Background Compared to chemical control, the use of naturally occurring biological agents to control invasive pests is less threatening to the environment and human health. Objectives Here, we assessed the ability of immature stages of the lacewing Ceraeochrysa caligata (Neuroptera: Chrysopidae) to prey upon different developmental stages of the red palm mite Raoiella indica (Acari: Tenuipalpidae), one of the most destructive invasive pests of palm trees in Neotropical regions. Methods Increasing densities of three stages of R. indica (eggs, immature stages, and adult females) were offered to C. caligata in coconut leaf arenas. The immature stages of C. caligata were less than 24 h old and were starved before being transferring to the arenas. The amount of prey consumed was recorded 6 h after releasing the C. caligata. Results Our results indicated that the ability of C. caligata to feed upon R. indica increased with the larval development of the predator. Higher feeding levels and shorter handling times were recorded for the first and second instars of C. caligata when preying upon the eggs and immature stages of R. indica. Furthermore, C. caligata individuals of different stages exhibited differential functional responses according to prey type (i.e., eggs, immatures, or adult females of R. indica). Ceraeochrysa caligata second instar individuals exhibited a sigmoid increase in consumption rate with increasing prey availability (i.e., a type III functional response) when preying upon immature stages of R. indica. However, when preying upon R. indica adult females, C. caligata second instar individuals exhibited a type II functional response (i.e., an increase in consumption rate with increasing prey availability, before reaching a plateau). Predator individuals of the first and third instar stages exhibited a type II functional response for all prey types. Conclusions Collectively, our findings demonstrate that C. caligata, especially at the second instar stage, has potential as a tool for ecological management of the red palm mite.

The cassava green mite, Mononychellus tanajoa, is a key pest of cassava, Manihot esculenta Crantz (Euphorbiaceae), and it may be kept in check by naturally occurring predatory mites of the family Phytoseiidae. In addition to predatory mites, abiotic factors may also contribute to regulate pest mite populations in the field. Here, we evaluated the population densities of both M. tanajoa and the generalist predatory mite Euseius ho DeLeon (Acari: Phytoseiidae) over the cultivation cycle (11 months) of cassava in four study sites located around the city of Miranda do Norte, Maranhão, Brazil. The abiotic variables rainfall, temperature and relative humidity were also recorded throughout the cultivation cycle of cassava. We determined the relative importance of biotic (density of E. ho) and abiotic (rainfall, temperature and relative humidity) factors to the density of M. tanajoa. The density of M. tanajoa increased whereas the density of E. ho remained constant throughout time. A hierarchical partitioning analysis revealed that most of the variance for the density of M. tanajoa was explained by rainfall and relative humidity followed by E. ho density and temperature. We conclude that abiotic factors, especially rainfall, were the main mechanisms driving M. tanajoa densities.

Neem (Azadirachta indica A. Juss.)-derived pesticides have been used against a wide range of agricultural pests including tetranychid mites. Approaches combining lethal and sublethal toxicity studies of neem pesticides towards tetranychid mites are necessary to a comprehensive evaluation of such products. Here, we evaluated the lethal and sublethal toxicity of the neem oil Bioneem to the cassava green mite Mononychellus tanajoa (Bondar) by integrating lethal concentration (LC) with population growth and biological parameter studies. According to Probit analyses the concentration of neem oil Bioneem which kills 50% of the population (LC50) of M. tanajoa was 3.28 µL cm -2 , which is roughly twice the field concentration recommended of this biopesticide to control pest mites (1.7 µL cm -2 ). The growth rate of the cassava green mite steadily decreased with dosages of neem oil. Furthermore, sublethal concentrations of the neem oil corresponding to the LC50 reduced the periods of the immature stages of M. tanajoa resulting in a shorter developmental time. Similarly, the number of eggs per day and the number of eggs per female per day, a proxy for fecundity, were drastically reduced in M. tanajoa females exposed to the LC50 of neem oil. Based on our comprehensive approach we conclude that the neem oil showed lethal as well as sublethal toxicity on growth rate and biological parameters such as duration of immature stages and fecundity of the cassava green mite M. tanajoa and it could be used as an ecological alternative for the management of this pest.

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Both prey density and developmental stage of pests and natural enemies are known to influence the effectiveness of biological control. However, little is known about the interaction between prey density and population structure on predation and fecundity of generalist predatory mites. Here, we evaluated the functional response (number of prey eaten by predator in relation to prey density) of adult females and nymphs of the generalist predatory mite Euseius concordis to densities of different developmental stages of the cassava green mite Mononychellus tanajoa, as well as the fecundity of adult females of the predator. We further assessed the instantaneous rate of increase, based on fecundity and mortality, of E. concordis fed on eggs, immatures and adults of M. tanajoa. Overall, nymphs and adults of E. concordis feeding on eggs, immatures and females of M. tanajoa had a type III functional response curve suggesting that the predator increased prey consumption rate as prey density increased. Both nymphs and adult females of the predator consumed more eggs than immatures of M. tanajoa from the density of 20 items per leaf disc onwards, revealing an interaction between prey density and developmental stage in the predatory activity of E. concordis. In addition, population growth rate was higher when the predator fed on eggs and immatures in comparison with females. Altogether our results suggest that E. concordis may be a good candidate for the biological control of M. tanajoa populations. However, the efficiency of E. concordis as a biological control agent of M. tanajoa is contingent on prey density and population structure.