Luís A. Foerster

Efeito da estocagem em baixa temperatura na capacidade reprodutiva e longevidade de Trissolcus basalis (Wollaston) e Telenomus podisi Ashmead (Hymenoptera: Scelionidae)

Female longevity and fecundity of Trissolcus basalis (Wollaston) and Telenomus podisi Ashmead were evaluated at 25oC after storage periods ranging from one to 140 days at 15oC, in intervals of 10 days. The oviposition capacity of both parasitoids was also evaluated at 15oC, following pre-ovipositional periods ranging from one to 60 days, also at 10-day intervals. Females of both species survived for more than five months when stored at 15oC, however fecundity was significantly reduced by the exposure to the low temperature. Despite the reduction in fecundity, both species were able to parasitize host eggs at 25oC after spending 140 days at 15oC. Although parasitism was observed at 15oC, only 3.1% and 0.2% of the exposed eggs were parasitized by T. basalis and T. podisi, respectively. The proportion of males was significantly increased in the progeny of T. basalis females, maintained at 15oC, for any of the storage periods investigated. Similar results were obtained for T. podisi stored at 15oC up to 50 days; however the females of this species, maintained at the lower temperature for longer periods, either laid no eggs or produced progenies with sex-ratio similar to the control insects, kept at 25oC. The presence of females in the offspring of both parasitoid species indicate that mating occurred at the lower temperature. The increased longevity and reduced fecundity of T. basalis and T. podisi obtained when the adults were stored at 15oC, show that both species hibernate, and this arrestment can be useful as a tool for mass production and storage of T. basalis and T. podisi during autumn and winter.

Egg parasitoids of Anticarsia gemmatalis Hübner (Lepidoptera: Noctuidae) in soybeans

Levantamentos em lavouras de soja foram conduzidos durante cinco safras (1994/95 a 1998/99) em tres localidades no Sul do Parana, para verificar a ocorrencia de parasitismo em ovos de Anticarsia gemmatalis Hubner (Lepidoptera: Noctuidae). Foram encontradas cinco especies pertencentes a tres familias de Hymenoptera: Trichogramma pretiosum Riley, T. rojasi Nagaraja & Nagarkatti, T. atopovirilia Oatman & Platner (Trichogrammatidae), Telenomus cyamophylax Polaszek (Scelionidae) e Encarsia porteri (Mercet) (Aphelinidae). Destas, T. atopovirilia e E. porteri sao citadas pela primeira vez parasitando ovos de A. gemmatalis na America do Sul. O elevado numero de especies encontrado demonstra que os parasitoides de ovos desempenham um papel relevante no controle natural da lagarta da soja; todavia, para o seu potencial ser efetivamente explorado, ha necessidade do uso racional de inseticidas seletivos que permitam a sobrevivencia desses parasitoides.

Importance of carbohydrate sources to the reproductive output of the wheat armyworm Pseudaletia sequax

1 The importance of nutrients consumed by adults differs among lepidopteran species. Knowledge of adult nutritional requirements is particularly useful when adopting biological control strategies that involve the use of flowering plants to improve the effectiveness of natural enemies. This is because nectar may also serve as a carbohydrate source for the pest. 2 We evaluated the effect of different sources and concentrations of carbohydrate consumed by adults on the performance and fitness of the wheat armyworm Pseudaletia sequax Franclemont, which is an important pest of cereal crops. 3 The consumption of carbohydrates by the adults significantly increased the length of the oviposition period, fecundity, fertility and longevity of P. sequax. Adult nutrition also affected the daily oviposition pattern of the females. 4 The demographic parameters estimated for each diet regime (i.e. intrinsic rate of increase, finite rate of increase and net reproductive rate) were influenced by adult nutrition. These parameters also varied according to the source and concentration of carbohydrates. 5 The results obtained in the present study suggest that the use of perennial flowering plants to provide a food source for natural enemies can also favour the pest.

Natural parasitism in eggs of Anticarsia gemmatalis Hübner (Lepidoptera, Noctuidae) by Trichogramma spp. (Hymenoptera, Trichogrammatidae) in Brazil

Field surveys were carried during four soybean seasons in Southern Brazil to evaluate the occurrence of parasitoids in eggs of Anticarsia gemmatalis Hubner, 1818 and their incidence along the crop season. Eggs were collected by visual search on soybean leaves and from plants kept inside cages where A. gemmatalis moths were allowed to lay eggs. Trichogramma acacioi Brun, Moraes & Soares, 1984 was recorded for the first time in eggs of A. gemmatalis and the citations in the literature of Trichogramma lasallei Pinto, 1998 in Brazil where based on the material collected in this survey. Apart from these species, Trichogramma pretiosum Riley, 1879, Trichogramma rojasi Nagaraja & Nagarkatti, 1973 and Trichogramma atopovirilia Oatman & Platner, 1983 were also collected, all of which have been previously recorded in this host. Parasitized eggs were collected all over the period of occurrence of A. gemmatalis, from January to April each year. Total parasitism ranged from 4.8% in 2000 and 2002, 23.3% in 2001 and 28.9% in 2003. T. pretiosum and T. acacioi accounted for more than 80% of the parasitoids emerged each year, followed by T. atopovirilia, T. rojasi and T. lasallei, with less than 20% of incidence. Both the sex ratio and the mean number of parasitoids/egg did not differ among the species. Searching for A. gemmatalis eggs proved to be time consuming in comparison to the collection of eggs laid by moths inside the cages, which showed to be a useful method to provide qualitative estimates of parasitism in eggs of A. gemmatalis.

Incidência natural e biologia de Trichogramma atopovirilia Oatman & Platner, 1983 (Hymenoptera, Trichogrammatidae) em ovos de Anticarsia gemmatalis Hübner, 1818 (Lepidoptera, Noctuidae)

Trichogramma atopovirilia Oatman & Platner is an egg parasitoid of the corn earworm Helicoverpa zea (Boddie) (Lepidoptera, Noctuidae), and has recently been collected from eggs of Anticarsia gemmatalis Hubner on soybeans. In order to evaluate the suitability of A. gemmatalis eggs as hosts of T. atopovirilia, field surveys were conducted in 1999 and 2000 on corn and soybeans, and a colony of the parasitoid was established in laboratory. At 25 oC, development from oviposition to emergence lasted nine days and a sex-ratio of 0.58 (females:males) was obtained. Females lived significantly longer (11.4 days) when kept in ovipositional activity, than in the absence of host eggs (6.6 days). Total fecundity averaged 104.5 parasitized eggs, resulting in the emergence of 138.3 descendents. Mean daily fecundity was highest (30 eggs/female) on the first day. Oviposition continued until one day before the death of the females, however 70% of the eggs were laid during the first four days after emergence. A female-biased progeny was produced during the first three days of oviposition, whereas further ovipositions were male-biased. Females lived significantly longer when exposed to host eggs in comparison to females deprived of eggs. The results show that eggs of A. gemmatalis are suitable for the development of T. atopovirilia, and this parasitoid should be considered in future programs of biological control of the velvetbean caterpillar.

Telenomus cyamophylax n. sp. (Hymenoptera: Scelionidae) attacking eggs of the velvetbean caterpillar, Anticarsia gemmatalis Hübner (Lepidoptera: Noctuidae)

Telenomus cyamophylax Polaszek, n. sp. is described from the eggs of the soybean pest velvetbean Anticarsia gemmatalis (Hubner) (Lepidoptera: Noctuidae) caterpillar. This new species belongs to the californicus-group sensu Johnson, 1984. Biological data, including one alternative host, are given.

Capacidade reprodutiva e longevidade de Glyptapanteles muesebecki (Blanchard) (Hymenoptera: Braconidae) parasitando lagartas de Pseudaletia sequax Franclemont (Lepidoptera: Noctuidae)

A capacidade reprodutiva de Glyptapanteles muesebecki (Blanchard) (Hymenoptera: Braconidae) foi estudada em laboratorio (20 ± 1oC; 12 horas de fotofase) utilizando-se como hospedeiros lagartas de segundo instar de Pseudaletia sequax Franclemont (Lepidoptera: Noctuidae). Femeas expostas a cinco lagartas por dia viveram em media 8,4 dias, enquanto que femeas criadas na ausencia de hospedeiro viveram em media 20,6 dias. Femeas de G. muesebecki parasitaram em media 20,8 lagartas durante a vida, produzindo um total de 666,8 descendentes. O parasitismo diario foi de 3,6 hospedeiros por femea no primeiro dia apos a emergencia e manteve-se acima de dois hospedeiros por femea ate o oitavo dia. Ate cinco lagartas foram parasitadas por femea em um periodo de 24 horas.

Damage by Tibraca limbativentris Stål (Pentatomidae) to Upland Rice Cultivated in Amazon Rainforest Region (Brazil) at Different Growth Stages

In this study, we evaluated the damage caused in the field by Tibraca limbativentris Stål adults at different levels of infestation (0, 1, 2, and 4 stink bugs) per three rice plants during three growth stages (V8, V13, and R4 stages) of upland rice cultivated in southwestern of Pará State, Amazon Rainforest region, Brazil. Heading time (panicle exertion) was affected by T. limbativentris infestations mainly in the vegetative stage and the whiteheads percentage in treatments ranged from 18.2 to 38%. The dead hearts percentages varied between 0 and 21.5%, and the mean number of primary branches (ramifications) ranged from 5.9 ± 0.4 to 12.3 ± 0.2. The number of empty spikelets was only affected in infestations with four insects/three plants, while the quantity of filled grains per panicle was affected only when infestations occurred during the vegetative stage. The total number of spikelets (filled + empty) per panicle decreased significantly in all phenological stages, and the percentage of damage ranged from 17 to 44% among treatments. Based on the proportion of damage observed, we suggest doubling the number of insects presently used as action threshold to 2 and 4 stink bugs per 15 stalks sampled for the vegetative stage, and of 1 or 2 stink bugs per 15 stalks sampled at the beginning of reproductive stage (R3/R4). Also, the field should be monitored during the entire vegetative stage, since most damage was observed in this phenological stage.

Effect of temperature on the development and progeny production of Glyptapanteles muesebecki (Blanchard) (Hymenoptera: Braconidae) parasitizing larvae of Pseudaletia sequax Franclemont (Lepidoptera: Noctuidae)

The developmental time of Glyptapanteles muesebecki (Blanchard) parasitizing the armyworm Pseudaletia sequax Franclemont, and the number of pupae/host were determined at six constant temperatures ranging from 14° to 30°C. The egg + larval stages lasted from 17.8 days at 26° and 29°C to 56.4 days at 14°C, while the pupal stage ranged from 6.4 days at 29°C to 34.5 days at 14°C. G. muesebecki required 291.9 degree-days (DD) above the lower threshold of 8.9°C to complete the egg + larval development, while the pupae required 107.0 DD above 11.1°C. Development from egg to adult was completed after 397.4 DD above the lower threshold of 9.6°C. The number of pupae/host was not significantly different between 18°° and 26°C, and ranged from 86.9 at 22°C to 92.1 at 18°C. At the lower (14°°C) and upper (29°C) threshold temperatures, this number was significantly lower, averaging 27.6 and 19.8 pupae/host, respectively. Moreover, at 14° and 29°C the proportion of parasitized caterpillars was significantly lower than in the range between 18° and 26°C and at the lower temperature there was no synchronism in the pupation of parasitoids from the same host. At 30°C, the host larvae died before the emergence of the parasitoids. At 18, 22 or 26°C, the development and progeny production of G. muesebecki was not affected in the laboratory after five consecutive generations.

Efeito do parasitismo por Glyptapanteles muesebecki (Blanchard) no consumo e utilização do alimento por Pseudaletia sequax Franclemont

Food consumption and utilization for unparasitized larvae of Pseudaletia sequax Franclemont (Lepidoptera: Noctuidae) in relation to parasitized larvae with Glyptapanteles muesebecki (Blanchard) (Hymenoptera: Braconidae) was evaluated in laboratory, using kikuyo grass (Pennisetum clandestinum) as larval food. Parasitized larvae consumed significantly less foliage than unparasitized ones, although the larval stage of parasitized larvae was longer than the healthy ones. Parasitized larvae which had seven instars produced more parasitoids and consumed significantly more foliage than parasitized larvae which had six instars. Relative consumption rate (RCR), relative metabolic rate (RMR) and approximate digestibility (AD) were significantly higher in parasitized larvae, but the relative growth rate (RGR) and the efficiency of ingested (ECI) and digested (ECD) food were higher in unparasitized larvae. G. muesebecki regulates growth and development of P. sequax through the number of eggs laid. The values obtained for the number of pupae/host were positively correlated with food consumption and final weight of the host. The development time of the parasitoid was also positively correlated to the number of pupae/host.