Biodiversity of Natural Enemies of Pseudococcidae in the Semiarid Region of Brazil

Pseudococcidae species, also known as mealybugs, comprises a complex of pests in various cultivated and non-cultivated plant species, among which fruit plants are most affected by both direct and indirect damage. The incidence of these pest species has been constant in productive environments, causing significant losses due to sap suction, virus transmission, and damage to fruit quality. Thus, this study aimed to know and investigate the population dynamics of natural enemies of Pseudococcidae in different fruit plants cultivated in the semiarid region of Brazil. For this, mealybugs associated with roots, stems, leaves, and fruits of vine, pear, apple, persimmon, guava, and acerola trees were collected biweekly in 14 properties in the São Francisco Valley region, from July 2016 to June 2017. These mealybugs were properly separated for the removal of their predators and the emergence of parasitoids associated with them (Pseudococcidae). Coccophagus sp., Aenasius sp., Anagyrus kamali, Anagyrus sp. 1, Anagyrus sp. 2, Anagyrus sp. 3, Anagyrus sp. 4, Coccidoxenoides perminutus, Gyranusoidea indica, Leptomastix dactylopii, Prochiloneurus sp., Aprostocetus sp., and Signiphora sp. were identified as parasitoids and Diadiplosis multifila, Cryptolaemus montrouzieri, Tenuisvalvae notata, Cycloneda sanguinea, and Hippodamia convergens were identified as predators, in addition to unidentified species of Coccinellidae and Chrysopidae.

Elevated CO2 Levels Impact Fitness Traits of Vine Mealybug Planococcus ficus Signoret, but Not Its Parasitoid Leptomastix dactylopii Howard

Carbon dioxide (CO2) is one of the primary factors driving climate change impacts on plants, pests, and natural enemies. The present study reports the effects of different atmospheric CO2 concentrations on the vine mealybug Planococcus ficus (Signoret) and its parasitoid wasp Leptomastix dactylopii (Howard). We investigated the life-history parameters of both species on grapevine Vitis vinifera (L.) plants grown under elevated (eCO2) and ambient (aCO2) CO2 levels in a greenhouse and in a vineyard free-air carbon dioxide enrichment (FACE) facility. The greenhouse experiments with an eCO2 level of around 800 ppm showed a significant increase in survival rates, a strong trend towards declining body size, and an increasing fecundity of female mealybugs, while fertility and development time did not change. However, none of these parameters were altered by different CO2 concentrations in the VineyardFACE facility (eCO2 level around 450 ppm). On the other hand, the parasitism success, development time and sex ratio of L. dactylopii, reared on P. ficus under eCO2 or aCO2, varied neither in the greenhouse nor in the FACE facility. These results suggest that future CO2 levels might cause small-scale changes in vine mealybug fitness; however, this is not necessarily reflected by parasitoid performance.

Effect of Potassium Bicarbonate (MilStop®) and Insecticides on the Citrus Mealybug, Planococcus citri (Risso), and the Natural Enemies Leptomastix dactylopii (Howard) and Cryptolaemus montrouzieri (Mulsant)

Both laboratory and greenhouse experiments were conducted to determine if the fungicide, MilStop® (BioWorks, Victor, NY), which contains the active ingredient, potassium bicarbonate, has direct activity on the citrus mealybug, Planococcus citri Risso. Spray applications of four different rates (4.5, 5.9, 7.4, and 14.9 g·L–1) were applied to green coleus, Solenostemon scutellarioides (L.) Codd., plants infested with citrus mealybugs. In addition, experiments were conducted to assess both the direct and indirect effects of MilStop® on two natural enemies of the citrus mealybug: the parasitoid, Leptomastix dactylopii (Howard), and the coccinellid beetle, Cryptolaemus montrouzieri (Mulsant). MilStop® provided between 56% and 86% mortality of citrus mealybug; however, the highest rate (14.9 g·L–1) was phytotoxic to coleus plants. Percent mortality associated with the second highest rate (7.4 g·L–1) was 82%, which was comparable to acetamiprid (84%) applied at 0.05 g·L–1. For the natural enemies, MilStop® treatment rates of 1.5 and 3.5 g·L–1 resulted in 16% mortality, whereas the 5.5- and 9.0-g·L–1 rates resulted in 33% mortality of L. dactylopii adults. MilStop® treatment rates of 3.5, 5.5, 9.0, and 12.0 g·L–1 resulted in 30%, 60%, 40%, and 90% mortality, respectively, of C. montrouzieri adults. Therefore, depending on the application rate, this fungicide may inadvertently kill citrus mealybugs when used to control fungal plant pathogens. It should not disrupt biological control programs targeting citrus mealybug in greenhouses that involve releases of L. dactylopii when used at low application rates, whereas MilStop® applications should be properly timed when using C. montrouzieri.