Infestation of Raoiella indica Hirst (Trombidiformes: Tenuipalpidae) on Host Plants of High Socio-Economic Importance for Tropical America

Resistance of dwarf Cocos nucifera L. (Arecaceae) cultivars to Raoiella indica Hirst (Acari: Tenuipalpidae)

The red palm mite Raoiella indica Hirst, 1924 (Acari: Tenuipalpidae) is an important pest of the coconut palm Cocos nucifera L. (Arecaceae) and has caused problems in coconut production worldwide. Research has been carried out aiming at controlling the mite through chemical, biological, alternative, and host plant resistance methods. Identifying coconut palm cultivars resistant to R. indica is important to reduce the problems caused to plantations. Therefore, the objective of this work was to evaluate the performance of R. indica in six dwarf coconut palm cultivars, to identify sources of resistance. The cultivars of the sub-varieties green, red, and yellow evaluated were Brazilian Green Dwarf-Jiqui (BGDJ), Brazilian Red Dwarf-Gramame (BRDG), Cameroon Red Dwarf (CRD), Malayan Red Dwarf (MRD), Brazilian Yellow Dwarf-Gramame (BYDG), and Malayan Yellow Dwarf (MYD). Confinement and free choice tests of R. indica on the cultivars were performed, in which biological parameters and preference were evaluated. Mite performance was different in the cultivars evaluated. In the confinement bioassay, R. indica had the worst performance in the cultivar BGDJ, the best performance in CRD, MRD, and BRDG, and intermediate performance in BYDG and MYD. In the free choice test, the cultivars MRD and MYD were preferred in relation to BGDJ, and CRD was less preferred in relation to BGDJ. Therefore, we considered that the cultivar BGDJ is the most resistant to R. indica, by antibiosis and antixenosis; CRD has resistance by antixenosis; and MRD, BRDG, BYDG, and MYD are susceptible.

Climate-based seasonal dynamics of the invasive red palm mite Raoiella indica

BACKGROUND

Raoiella indica Hirst (Acari: Tenuipalpidae) is the most critical coconut and banana pest recently introduced in Brazil. Once the mite pests are introduced, it is essential to understand their dynamics in important crops under open-field climatic conditions to implement strategies for their management and determine the periods when species populations may increase in the field. Modelling tools have been used to determine the potential distribution of species and implications for the management of invasive species. Thus, our aim in this study was to determine the seasonal variation in R. indica and the influence of the monthly climate using CLIMEX modelling. We adjusted the CLIMEX model for R. indica based on distribution data, additional biological characteristics, and fluctuations in the R. indica population in a commercial coconut plantation.

RESULTS

The model for the current climate shows a good match between the ecoclimatic index and the global distribution of R. indica. The model results demonstrate that most states of Brazil and several regions worldwide include areas with highly suitable climatic conditions for R. indica. We observed variations in the density of R. indica in commercial coconut crops, with the highest incidence occurring during the first months of the year.

CONCLUSION

Our results showed different alterations in seasonal suitability for R. indica that may provide information for the implementation of methods for time management, such as strategies for sampling and control during periods with a high degree of suitability for R. indica. © 2020 Society of Chemical Industry.

Potential of native palm species in Northeast Brazil as hosts for the invasive mite Raoiella indica (Acari: Tenuipalpidae)

The red palm mite, Raoiella indica Hirst (Tenuipalpidae), has mainly been registered on palm species (Arecaceae), and its expansion in Brazil has the potential to cause significant negative impact on cultivated as well as native palms. Here, we evaluate the potential of native palms from Northeast Brazil to act as hosts of R. indica. Specifically, we used in situ free-choice and confinement tests, in which sections of palm leaves/leaflets of various species were experimentally infested with R. indica. We tested the following species: Acrocomia aculeata, Acrocomia intumescens, Allagoptera caudescens, Attalea funifera, Attalea oleifera, Bactris acanthocarpa var. acanthocarpa, Bactris ferruginea, Bactris glassmanii, Bactris hirta var. spruceana, Bactris pickelii, Copernicia prunifera, Desmoncus orthacanthos, Desmoncus polyacanthos, Syagrus coronata and Syagrus schizophylla. All of these were compared with the mite's preferred host, the coconut palm, Cocos nucifera. In the free-choice test, both male and female R. indica preferred C. nucifera in comparison to each of the native palms. In the confinement test, we observed significant differences in the survivorship between mites on native palms and those on coconut palms after the second day of infestation. By the fifth day, survivorship of mites on the native palms was almost always significantly lower than on C. nucifera (excepting for C. prunifera). We conclude that, among all the native palms evaluated, only the carnauba palm (C. prunifera) is at risk from R. indica. This result is relevant as this palm is an economically important species in the region.

Life table parameters of the red palm mite Raoiella indica (Acari: Tenuipalpidae) at various temperatures and for sexual and asexual reproduction

The red palm mite, Raoiella indica Hirst, is a threat to coconut, banana and native Arecaceae and Heliconiaceae in Brazil. This mite originated in the Eastern Hemisphere and was first reported in 2004 in the Americas, where the pest is spreading quickly and causing severe damage to its host plants. The objective of this work was to determine the life-history parameters of R. indica at constant temperatures, estimate its thermal requirements [threshold temperature (Tb) and thermal constant (K)] and also compare its life table parameters between sexual reproduction and parthenogenesis. The life tables were constructed on leaflets of Adonidia merrillii at 15, 20, 24, 27, 30 and 34 °C and 65% RH and a 12-h photoperiod. The longevity and the number of laid eggs of non-copulated adult females were evaluated at 27 °C. Raoiella indica had complete development, from egg to adult, only at 20, 24, 27 and 30 °C. At 15 °C, the eggs did not hatch, and at 34 °C, the mites survived only until the larval stage. For sexual reproduction, the optimal temperature was 27 °C, under which the reproductive parameters were higher. The reproductive parameters for sexual reproduction were higher than those for parthenogenesis. The Tb was 14.79 °C, and the thermal constant was 208.33 degree days. The life parameters estimated in this study can be used for modelling and predicting the population growth of R. indica in the field and consequently for improving their management strategies.