Nymph and adult biology and seasonal abundance of Loxa deducta (Walker) on privet, Ligustrum lucidum

Biologia de ninfas e de adultos e abundância estacional de Loxa deducta (Walker) em ligustro, Ligustrum lucidum

Abstracts

Laboratory and field studies indicated that privet, Ligustrum lucidum (Oleaceae), is an important host plant of the neotropical stink bug, Loxa deducta (Walker) (Hemiptera: Pentatomidae) in northern Paraná state. Survivorship of nymphs was high (82.9%) when fed immature fruits of privet. Nymph developmental time (from the 2nd stadium to adult) lasted <FONT FACE=Symbol>»</FONT> 49 d. At adult emergence, females attained greater (199.5 mg) fresh body weight than males (180.0 mg). Survivorship of adult L. deducta decreased gradually with time. Mean total longevity was <FONT FACE=Symbol>»</FONT> 62 d for females and <FONT FACE=Symbol>»</FONT> 55 d for males. Of 30 females observed, 25 (83.3%) oviposited when fed fruits of privet. The preoviposition period was 13.9 (± 0.51) d; fecundity was 17.8 (± 1.60) egg masses/female, and 236.0 (± 21.98) eggs/female; egg hatchability was 65.0 (± 6.48)%. Considering the total period of 4-wks, the percentage increase in fresh body weight was <FONT FACE=Symbol>»</FONT> 70% for females, and <FONT FACE=Symbol>»</FONT> 45% for males. During summer months (December to February), relatively low numbers of insects were collected on privet. During March, nymph and adult populations increased reaching a peak during April, and decreasing in May at the end of autumn. This tendency continued throughout winter (June-July-August), reaching almost zero in September at the beginning of spring, and increasing somewhat again in October-November.

Insecta; Hemiptera; Heteroptera; Pentatomidae; bioecology; host plant

Estudos em laboratório e a campo indicaram que o ligustro (alfeneiro), Ligustrum lucidum (Oleaceae) é uma planta hospedeira importante do percevejo neotropical, Loxa deducta (Walker) (Hemiptera: Pentatomidae) no norte do estado do Paraná. A sobrevivência das ninfas foi alta (82,9%) quando se alimentaram de frutos imaturos do ligustro. O tempo de desenvolvimento ninfal (do 2º a adulto) foi de <FONT FACE=Symbol>»</FONT> 49 d. No dia da emergência dos adultos, as fêmeas alcançaram um peso maior (199,5 mg) do que os machos (180,0 mg). A sobrevivência de adultos de L. deducta decresceu gradualmente com o tempo. A longevidade média foi de <FONT FACE=Symbol>»</FONT> 62 d para as fêmeas e <FONT FACE=Symbol>»</FONT> 55 d para os machos. De 30 fêmeas observadas, 25 (83,3%) ovipositaram quando alimentadas de frutos imaturos de ligustro. O período de pré-oviposição foi de 13,9 (± 0,51) d; a fecundidade foi de 17,8 (± 1,60) massas de ovos/fêmea, e de 236,0 (± 21,98) ovos/fêmea; a eclosibilidade dos ovos foi de 65,0 (± 6,48)%. Considerando o período total de quatro semanas, a percentagem de aumento em peso corporal fresco foi <FONT FACE=Symbol>»</FONT> 70% para fêmeas e <FONT FACE=Symbol>»</FONT> 45% para os machos. Durante os meses de verão (dezembro a fevereiro), os insetos foram coletados em baixo número no alfeneiro. Em março, as populações de ninfas e de adultos aumentaram, alcançando o pico máximo em abril, decrescendo em maio no final do outono. Essa tendência de queda continuou durante os meses de inverno (junho-julho-agosto), atingindo quase zero em setembro, no início da primavera, aumentando novamente em outubro-novembro.

Insecta; Hemiptera; Heteroptera; Pentatomidae; bioecologia; planta hospedeira

ECOLOGIA, COMPORTAMENTO E BIONOMIA

Nymph and adult biology and seasonal abundance of Loxa deducta (Walker) on privet, Ligustrum lucidum

Biologia de ninfas e de adultos e abundância estacional de Loxa deducta (Walker) em ligustro, Ligustrum lucidum

Antônio R. Panizzi^I; Ana P. M. Mourão^II; Émerson D. M. Oliveira^I

^IEmbrapa, Centro Nacional de Pesquisa de Soja, Caixa postal 231, 86001-970, Londrina, PR

^IIUniversidade Estadual de Londrina, Departamento de Agronomia, Caixa postal 6001, 86051-970, Londrina, PR

ABSTRACT

Laboratory and field studies indicated that privet, Ligustrum lucidum (Oleaceae), is an important host plant of the neotropical stink bug, Loxa deducta (Walker) (Hemiptera: Pentatomidae) in northern Paraná state. Survivorship of nymphs was high (82.9%) when fed immature fruits of privet. Nymph developmental time (from the 2nd stadium to adult) lasted » 49 d. At adult emergence, females attained greater (199.5 mg) fresh body weight than males (180.0 mg). Survivorship of adult L. deducta decreased gradually with time. Mean total longevity was » 62 d for females and » 55 d for males. Of 30 females observed, 25 (83.3%) oviposited when fed fruits of privet. The preoviposition period was 13.9 (± 0.51) d; fecundity was 17.8 (± 1.60) egg masses/female, and 236.0 (± 21.98) eggs/female; egg hatchability was 65.0 (± 6.48)%. Considering the total period of 4-wks, the percentage increase in fresh body weight was » 70% for females, and » 45% for males. During summer months (December to February), relatively low numbers of insects were collected on privet. During March, nymph and adult populations increased reaching a peak during April, and decreasing in May at the end of autumn. This tendency continued throughout winter (June-July-August), reaching almost zero in September at the beginning of spring, and increasing somewhat again in October-November.

Key words: Insecta, Hemiptera, Heteroptera, Pentatomidae, bioecology, host plant.

RESUMO

Estudos em laboratório e a campo indicaram que o ligustro (alfeneiro), Ligustrum lucidum (Oleaceae) é uma planta hospedeira importante do percevejo neotropical, Loxa deducta (Walker) (Hemiptera: Pentatomidae) no norte do estado do Paraná. A sobrevivência das ninfas foi alta (82,9%) quando se alimentaram de frutos imaturos do ligustro. O tempo de desenvolvimento ninfal (do 2º a adulto) foi de » 49 d. No dia da emergência dos adultos, as fêmeas alcançaram um peso maior (199,5 mg) do que os machos (180,0 mg). A sobrevivência de adultos de L. deducta decresceu gradualmente com o tempo. A longevidade média foi de » 62 d para as fêmeas e » 55 d para os machos. De 30 fêmeas observadas, 25 (83,3%) ovipositaram quando alimentadas de frutos imaturos de ligustro. O período de pré-oviposição foi de 13,9 (± 0,51) d; a fecundidade foi de 17,8 (± 1,60) massas de ovos/fêmea, e de 236,0 (± 21,98) ovos/fêmea; a eclosibilidade dos ovos foi de 65,0 (± 6,48)%. Considerando o período total de quatro semanas, a percentagem de aumento em peso corporal fresco foi » 70% para fêmeas e » 45% para os machos. Durante os meses de verão (dezembro a fevereiro), os insetos foram coletados em baixo número no alfeneiro. Em março, as populações de ninfas e de adultos aumentaram, alcançando o pico máximo em abril, decrescendo em maio no final do outono. Essa tendência de queda continuou durante os meses de inverno (junho-julho-agosto), atingindo quase zero em setembro, no início da primavera, aumentando novamente em outubro-novembro.

Palavras-chave: Insecta, Hemiptera, Heteroptera, Pentatomidae, bioecologia, planta hospedeira.

The neotropical stink bug Loxa deducta (Walker) has been little investigated. It has been reported from several plants, but to feed and reproduce only on Citrus reticulata (D. Link, personal communication to ARP), and on the the legume trees Bauhinia candicans in Rio Grande do Sul state, south Brazil (Link & Grazia 1987), and leucaena, Leucaena leucocephala in Paraná and São Paulo states in the southeast (Panizzi & Rossi 1991). It has also been said to feed on soybean, Glycine max, but in low numbers (Link & Grazia 1987). Two other species of Loxa are recorded from Brazil [L. virescens Amyot & Serville, a former synonym of L. flavicollis (Drury), and L. viridis Palisot de Beauvois = L. picticornis Horwath) but all are of minor economic importance (Silva et al. 1968 revised by Grazia 1977; see also Eger 1978). In Argentina, L. virescens (referred as L. flavicollis) is reported as a secondary pest of soybean (Rizzo 1972).

During 1996, nymphs and adults of L. deducta were observed colonizing privet, Ligustrum lucidum (Oleaceae) in Londrina, Paraná state (latitude 23º 11' S, longitude 51º 11' S). This plant is very abundant and is used as an ornamental tree in the urban area of Londrina. It is an exotic plant, originating from China (Milano 1949). During most of the year plants carry fruits (berries), which are very abundant, especially on the outer surface of the plant. This gives to the plant a typical light-green coloration when fruits are immature, and darkish-purple at the time of fruit maturation.

In a previous study it was found that L. lucidum (which was misidentified as L. japonicum) is an important host of the southern green stink bug, Nezara viridula (L.) (Panizzi et al. 1996). Nymphs and adults performan very well on fruits of this plant, which are now used as a standard diet for mass rearing of the bug in our laboratory. Because of this, and because of the presence of L. deducta on this plant, this study was conducted to test the suitability of privet fruits for nymphal development and adult reproduction. In addition, surveys of L. deducta were carried out to determine the seasonal abundance of nymphs and adults on this host plant throughout the year.

Material and Methods

Laboratory Study with Nymphs. L. deducta adults were collected from L. lucidum and taken to the laboratory. A variable number (two to three) pairs were placed in plastic boxes (12.0 x 12.0 x 3.8 cm) lined with filter paper and covered with a lid. Adults were fed immature fruits of L. lucidum. Egg masses were collected on the day of oviposition and placed in petri dishes (9.0 x 1.5 cm) with moistened filter paper. On the 1st d of the 2nd stadium (1st instars do not feed), nymphs were removed and placed individually in petri dishes. Immature fruits of L. lucidum were offered to 82 nymphs (replicates).

Petri dishes were placed at random in an environmental chamber maintained at 25 ± 1 ºC and 65 ± 5% RH with a photoperiod of 14:10 (L:D) h. During September to November 1996, daily observations were made on molting and mortality, and food was replaced every 2 d. Nymphal development time and percentage of mortality of each instar (except the 1st) and from 2nd instar to adult, were calculated. Fresh body weight at adult emergence was taken using an electronic balance. Data on time of development among instars were submitted to analysis of variance and means compared using Duncan's multiple range test (P&lt 0.05). Fresh body weight between females and males were compared using student's t-test (P&lt 0.05).

Laboratory Study with Adults. From additional nymphs reared in the laboratory using immature fruits of L. lucidum, adults were obtained. Single female/male pairs were placed in a rearing plastic box (12.0 x 12.0 x 3.8 cm) with moistened filter paper and covered with a lid. Thirty pairs were fed immature fruits of L. lucidum. Food was replaced every 2 d.

During November 1996 to February, 1997, daily observations were made on adult survivorship and reproduction. Survivorship up to day 120 and total longevity, percentage of females ovipositing, female age at 1st oviposition, mean number of egg masses and eggs/female, and percentage of egg hatch were calculated. Adult body weight gain (%) during the 1st, 2nd, 3rd, 4th, and 1st-4th weeks of life was calculated. Data on total longevity, and percentage fresh body weight changes between females and males, and among weeks, were compared using Duncan's multiple range test (for more than two means) and student's t-test (for two means) at P &lt 0.05.

Field Survey of Nymphs and Adults. To monitor the abundance of L. deducta nymphs and adults on L. lucidum, weekly samples were taken from April 1996 to March 1997. Each sample consisted of shaking a branch section (30 cm) with fruits inside a sweep net. A total of 30 samples were taken each week, out of 10 trees (three samples/tree) chosen at random at the urban area of Londrina, and taken to the laboratory. The number of nymphs and adults L. deducta were recorded. Data were calculated as the total number of nymphs and adults obtained each month (total of 120 samples/month) for the 12 months covered during the study.

Results and Discussion

Laboratory Study with Nymphs. Survivorship of L. deducta nymphs was relatively great (17.1% mortality) (Table 1) compared to what has been observed for this bug fed on other hosts such as leucaena (53.9% mortality on immature seeds, and 82.6% on immature pods) or soybean (68.8% mortality on immature pods) (Panizzi & Rossi 1991). Feeding on fruits of the the same privet species, another pentatomid, N. viridula showed greater mortality (38.7%; Panizzi et al. 1996). Besides a possibly greater nutritional quality of privet fruits for nymphs, the fact that they fed on exposed fruits, which are free of pilosity allowing free access, may have enhanced nymph survivorship. Nymph mortality at each instar varied from 1.2% (for the 4th instar) to 7.3% (for the 3rd instar) (Table 1).

Nymph developmental time (from the 2nd stadium to adult) lasted ca. 49 d (Table 1). This value is lower than the one observed for L. deducta nymphs of immature pods of leucaena (» 56 d) but greater than the time needed to complete development on immature seeds of leucaena (» 44 d) or on immature soybean pods (» 36 d) (Panizzi & Rossi 1991). Second and 3rd stadia took less time to complete development, and the 4th and 5th stadia took 2-3 fold as much time (Table 1).

At adult emergence, females attained greater fresh body weight than males (Table 2), which is considered a common event among heteropterans. Compared with other phytophagous pentatomids, L. deducta may be considered a large species, females weighting » 200 mg, a weight greater than those referred to other pentatomids common in soybean fields (body weight range of females 56 - 134 mg; Panizzi 1987).

Laboratory Study with Adults. Survivorship of adult L. deducta decreased gradually with time. For instance, 20 d after adult life, » 90% of females and males were alive (Fig. 1). After 60 d, 60% of females and 45% of males were alive; less than 10% survived day 100, and no adults reached day 120. Mean total longevity was » 62 d for females and » 55 d for males (Fig. 1). These observed values of life span for L. deducta on L. lucidum fruits are much higher than those observed when they fed on other food plants. For example, on leucaena pods total longevity was 33.9 d for females and 18.5 d for males; on soybean these values were even smaller: 20 d for females and 15.6 d for males (Panizzi & Rossi 1991).

In a similar way, the adult reproductive performance of L. deducta on privet was impressive compared to that observed on other food plants [leucaena and soybean - Panizzi & Rossi (1991)]. Of 30 females observed, 25 (83.3%) oviposited when fed fruits of privet; on leucaena 60% of females oviposited, and on soybean only 12.5% of females laid eggs. The preoviposition period was 13.9 (± 0.51) d on privet; on leucaena it was 17.1 d, and up to 39.0 d on soybean. On privet, fecundity was 17.8 (± 1.60) egg masses/female, and 236.0 (± 21.98) eggs/female; on leucaena these values were 5.0 and 65.6, and on soybean 2.0 and 27.0, respectively. Egg hatchability on privet was 65.0 (± 6.48)%; on leucaena egg hatchability was 42.0%, and on soybean no eggs hatched. These values on reproduction indicate that L. lucidum is a very suitable food for female L. deducta, and that other hosts such as the legumes leucaena and soybean are much less appropriate for this insect's reproduction.

Adult L. deducta gained fresh body weight, especially during the 1st week of life (55% for females and 40% for males - Fig. 2). During the 2nd week of life, body weight increased an additional 11% for females and 8% for males; during the following 2-wks no substantial change in body weight was observed. Considering the total period of 4-wks, the percentage increase in fresh body weight was ca. 70% for females, and ca. 45% for males. These values are greater than those observed for L. deducta females and males fed on leucaena pods (51.7% and 33.9 %, respectively) or fed on soybean pods (27.7% and 26.0%, respectively) (Panizzi & Rossi 1991). Females gained significantly (P < 0.05) more weight than males during the 1st week, and during the total period of 4-wks (Fig. 2).

Field Survey of Nymphs and Adults. The seasonal abundance of L. deducta nymphs and adults on privet trees was variable, although the bugs were present year round. The nymph and adult populations showed similar trends. During summer months (December to February), relatively low numbers of insects were collected (Fig. 3). During March, nymph and adult populations increased substantialy, reaching a peak during April, and decreasing in May at the end of autumn. This tendency continued throughout winter (June-July-August), reaching almost zero in September at the beginning of spring, and rising up again in October (Fig. 3). The decrease in populations observed during spring, particularly of nymphs, may be explained by the low availability of plants carrying fruits, which at this time are initiating bloom. Thus, the rate of reproduction of L. deducta will decrease during spring-early summer. In Rio Grande do Sul state, L. deducta occurs on several host plants during autumn-winter-spring, including a species of privet, Ligustrum ovalifolium; no hosts plants were found during summer, except for the legume tree B. candicans (Lopes et al. 1974, Link & Grazia 1987).

In conclusion, these results demonstrate that privet, L. lucidum, is a very important host of L. deducta; nymphs develop on it and adults reproduce at a much higher rate than on other plant species, hosting the bugs year round. Therefore, this plant plays an important role in the build up of populations of this bug, as do many hosts of other pentatomid species (Panizzi 1997). Fortunately, L. deducta is a minor pest of economically important crops.

Acknowledgments

We thank Dr. Jocélia Grazia, Department of Zoology, Universidade Federal do Rio Grande do Sul (UFRGS), for the informations on the taxonomic status of Loxa species, and Dr. Bruno Irgang, Department of Botany, UFRGS, and Dr. Lucia Rossi, Instituto de Botânica, São Paulo, for the plant identification. Thanks are also due to Carl W. Schaefer, Flávio Moscardi, and Dionísio Brunetta for reviewing an early draft of the manuscript. This is a contribution of Embrapa Soja number 004/98, published with the approval of the technical director.

Literature Cited

Received 10/XII/97. Accepted 18/III/98.

• Eger, J.E. 1978. Revision of the genus Loxa (Hemiptera: Pentatomidae). J. N. Y. Entomol. Soc. 86: 224-259.
• Grazia, J. 1977. Revisão dos pentatomídeos citados no "Quarto Catálogo dos Insetos que Vivem nas Plantas do Brasil (Hemiptera: Pentatominae: Pentatomini). Dusenia 10: 161-174.
• Link, D. & J. Grazia. 1987. Pentatomídeos da região central do Rio Grande do Sul. An. Soc. Entomol. Brasil 16: 115-129.
• Lopes, O.J., D. Link, & I.V. Basso. 1974. Pentatomídeos de Santa Maria - lista preliminar de plantas hospedeiras. Rev. Cent. Cien. Rur. 4: 317-322.
• Milano, V.A. 1949. Las especies del genero "Ligustrum"cultivadas en la Argentina. Rev. Invest. Agric. 3: 353-380.
• Panizzi, A.R. 1987. Nutritional ecology of seed-sucking insects of soybean and their management. Mem. Inst. Oswaldo Cruz 82: 161-175.
• Panizzi, A.R. 1997. Wild hosts of pentatomids: ecological significance and role in their pest status on crops. Annu. Rev. Entomol. 42: 99-122.
• Panizzi, A.R & C.E. Rossi. 1991. Efeito da vagem e da semente de Leucaena e da vagem de soja no desenvolvimento de ninfas e adultos de Loxa deducta (Hemiptera: Pentatomidae). Rev. Bras. Biol. 51: 607-613.
• Panizzi, A.R., L.M. Vivan, B.S. Corrêa-Ferreira & L.A. Foerster. 1996. Performance of southern green stink bug (Heteroptera: Pentatomidae) nymphs and adults on a novel food plant (Japanese privet) and other hosts. Ann. Entomol. Soc. Am. 89: 822-827.
• Rizzo, H.F. 1972. Enemigos animales del cultivo de la soja. Rev. Inst. Bol. Cer., 2851, 6p.
• Silva, A.G. d'A., C.R. Gonçalves, D.M. Galvão, A.J.L. Gonçalves, J. Gomes, M.N. Silva & L. Simone. 1968. Quarto catálogo dos insetos que vivem nas plantas do Brasil - seus parasitas e predadores. Min. Agric., Rio de Janeiro, Parte II, vol I, 1-622.

Publication Dates

• Publication in this collection
  07 July 2006
• Date of issue
  June 1998

History

• Received
  10 Dec 1997
• Accepted
  18 Mar 1998