insects and spiders in soybean, and to detect remains of crop-specific alternative prey in predators' guts as markers of predator migration between soybean and adjacent cotton. M. cribraria was found exclusively on soybean. Eight native generalist predators over both crops screened positive by specific PCR for DNA of the pest: Geocoris punctipes (Say), Geocoris uliginosus (Say), Orius insidiosus (Say), Podisus maculicentris (Say), Hippodamia convergens Guérin-Méneville, Zelus renardii (Kolenati), Oxyopes salticus Hentz, and Peucetia viridans (Hentz); a ninth predator, the exotic Solenopsis invicta Buren, also screened positive for M. cribraria DNA. P. viridans was the only arthropod that tested positive for DNA of this invasive pest in only one crop, cotton. Two plant-feeding pentatomid species, Piezodorus guildinii (Westwood) and Thyanta custator (F.), were found exclusively on soybean, and another, Euschistus tristigmus (Say), was specific to cotton in the context of this study. Detection of predation on a combination of M. cribraria and P. guildinii and T. custator in cotton and M. cribraria and E. tristigmus in soybean demonstrated that these predators dispersed between crops. These results strongly support the use of soybean habitats adjacent to cotton as part of a conservation biological control strategy against M. cribraria. This is the first report documenting predation on this exotic pest in the field via molecular gut-content analysis.

Milkweed (Gentianales: Apocynaceae): a farmscape resource for increasing parasitism of stink bugs (Hemiptera: Pentatomidae) and providing nectar to insect pollinators and monarch butterflies

In peanut-cotton farmscapes in Georgia, the stink bugs Nezara viridula (L.) and Chinavia hilaris (Say) (Hemiptera: Pentatomidae) and the leaffooted bug, Leptoglossus phyllopus (L.) (Hemiptera: Coreidae), disperse at crop-to-crop interfaces to feed on bolls in cotton. The main objective of this study was to determine whether insecticide-free tropical milkweed (Asclepias curassavica L.), a nectar-producing plant, can increase parasitism of these bugs by Trichopoda pennipes (F.) (Diptera: Tachinidae) and provide nectar to monarch butterflies and insect pollinators in these farmscapes. Peanut-cotton plots with and without flowering milkweed plants were established in 2009 and 2010. Adult T. pennipes, monarch butterflies, honey bees, and native insect pollinators readily fed on floral nectar of milkweed. Monarch larvae feeding on milkweed vegetation successfully developed into pupae. In 2009, N. viridula was the primary host of T. pennipes in cotton, and parasitism of this pest by the parasitoid was significantly higher in milkweed cotton (61.6%) than in control cotton (13.3%). In 2010, parasitism of N. viridula, C. hilaris, and L. phyllopus by T. pennipes was significantly higher in milkweed cotton (24.0%) than in control cotton (1.1%). For both years of the study, these treatment differences were not owing to a response by the parasitoid to differences in host density, because density of hosts was not significantly different between treatments. In conclusion, incorporation of milkweed in peanut-cotton plots increased stink bug parasitism in cotton and provided nectar to insect pollinators and monarch butterflies.

Effect of field edges on dispersal and distribution of colonizing stink bugs across farmscapes of the southeast USA

Stink bugs (Heteroptera: Pentatomidae), including Nezara viridula (L.), Euschistus servus (Say), and Chinavia hilaris (Say), are economic pests in farmscapes where they move within and between closely associated crop and non-crop habitats. Thus, field edges in these farmscapes include not only crop-to-crop interfaces but also those edges adjoining non-crop habitats. We examined the influence of field edges on colonization of stink bugs in southeastern USA farmscapes composed of typical combinations of corn, peanut, and cotton. For E. servus and N. viridula, egg-to-adult development and presence of both sexes on all crops indicated that the crops served as reproductive plants. Adult C. hilaris were rarely found on corn and on crops associated with it, and they were present mainly in cotton in peanut-cotton farmscapes. Mature crop height was significantly higher for corn than for cotton and significantly higher for cotton over peanut, and an edge effect in dispersal of stink bugs into a crop was detected up to 4.6, 8.2, and 14.6 m from the crop-to-crop interface in corn, cotton, and peanut, respectively. These results suggest that stink bug dispersal into a crop decreases as crop height increases. The first stink bug-infested crop at the crop-to-crop interface was the most significant contributor of colonizing stink bugs to an adjacent crop. An edge effect in dispersal of stink bug adults was detected in corn next to non-woodlands and woodlands and in cotton adjacent to woodlands. Edge effects were never detected in side edges of peanut. Overall, our results indicate that both plant height and host plant suitability can influence edge-mediated dispersal of stink bugs at field edges.

Likelihood of stink bugs colonizing crops: a case study in southeastern farmscapes

Stink bugs, including Nezara viridula (L.), Euschistus servus (Say), and Chinavia hilaris (Say), are economic pests across agricultural farmscapes where they can colonize closely associated crops. This 4-yr on-farm study was conducted to examine the likelihood of these three stink bug species colonizing crops in corn-cotton, corn-peanut-cotton, and peanut-cotton farmscapes by using odds ratios. Corn (Zea mays L.), peanut (Arachis hypogaea L.), and cotton (Gossypium hirsutum L.) served as host plants for E. servus and N. viridula. Corn did not serve as a host plant for C. hilaris. Although peanut was a relatively poor host plant, cotton was a relatively good host plant for this stink bug. For N. viridula and E. servus adults, the risk of crop colonization was higher for peanut in peanut-cotton farmscapes with corn than without corn and was highest for cotton in corn-peanut-cotton, followed by peanut-cotton, and lastly corn-cotton farmscapes. The likelihood of oviposition by E. servus, though, was higher in cotton in corn-cotton than peanut-cotton farmscapes. For C. hilaris adults, the risk of crop colonization was highest for cotton in peanut-cotton, followed by corn-peanut-cotton, and lastly corn-cotton farmscapes. Corn was more likely than peanut or cotton to harbor adults and immatures, i.e., egg masses and young nymphs, of N. viridula and E. servus. Adults of all three stink bug species colonized cotton more often than peanut in peanut-cotton farmscapes. However, oviposition by N. viridula and E. servus occurred more often in peanut than in cotton. These assessments of the likelihood of stink bug colonization are essential for modeling predictions of stink bug colonization and designing more comprehensive landscape management approaches for control of stink bugs in these farmscapes.

Influence of corn on stink bugs (Heteroptera: Pentatomidae) in subsequent crops

In southeastern United States farmscapes, corn, Zea mays L., is often closely associated with peanut, (Arachis hypogaea L.), cotton, (Gossypium hirsutum L.), or both. The objective of this 3-yr on-farm study was to examine the influence of corn on stink bugs (Heteroptera: Pentatomidae), Nezara viridula (L.), and Euschistus servus (Say), in subsequent crops in these farmscapes. Adults of both stink bug species entered corn first, and seasonal occurrence of stink bug eggs, nymphs, and adults indicated that corn was a suitable host plant for adult survival and nymphal development to adults. Stink bug females generally oviposited on cotton or peanut near the interface, or common boundary, of the farmscape before senescence of corn, availability of a new food, or both. Adult stink bugs dispersed from crop to crop at the interface of a farmscape in response to senescence of corn, availability of new food, or both. In corn-cotton farmscapes, adult stink bugs dispersed from senescing corn into cotton to feed on bolls (fruit). In corn-peanut farmscapes, adult stink bugs dispersed from senescing corn into peanut, which apparently played a role in nymphal development in these farmscapes. In the corn-cotton-peanut farmscape, stink bug nymphs and adults dispersed from peanut into cotton in response to newly available food, not senescence of peanut. Stink bug dispersal into cotton resulted in severe boll damage. In conclusion, N. viridula and E. servus are generalist feeders that exhibit edge-mediated dispersal from corn into subsequent adjacent crops in corn-cotton, corn-peanut, and corn-peanut-cotton farmscapes to take advantage of suitable resources available in time and space for oviposition, nymphal development, and adult survival. Management strategies for crops in this region need to be designed to break the cycle of stink bug production, dispersal, and expansion by exploiting their edge-mediated movement and host plant preferences.

Parasitism and predation of stink bug (Heteroptera: Pentatomidae) eggs in Georgia corn fields

Nezara viridula L. and Euschistus servus (Say) are the predominant species of phytophagous stink bugs on corn, Zea mays L., in Georgia. Oebalus pugnax pugnax (F.) occurs in relatively low numbers, and the predatory stink bug Podisus maculiventris (Say) is commonly found. Limited information is available on natural biological control of these four stink bug species in Georgia corn fields; therefore, a 6-yr study of parasitism and predation of their eggs was initiated in 2003. Naturally occurring stink bug eggs were parasitized by six scelionid species, Trissolcus basalis (Wollaston), T. thyantae Ashmead, T. brochymenae (Ashmead), T. euschisti (Ashmead), Telenomus podisi Ashmead, Telenomus calvus Johnson, and one encyrtid species, Ooencyrtus sp. T. basalis was the most prevalent parasitoid of N. viridula, parasitizing E. servus and P. maculiventris eggs at low levels. T. podisi, the predominant parasitoid species emerging from eggs of E. servus and P. maculiventris, also parasitized O. p. pugnax eggs exclusively and parasitized N. viridula eggs at low levels. T. euschisti and T. thyantae parasitized E. servus egg masses. T. brochymenae parasitized eggs of both E. servus and P. maculiventris. T. calvus parasitized only P. maculiventris eggs. The same species of egg parasitoids that parasitized naturally occurring eggs of N. viridula and E. servus parasitized sentinel eggs of these bugs, except that no T. calvus and Ooencyrtus sp. were obtained from sentinel eggs, and T. thyantae and T. brochymenae emerged from sentinel eggs of N. viridula. Generally, parasitization of an egg mass was either greater than or equal to predation of sentinel eggs of N. viridula and E. servus. However, on some dates in late June and July, predation of sentinel egg masses was numerically approximately twice as high as parasitism. Results indicate stink bug egg parasitoids and predators are significant factors in the natural biological control of stink bugs in corn fields.

Pheromone attraction and cross-attraction of Nezara, Acrosternum, and Euschistus spp. stink bugs (Heteroptera: Pentatomidae) in the field

Detecting infestations of stink bugs (Heteroptera: Pentatomidae) using pheromones remains problematic, particularly so in the United States for the exotic stink bug, Nezara viridula L., and our native stink bug, Acrosternum hilare (Say). Therefore, we conducted a 2-yr on-farm study to examine the attractiveness and possible cross-attraction of the reported pheromones for N. viridula and A. hilare and those previously discovered for Euschistus servus (Say) and Plautia stali Scott to N. viridula, A. hilare, and E. servus. The attractiveness of selected pentatomid pheromones to tachinid parasitoids of stink bugs was also examined. We showed for the first time under field conditions that N. viridula can be trapped with its reported pheromone, a 3:1 trans- to cis-(Z)-alpha-bisabolene epoxide blend. In fact, attraction of N. viridula increased with higher pheromone doses. Traps baited with a 5:95 trans- to cis-(Z)-alpha-bisabolene epoxide blend, the reported male-produced A. hilare attractant pheromone, failed to attract significantly more A. hilare than did unbaited control traps. Instead A. hilare was significantly cross-attracted to the P. stali pheromone [methyl (E,E,Z)-2,4,6-decatrienoate]. The E. servus pheromone [methyl (E,Z)-2,4-decadienoate], either alone or in combination with P. stali pheromone, was more attractive to E. servus than to N. viridula, P. stali, or A. hilare pheromones. In general, tachinid parasitoids were found responsive to the male-specific volatiles of their known hosts, including the attractiveness of Trichopoda pennipes (F.) to sesquiterpenoid blends characteristic of A. hilare and N. viridula. A tachinid parasitoid of E. servus, Cylindromyia sp., seemed to be attracted to E. servus pheromone. In conclusion, our results indicate that stink bug traps baited with lures containing N. viridula pheromone blend, P. stali pheromone, and E. servus pheromone have the greatest potential for detecting populations of N. viridula, A. hilare, and E. servus, respectively, in diversified agricultural landscapes.

Spatiotemporal patterns and dispersal of stink bugs (Heteroptera: Pentatomidae) in peanut-cotton farmscapes

In the southeast United States, a field of peanuts, Arachis hypogaea L., is often closely associated with a field of cotton, Gossypium hirsutum L. The objective of this 4-yr on-farm study was to examine and compare the spatiotemporal patterns and dispersal of the southern green stink bug, Nezara viridula L., and the brown stink bug, Euschistus servus (Say), in six of these peanut-cotton farmscapes. GS(+) Version 9 was used to generate interpolated estimates of stink bug density by inverse distance weighting. Interpolated stink bug population raster maps were constructed using ArcMap Version 9.2. This technique was used to show any change in distribution of stink bugs in the farmscape over time. SADIE (spatial analysis by distance indices) methodology was used to examine spatial aggregation of individual stink bug species and spatial association of the two stink bug species in the individual crops. Altogether, the spatiotemporal analyses for the farmscapes showed that some N. viridula and E. servus nymphs and adults that develop in peanuts disperse into cotton. When these stink bugs disperse from peanuts into cotton, they aggregate in cotton at the interface, or common boundary, of the two crops while feeding on cotton bolls. Therefore, there is a pronounced edge effect observed in the distribution of stink bugs as they colonize the new crop, cotton. The driving force for the spatiotemporal distribution and dispersal of both stink bug species in peanut-cotton farmscapes seems to be availability of food in time and space mitigated by landscape structure. Thus, an understanding of farmscape ecology of stink bugs and their natural enemies is necessary to strategically place, in time and space, biologically based management strategies that control stink bug populations while conserving natural enemies and the environment and reducing off-farm inputs.

Effect of selected insecticides on the natural enemies Coleomegilla maculata and Hippodamia convergens (Coleoptera: Coccinellidae), Geocoris punctipes (Hemiptera: Lygaeidae), and Bracon mellitor, Cardiochiles nigriceps, and Cotesia marginiventris (Hymenoptera: Braconidae) in cotton

We evaluated the toxicity of three insecticides (lambda cyhalothrin, spinosad, and S-1812) to the natural enemies Bracon mellitor Say, Cardiochiles nigriceps Viereck, Coleomegilla maculata De Geer, Cotesia marginiventris (Cresson), Geocoris punctipes (Say), and Hippodamia convergens Guérin-Méneville, in topical, residual, and field assays. Lambda cyhalothrin exhibited the greatest toxicity to the natural enemies. In topical toxicity tests, lambda cyhalothrin adversely affected each natural enemy species studied. Residues of lambda cyhalothrin on cotton leaves were toxic to B. mellitor, C. nigriceps, C. maculata, and C. punctipes. Interestingly, residues of this insecticide were not very toxic to C. marginiventris and H. convergens. Geocoris punctipes and C. maculata numbers in the field generally were significantly lower for lambda cyhalothrin treatments than for the other four treatments, substantiating the previous tests. Although cotton aphids began to increase over all treatments around the middle of the test period, the number of cotton aphids in the lambda cyhalothrin plots was significantly higher than the number in any of the other treatments. As cotton aphids increased in lambda cyhalothrin field plots, the predator H. convergens also increased in number, indicating that lambda cyhalothrin did not adversely affect it in accordance with the residual tests. Spinosad exhibited marginal to excellent selectivity, but was highly toxic to each parasitoid species and G. punctipes in topical toxicity tests and to B. mellitor in residual tests. Spinosad generally did not affect the number of G. punctipes, H. convergens, and C. maculata in the field except for one day after the second application for G. punctipes. S-1812 exhibited good to excellent selectivity to the natural enemies. Some reduction of G. punctipes occurred for only a short period after the first and second application of this insecticide in the field. H. convergens and C. maculata were affected very little by S-1812.