Elena M. Rhodes

Comparison of single and combination treatments of Phytoseiulus persimilis, Neoseiulus californicus, and Acramite (bifenazate) for control of twospotted spider mites in strawberries.

Greenhouse and field experiments were conducted from 2003 to 2005 to determine the effectiveness of combining releases of two predatory mite species, Phytoseiulus persimilis Athias-Henriot and Neoseiulus californicus (McGregor), and a reduced-risk miticide, Acramite® (bifenazate), for control of twospotted spider mite (TSSM) (Tetranychus urticae Koch) in strawberries. In the greenhouse experiment, a combination treatment of P. persimilis and N. californicus was compared with single treatments of each species, Acramite application, and untreated control. All treatments significantly reduced TSSM numbers compared with the control. Field studies employed two approaches: one investigating the same five treatments as the greenhouse experiment and a second, comparing combination treatments of P. persimilis/N. californicus, Acramite/N. californicus, and Acramite/P. persimilis to single treatments of each and to control plots. Among the combination treatments, the P. persimilis/N. californicus treatment significantly reduced TSSM numbers compared with the control, but was not as effective as N. californicus alone during the 2003–2004 field season. Also, combination treatments of Acramite/N. californicus, and Acramite/P. persimilis significantly reduced TSSM populations compared with the control. These findings indicate that all three combination treatments are promising options for TSSM control in strawberries for growers in northern Florida and other strawberry producing areas of the world.

Evaluation of Predatory Mites and Acramite for Control of Twospotted Spider Mites in Strawberries in North Central Florida

Greenhouse and field experiments were conducted from 2003 to 2005 to determine the effectiveness of two predatory mite species, Phytoseiulus persimilis Athias-Henriot and Neoseiulus californicus (McGregor), and a reduced-risk miticide, Acramite 50 WP (bifenazate), for control of twospotted spider mite, Tetranychus urticae Koch, in strawberries (Fragaria x ananassa Duchesne). In greenhouse tests, three treatments consisting of releases of P. persimilis, N. californicus, and an untreated control were evaluated. Both species of predatory mites significantly reduced twospotted spider mite numbers below those found in the control during the first 3 wk of evaluation. However, during week 4, twospotted spider mite numbers on the plants treated with P. persimilis increased and did not differ significantly from the control. Field studies used releases of P. persimilis and N. californicus, applications of Acramite, and untreated control plots. Both N. californicus and P. persimilis significantly reduced populations of twospotted spider mite below numbers recorded in the control plots. During the 2003-2004 field season P. persimilis took longer than N. californicus to bring the twospotted spider mite population under control (< 10 mites per leaflet). Acramite was effective in reducing twospotted spider mite populations below 10 mites per leaflet during the 2003-2004 field season but not during the 2004-2005 field season, possibly because of a late application. These findings indicate that N. californicus releases and properly timed Acramite applications are promising options for twospotted spider mite control in strawberries for growers in north Florida and other areas of the southeast.

THE RESIDUAL AND DIRECT EFFECTS OF REDUCED-RISK AND CONVENTIONAL MITICIDES ON TWOSPOTTED SPIDER MITES, TETRANYCHUS URTICAE (ACARI: TETRANYCHIDAE) AND PREDATORY MITES (ACARI: PHYTOSEIIDAE)

Abstract The residual effects of several reduced-risk and conventional miticides were evaluated in strawberries (Fragaria × ananassa Duchesne) on the twospotted spider mite (TSSM), Tetranychus urticae Koch (Acari: Tetranychidae) and on 2 predatory mites, Neoseiulus californicus McGregor and Phytoseiulus persimilis Athias-Henriot (Acari: Phytoseiidae). Experiments were conducted in the laboratory and greenhouse. The greenhouse experiments also tested the direct effects of the miticides on TSSM. The efficacy of conventional and reduced-risk miticides was evaluated on strawberry leaf discs and on whole plants for control of TSSM. Furthermore, the residual effects of these miticides were evaluated on whole strawberry plants against selective predatory mites. For TSSM, 5 treatments were evaluated: a conventional miticide; fenbutatin-oxide (Vendex®) and 3 reduced-risk miticides; binfenazate (Acramite 50WP®), activated garlic extract (Repel®), sesame seed and castor oil (Wipeout®), and a water-treated control. For predatory mites, the residual effects of only Acramite® and Vendex® were evaluated. Acramite® was the most effective acaricide in reducing TSSM populations in both the laboratory and greenhouse experiments. Vendex® and Wipeout® were also effective in the laboratory, but did not cause significant reduction of TSSM in the greenhouse. Repel® was the least effective of the 4 pesticides evaluated. Neither Acramite® nor Vendex® had a significant effect on either predatory mite species. However, there appeared to be more predatory mites on the Vendex®-treated plants than on the Acramite®-treated plants. There were significantly more predatory mites of both species on the cue plants, which were inoculated with TSSM versus the non-cue plants, which were not inoculated.

Species Composition, Monitoring, and Feeding Injury of Stink Bugs (Heteroptera: Pentatomidae) in Blackberry

ABSTRACT Blackberry (Rubus spp.) production in Florida has increased >100% within the past two decades, and several insect pests, including stink bugs (Heteroptera: Pentatomidae), have been observed feeding on this crop. The objectives for this study were to determine the stink bug species present in blackberry; to develop monitoring tools for stink bugs in blackberry; and to describe feeding injury to blackberries by Euschistus quadrator Rolston, a relatively new stink bug pest to Florida, that has spread throughout the state. In a field survey, E. quadrator was the most abundant stink bug species, followed by Euschistus servus Say, Euschistus obscurus (Palisot de Beauvois), Thyanta custator (F.), Proxys punctulatus (Palisot de Beauvois), and Podisus maculiventris Say. Yellow pyramid traps caught more stink bugs than tube traps with or without the addition of Euschistus spp. pheromone lures. There were no statistical differences between traps baited with a Trécé Pherocon Centrum lure, a Suterra Scenturion lure, and an unbaited trap. These results were supported by Y-tube olfactometer assays with E. quadrator where there were no differences between pheromone baited lures and a control. Injury to berries caused by E. quadrator adults and third instars was similar, and both adults and third instars fed more on green berries compared with turning berries. In addition, adults fed more on green berries compared with ripe fruit. The most common injury to green berries was discoloration. In contrast, misshapen drupelets were commonly seen on turning and ripe berries. The potential for managing stink bugs in blackberries to prevent them from reaching damaging levels is discussed.

Effects of Southern Highbush Blueberry Cultivar and Treatment Threshold on Flower Thrips Populations

ABSTRACT In Florida, southern highbush (SHB) blueberries (Vaccinium corymbosum L. × Vaccinium darrowi Camp) are grown for a highly profitable early season fresh market. Flower thrips are the key pest of SHB blueberries, and Frankliniella bispinosa (Morgan) is the most common species found. Flower thrips injure blueberry flowers by feeding and ovipositing in all developing tissues. These injuries can lead to scarring of developing fruit. The objectives of this study were to determine the relationship between thrips and yield in different SHB blueberry cultivars and to determine an action threshold. Experiments were conducted during early spring 2007 and 2008 on four farms; a research farm in Citra, FL; and three commercial farms, two in Hernando Co., FL., and one in Lake Co., FL. At the Citra farm, ‘Emerald’, ‘Jewel’, ‘Millennia’, and ‘Star’ blueberries were compared in 2007, and all but Star were compared in 2008. On the Hernando and Lake Co. farms, two treatment thresholds (100 and 200 thrips per trap) and an untreated control and four cultivars (Emerald, Jewel, Millennia, and ‘Windsor’) were compared. Emerald consistently had more thrips per trap and per flower than the other cultivars on all four farms. However, this did not always lead to an increase in fruit injury. Thrips numbers exceeded the threshold on only one farm in 2007, and there was a significantly lower proportion of injured and malformed fruit in the 100 thrips per trap threshold treatment compared with the control on this farm.

Flower Thrips (Thysanoptera: Thripidae) Dispersal from Alternate Hosts into Southern Highbush Blueberry (Ericales: Ericaceae) Plantings

ABSTRACT Frankliniella bispinosa (Morgan) is the key pest of southern highbush blueberries (Vaccinium corymbosum L. × V. darrowi Camp) in Florida. Thrips feeding and oviposition injury to developing flowers can result in fruit scarring that renders the fruit unmarketable. Previous studies have shown that flower thrips can disperse into cultivated crops from surrounding host plants. Therefore, the objectives of this study were to identify alternate hosts of F. bispinosa adjacent to blueberry plantings and to determine if F. bispinosa emigrates into blueberry plantings from these hosts. Plant surveys conducted in Apr of 2007 and from Nov 2007 until Mar 2008 revealed several reproductive hosts of F. bispinosa, including: Carolina geranium (Geranium carolinianum L.), white clover (Trifolium repens L.), and wild radish (Raphanus raphanistum L.). In a subsequent study, we monitored thrips population development in a blueberry planting and in an adjacent white clover field during early spring in 2009 and 2010. Flower thrips populations in the white clover and blueberry planting developed at the same time with the highest numbers of thrips recorded from the center of the blueberry field in both years. Although white clover grows abundantly adjacent to blueberry plantings in the spring our findings indicate that clover does not appear to be a significant source for thrips inoculation of southern highbush blueberry plantings in Northern Florida.

Management of Yellowmargined Leaf Beetle Microtheca ochroloma (Coleoptera: Chrysomelidae) Using Turnip as a Trap Crop.

ABSTRACT The yellowmargined leaf beetle, Microtheca ochroloma Stål, is a major pest of cruciferous vegetable crops in organic production systems. Very few organically acceptable management options are currently available for this pest. Field studies were conducted at a research station in Alabama and at a commercial organic vegetable farm in Florida to investigate the effectiveness of turnip, Brassica rapa rapa, as a trap crop for M. ochroloma. In the research station trial with cabbage planted as the cash crop, perimeter planting of turnip as a trap crop effectively reduced beetle numbers and crop damage below levels recorded in the control. During the first season of our on-farm trial, with napa cabbage and mustard as the cash crops, using turnip as a trap crop effectively reduced both beetle numbers and cash crop damage below levels found in the control plots, but economic damage was still high. In the second season, beetle populations were too low for significant differences in damage levels to occur between the trap crop and control plots. Together, these results suggest that turnip planted as a trap crop can be an effective control tactic for cruciferous crops, like cabbage, that are much less attractive to M. ochroloma than turnip. In crops, like mustard and napa cabbage, that are equally or only slightly less attractive than turnip, planting turnip as a trap crop would have to be used in combination with other tactics to manage M. ochroloma.

Field distribution of Dasineura oxycoccana (Diptera: Cecidomyiidae) adults, larvae, pupae, and parasitoids and evaluation of monitoring trap designs in Florida.

ABSTRACT Blueberry gall midge, Dasineura oxycoccana (Johnson), is a pest of cultivated blueberries throughout the world. Larvae feed and develop in developing leaf buds, and also in flower buds of rabbiteye blueberries, which causes buds to fall off the plant. These injuries can cause up to 80% yield loss in heavy infestations. As the larvae are protected from insecticides, adults must be targeted with foliar applications. Consequently, the detection of adults through an effective monitoring program is critical to time insecticide sprays against the blueberry gall midge. Understanding the distribution of the midge and its parasitoids is also important information for developing a more effective pest management program. A comparison of three monitoring trap types demonstrated that bucket emergence traps and clear panel traps captured similar numbers of midges, although the bucket trap is more sensitive at low population levels. Using bucket emergence traps, we found that nearly 80% of the midges collected pupated within 48 cm of the blueberry bush, suggesting that a targeted soil treatment may be a viable integrated pest management tactic that could be included in a midge management program. Traps and bud samples demonstrated that adult and larval midges and parasitoids were randomly distributed throughout the field in both years, with the exception of larval aggregation in early 2012. As parasitoid distribution is parallel to host occurrence within blueberry plantings, this increases the potential for biological control activities against the blueberry gall midge in fields that do not receive broad-spectrum insecticide applications.

Efficacy of Entomopathogenic Fungal Products for Biological Control of Spotted Wing Drosophila (Diptera: Drosophilidae) under Laboratory Conditions

Summary Spotted wing drosophila, Drosophila suzukii Matsumura (Diptera: Drosophilidae), is a major pest of bushberries, caneberries, and other thinskinned fruits around the world. Current control programs rely solely on the use of frequent insecticide applications. Entomopathogenic fungi have shown some efficacy for tephritid fruit flies and D. suzukii. In this study, formulated products BotaniGard ES (Beauveria bassiana), and PFR-97 20% WDG (Isaria fumosorosea) were evaluated for efficacy on adult D. suzukii in laboratory fruit-dip studies. Blueberry fruits were dipped in high and low label rates of each fungal suspension before exposure to D. suzukii. Mortality was assessed at 24, 48, 72, and 168 h (1 wk) after D. suzukii release. After 1 wk exposure, the remaining live flies, dead flies, and fruit were removed from containers. The live flies were discarded whereas dead flies were placed in separate containers and checked for mycosis after 1 wk. Fruits were placed in small solo cups with lids and checked after 2 wk for emergence of D. suzukii. The high rate of BotaniGard ES caused significant mortality after 24 h and both rates of BotaniGard ES reduced emergence from fruit compared with the control. BotaniGard ES may be useful in rotation with other effective compounds, but further research under field conditions is needed to confirm this finding.

Multistate Comparison of Attractants and the Impact of Fruit Development Stage on Trapping Drosophila suzukii (Diptera: Drosophilidae) in Raspberry and Blueberry

Abstract Spotted-wing drosophila, Drosophila suzukii Matsumura (Diptera: Drosophilidae), is an invasive pest of softskinned fruits across the globe. Effective monitoring is necessary to manage this pest, but suitable attractants are still being identified. In this study, we combined lures with fermenting liquid baits to improve D. suzukii trapping specificity and attractiveness. We also measured the efficiency and specificity of baits/lures during different times of the season; the reproductive status of females among baits/lures; and the effects of locations and crop type on these response variables. We developed a metric that combined mating status and fat content to determine differences in types of females attracted. Lures utilizing yeast and sugar-based volatiles trapped the most D. suzukii. The addition of a commercial lure to yeast and sugar-based lures increased catches in most locations, but was also the least specific to D. suzukii. Apple juice-based chemical lures tended to be most specific to D. suzukii, while lures comprised of a singular attractant tended to trap more D. suzukii with a higher reproductive potential than combinations of attractants. Trap catch and lure specificity was lower during fruit development than fruit ripening. While catch amounts varied by geographic location and crop type, attractants performed similarly relative to each other in each location and crop. Based on the metrics in this study, the yeast and sugar-based attractants were the most effective lures. However, further work is needed to improve early season monitoring, elucidate the effects of physiological status on bait attraction, and understand how abiotic factors influence bait attraction.