Presence of a predator image in potential breeding sites and oviposition responses of a dengue vector

In dengue vector control, attempts to minimize or replace the use of pesticides have mostly involved use of predators, but success has been severely impeded by difficulties associated with financial and environmental costs, predator mass production, and persistence in target habitats. Visual deterrents have been used successfully to control animal pests, in some cases in an effort to replace pesticide use. Despite evidence that visual signals are crucial in site choice for egg deposition by dengue vectors, and that female mosquitoes respond to artificial predation, the role of predator intimidation as it affects the oviposition behavior of dengue vectors remains largely unexplored. Here, we examined the oviposition responses of Aedes aegypti exposed to various mosquito predator pictures. Gravid females were presented with equal opportunities to oviposit in two cups with predator images [Toxorhynchites splendens—TXI, Goldfish (Carassius auratus)—small (SFI) and large (LFI) and Tx. splendens + Goldfish—TXFI] and two others without pictures. Differences in egg deposition were examined between sites with and without these images. When given a chance to oviposit in cups with and without TXI, Ae. aegypti females were similarly attracted to both sites. When provided an opportunity to oviposit in cups displaying pictures of fish (SFI or LFI) and blank cups, egg deposition rates were much lower in the fish picture sites. Females showed a preference for blank cups over TXFI for egg deposition. They also equally avoided cups with pictures of fish, regardless of the size of the picture. Our results indicate that the presence of images of goldfish and their association with Tx. larvae significantly reduced egg deposition by Ae. aegypti, and this was not the case with the predatory larvae alone. The observations that the images of natural predators can repel gravid females of a dengue vector provide novel possibilities to develop effective and inexpensive alternative tools to harmful insecticides

Exposure of a Dengue Vector to Tea and Its Waste: Survival, Developmental Consequences, and Significance for Pest Management

Dengue mosquitoes are evolving into a broader global public health menace, with relentless outbreaks and the rise in number of Zika virus disease cases as reminders of the continued hazard associated with Aedes vectors. The use of chemical insecticidesthe principal strategy against mosquito vectorshas been greatly impeded due to the development of insecticide resistance and the shrinking spectrum of effective agents. Therefore, there is a pressing need for new chemistries for vector control. Tea contains hundreds of chemicals, and its waste, which has become a growing global environmental problem, is almost as rich in toxicants as green leaves. This paper presents the toxic and sublethal effects of different crude extracts of tea on Aedes albopictus. The survival rates of larvae exposed to tea extracts, especially fresh tea extract (FTE), were markedly lower than those in the control treatment group. In addition to this immediate toxicity against different developmental stages, the extracts tested caused a broad range of sublethal effects. The developmental time was clearly longer in containers with tea, especially in those with young larvae (YL) and FTE. Among the survivors, pupation success was reduced in containers with tea, which also produced low adult emergence rates with increasing tea concentration. The production of eggs tended to be reduced in females derived from the tea treatment groups. These indirect effects of tea extracts on Ae. albopictus exhibited different patterns according to the exposed larval stage. Taken together, these findings indicate that tea and its waste affect most key components of Ae. albopictus vectorial capacity and may be useful for dengue control. Reusing tea waste in vector control could also be a practical solution to the problems associated with its pollution

Differential Protein Contents in Two Members of the White fly Bemisia tabaci(Hemiptera:Aleurodidae)Complex:Reproductive and Invasive Implications

Abstract: Although the displacement of some native whitefly species by he B biotype of Bemisia tabaci ha been noted in China, it is still unclear physiological and molecular mechanisms predominate during such invasions. Here, we investigated proteome varialibility in both B biotype and the native ZHJI haplotype.ZHJI eggs showed larger numbers of specific proteins than B eggs. A set of proteins found in B eggs were present at higher levels in ZHJI.Three ZHJI egg proteins were present at higher levels in B eggs. ZHJI males possessed four specific proteins, and at least five other male proteins were shared by two whiteflies.Two proteins identified in ZHJI males were present at higher levels in B males. Three other shared male proteins weere found at much higher levels in ZHJI than in the B biotype. Both ZHJI and B expressed three specific female proteins. Most of the female proteins identified in ZHJI were present at much higher levels in B. In conclusion, protein content indexed by electrophoretic profiling has likely played an important role during the displacement of natives by the B biotype

The effects of moisture on ovipositional responses and larval eclosion of Aedes albopictus

Moisture plays a major role in the dynamics of mosquito populations, especially those breeding in container habitats. Despite this importance, the role of moisture conditions as they affect oviposition and egg development in Aedes vectors remains largely unexplored. We investigated the effect of exposing gravid female Aedes albopictus mosquitoes and their eggs to different moisture levels (MLs) for various periods on oviposition and hatching. Overall, high-moisture substrates (HMSs; 66 and 72) provided better environments for egg laying. The timing of initial egg laying was far longer at the lowest substrate moisture level (LSML, 25 and 41.2) than at HMSs. The numbers of eggs laid were much lower in the drier environments. At LSMLs, gravid females retained increasing numbers of mature eggs until death, and egg retention decreased gradually with increasing ML. The HMSs also provided better environments for larval eclosion. The numbers of eggs hatched were lower at the LSML than the HSML environment. No egg hatching occurred after 1 h exposure to moisture. However, egg hatching occurred by installment, with spontaneous hatching (SH) increasing gradually with increasing ML. High-moisture conditions combined with long exposure (30 h and 48 h) favored SH. These results suggest that Ae. albopictus females can respond to better moisture conditions for increased success of embryonation and larval eclosion. This information may be useful in the colonization of floodwater Aedes species

Peroxidase activity after viral infection and whitefly infestation in juvenile and mature leaves of solanum lycopersicum

Whitefly infestation and the begomoviruses that they transmit have been shown to affect the activities of plant defence proteins, but with no relation to heterophylly, a process of great importance underlying the overall biology of plants. Here, we have assessed the effects of Tomato yellow leaf curl virus (TYLCV) infection on Solanum lycopersicum peroxidase (POD) activity and have examined whether leaves of different ages exhibit differential POD activity in response to infection and infestation with Bemisia tabaci B biotype. We used leaf discs of two ages (juvenile and mature) with two different infection statuses (infected and healthy) to examine the activity of the tomato plant peroxidase using guaiacol as a substrate and taking exposure time into account. S. lycopersicum showed increased POD activity in the presence of TYLCV. The activity of the enzyme was higher in mature than in juvenile leaves. In general, both infected and healthy leaves exhibited greater POD activity during whitefly infestation. In the infested juvenile leaves, POD activity was much lower in the healthy leaves and increased gradually with period of exposure to B. tabaci B infestation. In contrast, the activity of the enzyme remained low in infested mature leaves in both the presence and absence of the virus even with increased exposure time. Determination of the distribution of an insect pest is critical for sampling and management. Leaf age is presumed to be associated with the within-host distribution of the geminivirus vector B. tabaci. Juvenile leaves will usually attract more insects due to increased nutritional value and weaker defences. Our results highlight the importance of leaf age/position on the whitefly - host plant - geminivirus interactions and have important implications for sampling and control strategies

Unusual developing sites of dengue vectors and potential epidemiological implications

Objective: To identify the unusual breeding sites of two dengue vectors, i.e. Aedes albopictus (Ae. albopictus) and Aedes aegypti (Ae. aegypti). Methods: During the second half of 2010, we performed an occasional survey in rural (Teluk Tempoyak) and urban (Gelugor) areas ofPenang Island, Malaysia, to identify cryptic breeding sites. Results: In the rural area, we found heterogeneous immature stages of Ae. albopictus in the water bowl of an encaged bird. We also observed Ae. aegypti eggs deposited in the flush tank of a toilet in the urban area. Conclusions:It can be concluded that both breeding patterns can increase contact with hosts (humans and birds) and presumably population densities of Ae. albopictus and Ae. aegy