A Comparison of Growth and Development of Three Major Agricultural Insect Pests Infected with Heliothis virescens ascovirus 3h (HvAV-3h)

Abstract

Ascoviruses are double-stranded DNA viruses that are pathogenic to lepidopteran hosts, particularly noctuid larvae. Infection of a larva is characterized by retarded growth, reduced feeding and yellowish body color. In this paper, we reported the growth and development of three major agricultural noctuid insect pests, Helicoverpa armigera (Hübner), Spodoptera exigua (Hübner) and Spodoptera litura (Fabricius), infected with Heliothis virescens ascovirus 3h (HvAV-3h). Using 10-fold serial dilutions (0 to 7) of HvAV-3h-containing hemolymph to infect S. litura larvae, we found no significant difference in larval mortalities from 0 to 103-fold dilutions; however, significant differences were observed at 104-fold dilution and above. Using a 10-fold dilution of HvAV-3h-containing hemolymph to infect H. armigera, S. exigua and S. litura larvae, we found that the growth and development were significantly affected. All infected larvae could not pupate; the survival times of treated H. armigera, S. litura and S. exigua larvae were significantly longer than untreated control larvae. Body weight showed significant difference between treated and untreated control group from day 1 after inoculation in H. armigera and S. exigua, but day 2 in S. litura. Additionally, food intake also showed significant difference between treated and untreated control group from day 2 after inoculation in H. armigera and S. litura, but day 3 in S. exigua.

Development ofMicroplitis similis(Hymenoptera: Braconidae) on Two Candidate Host Species,Spodoptera lituraandSpodoptera exigua(Lepidoptera: Noctuidae)

“…Spodoptera litura, S. exigua, and H. armigera larvae were from colonies developed in our laboratory (Li et al 2013). These colonies were established from wild-collected individuals in a cotton field near Hunan Agricultural University, Changsha, Hunan, China.…”

“…For percentage parasitism, a Student's t-test was performed to analyze the significance among data of the 2 candidate hosts S. exigua and S. litura and the negative control host H. armigera. For daily body weight after parasitism of the 2 candidate hosts, a 1-way analysis of variance (ANOVA) was used to compare the overall differences among treatments (Li et al 2013). For head capsule width data, a 2-way ANOVA was conducted to show the impact of both species and status (parasitized and non-parasitized) on the change of head capsule width of S. exigua and S. litura (McLoud 2011).…”

Altering of host larval (Spodoptera exigua) calcineurin activity in response to ascovirus infection

“…SfAV‐1a), HvAV‐3h appears to be a strain with a relatively broad host range. The mortalities of cotton bollworms ( H. armigera ), beet armyworms ( S. exigua ) and tobacco cutworms ( S. litura ) infected by HvAV‐3h are 94.4 ± 3.7%, 88.9 ± 3.7% and 94.4 ± 1.5%, respectively . Prior to succumbing to HvAV‐3h, infection normally leads to observed stunted growth and reduced diet consumption in the host larvae.…”

“…13,14 The effects of ascovirus infection on larval growth and development have been studied in several noctuid species, including Trichoplusia ni, Spodoptera frugiperda, S. exigua, S. litura, Helicoverpa armigera, H. zea and Heliothis virescens. 4,12,14,15 Heliothis virescens ascovirus 3h (HvAV-3h), which is transmitted by the braconid wasp (Microplitis similis), was the first ascovirus isolated in China by Huang et al 9 Compared to a typical ascovirus species (e.g. SfAV-1a), HvAV-3h appears to be a strain with a relatively broad host range.…”

“…The mortalities of cotton bollworms (H. armigera), beet armyworms (S. exigua) and tobacco cutworms (S. litura) infected by HvAV-3h are 94.4 ± 3.7%, 88.9 ± 3.7% and 94.4 ± 1.5%, respectively. 15,16 Prior to succumbing to HvAV-3h, infection normally leads to observed stunted growth and reduced diet consumption in the host larvae. Ascoviruses appear to be sufficiently efficient to warrant consideration for development into biological insecticides.…”