P. G. Tillman

Spatiotemporal Patterns and Dispersal of Stink Bugs (Heteroptera: Pentatomidae) in Peanut-Cotton Farmscapes

ABSTRACT 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.

Sorghum as a Trap Crop for Nezara viridula L. (Heteroptera: Pentatomidae) in Cotton in the Southern United States

Abstract The southern green stink bug, Nezara viridula L., may disperse from alternate host plants, especially corn, Zea mays L., and peanuts, Arachis hypogaea L., into cotton, Gossypium hirsutum L. Trap crops may be useful to intercept dispersing stink bugs. Therefore, the ability of sorghum, Sorghum bicolor L. Moench, to trap N. viridula adults in cotton was studied for 3 yr. The 2002 experiment was designed to compare the ability of small plots of sorghum and cotton to trap N. viridula along the interface, or common boundary, of a corn and cotton field. In the 2003 experiment, cotton fields with sorghum and cotton plots planted along the interface of a corn–cotton farmscape were compared with cotton fields without these interface plots. In both experiments, N. viridula adults strongly preferred sorghum to cotton, and marking studies revealed that most N. viridula adults that dispersed into sorghum remained in sorghum instead of moving into cotton. Overall, percent parasitism of N. viridula adults by T. pennipes was higher in sorghum trap crop plots than in interface cotton control plots. In 2003, density of N. viridula adults was lower in cotton fields adjoining sorghum trap crop plots than in control cotton fields. Furthermore, economic threshold for N. viridula was not reached along the interface of the corn–cotton farmscape in any cotton field with sorghum plots. In contrast, economic threshold was reached in 61.5% of the control cotton fields. In the third season, a full-scale field experiment was conducted to determine the effectiveness of sorghum, planted in a strip along the length of the interface of a peanut–cotton farmscape, as a trap crop in cotton. Before the test, each cotton field was partitioned into eight side-edge and three interior block locations. Each field had four sides with side A occurring along the interface of the field. Edge 1 was 0–3.66 m from the outside edge of the field, and edge 2 was 3.66–7.31 m from the outside edge of the field. In control cotton fields, density of N. viridula adults was much higher in the interface side in edge one than in any other side-edge location, strongly indicating that N. viridula adults dispersed from peanuts into these cotton fields. Control cotton fields had higher numbers of N. viridula adults in the interface side in edge one compared with cotton fields with sorghum trap crops. Overall, in 2004, control cotton fields were treated with insecticides for control of N. viridula 1.4 times, whereas cotton fields with sorghum trap crops were treated for control of this stink bug only 0.2 times. These results show that sorghum can serve as a trap crop for N. viridula adults in cotton fields.

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

ABSTRACT 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 stall 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)-&agr;-bisabolene epoxide blend. In fact, attraction of N. viridula increased with higher pheromone doses. Traps baited with a 5:95 trans- to cis-(Z)-&agr;-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.

Natural Biological Control of Stink Bug (Heteroptera: Pentatomidae) Eggs in Corn, Peanut, and Cotton Farmscapes in Georgia

ABSTRACT In southeastern United States farmscapes, corn, peanut, and cotton fields are often closely associated with each other. Thus, this 5-yr study was conducted to determine parasitism and predation of sentinel and natural occurring Euschistus servus (Say) and Nezara viridula (L.) egg masses in farmscapes in Georgia. A variety of parasitoids including six scelionids, Trissolcus basalis (Wollaston), T. brochymenae (Ashmead), T. euschisti (Ashmead), T. thyantae Ashmead, Telenomus podisi Ashmead, and Gyron obesum Masner, and one encyrtid, Ooencyrtus spp., was recovered from E. servus and N. viridula eggs, but overall the greatest diversity of parasitoids emerged from stink bug eggs in corn. Only T. basalis and T. podisi parasitized both N. viridula and E. servus eggs in all three crops over all farmscapes. A wide variety of predators, including Orius insidiosus (Say), Geocoris punctipes (Say), G. uliginosus (Say), Coccinella septempunctata (L.), Hippodamia convergens Guérin-Méneville, Harmonia axyridis (Pallas), Coleomegilla maculata (De Geer), Scymnus loewii Mulsant, Scymnus ardelio Horn, and Solenopsis invicta Buren, preyed on stink bug eggs in each crop. When differences were detected, generally percent parasitization per egg mass was higher than predation in corn, and percent predation was higher than parasitization in peanut. Overall, percent predation per egg mass was higher than parasitization in cotton, but on one occasion percent parasitization was higher than predation in cotton associated with corn. Seasonal occurrence and abundance of natural enemies, levels of parasitization and predation of stink bug eggs, and percent egg predation by sucking and chewing predators indicated that natural enemies of stink bug eggs disperses from crop to crop in the farmscapes. Stink bug egg predators and parasitoids are likely responding to host plant switching by their prey or hosts. In conclusion, this study has shown that natural enemies of stink bugs are prevalent and important biological control agents in these farmscapes.

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

ABSTRACT Nezara viridula L. and Euschistus servus (Say) are the predominant species of phyto-phagous 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.

Influence of Corn on Stink Bugs (Heteroptera: Pentatomidae) in Subsequent Crops

ABSTRACT 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 (Hetcroptera: 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.

Effect of Prey Species on Plant Feeding Behavior by the Big-Eyed Bug, Geocoris punctipes (Say) (Heteroptera: Geocoridae), on Cotton

Abstract The effect of prey species on plant feeding behavior by Geocoris punctipes (Say) females was determined by observing prey and plant feeding behavior on cotton plants for three prey treatments: 1) corn earworm, Helicoverpa zea (Boddie), eggs, 2) H. zea first instars, and 3) cotton aphid, Aphis gossypii Glover, adults. Feeding behavior of individual G. punctipes females was observed in the laboratory using caged cotton terminals with prey on the leaves. A. gossypii adults were less acceptable to G. punctipes females as prey than H. zea eggs and first instars. Female G. punctipes fed much less on cotton plants than prey when more acceptable prey, H. zea eggs and first instars, were available but exhibited no feeding preference for the cotton plant versus prey when less acceptable prey, A. gossypii adults, were available. Nevertheless, because G. punctipes females fed on cotton plants regardless of acceptability of prey even in the presence of abundant prey, we conclude that plant feeding is an integral part of the feeding behavior of G. punctipes in cotton. Conservation of G. punctipes by reducing applications of insecticides that are toxic to these predators when they feed on insecticide-treated foliage or by providing nutritionally good plant resources could increase their effectiveness as natural enemies of H. zea and other pests in cotton.

Likelihood of Stink Bugs Colonizing Crops: A Case Study in Southeastern Farmscapes

ABSTRACT 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.

Grain Sorghum as a Trap Crop for Corn Earworm (Lepidoptera: Noctuidae) in Cotton

Abstract This 2-yr on-farm study was designed to evaluate the ability of grain sorghum, Sorghum bicolor (L.) Moench, to serve as a trap crop for the corn earworm, Helicoverpa zea (Boddie), by attracting corn earworm females into the sorghum as they emerged from cornfields. Three plots of sorghum trap crops and three equally sized plots of cotton, Gossypium hirsutum L., trap crops were planted in a strip between a commercial cornfield and a commercial cotton field. The cotton field adjacent to the trap crop plots was divided into field cotton plots associated with the sorghum trap crop plots and field cotton plots associated with the cotton trap crop plots. Three commercial cotton fields adjacent to corn, but without trap crops, also were sampled. The number of corn earworm eggs per plant and the percentage of plants with corn earworm eggs was higher in the sorghum trap crop plots than in the cotton trap crop plots for both years, demonstrating that corn earworm females preferred to oviposit in the grain sorghum over cotton. A higher percentage of plants with corn earworm eggs was found in cotton in control fields compared with fields with trap crops, indicating that the grain sorghum trap crop was not the source of corn earworm. An economic threshold of 5% corn earworm young (first and second instars) was exceeded more times for cotton in control fields compared with cotton in fields with trap crops. Thus, for two seasons the grain sorghum trap crops helped reduce the need for insecticide applications for this pest. Percentage of parasitization by the egg parasitoid Trichogramma pretiosum Riley and the number per plant of the predator Orius insidiosus (Say) were higher in the sorghum trap crop plots than the cotton plots. However, the grain sorghum trap crop plots were not sinks for these natural enemies. We conclude that grain sorghum could serve as an effective trap crop for corn earworm in cotton.

Milkweed (Gentianales: Apocynaceae): A Farmscape Resource for Increasing Parasitism of Stink Bugs (Hemiptera: Pentatomidae) and Providing Nectar to Insect Pollinators and Monarch Butterflies

ABSTRACT 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.