Eleven studies met inclusion criteria. In studies using the room method, citronella oil and/or the combination of citronella oil and vanillin provided complete repellency at least 3 hours. In the cage-method meta-analysis, the protection time of citronella oil for preventing Aedes mosquitoes was shorter than DEET by 253 minutes (95% CI: 169–336). This review addresses repellency duration, not adult mosquito mortality, and it does not report statistically significant adulticidal effects for citronella preparations.

This systematic review demonstrates that citronella oil used in a variety of preparations is less effective than DEET in terms of duration of protection. Eleven studies met inclusion criteria. In studies using the room method, citronella oil and/or the combination of citronella oil and vanillin provided complete repellency at least 3 hours.

The study found that the mortality rate of Aedes aegypti exposed to 50% citronella oil spray was 97.3%, with some replications achieving 100% mortality. The statistical test results showed that the anti-mosquito spray made from citronella oil had a significant difference between the treatment and control groups (p value: 0.000).

This study aims to compare the knockdown time and Aedes aegypti mosquito mortality in the thermal fogging system between the use of citronella (Cymbopogon nardus) extract and malathion. The ANOVA test result was p = 0.004, indicating a significant effect on mean knockdown time and mosquito mortality.

The IR3535-based repellent protected against mosquito bites for an average of 22.9 minutes. The citronella-based repellents we tested protected for 20 minutes or less. There was no significant difference in protection time between the slow-release formulation containing 12 percent citronella and the formulation containing 5 percent citronella (P=0.07) or the two formulations containing 10 percent citronella (P=0.16 and P=0.80). The repellent containing only 0.05 percent citronella provided less protection than the Skin-So-Soft mineral-oil–based moisturizer (Avon) (P<0.001).

The repellency of citronella oil decreased over time, from 97.9% at 0 h to 71.4% at 1 h and 57.7% at 2 h, as did the repellency of fennel oil, from 88.6% at 0 h. ... These results indicated that the average CPT (complete protection time) of citronella oil for these 20 volunteers was 10.50 ± 1.20 min. ... The mean CPTs of 23.8% DEET and 5% citronella were 301.5 ± 37.6 min and 13.5 ± 7.5 min, respectively (Table 4).

Researchers tested the high-larval-efficacy group on adult mosquitoes using the CDC bottle bioassay protocol. In a 10% essential oil solution, adult mortality rates ranged from 44% to 100% depending on the oil tested. The article discusses adulticidal activity for several essential oils, supporting that some plant oils can kill adult mosquitoes under controlled conditions.

We determined the degree of personal protection provided by citronella, linalool, and geraniol in the form of commercially available candles or diffusers, both indoors and outdoors. Under the uniform conditions of the experiments, all substances repelled significantly more mosquitoes than the unprotected control. ... Indoors, the repellency rate of citronella candles was only 14% while the repellency rate of citronella diffusers was 68%. Outdoors, citronella diffusers placed 6 m from mosquito traps repelled female mosquitoes by 22%. We concluded that geraniol had significantly more repellent activity than citronella or linalool in both indoor and outdoor settings.

This 2024 critical review covers laboratory methods used to evaluate mosquito behavioral responses to repellents and summarizes multiple citronella studies. It reports that in arm-in-cage tests, products containing DEET displayed a significant reduction in attraction at all time points, whereas plant-based repellents like citronella showed shorter protection times and more variable effects. Citronella oil at 5% concentration was ranked behind hairy basil and lemongrass oils in repellent strength. The review emphasizes that most laboratory citronella studies measure landing/biting reduction rather than mortality, and notes that some plant-based repellents fail to show statistically significant differences from controls under certain conditions, highlighting variability and the absence of adult mosquito killing as an endpoint in many controlled experiments.

Citronella is a plant-derived essential oil used as an insect repellent. In addition to its known effects against mosquitoes, ticks, and fleas, the current literature has shown that citronella oil has yielded satisfactory results in repelling mosquitoes when applied to the skin, especially in short-term exposures. Citronella-based products are generally regarded as repellents rather than insecticides for adult mosquitoes.

This ScienceDirect topical overview on citronellal notes: "In general, studies of citronella-based repellents show that they are less effective than DEET repellents. Citronella provides a shorter protection time..." and that conflicting data exist on the efficacy of citronella-based products, varying greatly depending on study methodology, location, and species of biting insect tested. It describes one study where subjects near citronella candles had 42% fewer bites than controls, a statistically significant difference, but also reports that no difference in efficacy between citronella incense and plain candles was found, indicating that in that controlled comparison the citronella-based product did not produce a statistically significant effect on mosquito biting. The discussion focuses on repellency outcomes and does not report adult mosquito mortality as an endpoint, implying negligible or unmeasured lethal effects in these controlled trials.

Our study results showed that the average of died mosquitoes from the first to fifth treatments sprayed by the anti-mosquito spray made from citronella oil with a concentration of 50% was 29.2 mosquitoes, and the mortality rate was 97.3%. Meanwhile, for the treatment of anti-mosquito spray with negative control, there were no deaths against mosquitoes. The statistical test results showed that the anti-mosquito spray made from citronella oil had a significant difference between the control sprayer to kill Aedes aegypti mosquitoes (p value: 0.000, 95% CI: 28.16–30.24).

Citronella oil is regarded by the US Food and Drug Administration as generally recognized as safe. While it can prevent mosquito bites for up to two hours, citronella oil is not as effective as DEET at keeping mosquito bites at bay for as long. The chapter also notes that adult mosquito mortality was considerably lower in repellency-focused studies than in insecticidal assays.

Field trials conducted over two days, with six-hour sessions each day, indicated a promising 90% efficacy for the mosquito repellent spray in deterring mosquitoes. The study was framed as a repellent-efficacy evaluation rather than a mortality assay, so it does not directly establish adult mosquito mortality.

Effectiveness of plant-based repellents against different Anopheles species is discussed. In this context, a previous systematic review, "Effectiveness of citronella preparations in preventing mosquito bites: systematic review of controlled laboratory experimental studies," is cited as evidence that citronella oil provides protection but has a shorter duration than DEET. The emphasis of these controlled experimental studies is on repellent (bite-preventing) efficacy, not on adult mosquito mortality.

This study used citronella oil as a larvicide of mosquitoes and reported that citronella extract did have a significant effect on larvae mortality. The overall effectiveness of citronella oil as a larvicide was 52%. Because this is a larval assay, it does not address adult mosquito mortality directly.

This uploaded document describes a survey-based study on mosquito repellent effectiveness using both natural repellents (including citronella) and artificial ones, analyzed with dependent-sample t‑tests. The results state that "the difference between the natural mosquito repellents is not significant" as the p value is less than 0.05, and that the level of effectiveness of both natural and artificial mosquito repellents is moderately effective. While this is based on perceived effectiveness rather than entomological mortality data, it shows that, in at least one controlled comparison, citronella-containing natural repellents did not demonstrate a statistically significant difference in effectiveness from other natural repellents, and adult mosquito mortality was not an assessed outcome.

This article summarizing scientific literature on citronella notes that citronella-based skin products generally act as short-duration repellents rather than killing adult mosquitoes. It states: "Applied directly to skin, however, the picture is much less impressive. Scientific studies have consistently shown that citronella-based skin products provide meaningful protection for fewer than 20 minutes before the active compounds have evaporated." It also mentions that as candles or diffusers, citronella can help deter mosquitoes in the surrounding area, but does not describe statistically significant adult mosquito mortality from these consumer repellent formats.

Citronella oil has been noted for its ability to repel mosquitoes. The article focuses on microencapsulation to reduce evaporation and improve repellent application, rather than reporting adult mosquito mortality outcomes.

Citronella insect repellent products are generally designed to repel biting mosquitoes rather than to kill them. Most controlled human-use studies report protection time, reduction in bites, or percent repellency, and do not report statistically significant adult mosquito mortality as an endpoint. Adult mortality is more commonly studied in larvicide or contact-toxicity assays, where citronella’s primary role is not as an adulticide.

This 2023 study of a local indigenous knowledge-based repellent in Thailand evaluates products for their repellent effect against mosquitoes, with outcomes such as landing rates and protection time. The abstract explains that the research "aims to assess the effectiveness of mosquito repellent from local learning" and focuses on deterring mosquito bites, not on killing adult mosquitoes. Citronella-containing preparations, where used, are assessed for repellency rather than adult mosquito mortality, and the paper does not report significant lethal effects on adult mosquitoes.