Host plant preference of harlequin bug (Hemiptera: Pentatomidae), and evaluation of a trap cropping strategy for its control in collard

Trap Cropping Harlequin Bug: Distance of Separation Influences Female Movement and Oviposition

To evaluate perimeter trap crops for management of harlequin bug, Murgantia histrionica (Hahn), we undertook greenhouse and field experiments with mustard greens as trap crop for a collard cash crop. We confirmed that harlequin bugs prefer to immigrate to and reside on mustard. Females, however, in greenhouse cage experiments, 'commuted' to collards to lay their eggs. In separate spring and fall field plantings, using replicated 12 m by 12 m collard plots in 1-ha fields, we tested mustard planted as an adjacent perimeter trap crop, or a perimeter trap crop separated by 2 unplanted rows (2.3 m), or with no trap crop. Adults accumulated on the spring mustard crop but overall numbers remained low, with all collards sustaining <1% leaves damaged. In the fall, the separation of 2.3 m reduced oviposition on collards fourfold, and feeding damage approximately 2.5-fold, compared to collards with an adjacent trap crop. Fall control plots with no border trap crop showed even lower foliar damage; likely result of preferential immigration of harlequin bugs to mustard at the field scale, resulting in fewer bugs near the control treatment plots. Thus, the spatial arrangement of the mustard trap crop, and its separation from the cash crop, influences pest abundance and damage. A separated mustard border can reduce bug movement including female commuting and egg-laying, thus better protecting the collard cash crop. Future research should address reduction in area of trap crops, deployment of semiochemicals, and possible changes in timing, to promote trap cropping that is practical for grower implementation.

Role of chemical cues in cabbage stink bug host plant selection

The cabbage stink bugs of the genus Eurydema, encompassing several oligophagous species, such as Eurydema oleracea (L.), are known to be important pests of cabbage, broccoli, and other cole crops in Europe. Despite their economic importance, the knowledge regarding the role of chemical cues in host plant selection of these species is very limited. The present investigation on E. oleracea at the adult stage revealed the use of olfaction in host plant selection of this species and demonstrated with behavioural tests that E. oleracea preferred feeding on wild Eruca sativa, rather than on Brassica oleracea. Moreover, ultrastructural data revealed the antennal sensilla of E. oleracea, encompassing single walled and double walled olfactory sensilla, and electroantennographic recordings revealed their sensitivity to several host plant VOCs from E. sativa and B. oleracea. The data shown in the present research may be useful in the development of semiochemical-based strategies or trap crops for the control of this pest in the field.

Evaluation of Mexican Bean Beetle (Coleoptera: Coccinellidae) Host Selection, Survival, and Feeding Injury Among Snap Bean and Lima Bean Cultivars

Mexican bean beetle, Epilachna varivestis Mulsant (Coleoptera: Coccinellidae), is a serious pest of snap bean, Phaseolus vulgaris L. (Fabales: Fabaceae), lima bean, Phaseolus lunatus L. (Fabales: Fabaceae), and an occasional pest of soybean, Glycine max (L.) Merr. (Fabales: Fabaceae), in the United States. Past research indicates that some bean cultivars endure greater injury from this pest than others, suggesting that such crops are either more preferred, better hosts, and/or have poorer defenses. This study characterizes injury potential among three snap bean and three lima bean cultivars by measuring ovipositional preference, survival, and feeding injury of E. varivestis in field and greenhouse experiments. Snap beans, as a group, were more preferred and susceptible to injury than lima beans. The purple wax snap bean, Dragon's Tongue, was the most susceptible overall; while the dwarf bush lima bean, Henderson, was the least susceptible. The results of this study will aid in the development of integrated pest management strategies for E. varivestis, while also providing broader biological information for future research on this pest and others.

Avoiding Unwanted Vicinity Effects With Attract-and-Kill Tactics for Harlequin Bug, Murgantia histrionica (Hahn) (Hemiptera: Pentatomidae)

In the development of an attract-and-kill approach for the management of harlequin bug (HB), Murgantia histrionica (Hahn), we evaluated attraction and retention of HB by pheromone-baited traps in the field. In release-recapture and on-farm experiments, traps with collard plants with lures-containing HB aggregation pheromone (murgantiol = 10,11-epoxy-1-bisabolen-3-ol) arrested and retained more HB than traps with either plant or lure. In order to avoid unwanted vicinity effects (increased feeding injury to neighboring crop plants due to halo or spillover effects), we also investigated two methods of retaining HB that were attracted to traps: a systemic toxicant (neonicotinoid applied to the trap plant as a drench) and a contact toxicant (long-lasting insecticidal netting [LLIN] with incorporated pyrethroid). More HB adults and more HB-feeding injury were observed on collard plants in the vicinity of lures compared with those neighboring lures in combination with a systemic toxicant. This difference indicates that improvements to trap retention acted to mitigate spillover effects, thereby avoiding unwanted vicinity effects. We also conducted laboratory assays in order to estimate the length of exposure to LLIN necessary to knock down HB adults and nymphs, calculating a knockdown time (KDT50) of 78.3, 2.6, and 2.1 s for females, males, and nymphs, respectively.

Fooling the Harlequin Bug (Hemiptera: Pentatomidae) Using Synthetic Volatiles to Alter Host Plant Choice

Harlequin bug, Murgantia histrionica (Hahn) (Hemiptera: Pentatomidae), is a widespread pest that feeds on a variety of brassicaceous crops and other plants. To understand olfactory cues that mediate host-finding, and their possible utility in pest management, we deployed aggregation pheromone (mixed murgantiols = 10,11-epoxy-1-bisabolen-3-ols) and/or isothiocyanate (ITC) host plant volatiles with potted host plants and nonhost soybean, in field choice bioassays. Adults of both sexes were strongly attracted (10-31×) to collard host plants baited with pheromone lures, compared with unbaited collards, as were nymphs. Collard plants baited with lures containing allyl and/or benzyl-ITC showed a 1.3× and 1.9× increase in attractiveness, respectively, neither differing by life-stage nor sex; multiple lures showed additive attraction. Nonhost soybean, baited with pheromone lure, was 4.6-7.5× more attractive to adults than unbaited collard; conversely, baited collard was 124× more attractive than unbaited soybean. The stark difference in observed effect of pheromone lure between unpoisoned plants, and those poisoned with imidacloprid, indicated that attraction was underestimated by circa-daily counts of unpoisoned plants, presumably because if not poisoned, bugs rapidly abandoned the baited nonhost soybean plant. Results indicate that harlequin bugs can be misled to encounter and feed on nonhosts by their aggregation pheromone, but additional means may be needed to retain them. Attraction to hosts is increased both by the aggregation pheromone, and at least two host plant volatiles, allyl and benzyl-ITC. These results contribute to our knowledge of host finding in harlequin bug, and to possible trapping and trap cropping schemes for pest management.