Oil of citronella repels insects rather than killing them. It works by masking scents that are attractive to insects. Oil of citronella repels target pests rather than killing them.

Researchers then tested the high larval efficacy group on adult mosquitoes, utilizing the U.S. Centers for Disease Control and Prevention's bottle bioassay testing protocol. In a solution of 10% essential oil, mortality rates post treatment were 49% for garlic, 88% for dill, 64% for the tea plant, 51% for fennel, 93% for fennel flower, 44% for sage, 72% for garden thyme, and 100% for sweet violet.

Citronella insect repellant products do not kill the adult insects they target. The components of citronella leaf extract could cause larval mortality, but the product is described as a repellent rather than an adulticide.

Further effects include **poisoning of adult insects**, disruption of reproduction, and damage to the integuments due to its irritant properties (Baker et al.). Citronella oil, rich in monoterpenoids such as citronellal, citronellol, and geraniol, is used as an insect repellent but also exhibits **insecticidal activity** in various bioassays, including contact and fumigant exposure of adults.

This study tested the repellency and CPT of 5% citronella and fennel oil-containing products according to KFDA guidelines. The mean CPTs of DEET and citronella repellent were 360 min and 9.5 min, respectively, similar to previous findings.

Citronella essential oil (Cymbopogon nardus (L.) Rendle) is an alternative mosquito repellent safe for humans and animals when used in appropriate concentrations.[4] Citronella essential oil has been shown to be effective as a mosquito repellent in humans against A. aegypti, C. quinquefasciatus, and Anopheles stephensi.[4] Amer and Mehlhorn reported that a 20% concentration of citronella essential oil showed 75.70% repellency against A. aegypti for 2 h, with 52.4% repellency against Anopheles dirus and 100% repellency against C. quinquefasciatus for 8 h.[4]

Essential oils from the stems of citronella and clove leaves contain chemical compounds, namely citronellal, eugenol, and geraniol, which function as mosquito killers.[1] The study concludes that volatile oils of Lemon grass possess mosquito (A. gambiae and An. funestus) repellent and adulticidal effects, especially at higher concentrations and can be used to reduce human-mosquito contacts and hence mosquito-borne diseases and irritation caused by their bites.[1] All formulation exhibited adulticidal activities, with the 60% (v / v) formulation having higher impact, causing fast immobilization or paralyzing effect on some mosquitoes that were at close range to treated volunteer's body.[1]

Citronella oil demonstrates significant biological and insecticidal effects against pests, enhancing crop productivity. The oil contains key compounds like citronellal, citronellol, and geraniol, which show **toxicity to adult insects** and other life stages in laboratory bioassays. Several studies report knockdown and mortality of adult mosquitoes and other insect pests when exposed to citronella oil via contact or fumigation, indicating its potential **adulticidal** properties.

Citronellol, a major part of citronella oil, was ranked as the number one mosquito repellent by Bunker and Hirschfelder (1925) in their study. However, more recent studies showed different effectiveness of citronella-based insect repellents. Lindsay et al. (1996) did not find that citronella candles had any effect on mosquito biting pressure. Fradin and Day (2002) found that citronella-based spray-on repellents only protected for very short times from mosquito bites. Our tests of the Java type citronella oil confirmed our earlier results that Ae. aegypti is not repelled by this oil. Therefore, we conclude that citronella oil is not an effective repellent for Ae. aegypti and should not be recommended for use in areas with mosquito-borne pathogens transmitted by this species.

Citronella oil is possibly safe for most people when used as an insect repellent. People most commonly use citronella oil as a mosquito repellent on the skin. Applying citronella oil to the skin seems to help prevent mosquito bites for a short period of time.

Essential oils extracted by steam distillation from Cymbopogon citratus (DC.) and C. nardus were evaluated as topical repellents against Anopheles arabiensis.[2] At 10% and 20% concentrations, all the oils showed a minimum of 90% and 95% relative protection, respectively, soon after application.[2] The oil of C. nardus in oleaginous ointment (i.e. Vaseline) provided above 80% relative protection for as long as 4 h which was better than the effect of the 20% oil.[2] This study demonstrated the potential of essential oil of C. nardus as topical repellent against An. arabiensis.[2]

The two essential oils exhibited moderate repellency against Ae. aegypti, An. dirus and Cx. quinquefasciatus, at 60, 90 and 78 min with C. nardus, and 54, 96 and 84 min with C. winterianus, respectively.[8] Both essential oils showed moderate knockdown against Ae. aegypti.[8]

Citronella essential oil (CEO) caused significant **mortality of Bemisia tabaci adults** in contact bioassays, with LC50 values indicating moderate toxicity. In addition to its toxic effects, CEO was highly repellent against B. tabaci in a dual-choice bioassay and significantly deterred females from laying eggs on treated surfaces. The authors concluded that citronella EO has "toxic, repellent, and deterrent effects" on this adult flying insect pest.

Citronella oil (CO) has been noted for its ability to repel mosquitoes. Citronella oil (CO) has been reported to possess a mosquito-repellent action. However, its application in topical preparations is limited due to its rapid evaporation and poor retention on the skin surface. Thus, microencapsulation is effective in decreasing the membrane permeation of CO while ensuring a steady supply of the oil.

Citronella candles are only effective at repelling mosquitoes in the immediate radius around the candle and in the absence of a breeze. A common myth is that essential oils like citronella, lavender, or eucalyptus can provide effective, long-lasting protection against mosquito bites.

Bioassay results revealed that **nano-citronella exhibited the highest insecticidal activity**, with the lowest LC₅₀ value (0.4111 × 10⁴ ppm) and a strong knockdown effect on adult insect pests in laboratory tests. The study compared nano-formulated citronella with conventional formulations against a lepidopteran vegetable pest and reported enhanced adult mortality, indicating that formulation can increase the **adulticidal efficacy** of citronella-based products.

Citronella oil is often used as an insect repellent, although research has indicated it may also have antifungal properties and help with wound healing. A 2011 review of 11 studies looked at the effectiveness of various citronella preparations in preventing mosquito bites. It concluded that using citronella oil together with vanillin (found in vanilla beans) provided mosquito protection for up to three hours. A 2015 study compared the ability of DEET, citronella oil, and fennel oil to repel mosquitoes. Researchers found that DEET had a protection rating of over 90 percent over six hours. Citronella and fennel oil had protection ratings of about 57 percent and 47 percent, respectively, after only two hours.

Citronella repels A. aegypti mosquitoes for between 12 and 480 minutes, depending on the concentration and formulation of the product.[6] Considering its protection time, reapplying the product doubles the protective effect.[6] Citronella is not absorbed through the skin like DEET products, making it less toxic.[6] Citronella-based products can be used as a complementary measure of protection against arboviruses.[6]

The results showed that citronella oil could **suppress the population of Plutella xylostella** in the field and harm the growth and behavior of this pest. Application of citronella oil reduced the number of larvae and adults observed per plant compared with control plots, showing both feeding deterrent and toxic effects. The authors suggest citronella oil is effective in managing this adult moth pest on cabbage under field conditions.

The larvicidal action of OECN was tested against the third and fourth larval stages of Aedes aegypti at concentrations (2.5, 5.0, 7.5 and 10 μL/20 ml) for 24 to 48 hours.[7] Mortality of 100% of the larvae was observed at concentrations of 7.5 and 10.0 µl/20 ml in 24 hours.[7] OECN has a larvicidal action and antifungal activity at the tested concentrations.[7]

The purpose of this study is to assess the toxicity of Cymbopogon nardus, also known as citronella essential oil (CEO), and how well it inhibits eating in FAW (Spodoptera frugiperda). CEO was tested in antifeedant and toxicity bioassays, and exposure led to increased mortality and reduced feeding in treated insects. The authors report **significant toxicity** of citronella EO to this lepidopteran pest, including effects observed on older larval and pre-adult stages that more closely resemble adult physiology.

In this context, the present review critically evaluates whether commonly used laboratory bioassays adequately reflect real-world application scenarios for essential oils as insecticides. It notes that EOs and/or their individual components can enter the insect body through inhalation, contact with treated surfaces, or direct topical application, leading to hyperactivity, incoordination, tremors, lethargy, knockdown, and death in adult insects. However, the review warns that conventional contact bioassays often **overestimate EO toxicity** under laboratory conditions because confined environments limit avoidance behaviors and enhance fumigant exposure, so observed adult mortality may not directly translate to field adulticidal performance.

We found that the performance of the citronellal derivatives mixture is comparable (95% protection for ≤3.5 h) with those of the most widespread synthetic repellents DEET and Icaridin, tested at a four-fold higher doses. Under laboratory conditions, the hydroxylated cyclic acetals mixture, as obtained from the condensation between glycerol and citronellal give 99% protection efficacy against A. albopictus when applied on the skin at a dose of 16.67 μg cm−2. The citronellal derivatives maintained an efficacy against A. albopictus >90% for 8 h at 0.17 mg cm−2, much longer than citronellal, reported to protect for <1 h from A. aegypti. These citronellal derivatives act as mosquito repellents, not as toxicants, providing high protection times by repelling mosquito landings and bites.

I studied the effectiveness of citronella grass, Cymbopogon nardus, as a larvicide against Culex quinquefasciatus and Culex nigripalpus mosquito larvae and how it affected their behaviors.[3] The results I obtained from this study suggest that the leaf and aerial parts essential oils of C. nardus are potential natural larvicides against C. quinquefasciatus and C. nigripalpus larvae.[3]

This site claims that citronella oil can be used against mosquitoes and other flying insects, but it is not a primary scientific source and does not provide evidence of adulticidal effects.

So, we return to our initial question: does citronella oil actually work against mosquitoes? The answer, supported by both historical use and modern scientific validation, is a resounding yes. It absolutely works. The caveat, however, is that it works best when harnessed correctly. The raw oil alone is too volatile for sustained protection, but modern, technologically advanced formulations have successfully overcome the traditional limitations of this botanical extract. This discussion focuses on repelling mosquitoes and does not describe citronella oil as killing adult mosquitoes or other insects.

This blog post repeats that citronella is a natural repellent and emphasizes masking odors rather than killing insects, but it is not a reliable source for the claim.