Trap Crops and Insectary Plants in the Order Brassicales

This paper reviews the most important cases of trap crops and insectary plants in the order Brassicales. Most trap crops in the order Brassicales target insects that are specialist in plants belonging to this order, such as the diamondback moth, Plutella xylostella L. (Lepidoptera: Plutellidae), the pollen beetle, Meligethes aeneus Fabricius (Coleoptera: Nitidulidae), and flea beetles in the genera Phyllotreta and Psylliodes (Coleoptera: Chrysomelidae). In most cases, the mode of action of these trap crops is the preferential attraction of the insect pest for the trap crop located next to the main crop. With one exception, these trap crops in the order Brassicales have been used with brassicaceous crops. Insectary plants in the order Brassicales attract a wide variety of natural enemies, but most studies focus on their effect on aphidofagous hoverflies and parasitoids. The parasitoids benefiting from insectary plants in the order Brassicales target insects pests ranging from specialists, such as P. xylostella, to highly polyfagous, such as the stink bugs Euschistus conspersus Uhler and Thyanta pallidovirens Stål (Hemiptera: Pentatomidae). In the order Brassicales, the three most common trap crops are Indian mustard, Brassica juncea (L.) Czern, Chinese cabbage, Brassica rapa L., and yellow rocket, Barbarea vulgaris R. Br., while the three most common insectary plants are sweet alyssum, Lobularia maritima (L.) Desv., white mustard, Sinapis alba L, and B. vulgaris. Except for Tropaeolum majus L. (Tropaeolaceae) and Capparis decidua (Forssk.) Edgew. (Capparaceae), the tested trap crops and insectary plants in the order Brassicales belong to the family Brassicaceae.

Substrate-borne vibrational signals of the Consperse stink bug (Hemiptera: Pentatomidae)

There is increasing evidence that short-range reproductive behaviors of phytophagous pentatomid bugs are mediated by vibrational signals. These signals have not yet been examined for bugs in the genus Euschistus, which contains several species native to the Americas. Substrate-borne vibrational signals (songs) were recorded from both sexes of the Consperse stink bug, Euschistus conspersus Uhler, an economically important agricultural pest in western North America. Females produced two songs (FS-1 and FS-2), each consisting of a series of frequency-modulated pulses with a pulse duration of 352 ± 105 (mean ± SD) and 163 ± 36 ms, respectively. Males produced four distinct songs, two composed of frequency-modulated pulses (MS-1 and MS-3), one consisting of narrowband pulses (MS-2), and one composed of a series of 1–6 short pulses, many of which were fused to form distinct pulse trains (MS-4). For both males and females, songs consisting of very short, frequency-modulated pulses (FS-2 and MS-3), with a mean pulse duration <170 ms, were emitted when the other member of the pair was silent. Songs made up of longer, frequency-modulated pulses (FS-1 and MS-1) were produced spontaneously and in response to songs from conspecifics. Pulses of MS-2 were produced by a male once a duet with a female had been initiated. This song had no frequency modulation and a longer mean pulse repetition time than MS-1. The two female songs and three of the male songs (MS-1, MS-2, and MS-3) were produced during the calling phase of mating behavior. Pulse trains of MS-4 were emitted during close-range courtship. During copulation males produced intermittent pulses of MS-1, the function of which is unknown. Dominant frequencies of all songs ranged from 102 to 136 Hz, comparable with those of other pentatomid songs. Although there were superficial similarities in the song structures of E. conspersus when compared with those of other pentatomid species, the song repertoire of E. conspersus was distinct and unique.

Parasitoids of the Consperse Stink Bug (Hemiptera: Pentatomidae) in North Central Washington and Attractiveness of a Host-Produced Pheromone Component

The parasitoid complex of the consperse stink bug, Euschistus conspersus Uhler, was investigated in a series of field experiments conducted in native vegetation surrounding commercial apple orchards in the state of Washington. Rearing of parasitoids from adult E. conspersus confirmed the presence of two tachinid species, Gymnosoma filiola Loew and Gymnoclytia occidentalis Townsend. Three species of scelionids were reared from fresh egg masses placed on mullein plants (Verbascum thapsus L.) with Trissolcus utahensis (Ashmead) being the most common species. Though some parasitism was recorded in all study sites by both tachinids and scelionids, overall levels of parasitism were low (&lt;10%). Predation comprised the major source of egg mortality in the field. Bucket traps baited with the male-produced aggregation pheromone component, methyl (2E,4Z)-decadienoate, captured significantly more G. occidentalis than unbaited controls, suggesting that it may use this compound as a host-finding kairomone. A test comparing E. conspersus egg masses placed on baited vs. unbaited V. thapsus revealed no differences in the rate of parasitism by scelionid parasitoids.