RESUMEN
This study aimed to characterize and correlate the stylet penetration behaviors of nymphs of the Neotropical brown stink bug, Euschistus heros (F.), on immature soybean pods. Waveforms were obtained using electropenetrography (EPG). The findings revealed that the nymphs exploited the xylem vessels and the seed tegument or endosperm. Primarily 4 phases were characterized: nonfeeding, pathway, salivation, and ingestion. The waveforms of each phase were similar in appearance across instars. The biological meanings of waveforms were based on visual observations, comparison with waveforms of adults, and histological studies. Np represents the insect resting or walking on soybean pod surface. Eh1 represents the first contact between the mouthparts (stylets) and plant tissue. Eh2 represents xylem sap ingestion, and Eh3 represents seed activities (including tegument and endosperm). The number of waveform events did not differ among instars for all waveforms. However, for Eh3, fifth instars performed more activities than other instars. The second instars had the smallest value, and third and fourth instars had intermediate values. For total duration, all waveforms differed among instars. Np duration was shorter for third compared with second and fourth instars and intermediate for fifth instar. For Eh1, second and third instars had the longest duration (1.5× to 2× greater) compared with fourth and fifth instars. For Eh2 and Eh3, the second-instar showed the longest (~2× greater) and shortest durations, respectively. Overall, this study provides important insights into the feeding behavior of E. heros nymphs so that effective pest management programs can be developed to contain this pest.
Asunto(s)
Heterópteros , Animales , Glycine max , Conducta Alimentaria , Semillas , NinfaRESUMEN
Laboratory and greenhouse studies were conducted with the Neotropical brown stink bug, Euschistus heros (F.), to evaluate and compare adult damage at two infestation levels (2 and 4 adults/plant) and feeding behavior on seeds of three resistant soybean cultivars bearing the Block technology ('BRS 1003 IPRO', 'BRS 543 RR', and 'BRS 391') compared to a susceptible cultivar ('BRS 5601 RR'). No difference in number or weight of damaged seeds (as percentages) was found among the cultivars at either infestation level. Differences were only observed between infestation levels within cultivar; higher values were reported with 4 adults/plant, except for 'BRS 543 RR'. At 2 adults/plant, total seed area damaged (mm2) and percentage of seed area damaged were significantly lower only on 'BRS 1003 IPRO'; significant differences among cultivars were found in damage to internal but not external seed surfaces. At 4 adults/plant, all Block cultivars differed from 'BRS 5601 RR' in overall seed damage, and greater percent damage occurred on both seed surfaces on 'BRS 5601 RR'. Electropenetrography (EPG) demonstrated that adults reached and fed in the seeds of all soybean cultivars. However, the feeding event duration in seeds of Block cultivars was much shorter than on 'BRS 5601 RR', which likely explains differences between internal and external seed damage. Furthermore, the total duration of feeding activities on seeds of Block cultivars was ca. 4-6 times shorter than on the susceptible cultivar; these two EPG feeding variables account for the lower seed damage observed for the Block cultivars. These cultivars represent an important new strategy for pest control on soybean.
Asunto(s)
Glycine max , Heterópteros , Animales , Conducta Alimentaria , Semillas , Glycine max/genética , TecnologíaRESUMEN
The stink bug Dichelops furcatus (F.) (Heteroptera: Pentatomidae) has increased in abundance in recent years on the wheat, Triticum aestivum L., crop cultivated in the southern region of Brazil. To investigate the probing (stylet penetration) behaviors and nonprobing behaviors of D. furcatus on wheat plants, the electrical penetration graph or electropenetrography (EPG) technique was applied. Nine EPG waveforms (types/subtypes) were identified and described on stem and on ear head of wheat plants, as follows: Z, Np, Df1a, Df1b, Df2, Df3a, Df3b, Df4a, and Df4b. For the waveforms Df1, Df2, Df3, and Df4, stylets were severed to determine, via histological studies, the location of the stylet tip and/or salivary sheath tip in plant tissue. Waveform Z was visually correlated with the bug standing still on the plant surface, whereas during Np the bug was walking. Df1a and Df1b represent initial stylet insertion, deep penetration of the stylets into the plant tissue, and secretion of salivary sheath. Df2 represents xylem sap ingestion on stem and on ear head. Waveforms Df3a and Df4a were related to the cell rupturing feeding strategy (laceration and maceration tactics) on stem and on ear head (seed endosperm), respectively. Waveforms Df3b and Df4b represent ingestion of cellular contents derived from cell rupturing activities on stem and on ear head (seed endosperm), respectively. With this fundamental knowledge in hand, future studies can use EPG to develop novel pest management solutions.