TY - JOUR
AU - Grafton-Cardwell, E E
AB - Abstract Tarsonemus bakeri Ewing (Acari: Tarsonemidae) is a species of mite commonly associated with citrus in many countries including the United States. A short report in 1942 suggested this species is phytophagous, but it has not been reported as a pest in citrus or any other crop since then. A single survey of 78 orchards in three growing regions in California demonstrated that Tarsonemus spp. mites were only associated with leaf samples that had visible sooty mold. A seasonal population study in one citrus orchard showed that all life stages of Tarsonemus spp. were present year-round on leaves and fruit, with the population on fruit reaching a peak in December (59.7 ± 15.2 mites per fruit). Results from a food suitability study showed that the population declined sharply on both plastic and leaf substrate when the mites were not provided a supplementary food source. When supplementary food was provided in the form of Alternaria, honeydew, molasses, or combinations of these, mites survived and multiplied throughout the 29-d study, irrespective of the substrate. Tarsonemus bakeri were found on excised, decaying leaves collected from an orchard. These studies verify that Tarsonemus spp. are associated only with sooty mold in citrus orchards. T. bakeri populations cannot sustain themselves on leaf tissue alone, indicating that they are nondamaging to citrus and therefore need not be considered a phytosanitary concern by importing countries. Tarsonemus, citrus, mites, sooty mold Tarsonemid mites (Acari: Tarsonemidae) are frequently encountered in citrus (Beer 1954, McGregor 1956, Attiah 1970, Lindquist 1978, 1986, Vacante and Nucifora 1985, Nucifora and Vacante 2004). The majority of Tarsonemidae mites found on citrus are mycophagous, except Polyphagotarsoneums latus (Banks), commonly known as broad mite, which can cause serious injury to citrus (Vacante 2010). Tarsonemus bakeri Banks (Acari: Tarsonemidae) was originally described in 1939 where it was collected from Chrysanthemum sp. (Asterales: Asteraceae) and was described as Tarsonemus setifer Ewing (Acari: Tarsonemidae) (Ewing 1939). In 1954, Beer stated that Tarsonemus bakeri is conspecific with Tarsonemus setifer. According to Beer (1954), T. bakeri was easily reared on Alternaria fungus cultures grown on artificial media. Lindquist (1978) later reported Tarsonemus setifer is conspecific with Tarsonemus waieti Banks (Acari: Tarsonemidae) and that Tarsonemus bakeri is a distinct species. Besides the literature arguing the taxonomic specificity of T. bakeri, the only other mention of T. bakeri is a short report published in Citrograph (McGregor 1942). This article reports the presence of T. bakeri mites on lemons in Southern California and states that higher mite populations were associated with lopsided growth of fruit (McGregor 1942). In the last 90 yr, there has been no other mention of T. bakeri or any other Tarsonemus mite as a pest of citrus in the United States or any other country. Tarsonemus mites are not a pest of concern for California citrus growers and observations made by pest control advisors associate this mite with sooty mold, mixed species of black fungus that grow on honeydew produced by sap-sucking insects. California is the leading producer of citrus in the United States producing 51% of the total citrus production (NASS 2019). The export value of California citrus in 2018 was $922 million (CCQC 2020). Several arthropod pests or pathogens present on California grown citrus fruit, if not present in the importing countries, can be considered a phytosanitary concern, requiring mitigation measures by California growers to minimize the risk of introduction (CCQC 2020). Between the period of 2013–2017, Tarsonemus bakeri was intercepted 104 times by the Ministry of Primary Industries, New Zealand. Regular interceptions and the 1942 report suggesting the pest nature of T. bakeri (McGregor 1942) made it a species of export concern to New Zealand. Lorryia formosa Cooreman (Acari: Tydeidae), a species considered phytophagous in early reports published in the 1950s was later confirmed to be a species feeding on honeydew and fungus developing on honeydew (Mendel and Gerson 1982, Aguilar 2001, Gautam et al. 2018). It is possible that Tarsonemus mites are also part of the natural fauna of fungal feeders in California and not a pest species. We investigated the presence or absence of Tarsonemus mites and sooty mold in 78 orchards in California during a single field survey to determine whether sooty mold favored mite populations. We then conducted a year-round study in one orange orchard to determine the seasonal population dynamics of Tarsonemus mites. The third objective of this study was to determine the suitability of different food types to support population growth of T. bakeri, namely, Alternaria spp., honeydew, molasses, and a combination of these food types on a leaf or a plastic substrate. The overall purpose of this study was to determine whether Tarsonemus spp. are pests in citrus. Materials and Methods Field Survey of 78 Citrus Orchards In 2018, we conducted a one-time field survey of 78 citrus orchards, 17 in Ventura County (July), 16 in Riverside County (August), and 45 in the desert areas of the Coachella and Imperial Valleys (November/December) of California for Tarsonemus mites and sooty mold. The citrus orchards were selected as representatives of different management practices (conventional/organic) and citrus varieties (lemons, oranges, mandarins, grapefruit) in each area. The percentage of sooty mold-infested trees in each orchard was determined by examining five randomly chosen perimeter trees along the north, south, east, west sides as well as a center row and noting if sooty mold was present. To evaluate the relationship between sooty mold and tarsonemid mites, 10 leaves were collected from each of these trees. If sooty mold was present, then leaves with sooty mold were preferentially collected, if sooty mold was not present, then leaves were randomly collected. Collected leaves were kept in a brown paper bag, stored in an ice-chest, and transported to a hotel room where they were evaluated. The restrictions imposed by the California Department Food and Agriculture for limiting the geographical distribution of Asian citrus psyllid (Diaphronia citri Kuwayama) (Hemiptera: Psyllidae), between quarantine zones, did not permit the movement of plant materials between the quarantine zones. Therefore, field-collected leaves were evaluated under the stereoscope in a hotel room within each geographical quarantine region (CDFA 2020). For each site, mites were counted and transferred to a 50-ml glass vial containing 75% ethyl alcohol for later identification. Vials containing mites were brought to the laboratory at the Kearney Agricultural Research and Extension Center (KAREC), Parlier CA. For identification, each mite was mounted onto a glass slide on a Hoyer’s medium (50 ml water, 30g gum arabic, 200g chloral hydrate, 20 ml glycerol) using a fine brush (5/0 size artist brush) and observed under a compound microscope with oil emersion (Olympus CX41, Wesco Western Scientific Co. Inc. Valencia, CA). Identification of T. bakeri was performed using the key of Lindquist (1978). Seasonal Abundance and Population Structure of Tarsonemus Mites in an Orange Orchard A field study was conducted from June 2018 to May 2019 in a commercial ‘Washington’ navel orange orchard (Citrus sinensis L. Osbeck) located in Sanger, Fresno County, California. Organic insecticides were applied during this period to the orchard for routine management of arthropod pests and diseases. These treatments included 8.97 kg/hectare copper (Nordox 75 WDG, Nordox As, Oslo, Norway) in 3,028 liters of water on 1 January 2019, and 0.29 liter/hectare Spinosad (Entrust SC, Corteva Agriscience, Wilmington DE) in 1,514 liters of water applied on 1 May 2019. To monitor the Tarsonemus mite population and its association with leaves and fruit, 30 trees were randomly selected throughout the orchard each month for assessment and border rows were avoided to minimize any border effect. Five leaves and one fruit (current year or previous season) infested with sooty mold were collected from each tree. Fruit collected in May, June, and July had carried over from the previous season while the remainder of fruit samples were collected from the current season. Collected samples were placed in a paper bag, stored in an ice chest and brought back to the laboratory at the KAREC. Each sample (leaf or fruit) was examined under a stereomicroscope and the number of Tarsonemus spp. immatures (larvae + nymphs), and adults (males and females) was counted. A sample of adult male and female mites, up to 5 (at least 1 male when present) per leaf or fruit per month, were mounted individually in Hoyer’s medium and identified to species using the keys by Lindquist (1978). The presence of Homopteran insects on the leaves was also noted for leaf or fruit samples each month. Statistical procedures were accomplished using Statgraphics (Statpoint Technologies, Inc., 2018). A two-way ANOVA analysis was conducted to determine whether there was an interaction between month and plant part sampled. A one-way ANOVA analysis was also conducted to determine whether the mean number of mites (all stages), and the mean number of eggs, immatures, and adults sampled varied according to plant parts or months sampled. Data for leaves were averaged for each tree and only one data point for leaf or fruit per tree was used in the analysis, for a total of 360 data points for each plant part (30 trees × 12 mo). The number of mites per sample was transformed using the square root (x) transformation to stabilize variances before analysis. Untransformed means and standard errors are reported to simplify interpretation. We used Tukey’s least significant difference test (α = 0.05) to determine differences among mean numbers of mites sampled on fruit and leaves in different months and years. Correlation between the number of Tarsonemus spp. with rainfall or temperature was analyzed by the simple regression procedure of the Statgraphics (Statpoint Technologies, Inc. 2018). Weather data for station 39, Parlier, Fresno County was obtained from the California Irrigation Management Information System (CIMIS) California Department of Water Resources. Association of Tarsonemus Mites with Sooty Mold To provide confirmation that the Tarsonemus population in the ‘Washington’ navel orange orchard was associated with the presence of sooty mold, leaves were examined for sooty mold and mites during the fall (September 2018) and spring (May 2019). Five trees were chosen in each of the cardinal directions (North, South, East, and West) and in a center row (middle) of the orchard. Samples were taken from the second row or tree in from the perimeter to eliminate any border effect. Twenty leaves, 10 showing visible signs of sooty mold infestation and ten without any visible sign of sooty mold infestation, were collected from each of 25 trees for a total of 500 leaves. Sooty mold-infested leaves and leaves without visible signs of sooty mold from each tree were placed separately in brown bags, kept in an ice-chest and transported to the laboratory. In the laboratory, the leaves were observed under the stereoscope and any mites found were counted and identified. The presence of Homopteran insects on the leaves was also noted for leaf or fruit samples each month. The experiment was a completely randomized design and each tree served as a replicate. As we did not find any mites on leaves without visible signs of sooty mold, no statistical test was conducted. The mean number (±SE) of mites found on leaves on each of the cardinal directions and the center tree are reported. Suitability of Different Food Types for Population Growth of T. bakeri Tarsonemus bakeri adults were collected from the ‘Washington’ navel orange orchard in 2018 and used to initiate a laboratory colony. Mites obtained from sooty mold-infested orange leaves were individually transferred onto a freshly picked expanded-mature-orange-leaf, approximately 5 cm × 10 cm. Before transferring mites, the leaves were washed with tap water and any debris or insects present were removed. Each leaf was then placed lower side up on a 2.5 cm thick sponge in a plastic container 19.5 × 20.5 × 6.9 cm (l × b × h) (Rubbermaid, Atlanta, GA). Fifty milliliters of tap water were added to saturate the sponge to maintain high relative humidity. The edges of leaves were covered with a strip of absorbent wadding (Curity absorbent wadding, Kendall Boston, MA) to provide water for the leaves and ensure leaves were held in place. Citricola scale-infested leaves (Coccus psuedomagnoliarum Bartlet (Hemiptera: Coccidae)) were collected from the same orchard. Two small drops of fresh honeydew produced by citricola scale were added to the leaves for rearing the mites every 2–3 d using a fine brush. In addition to the honeydew, a 5 × 5 mm piece of Alternaria spp. culture grown on potato dextrose agar obtained from Dr. Chang Lin Xiao’s laboratory at the San Joaquin Valley Agricultural Sciences Center, USDA ARS Parlier, CA was added every 2–3 d using a fine brush. Mites were allowed to develop and multiply on each leaf setup and placed in an incubator maintained at 26 ± 2°C. After 4–5 wk, the population generated by a single female was confirmed to the species level using a morphological key (Lindquist 1978). Species other than T. bakeri were discarded and T. bakeri was continuously reared on honeydew produced by citricola scale and Alternaria spp. until a single species colony was obtained. The colony of T. bakeri maintained as described above were used to determine the suitability of different food types for population development on a leaf and a plastic substrate. The experimental setup for leaves was similar to that described above for mite rearing. For the plastic substrate, a black 1-mm thick PVC sheet (Celtec Expanded PVC Sheet, Satin Smooth Finish) was cut into a 5 × 10 cm piece and placed on a 2.5 cm thick sponge in a 10-cm Petri dish. Fifty milliliters of tap water was added to saturate the sponge to maintain relative humidity. The edges of the leaves or plastic substrate were covered with a strip of absorbent wadding to maintain high humidity and to ensure the leaves were held in place. The inside edge of the absorbent wadding strip was lined with tanglefoot sticky glue (Tangle Trap Sticky Coating) to keep mites on the leaves. Eight treatments were tested, namely: 1) leaf only—no additional food, 2) leaf + Alternaria spp., a 5-mm square transferred using an artist brush (5/0 Atlas brush and Co. Inc, Cleveland, OH), 3) leaf + sugar source (3 drops of citricola scale honeydew + 3 drops of molasses, transferred using the artist brush) 4) leaf + sugar source + Alternaria spp., 5) plastic only—no additional food, 6) plastic + Alternaria spp., a 5-mm square transferred using an artist brush, 7) plastic + sugar source (3 drops of citricola scale honeydew + 3 drops of molasses), 8) plastic + sugar source + Alternaria spp. The honeydew, molasses, and Alternaria spp. were placed on both sides of the midrib of leaves and randomly on the plastic substrate. All treatments were applied just prior to transferring mites for the first time and every 2–3 d thereafter. For each treatment, 25 adult T. bakeri were transferred to each leaf or plastic substrate and the Petri dishes were placed in an incubator maintained at 26 ± 2°C, 70 ± 5% RH, and 14:10 (L:D). Each treatment had four replications. The number of live adults, cumulative eggs deposited, and the immatures that developed were counted three times/week for 29 d. During data collection, we noticed that T. bakeri mites preferred feeding and depositing eggs inside Alternaria masses. Dissecting the mass of Alternaria for counting could destroy the eggs and immatures, therefore, only motile stages on the exterior of the mass of Alternaria were counted through Day 27. On Day 29, the mass of Alternaria was dissected to account for all eggs, immatures, and adults. The experimental design for determining the suitability of different diets for T. bakeri population development was a completely randomized design with four replications. Statistical procedures were accomplished using Statgraphics (StatPoint Technologies, Inc. 2018). A one-way repeated measures ANOVA was conducted to compare the effects of time on population of T. bakeri for each treatment over a 29-d evaluation period. A two-way ANOVA analysis was conducted to determine the effects of substrate and food types on T. bakeri population development followed by a one-way ANOVA to compare effects of food type or the substrate on population of mites. Tukey’s least significant difference (LSD) procedure was used for mean separation. Population Structure of T. bakeri in Fallen/Decaying Leaves Observations made during the laboratory rearing of T. bakeri indicated that mites reproduced faster when the leaves started decaying and a colony could be reared on the same leaf for 12 mo if supplementary food types such as sugar and Alternaria were supplied. To determine if the mites could feed and multiply on decaying leaves in the absence of supplementary food, we collected fallen and decaying leaves from the ‘Washington’ navel orange orchard. Ten decaying leaves were randomly collected from under five trees, brought back to the laboratory and assessed for tarsonemid mites (eggs, nymphs, and adults). This process was repeated five times over 2 mo. Observed numbers of mites in fallen/decaying leaves are reported, no statistical analysis was conducted. Results Field Survey of 78 Citrus Orchards All citrus orchards sampled in Ventura County surveyed had visible sooty mold present on leaves. In contrast, 25% of orchards in Riverside County had sooty mold and none of the orchards in the Imperial and Coachella valleys had any visible sooty mold (Table 1). Sooty mold infestation levels in Ventura ranged from low (~10% of trees) to very high (~100%). Riverside County orchards had less than ~40% of trees with visible sooty mold in the four orchards where sooty mold was found. Higher sooty mold incidence in Ventura could be attributed to a higher incidence of honeydew producing insects. There were higher percentages of orchards infested with Asian citrus psyllid, brown soft scale (Coccus hesperidum L.), whitefly spp., mealybug spp., and aphid spp. in Ventura compared with Riverside or Coachella (Table 1). In addition, the relative humidity in Ventura was higher (78% RH) than Riverside County (63% RH) or Imperial and Coachella Valleys (53% RH) (Table 1). Tarsonemus bakeri was only present in Ventura and Riverside counties (Table 1) and were only found where sooty mold was present, irrespective of the citrus variety, or the orchard management style. T. bakeri was found more frequently than L. formosa. Leaves that did not have sooty mold did not have any mites. When present, mites were found aggregating around a honeydew-producing insect or sooty mold along the midrib on the underside of the leaf or under the calyces of fruit. Table 1. The percentages of sooty mold, homopteran insects, mites, and the environmental conditions during the one-time sampling of citrus orchards Parameters . Location (month surveyed) . . Ventura (July) . Riverside (Aug.) . Imperial/Coachella (Nov./Dec.) . # orchards sampled 17 16 45 % of orchards with sooty mold 100 25 0 % of trees with sooty mold 12–96 4–36 NA % of orchards with Homopteran insects  Asian citrus psyllid 94 0 0  Brown soft scale 82 12 11  Whitefly spp 59 6 0  Mealybug spp 18 12 0  Aphid spp 41 0 28 % of orchards with Tarsonemus bakeri mites 70.6 18.8 0 % of orchards with Lorryia formosa mites 27.5 0 0 Parameters . Location (month surveyed) . . Ventura (July) . Riverside (Aug.) . Imperial/Coachella (Nov./Dec.) . # orchards sampled 17 16 45 % of orchards with sooty mold 100 25 0 % of trees with sooty mold 12–96 4–36 NA % of orchards with Homopteran insects  Asian citrus psyllid 94 0 0  Brown soft scale 82 12 11  Whitefly spp 59 6 0  Mealybug spp 18 12 0  Aphid spp 41 0 28 % of orchards with Tarsonemus bakeri mites 70.6 18.8 0 % of orchards with Lorryia formosa mites 27.5 0 0 In total, 78 orchards were surveyed in Ventura, Riverside, and Imperial and Coachella. Twenty-five trees were observed in each orchard sampled. Open in new tab Table 1. The percentages of sooty mold, homopteran insects, mites, and the environmental conditions during the one-time sampling of citrus orchards Parameters . Location (month surveyed) . . Ventura (July) . Riverside (Aug.) . Imperial/Coachella (Nov./Dec.) . # orchards sampled 17 16 45 % of orchards with sooty mold 100 25 0 % of trees with sooty mold 12–96 4–36 NA % of orchards with Homopteran insects  Asian citrus psyllid 94 0 0  Brown soft scale 82 12 11  Whitefly spp 59 6 0  Mealybug spp 18 12 0  Aphid spp 41 0 28 % of orchards with Tarsonemus bakeri mites 70.6 18.8 0 % of orchards with Lorryia formosa mites 27.5 0 0 Parameters . Location (month surveyed) . . Ventura (July) . Riverside (Aug.) . Imperial/Coachella (Nov./Dec.) . # orchards sampled 17 16 45 % of orchards with sooty mold 100 25 0 % of trees with sooty mold 12–96 4–36 NA % of orchards with Homopteran insects  Asian citrus psyllid 94 0 0  Brown soft scale 82 12 11  Whitefly spp 59 6 0  Mealybug spp 18 12 0  Aphid spp 41 0 28 % of orchards with Tarsonemus bakeri mites 70.6 18.8 0 % of orchards with Lorryia formosa mites 27.5 0 0 In total, 78 orchards were surveyed in Ventura, Riverside, and Imperial and Coachella. Twenty-five trees were observed in each orchard sampled. Open in new tab Seasonal T. bakeri population Structure in an Orange Orchard Tarsonemus bakeri was present in the citrus orchard on leaves and/or fruit during every sampling period from June 2018 through May 2019 (Fig. 1). There was significant interaction between the month and plant parts sampled (F = 6.79; df = 11, 696; P < 0.001). The mean total number of mites (sum of immatures, males and females) per sample (leaves or fruit) varied according to months (F = 15.01; df = 11, 708; P < 0.001) and sample type (F = 5.00; df = 1, 718; P = 0.03). Our data show that mite populations increased from September through December and started to decline from January and that the increase in population was positively correlated with relative humidity (r = 0.67; P = 0.015) but temperature had a negative effect (r = −0.63; P = 0.027) (Fig. 1). Mite populations were significantly higher on fruit (F = 5; df = 1, 718; P = 0.025) compared with leaves collected during October through February (Fig. 1). It is likely that mites moved to mature fruit from leaves. We did not observe any damage on leaves or fruit infested with Tarsonemus mites. Fig. 1. Open in new tabDownload slide The mean populations of T. bakeri in fruit and leaf samples for each month from June 2018 to May 2019, with monthly average temperature and relative humidity data. Fig. 1. Open in new tabDownload slide The mean populations of T. bakeri in fruit and leaf samples for each month from June 2018 to May 2019, with monthly average temperature and relative humidity data. The mean number of immatures (eggs, nymphs, and larvae) per sample varied between months (F = 9.66; df = 11, 708; P < 0.001) but were similar for fruit or leaves (F = 1.29; df = 1, 718; P = 0.25) suggesting that T. bakeri immatures did not prefer fruit over leaves and that the adults did not prefer fruit over leaves to deposit eggs (Fig. 2A). Immatures were found year-round but were the least abundant life stage found. The highest mean number of immatures, 5.3 ± 1.5 immatures/fruit, was recorded in December 2018 (Fig. 2A). The number of males also varied between months (F = 9.66; df = 11, 708; P < 0.001) but was similar for fruit or leaves (F = 0.11; df = 1, 718; P = 0.73). The highest mean number of males, 7.4 ± 2.3 males/fruit was recorded in December 2018. Interestingly, the number of females varied between months (F = 14.2; df = 11, 708; P < 0.001) and for fruit or leaves (F = 9.16; df = 1, 718; P = 0.002). Females were the most abundant life stage found and preferred fruit over leaves, especially from October through February. The highest number of females recorded was 43.5 ± 5.7 in December. The honeydew-producing citricola scale (Coccus psuedomagnoliarum Kuwana (Hemiptera: Coccidae)) was the only Hemipteran found and was present in all months sampled. In the field, T. bakeri preferred interior canopy leaves, the shady side of the tree with higher sooty mold growth, and were usually found on the lower part of leaves, on developing mold or cast skin of citricola scale or cottony cushion scale or under sepals of the fruit. Fig. 2. Open in new tabDownload slide The mean number of immatures (A), males (B), and females (C) of T. bakeri per leaf or fruit on samples collected from an orange orchard during June 2018 to July 2019. Arrows indicate pesticide treatments. Fig. 2. Open in new tabDownload slide The mean number of immatures (A), males (B), and females (C) of T. bakeri per leaf or fruit on samples collected from an orange orchard during June 2018 to July 2019. Arrows indicate pesticide treatments. Association of Tarsonemus Mites With Sooty Mold One-way ANOVA analysis of leaves with and without visible sooty mold collected from the Sanger orchard during two seasons showed that mites were only present on leaves that had visible signs of sooty mold (F = 62.2; df = 1, 198; P < 0.001). For the leaves with visible signs of sooty mold, the number of mites/leaf (x̄ ± SE) ranged from 0.6 ± 0.3 to 31.6 ± 21.4. Mites were found in all five regions of the orchard sampled. The percentage incidence of sooty mold in the orchard was lowest for the north direction (60%) compared with East, West, South, and through the center of the orchard (100%). Although the number of mites found on leaves from different regions of the orchard varied, there was no effect of sampling direction (F = 1.81; df = 4, 94; P = 0.13) or month sampled (F = 0.03; df = 1, 98; P = 0.87) (Fig. 3). Fig. 3. Open in new tabDownload slide The mean number Tarsonemus mites present in sooty mold-infested leaves in May and September 2019. No mites were found on leaves without sooty mold. Fig. 3. Open in new tabDownload slide The mean number Tarsonemus mites present in sooty mold-infested leaves in May and September 2019. No mites were found on leaves without sooty mold. Suitability of Different Food Types T. bakeri There was no significant interaction between substrate and food type on the total number (eggs, immatures, and adults) of mites on day 29 (F = 1.24; df = 3, 24; P = 0.31). Similarly, substrate did not have significant effect on the total number of mites (F = 3.0; df = 1, 30; P < 0.093). But food source significantly affected the total number of mites (F = 19.2; df = 3, 28; P < 0.001). Without supplemental food, T. bakeri population decreased to 1.0 mite/leaf on Day 25 and no mites were found on plastic substrate from Day 15 (Table 1). For both substrates, population of mites increased when supplemental food was provided. With the addition of Alternaria spp., T. bakeri population increased to 136.3 mites/leaf and to 71.5 mites/plastic. Similarly, addition of sugary substances increased T. bakeri population to 85.3 mites/leaf and to 15.5 mites/plastic substrate (Table 2). Interestingly, within a substrate, the sugars and Alternaria did not produce significant differences (Table 2). For both substrates, the highest numbers of mites were observed when all food types, that sugar source and Alternaria, were combined to 322.8/leaf and to 123.5 mites/plastic substrate. Table 2. The mean cumulative number of total mites per treatment (±SE) produced by Tarsonemus bakeri on various food types on a leaf or plastic substrate . Treatments . . Leaf only . Leaf + Alternaria . Leaf + Honeydew + Molasses . Leaf + Honeydew + Molasses + Alternaria . Plastic only . Plastic + Alternaria . Plastic + Honeydew + Molasses . Plastic + Honeydew + Molasses + Alternaria . F (7,24) . P . Day 1 13.0 ± 1.3 aa 10.3 ± 1.3 a 13.8 ± 2.2 a 12.5 ± 2.2 a 11.0 ± 1.7 a 9.0 ± 0.9 b 10.3 ± 0.3 a 10.0 ± 0.8 a 5.78 0.0005 Day 4 25.5 ± 4.1 a 15.0 ± 5.6 b 35.0 ± 6.8 a 21.5 ± 5.2 b 9.5 ± 2.6 b 13.5 ± 3.4 b 10.8 ± 1.5 b 13.8 ± 4.1 b 2.39 0.0590 Day 6 27.5 ± 6.7 b 20.5 ± 7.7 bc 46.8 ± 12.2 a 32.0 ± 10.3 a 7.3 ± 1.3 d 12.0 ± 1.3 c 11.8 ± 2.1 c 16.8 ± 4.5 bc 3.93 0.0050 Day 8 24.3 ± 7.9 ab 30.5 ± 15.1 ab 50.0 ± 12.9 a 37.0 ± 14.8 ab 3.0 ± 1.8 c 11.3 ± 2.8 bc 9.8 ± 1.8 bc 15.8 ± 4.6 bc 3.40 0.0100 Day 11 18.5 ± 6.8 b 33.8 ± 15.8 a 48.3 ± 9.9 a 58.5 ± 28.2 a 1.3 ± 1.3 c 8.5 ± 1.4 b 8.8 ± 1.1 b 20.3 ± 1.4 b 4.92 0.0015 Day 13 19.75 ± 9.6 abc 50.0 ± 23.9 a 67.5 ± 23.2 a 55.8 ± 25.9 a 1.8 ± 1.8 d 12.8 ± 4.5 bc 11.0 ± 2.4 bc 18.0 ± 5.6 bc 4.41 0.0029 Day 15 13.8 ± 7.3 b 46.8 ± 21.5 a 72.3 ± 23.3 a 65.5 ± 23.7 a 0.0 ± 0.0 c 6.8 ± 1.6 b 10.5 ± 0.9 b 10.25 ± 1.3 b 7.91 0.0001 Day 18 4.8 ± 3.5 bc 47.0 ± 22.1 ab 66.5 ± 28.3 ab 79.5 ± 25.8 a 0.0 ± 0.0 d 7.3 ± 2.1 bc 10.3 ± 2.7 bc 22.8 ± 6.5 b 6.48 0.0002 Day 20 1.5 ± 0.9 cd 52.5 ± 25.4 ab 67.0 ± 31.5 ab 90.8 ± 30.6 a 0.0 ± 0.0 d 9.3 ± 3.2 c 11.5 ± 5.2 c 23.5 ± 10.6 bc 5.45 0.0008 Day 23 1.8 ± 1.0 cd 63.3 ± 32.5 ab 74.5 ± 38.0 ab 107.0 ± 35.2 a 0.0 ± 0.0 d 11 ± 4.1 c 13.5 ± 7.5 c 22.8 ± 6.4 bc 5.19 0.0011 Day 25 0.5 ± 0.3 cd 68.0 ± 33.2 ab 79.0 ± 32.0 ab 108.0 ± 33.6 a 0.0 ± 0.0 d 12.5 ± 2.7 c 11.3 ± 5.9 c 25.2 ± 12.9 bc 5.68 0.0006 Day 27 1.0 ± 0.0 c 74.0 ± 15.6 b 86.0 ± 39.7 b 179.3 ± 34.8 a 0.0 ± 0.0 c 31.8 ± 10.3 b 13.0 ± 8.3 b 69.0 ± 41.5 b 7.49 0.0001 Day 29 1.0 ± 0.7 de 136.3 ± 42.2 b 85.3 ± 38.4 bc 322.8 ± 86.3 a 0.0 ± 0.0 e 71.5 ± 17.2 bcd 15.5 ± 7.6 d 123.5 ± 30.2 b 13.2 <0.0001 . Treatments . . Leaf only . Leaf + Alternaria . Leaf + Honeydew + Molasses . Leaf + Honeydew + Molasses + Alternaria . Plastic only . Plastic + Alternaria . Plastic + Honeydew + Molasses . Plastic + Honeydew + Molasses + Alternaria . F (7,24) . P . Day 1 13.0 ± 1.3 aa 10.3 ± 1.3 a 13.8 ± 2.2 a 12.5 ± 2.2 a 11.0 ± 1.7 a 9.0 ± 0.9 b 10.3 ± 0.3 a 10.0 ± 0.8 a 5.78 0.0005 Day 4 25.5 ± 4.1 a 15.0 ± 5.6 b 35.0 ± 6.8 a 21.5 ± 5.2 b 9.5 ± 2.6 b 13.5 ± 3.4 b 10.8 ± 1.5 b 13.8 ± 4.1 b 2.39 0.0590 Day 6 27.5 ± 6.7 b 20.5 ± 7.7 bc 46.8 ± 12.2 a 32.0 ± 10.3 a 7.3 ± 1.3 d 12.0 ± 1.3 c 11.8 ± 2.1 c 16.8 ± 4.5 bc 3.93 0.0050 Day 8 24.3 ± 7.9 ab 30.5 ± 15.1 ab 50.0 ± 12.9 a 37.0 ± 14.8 ab 3.0 ± 1.8 c 11.3 ± 2.8 bc 9.8 ± 1.8 bc 15.8 ± 4.6 bc 3.40 0.0100 Day 11 18.5 ± 6.8 b 33.8 ± 15.8 a 48.3 ± 9.9 a 58.5 ± 28.2 a 1.3 ± 1.3 c 8.5 ± 1.4 b 8.8 ± 1.1 b 20.3 ± 1.4 b 4.92 0.0015 Day 13 19.75 ± 9.6 abc 50.0 ± 23.9 a 67.5 ± 23.2 a 55.8 ± 25.9 a 1.8 ± 1.8 d 12.8 ± 4.5 bc 11.0 ± 2.4 bc 18.0 ± 5.6 bc 4.41 0.0029 Day 15 13.8 ± 7.3 b 46.8 ± 21.5 a 72.3 ± 23.3 a 65.5 ± 23.7 a 0.0 ± 0.0 c 6.8 ± 1.6 b 10.5 ± 0.9 b 10.25 ± 1.3 b 7.91 0.0001 Day 18 4.8 ± 3.5 bc 47.0 ± 22.1 ab 66.5 ± 28.3 ab 79.5 ± 25.8 a 0.0 ± 0.0 d 7.3 ± 2.1 bc 10.3 ± 2.7 bc 22.8 ± 6.5 b 6.48 0.0002 Day 20 1.5 ± 0.9 cd 52.5 ± 25.4 ab 67.0 ± 31.5 ab 90.8 ± 30.6 a 0.0 ± 0.0 d 9.3 ± 3.2 c 11.5 ± 5.2 c 23.5 ± 10.6 bc 5.45 0.0008 Day 23 1.8 ± 1.0 cd 63.3 ± 32.5 ab 74.5 ± 38.0 ab 107.0 ± 35.2 a 0.0 ± 0.0 d 11 ± 4.1 c 13.5 ± 7.5 c 22.8 ± 6.4 bc 5.19 0.0011 Day 25 0.5 ± 0.3 cd 68.0 ± 33.2 ab 79.0 ± 32.0 ab 108.0 ± 33.6 a 0.0 ± 0.0 d 12.5 ± 2.7 c 11.3 ± 5.9 c 25.2 ± 12.9 bc 5.68 0.0006 Day 27 1.0 ± 0.0 c 74.0 ± 15.6 b 86.0 ± 39.7 b 179.3 ± 34.8 a 0.0 ± 0.0 c 31.8 ± 10.3 b 13.0 ± 8.3 b 69.0 ± 41.5 b 7.49 0.0001 Day 29 1.0 ± 0.7 de 136.3 ± 42.2 b 85.3 ± 38.4 bc 322.8 ± 86.3 a 0.0 ± 0.0 e 71.5 ± 17.2 bcd 15.5 ± 7.6 d 123.5 ± 30.2 b 13.2 <0.0001 aMeans within a row followed by different letters are significantly different. Open in new tab Table 2. The mean cumulative number of total mites per treatment (±SE) produced by Tarsonemus bakeri on various food types on a leaf or plastic substrate . Treatments . . Leaf only . Leaf + Alternaria . Leaf + Honeydew + Molasses . Leaf + Honeydew + Molasses + Alternaria . Plastic only . Plastic + Alternaria . Plastic + Honeydew + Molasses . Plastic + Honeydew + Molasses + Alternaria . F (7,24) . P . Day 1 13.0 ± 1.3 aa 10.3 ± 1.3 a 13.8 ± 2.2 a 12.5 ± 2.2 a 11.0 ± 1.7 a 9.0 ± 0.9 b 10.3 ± 0.3 a 10.0 ± 0.8 a 5.78 0.0005 Day 4 25.5 ± 4.1 a 15.0 ± 5.6 b 35.0 ± 6.8 a 21.5 ± 5.2 b 9.5 ± 2.6 b 13.5 ± 3.4 b 10.8 ± 1.5 b 13.8 ± 4.1 b 2.39 0.0590 Day 6 27.5 ± 6.7 b 20.5 ± 7.7 bc 46.8 ± 12.2 a 32.0 ± 10.3 a 7.3 ± 1.3 d 12.0 ± 1.3 c 11.8 ± 2.1 c 16.8 ± 4.5 bc 3.93 0.0050 Day 8 24.3 ± 7.9 ab 30.5 ± 15.1 ab 50.0 ± 12.9 a 37.0 ± 14.8 ab 3.0 ± 1.8 c 11.3 ± 2.8 bc 9.8 ± 1.8 bc 15.8 ± 4.6 bc 3.40 0.0100 Day 11 18.5 ± 6.8 b 33.8 ± 15.8 a 48.3 ± 9.9 a 58.5 ± 28.2 a 1.3 ± 1.3 c 8.5 ± 1.4 b 8.8 ± 1.1 b 20.3 ± 1.4 b 4.92 0.0015 Day 13 19.75 ± 9.6 abc 50.0 ± 23.9 a 67.5 ± 23.2 a 55.8 ± 25.9 a 1.8 ± 1.8 d 12.8 ± 4.5 bc 11.0 ± 2.4 bc 18.0 ± 5.6 bc 4.41 0.0029 Day 15 13.8 ± 7.3 b 46.8 ± 21.5 a 72.3 ± 23.3 a 65.5 ± 23.7 a 0.0 ± 0.0 c 6.8 ± 1.6 b 10.5 ± 0.9 b 10.25 ± 1.3 b 7.91 0.0001 Day 18 4.8 ± 3.5 bc 47.0 ± 22.1 ab 66.5 ± 28.3 ab 79.5 ± 25.8 a 0.0 ± 0.0 d 7.3 ± 2.1 bc 10.3 ± 2.7 bc 22.8 ± 6.5 b 6.48 0.0002 Day 20 1.5 ± 0.9 cd 52.5 ± 25.4 ab 67.0 ± 31.5 ab 90.8 ± 30.6 a 0.0 ± 0.0 d 9.3 ± 3.2 c 11.5 ± 5.2 c 23.5 ± 10.6 bc 5.45 0.0008 Day 23 1.8 ± 1.0 cd 63.3 ± 32.5 ab 74.5 ± 38.0 ab 107.0 ± 35.2 a 0.0 ± 0.0 d 11 ± 4.1 c 13.5 ± 7.5 c 22.8 ± 6.4 bc 5.19 0.0011 Day 25 0.5 ± 0.3 cd 68.0 ± 33.2 ab 79.0 ± 32.0 ab 108.0 ± 33.6 a 0.0 ± 0.0 d 12.5 ± 2.7 c 11.3 ± 5.9 c 25.2 ± 12.9 bc 5.68 0.0006 Day 27 1.0 ± 0.0 c 74.0 ± 15.6 b 86.0 ± 39.7 b 179.3 ± 34.8 a 0.0 ± 0.0 c 31.8 ± 10.3 b 13.0 ± 8.3 b 69.0 ± 41.5 b 7.49 0.0001 Day 29 1.0 ± 0.7 de 136.3 ± 42.2 b 85.3 ± 38.4 bc 322.8 ± 86.3 a 0.0 ± 0.0 e 71.5 ± 17.2 bcd 15.5 ± 7.6 d 123.5 ± 30.2 b 13.2 <0.0001 . Treatments . . Leaf only . Leaf + Alternaria . Leaf + Honeydew + Molasses . Leaf + Honeydew + Molasses + Alternaria . Plastic only . Plastic + Alternaria . Plastic + Honeydew + Molasses . Plastic + Honeydew + Molasses + Alternaria . F (7,24) . P . Day 1 13.0 ± 1.3 aa 10.3 ± 1.3 a 13.8 ± 2.2 a 12.5 ± 2.2 a 11.0 ± 1.7 a 9.0 ± 0.9 b 10.3 ± 0.3 a 10.0 ± 0.8 a 5.78 0.0005 Day 4 25.5 ± 4.1 a 15.0 ± 5.6 b 35.0 ± 6.8 a 21.5 ± 5.2 b 9.5 ± 2.6 b 13.5 ± 3.4 b 10.8 ± 1.5 b 13.8 ± 4.1 b 2.39 0.0590 Day 6 27.5 ± 6.7 b 20.5 ± 7.7 bc 46.8 ± 12.2 a 32.0 ± 10.3 a 7.3 ± 1.3 d 12.0 ± 1.3 c 11.8 ± 2.1 c 16.8 ± 4.5 bc 3.93 0.0050 Day 8 24.3 ± 7.9 ab 30.5 ± 15.1 ab 50.0 ± 12.9 a 37.0 ± 14.8 ab 3.0 ± 1.8 c 11.3 ± 2.8 bc 9.8 ± 1.8 bc 15.8 ± 4.6 bc 3.40 0.0100 Day 11 18.5 ± 6.8 b 33.8 ± 15.8 a 48.3 ± 9.9 a 58.5 ± 28.2 a 1.3 ± 1.3 c 8.5 ± 1.4 b 8.8 ± 1.1 b 20.3 ± 1.4 b 4.92 0.0015 Day 13 19.75 ± 9.6 abc 50.0 ± 23.9 a 67.5 ± 23.2 a 55.8 ± 25.9 a 1.8 ± 1.8 d 12.8 ± 4.5 bc 11.0 ± 2.4 bc 18.0 ± 5.6 bc 4.41 0.0029 Day 15 13.8 ± 7.3 b 46.8 ± 21.5 a 72.3 ± 23.3 a 65.5 ± 23.7 a 0.0 ± 0.0 c 6.8 ± 1.6 b 10.5 ± 0.9 b 10.25 ± 1.3 b 7.91 0.0001 Day 18 4.8 ± 3.5 bc 47.0 ± 22.1 ab 66.5 ± 28.3 ab 79.5 ± 25.8 a 0.0 ± 0.0 d 7.3 ± 2.1 bc 10.3 ± 2.7 bc 22.8 ± 6.5 b 6.48 0.0002 Day 20 1.5 ± 0.9 cd 52.5 ± 25.4 ab 67.0 ± 31.5 ab 90.8 ± 30.6 a 0.0 ± 0.0 d 9.3 ± 3.2 c 11.5 ± 5.2 c 23.5 ± 10.6 bc 5.45 0.0008 Day 23 1.8 ± 1.0 cd 63.3 ± 32.5 ab 74.5 ± 38.0 ab 107.0 ± 35.2 a 0.0 ± 0.0 d 11 ± 4.1 c 13.5 ± 7.5 c 22.8 ± 6.4 bc 5.19 0.0011 Day 25 0.5 ± 0.3 cd 68.0 ± 33.2 ab 79.0 ± 32.0 ab 108.0 ± 33.6 a 0.0 ± 0.0 d 12.5 ± 2.7 c 11.3 ± 5.9 c 25.2 ± 12.9 bc 5.68 0.0006 Day 27 1.0 ± 0.0 c 74.0 ± 15.6 b 86.0 ± 39.7 b 179.3 ± 34.8 a 0.0 ± 0.0 c 31.8 ± 10.3 b 13.0 ± 8.3 b 69.0 ± 41.5 b 7.49 0.0001 Day 29 1.0 ± 0.7 de 136.3 ± 42.2 b 85.3 ± 38.4 bc 322.8 ± 86.3 a 0.0 ± 0.0 e 71.5 ± 17.2 bcd 15.5 ± 7.6 d 123.5 ± 30.2 b 13.2 <0.0001 aMeans within a row followed by different letters are significantly different. Open in new tab Different treatments had significant effect on number of eggs laid by T. bakeri, but there was no interaction between the substate and food type (Fig. 4A; Table 3). The number of eggs deposited by females increased through time on all food types and was significantly higher on the leaf substrate compared with the plastic in all 4 wk. The highest number of eggs, 123.7 ± 62.5, was observed on the leaf substrate with all supplemental food types on Week 4. Fig. 4. Open in new tabDownload slide The mean number of eggs (A), immatures (B), and adults (C) of T. bakeri on different food types. Fig. 4. Open in new tabDownload slide The mean number of eggs (A), immatures (B), and adults (C) of T. bakeri on different food types. Table 3. ANOVA analyses of number of mites, namely, eggs, immatures, and adults produced on different food types on leaf or plastic substrate (n = 8) Life stage . Time . F . P . Eggs Week 1 4.9 <0.01 Week 2 4.4 <0.01 Week 3 6.6 <0.01 Week 4 3.7 <0.01 Immature Week 1 4.8 <0.01 Week 2 4.4 <0.01 Week 3 7.0 <0.01 Week 4 11.9 <0.01 Adults Week 1 0.73 0.54 Week 2 6.6 <0.01 Week 3 7.6 <0.01 Week 4 12.2 <0.01 Life stage . Time . F . P . Eggs Week 1 4.9 <0.01 Week 2 4.4 <0.01 Week 3 6.6 <0.01 Week 4 3.7 <0.01 Immature Week 1 4.8 <0.01 Week 2 4.4 <0.01 Week 3 7.0 <0.01 Week 4 11.9 <0.01 Adults Week 1 0.73 0.54 Week 2 6.6 <0.01 Week 3 7.6 <0.01 Week 4 12.2 <0.01 Degrees of freedom for one-way analysis of number of eggs, immatures, or adults produced on different food sources was 7, 24. Open in new tab Table 3. ANOVA analyses of number of mites, namely, eggs, immatures, and adults produced on different food types on leaf or plastic substrate (n = 8) Life stage . Time . F . P . Eggs Week 1 4.9 <0.01 Week 2 4.4 <0.01 Week 3 6.6 <0.01 Week 4 3.7 <0.01 Immature Week 1 4.8 <0.01 Week 2 4.4 <0.01 Week 3 7.0 <0.01 Week 4 11.9 <0.01 Adults Week 1 0.73 0.54 Week 2 6.6 <0.01 Week 3 7.6 <0.01 Week 4 12.2 <0.01 Life stage . Time . F . P . Eggs Week 1 4.9 <0.01 Week 2 4.4 <0.01 Week 3 6.6 <0.01 Week 4 3.7 <0.01 Immature Week 1 4.8 <0.01 Week 2 4.4 <0.01 Week 3 7.0 <0.01 Week 4 11.9 <0.01 Adults Week 1 0.73 0.54 Week 2 6.6 <0.01 Week 3 7.6 <0.01 Week 4 12.2 <0.01 Degrees of freedom for one-way analysis of number of eggs, immatures, or adults produced on different food sources was 7, 24. Open in new tab Similarly, the cumulative number of immatures (larvae + nymphs) produced by females on all treatments were significantly different through time (Fig. 4B; Table 3). The highest number of immatures, 132 ± 21.1, was observed on the leaf substrate with all supplemental food on Week 4. The number of adults (male + females) were statistically the same in all treatments in Week 1, but significantly different for all treatments for Weeks 2–4; Week 2 (Fig. 4C; Table 3). The highest number adults, 99.1 ± 22.7 was observed on the leaf substrate all supplemental food on Week 4. T. bakeri in Fallen/Decaying Leaves Evaluation of the fallen decaying leaves confirmed that Tarsonemus spp. mites were present on decaying leaves and the population density averaged 2.8 ± 0.9 mites/leaf. Discussion Field survey of citrus orchards in Ventura, Riverside, Imperial, and Coachella confirmed that T. bakeri was associated with sooty mold, a black fungus that grows on honeydew produced by sap-sucking insects but was not present in fields without sooty mold. Mites were abundant in Ventura county, 65% of the leaves with sooty mold had mites compared with 20% in Riverside. Both sooty mold and mites were absent in Imperial and Coachella valley orchards. Tarsonemus spp. have been reported from citrus in California (Beer 1954), Florida (Attiah 1970), and Italy (Vacante and Nucifora 1985). These studies are heavily focused on Tarsonemid taxonomy and do not provide any other detail on conditions in which they were collected. Seasonal field survey data in Sanger CA showed that Tarsonemus mites were present in the navel orange orchard year-round and that their populations fluctuated. Earlier reports have shown that T. bakeri is the most common tarsonemid species in citrus and is widespread (Beer 1954, McGregor 1956). McGregor (1956) observed T. setifer (syn. T. bakeri) in colonies of Alternaria spp. in citrus, but also observed in uncontaminated situations. Beer 1954 reported that T. bakeri mites can be reared on artificially grown Alternaria spp. McGregor (1942) also reports that T. bakeri is associated with Alternaria spp. and may be responsible for spreading fungal pathogens. We only found Tarsonemus mites on sooty mold-infested leaves and fruits and did not observe mites on leaves without sooty mold. McGregor reported that 62.5% of lemons sampled had T. bakeri mites and fruit that were infested with 40–50 mites developed lopsided growth symptoms, suggesting they caused fruit damage. In contrast, we did not observe any malformation of fruits (oranges) despite examining fruit samples that had ~100 mites. Similarly, we did not observe any crinkling of leaves, nor any feeding lesions in leaves of the orange orchard where Tarsonemus mites were present year-round. Instead, mites were only observed associated with sooty mold in field samples and food suitability studies results indicates that tarsonemid mites probably feed on honeydew and sooty mold developing on honey dew in the field. Beer (1954) reported that despite previously documented as pest mites, T. waitei and T. setifer (syn. T. bakeri) were secondary invaders of dead or diseased plant tissue. We reared T. bakeri populations on decaying excised leaves for more than 12 mo and the fact that T. bakeri populations were found on decaying leaves under the tree canopy corroborates reports by Beer. Overall, mite populations were higher from October through February, when temperature declined, and relative humidity increased. Although there are no studies showing the effects of relative humidity on Tarsonemus mites, a study evaluating constant humidity air-flow technique reported strong effect of temperature and humidity on citrus red mite [Phyllocoptruta oleivora (Ashmead) Acari: Eriophyidae] population (Hobza and Jeppson 1974). It is also likely that, a higher number of mites on fruit, especially in winter months, suggest that Tarsonemus populations thrive on sooty mold on leaves and migrate from leaves to fruit in winter months. McGregor (1942) reported that T. bakeri mites migrate from leaves to young lemons. Populations as high as ~40–50 mites per fruit have been reported in lemons (McGregor 1942). Although reported as the most common invader of citrus, the population density of mites was not reported in other studies (Beer 1954). In our study, the highest number of motile stages (immatures + adults), 59.7 ± 15.9 observed was in December on fruit and consisted predominantly of females. The highest number of mites found on a single fruit was 396. High adult mortality on excised leaves or a plastic substrate free of sugary substances and Alternaria suggests that T. bakeri cannot sustain or continue development on citrus leaves alone and will eventually die because of a lack of suitable food to support development. A common citrus mite, L. formosa, also cannot survive on leaves alone without supplementary food (Gautam et al. 2018). T. bakeri mites multiplied on the plastic substrate on Alternaria, honeydew, molasses, and combinations of these food types but performed better on the leaf substrate. The highest population growth was observed on Week 4 leaf substrate with Alternaria, molasses, and honeydew, suggesting that decaying leaves provide additional nutrition to fungus, therefore, to mites. We also observed Tarsonemus mites on fallen decaying leaves collected from under the canopy, further confirming that Tarsonemus mites are not phytophagous. Although it needs to be confirmed via experiments, it is likely that Tarsonemus mites also feeds on other saprophytic organisms that facilitate tissue decomposition. In summary, our results show that Tarsonemus mites are present in the field throughout the year and at least in three regions suggesting that this species is found in California citrus and may be present year-round in orchards with active sooty mold populations. Our observation that mites were only found on leaves where sooty mold is present indicates that controlling sap-sucking insects that produce honeydew on which sooty mold grows, will help to reduce mite incidence in the field. The food suitability study showed that T. bakeri does not survive on excised leaves without supplemental food in the form of sugary substances and/or fungus and the absence of leaf or fruit damage in the field or laboratory studies suggests that this species is not a pest, rather a fungivore/detritivore that prefers feeding on decaying leaves, molds and sugary substances and, therefore, is a very low-risk species for importing countries. Acknowledgments We would like to thank Joel Leonard, California Polytechnic State University, San Luis Obispo, and Kevin Gonzalez, University of California, Riverside for assistance with the field surveys. We also thank Thomas Benzler for allowing us to conduct a year-round survey in his orchard. Dr. Chang Lin Xiao’s laboratory at the San Joaquin Valley Agricultural Sciences Center, USDA ARS Parlier, California provided Alternaria spp. used in the study. The California Citrus Research Board grant #5500–501 funded this work. References Cited Aguilar , H. , C. C. Childers, and W. C. Welbourn. 2001 . Relative abundance and seasonal occurrence of mites in the family Tydeidae on citrus in Florida, pp. 376 – 380 . In R. B. Halliday, D. E. Walter, H. C. Proctor, R. A. Norton, and M. J. Colloff (eds.), 10th International Congress . CSIRO pub, Canberra, Collingswood, Victoria, Australia . Attiah , H. H . 1970 . New Tarsonemid mites associated with citrus in Florida (Acarina: Tarsonemidae) . Fl. Entomol . 53 : 179 – 201 Google Scholar Crossref Search ADS WorldCat Beer , R. E . 1954 . A revision of Tarsonemidae of the Western Hemisphere (Order: Acarina) Kansas . Univ. Sci. Bull . 36 : 1091 – 1387 . 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A first list of mites in citrus orchards in Italy, pp. 177–188. In R. Cavalloro and E. DI Martino (eds.), Proceedings, experts’ meeting integrated pest control in citrus-groves, 26–29 March 1985. A.A. Balkema, Rotterdam, Netherlands. © The Author(s) 2021. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model)
TI - Field Ecology and Food Suitability of Tarsoneums spp. (Acari: Tarsonemidae)
JO - Environmental Entomology
DO - 10.1093/ee/nvab013
DA - 2021-03-02
UR - https://www.deepdyve.com/lp/oxford-university-press/field-ecology-and-food-suitability-of-tarsoneums-spp-acari-POcDSpomFT
SP - 1
EP - 1
VL - Advance Article
IS - 
DP - DeepDyve
ER -