Search Results (6)

Strawberry is frequently attacked by mites, which directly affects the yield and quality of this fruit species. The WRKY Group III transcription factors (TFs) play an important role in plant tolerance to biotic sources of stress, such as pathogens and insect pests. In this study, six Group III WRKY TFs (FaWRKY25, FaWRKY31, FaWRKY32, FaWRKY43, FaWRKY44, and FaWRKY45) were identified in strawberry. A phylogenetic analysis showed that the six WRKY III TFs were divided into two clades and all had a conserved WRKYGQK domain and the C-X₇-C-X₂₃-H-T-C zinc finger motif. An interaction network analysis revealed that FaWRKY44 was co-expressing with FaWRKY25 and FaWRKY45. The expression patterns showed that the WRKY Group III genes responded to plant hormones and mite infestation in strawberry. To further verify the role of FaWRKY25 in plant resistance to mites, we cloned the FaWRKY25 gene and overexpressed it in transgenic plants. An in vivo subcellular localization analysis indicated that the FaWRKY25 protein was localized in the nucleus. Fewer mites were also detected on the wild-type plants than on FaWRKY25-overexpressing transgenic plants, suggesting that FaWRKY25 negatively regulates the resistance of strawberry to mites. The present study advances our understanding on a potential target that mites use to manipulate host plant defenses. Full article

Tetranychid outbreaks have been detected since 2016 in southern highbush blueberries (SHB); however, it was not until 2019 that the southern red mite (SRM), Oligonychus ilicis (Acari: Tetranychidae) was confirmed as the pest causing severe bronzing and stunting, in multiple Florida and Georgia commercial blueberry plantings. To date, only three miticides (fenazaquin, fenpyroximate, and acequinocyl) have been registered for use in SHB and there are no clear guidelines on how to manage SRM in SHB. Similarly, there is no knowledge regarding the existence of natural enemies of SRM in SHB. This is the first report of naturally occurring predatory mites (Amblyseius sp. and Neoseiulus ilicis) associated with SRM in SHB. Predatory mites were recorded in blueberry bushes after treatment with seven miticides used to suppress SRM populations including spiromesifen, acequinocyl, sulfur, sulfur + molasses, bifenazate, fenpyroximate, and fenazaquin. The number of SRM recorded per leaf and averaged plant damage ratings (0 = no bronzing–4 = 100% bronzing) were used to evaluate miticide efficacy. Additionally, the presence or absence of predatory mites per sample was recorded. Fenpyroximate used as the standard miticide, significantly reduced mite numbers seven days after application, as well as acequinocyl and fenazaquin. Fenpyroximate and fenazaquin demonstrated the best performance for managing O. ilicis on SHB and treated bushes demonstrated significantly less bronzing compared with the control plants. These miticides were also safe to naturally occurring predatory mites. Lastly, the level of growers’ awareness regarding SRM was assessed using surveys in 2020 to design adequate educational materials available to the grower community. Full article

The quality of the host plant affects the life history parameters of tetranychid mites. The biology and fertility life tables of Tetranychus merganser on five host plants (Carica papaya, Phaseolus vulgaris, Capsicum annuum var. glabriusculum, Helietta parvifolia, and Rosa hybrida) were assessed under laboratory conditions at 28 ± 1 °C and 70–80% relative humidity (RH) with a photoperiod of 12:12 h (L:D). The development period of immature females differed among the tested host plants and ranged from 9.32 days on P. vulgaris to 11.34 days on H. parvifolia. For immature males, it ranged from 9.25 days on P. vulgaris to 11.50 days on H. parvifolia. The female survival rate varied from 53.97% on H. parvifolia to 94.74% on P. vulgaris. The highest total fecundity rate was recorded on P. vulgaris (125.40 eggs/female) and the lowest on H. parvifolia (43.92 eggs/female). The intrinsic rate of increase (rm) varied from 0.271 (H. parvifolia) to 0.391 (P. vulgaris). The net reproductive rate (R_O) was higher on P. vulgaris than on the other host plants. The longest mean generation time (GT) was calculated on C. annuum var. glabriusculum and the shortest on Rosa hybrida. The demographic parameters suggest the unsuitability of H. parvifolia as the host for the development of red spider mites, and the best performance of T. merganser was on P. vulgaris. Full article

Pesticides are commonly used to control weeds, diseases, and pests in soybean crops, although natural enemies are also key components of integrated pest management programs protecting soybean from pests. The predatory mite Neoseiulus idaeus Denmark & Muma is commonly found in soybeans associated with tetranychid mites. We determined the compatibility of some pesticides used in Brazilian soybean fields with N. idaeus on the basis of their lethal and sub-lethal effects. We assessed the acute toxicity of pesticides that are considered harmless to females of N. idaeus and evaluated the effects on the mite offspring. Acephate as well as imidacloprid and bifenthrin were most toxic to adult females and were classified as harmful. Chlorfenapyr, indoxacarb, and the neonicotinoid and pyrethroid mixtures were classified as slightly to moderately harmful. Immatures of N. idaeus were able to develop and reach the adult stage when treated with chlorantraniliprole, flubendiamide, glyphosate, and teflubenzuron, but immature survival was reduced to 42 and 64% for offspring of females treated with chlorantraniliprole or teflubenzuron, respectively. Reproduction was most affected in females exposed to chlorantraniliprole and teflubenzuron; these females had daily oviposition rates of 0.5 and 0.4 egg/female/day, respectively, and mean fecundities of 2.7 and 5.8 eggs/female, respectively. On the basis of sublethal effects and life table parameters, chlorantraniliprole was classified as moderately harmful, while the other pesticides tested were classified as harmless. In considering the use of pesticides while targeting the conservation of N. idaeus as a predator of important pests in soybean crops, one must prioritize pesticides that will most likely have less harmful effects on this predator in the field. Full article

Background: The ladybird beetle Stethorus gilvifrons (Mulsant) is an important natural enemy of tetranychid mites and functions as a biological control of these plant pests. The development, survival and reproduction of S. gilvifrons were studied when fed on three artificial diets. The components of the artificial diet that S. gilvifrons could be reared successfully on for one generation with no use of tetranychid mites were examined. Methods: Artificial diets consisted of sucrose, honey, royal jelly, agar, yeast, date palm pollen supplemented in different diets with hen’s egg yolk (AD1, as basic diet), Ephestia kuehniella Zeller eggs (AD2), or E. kuehniella eggs and 2,4-dihydroxybenzoic acid (AD3). Results: Adults and larvae of Stethorusgilvifrons fed on AD1 had a shorter immature development and preoviposition periods than those fed on AD2 and AD3. The total number of deposited eggs was significantly higher for the females fed on AD3 than on the other diets. The intrinsic rate of increase (r) of S. gilvifrons was highest on AD3, followed by AD2, and AD1. Conclusion: Stethorus gilvifrons performed best on AD3, indicating the potential of this artificial diet for the mass rearing of this important predatory ladybird beetle. Full article

Reports of severe infestations caused by southern red mites (SRM), Oligonychus ilicis McGregor (Acari: Tetranychidae), have increased in recent years in southern highbush blueberries (SHB). Currently, there is little known about the management of tetranychids in SHB, and only two miticides (fenazaquin and fenpyroximate) have recently been labeled for use in SHB. Oligonychus ilicis has caused up to 80%–100% losses in some blueberry plantings, and growers are looking for management tools for this new pest of blueberries. We report on injury to SHB from O. ilicis and the performance of seven miticides used to manage SRM populations, including spiromesifen, spiromesifen plus surfactant, vegetable oil concentrate, fenazaquin, “proprietary miticide” (referred to as Pro1), bifenazate, and fenpyroximate. Miticide efficacy was rated based on the number of SRM recorded on collected leaves and plant damage ratings using an arbitrary index (from 0 = no bronzing to 4 = 100% bronzing). Characteristic symptoms of leaf injury included purple or bronzed leaf color, leaf dryness and roughening. Fenpyroximate significantly reduced mite numbers three days after application. Additionally, plants treated with fenpyroximate or fenazaquin showed significantly less bronzing compared with the control plants. Overall, fenpyroximate and fenazaquin showed the best performance for the management of O. ilicis on SHB. Full article