La Jolla Virus: The Pathology and Transmission in Its Host Drosophila suzukii

Abstract

Drosophila suzukii, commonly known as spotted-wing drosophila, has emerged as a highly destructive pest in global fruit and wine production. The effectiveness of chemical control is significantly compromised by rapid resistance development and a limited range of insecticide options. Biological control presents a promising sustainable alternative. Our previous work suggested the La Jolla Virus (LJV) as a suitable candidate for the development of an insect virus-based control option. Here, we characterized the natural transmission and pathology of the virus. We tested various modes of horizontal transmission, including airborne, venereal and oral, and fecal routes. To understand LJV pathology in infected flies, we studied feeding behavior and demonstrated changes in food absorption compared to non-infected flies. We also investigated the impact on fecundity and egg-to-adult success rate. Altogether, these results collectively improve our understanding of LJV transmission in natural populations and the implication of infected flies in food ingestion and overall fitness.

Keywords: Drosophila suzukii; La Jolla virus; biological pest control; food intake; iflavirus; transmission.

Figure 1

The results of the real-time PCR after several days of the flies being in the vicinity of an infected fly culture. The graph demonstrates no significant change in the Ct of the extracted samples, concluding there was no infection. Results show no significant difference in the infection levels as the days went on. SD of day followed by top/bottom: Day 3: 2.136/1.788; Day 6: 1.567/0.925; Day 9: 1.755/2.241; Day 12: 2.183/2.277. The error bars represent the standard error mean (SEM). p-value = 0.38 alpha = 0.05.

Figure 2

The infection levels after the flies were allowed to mate for 3 days. The first two sets are the positive (IM × IVF, red dots) and negative controls (NIM × NIVF, orange dots), followed by the different combinations tested. All infection levels are significant compared to the negative control (NIVF + NIM) alpha = 0.05.

Figure 3

The infection levels in the flies ((A) Fecal transmission; (B) Oral Transmission) after several days of infection. The figure shows a steady infection rate in both experiments. Infected flies showed a significant difference to the non-infected control (p-value < 0.0001 in A,B).

Figure 4

Egg-to-adult success rate of non-infected versus infected flies for larvae (yellow bars), pupa (orange bars), and adults (gray bars). All differences are significant when α = 0.05. SE of difference = 3.274.

Figure 5

Cumulative duration of activity bouts. (A) The feeding activity of the non-infected females (blue) vs. the infected females (red). The software conducted a Mann–Whitney test and shows a p-value of 0.036. (B) The feeding activity of the non-infected males (blue) vs. the infected males (red) The software conducted a Mann–Whitney test and shows a p-value of 0.93.

Figure 6

Shows the cumulative number of feeding bursts. (A) The feeding activity of the non-infected females (blue) vs. the infected females (red). The software conducted a Mann–Whitney test and shows a p-value of 0.068. (B) The feeding activity of the non-infected males (blue) vs. the infected males (red) The software conducted a Mann–Whitney test and shows a p-value of 0.12.