Oscar E. Liburd

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.

Effects of Living and Synthetic Mulch on the Population Dynamics of Whiteflies and Aphids, Their Associated Natural Enemies, and Insect-Transmitted Plant Diseases in Zucchini

Abstract Living and synthetic mulches were evaluated for control of the silverleaf whitefly, Bemisia argentifolii Bellows and Perring, and aphids in zucchini plantings. Two living mulches, buckwheat, Fagopyrum esculentum Moench, and white clover, Trifolium repens L., and two synthetic mulches (reflective and white) were evaluated during the fall of 2002 and 2003. Results from pan-traps, yellow sticky traps, and foliar counts showed that reflective and buckwheat mulches consistently had fewer numbers of adult whiteflies and aphids compared with the standard white mulch treatments. In 2003, a significant increase in the abundance of natural enemies was recorded in all treatments. Living mulch treatments had higher natural enemy populations than synthetic mulch and bare-ground treatments. However, there were no differences in the species diversity of natural enemies found between treatments. The effectiveness of mulches for controlling immature whitefly numbers and the incidence of squash silverleaf disorder were inconsistent between years. Additional data taken at the end of the 2003 season revealed that two viral strains (PRSV-W and WMV-2) were present in the field. However, visual symptoms associated with these viral diseases did not occur until the end of the season.

Effect of Trap Design, Bait Type, and Age on Captures of Drosophila suzukii (Diptera: Drosophilidae) in Berry Crops

ABSTRACT Field experiments were conducted in commercial southern highbush blueberries and wild blackberries to evaluate the attractiveness of different trap designs, bait types, and bait age on captures of the spotted wing drosophila, Drosophila suzukii (Matsumura) (Diptera: Drosophilidae). During the 2012 trap design study, the five treatments evaluated were four 1-liter clear plastic cup traps (with and without a yellow visual stimulus or odorless dish detergent) and the fifth treatment was a Pherocon AM yellow sticky card trap. Cup traps were baited with 150 ml of apple cider vinegar (ACV) and the Pherocon AM trap had a 7.4-ml glass vial containing ACV. In 2013, the Pherocon AM yellow sticky card was omitted because of low spotted wing drosophila captures in 2012. The four treatments evaluated were four 1-liter cup traps with and without a yellow visual stimulus. One cup trap (with a yellow stimulus) was baited with yeast + sugar in place of ACV and the other cup traps were baited with ACV. In both years, there were no differences in spotted wing drosophila captures among cup traps baited with ACV with and without yellow visual stimulus. However, the cup trap baited with yeast + sugar and yellow visual stimulus captured more spotted wing drosophila than the ACV-baited cup traps irrespective of visual stimulus or detergent. In another study, four baits including 1) ACV, 2) yeast + sugar mixture, 3) yeast + flour mixture (yeast, sugar, water, whole wheat flour, and ACV), and 4) wine + vinegar mixture (rice vinegar and merlot wine) were evaluated in a commercial blueberry planting using 1-liter clear plastic cup traps (as described above). The experiment was repeated in wild blackberries but the yeast + flour bait was replaced with ACV + merlot wine + sugar. Results indicated that the two yeast baits captured significantly more spotted wing drosophila and more nontarget organisms than the vinegar baits. In the final study, although we found that the attraction of ACV and yeast + sugar to spotted wing drosophila did not change with bait age, the attraction to other Drosophilidae flies decreased with age. The ease of implementing a trap-and-lure system for spotted wing drosophila is discussed.

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.

Suppression of Whiteflies, Bemisia tabaci (Hemiptera: Aleyrodidae) and Incidence of Cucurbit Leaf Crumple Virus, a Whitefly-transmitted Virus of Zucchini Squash New to Florida, with Mulches and Imidacloprid

Abstract The sweetpotato whitefly, Bemisia tabaci B biotype (Gennadius) (Homoptera: Aleyrodidae) also known as Bemisia argentifolii (Bellows and Perring) is a key pest in zucchini squash (Cucurbita pepo L.) causing both direct and indirect damage. A field experiment was conducted in the fall of 2005 and repeated in the fall of 2006 to investigate the effect of mulches alone or in combination with a reduced-risk insecticide, imidacloprid (Admire® 2F) on whiteflies and related problems in zucchini squash. UV-reflective mulch and the living mulch, buckwheat (Fagopyrum esculentum Moench), with and without imidacloprid, were evaluated in a randomized complete block design with 4 replications. White mulch (standard) was included as a control in the experiment. Mulches in combination with imidacloprid resulted in fewer whiteflies per leaf than those without imidacloprid in 2005 and 2006. More whiteflies were recorded on zucchini plants growing on white synthetic mulch than all other treatments in both years. In the 2006 growing season, these plants also showed the first symptoms of viral infection caused by Cucurbit leaf crumple virus (CuLCrV), a whitefly-transmitted geminivirus. Both living and reflective mulches were more effective than white mulch in reducing the densities of whiteflies and the incidence of CuLCrV on zucchini plants.

Biology of Parasitoids (Hymenoptera) Attacking Dasineura oxycoccana and Prodiplosis vaccinii (Diptera: Cecidomyiidae) in Cultivated Blueberries

Abstract The blueberry gall midge, Dasineura oxycoccana (Johnson), and blueberry tip midge, Prodiplosis vaccinii (Felt) (Diptera: Cecidomyiidae), are recurring cecidomyiid pests of cultivated blueberries in the southern United States and Mediterranean Europe. Insecticides can give short-term control, but overlap in parasitoid phenologies indicates the potential for natural control of midge populations. Using a combination of laboratory rearing and mitochondrial DNA analysis of field samples, we identified five species of solitary endoparasitoids that killed 30–40% of midges. These species include at least three undescribed platygastrids in the genera Synopeas, Platygaster, and Inostemma. An undescribed prepupal idiobiont, Aprostocetus sp. (Eulophidae: Tetrastichinae) was the only midge parasitoid that was consistently active when rabbiteye blueberries, Vaccinium ashei Reade, were in flower. Six percent of midge prepupae, half of which already contained platygastrid larvae, were parasitized by Aprostocetus.

Effect of Trap Color on Captures of Grape Root Borer (Lepidoptera: Sesiidae) Males and Non-Target Insects

Abstract The effect of bucket trap color on grape root borer (GRB), Vitacea polistiformis Harris, captures was evaluated in 2005 and 2006. Traps were deployed in a commercial vineyard consisting of muscadine (Vitis rotundifolia Michx) grapes in North-Central Florida. Experimental designs were randomized complete block with four tratments including green, yellow, white and blue traps in 2005. In 2006, five treatments (green, yellow, green top, yellow top, and multicolor) and four replicates were evaluated. All traps were baited with GRB female sex pheromone. Trap color had a significant effect on the number of GRB males captured. In 2005, green and yellow traps caught more GRB males than other trap colors. In addition, first GRB male captures were in yellow and green traps. In 2006, the multicolor trap caught more GRB males than any other trap and had the first GRB capture. Grape root borer males prefer green and yellow pheromone-baited traps, but do not appear to distinguish between these two colors, which have similar spectral reflectance. Trap color had a significant effect on the number of Apoidea captured, with highest captures in multicolor traps. Choice of trap color can improve the effectiveness of pheromone-baited bucket traps for GRB in both early detection and total number captured over the season. Negative impacts on beneficial insects appear minimal.

Horizontal and Vertical Distribution of Flower Thrips in Southern Highbush and Rabbiteye Blueberry Plantings, with Notes on a New Sampling Method for Thrips Inside Blueberry Flowers

Abstract The dispersal behavior of flower thrips was studied during two field seasons within blueberry (Vaccinium spp.) plantings in Florida and southern Georgia. A “shake and rinse” technique used to extract thrips from inside the blueberry flowers was not significantly different from the conventional dissecting technique, but the time taken to complete the extraction of thrips was significantly shorter. Overall, the highest concentration of thrips was captured inside the canopy of blueberry bushes. Using a grid of traps to monitor the dispersal of thrips during the blueberry flowering season, we analyzed their dispersion with graphical and analytical methods to determine and describe their distribution within blueberry plantings. Thrips began to form “hot-spots” 5–7 d after bloom initiation. A hot-spot is defined as a large number of thrips concentrated in a small area of the field, whereas the rest of the field has a low population. The behavior of the population inside these hot-spots fit a Gaussian tendency and a regression was conducted to describe this tendency. Green’s and Standardized Morisita’s indices were used to determine thrips level of aggregation. Results showed significantly aggregated populations of thrips in both years. Formation of hot-spots in blueberry plantings seemed to be random. However, the formation of hot-spots was higher in places where more than seven thrips per day were captured on sticky traps, 5 to 7 d after the bloom begins. With these results, producers will be able to monitor thrips populations and locate and manage hot-spots before they become a more serious a problem on blueberry farms.

Effect of Tetranychus urticae (Acari: Tetranychidae), on Marketable Yields of Field-Grown Strawberries in North-Central Florida

ABSTRACT Understanding the impact of a pest species on a particular crop is critical for the success of a pest management program. Field studies were conducted to determine the effect of the twospotted spider mite, Tetranychus urticae Koch, on marketable yield of strawberries during the 2008/2009 and 2009/2010 growing seasons. Low, medium, and high mite infestation levels were established by initial inoculations of 5, 10, and 20 twospotted spider mites per strawberry leaf, respectively. A control treatment maintained at near zero mites through applications of an acaricide, bifenazate (Acramite 50 WP), was also included. Weekly records of motile twospotted spider mites were obtained over 13 and 16 wk during the 2008/2009 and 2009/2010 growing seasons, respectively. Degree-days and weather parameters were monitored to determine their effect on mite population. In addition, mite-days were calculated for each year from weekly mite counts to determine the effect of mites on marketable yield of strawberries. In both years, twospotted spider mite population increased throughout the growing seasons. More degree-days were accumulated during the 2008/2009 growing season, and mite population was higher in 2008/2009 than in 2009/2010. Mite population density per leaf increased up to 278 motiles per leaf in 2008/2009 growing season as compared with 137 in 2009/2010 within the high-infestation-level treatment. The divergence in mite population between the two growing seasons was attributed mainly to temperature differences between the two seasons that affected mite population development and establishment. During both growing seasons, the high mite infestation level had lowest marketable yield. A negative correlation between cumulative mite-days and harvested marketable yields was detected in both seasons, but it was only significant during the 2008/2009 growing season. Strawberry yield reduction was detected when plants attained 80 mites per leaf in 2008/2009 and 50 mites per leaf in 2009/2010 within the high mite infestation treatment. Factors that affect mite population establishment and management for twospotted spider mites on strawberries are discussed.