Regis Sivori Silva dos Santos

Ocorrência de Parasitismo em Ovos de Spartocera dentiventris (Berg) (Hemiptera: Coreidae) em Cultura de Fumo

The paucity of information about egg parasitoids of Spartocera dentiventris (Berg) motivated the present work. This study aimed to determine the parasitoid species involved as well as to quantify the mortality caused by these natural enemies in field conditions. The investigation was carried out in a tobacco crop (cultivar Virginia, var. K-326) in Porto Alegre, RS. From December/97 to February/98, 20 egg masses of known age were left exposed to all causes of mortality for a period of 13 days. Two species of parasitoids were found on eggs of S. dentiventris: Gryon gallardoi (Brethes) (Hym.: Scelionidae) and Neorileya ashmeadi Crawford (Hym.: Eurytomidae). From a total of 321 observed eggs, only 34.3% (110 eggs) originated nymphs of S. dentiventris. Parasitism was the main mortality factor, killing 148 eggs (46.1%) from the total observed.

SEASONAL ABUNDANCE AND MORTALITY OF Oebalus poecilus (DALLAS) (HEMIPTERA: PENTATOMIDAE) IN A HIBERNATION REFUGE

Oebalus poecilus (Dallas) is an important pest affecting irrigated rice in Rio Grande do Sul, Brazil. It hibernates during the coldest months of the year in refuges such as bamboo litter. This study examined O. poecilus hibernation to determine the causes of mortality during this period. The study was conducted in a 140 m(2) bamboo plantation located in a rice-growing area in Eldorado do Sul County (30 degrees 02 S and 51 degrees 23 W), RS. During June 2000 to April 2002, 63 samples of litter were taken in weekly or fortnightly intervals, and the number of bugs recorded in the laboratory. The arrival at the hibernation site (bamboo litter) began in the first fortnight of March, and was completed in the beginning of May. O. poecilus left this refuge from middle October to the end of December. Parasitism by tachinid flies and Beauveria bassiana (Bals.) Vuill. fungus were the most important mortality factors.

Consumo alimentar comparativo de larvas de Phytalus sanctipauli Blanch. (Coleoptera: Scarabaeidae)

Food intake of 3rd instar larvae of Phytalus sanctipauli Blanch. was studied in the laboratory. Individually reared insects were given newly emerged seedlings of oat (Avena sativa), corn (Zea mays) or wheat (Triticum aestivum), or the three species together. The amount (dry mass) respectively of roots and seeds ingested was larger for wheat (28.5 and 41.5 mg), lower for oat (16.4 and 2.0 mg) and intermediate (22.6 and 24.9 mg) for corn. Leaf intake was similar for oat (18.2 mg) and wheat (19.8 mg) and larger for corn (2.1mg). Considering the seedling, consumption was larger for wheat either offered singly (89.8 mg) or not (56.9 mg). Grubs fed on wheat (100.2 mg) and corn (102.2 mg) were heavier than those fed on oat (85.9 mg). The average number of seedlings damaged/grub was larger for wheat (27.4) and oat (24.9) when compared to corn (0.9).