Progress 08/01/02 to 07/31/04
Outputs
The Cranberry tipworm [blueberry gall midge], Dasineura oxycoccana (Johnson), and flower thrips, Frankliniella spp., are the primary insect pests infesting Rabbiteye, Vaccinium ashei Reade, and southern highbush, Vaccinium corymbosum L. x V. darrowi Camp blueberries in the southeastern United States. During 2002-2004 several monitoring techniques, including sticky boards, collection of bud samples for emergence, and bud dissection techniques, were evaluated for detecting cranberry tipworm in blueberry plantings. The emergence technique performed better than sticky traps or bud dissection techniques for detecting cranberry tipworn adults. Emergence and dissection techniques performed equally well for detecting cranberry tipworm larvae. However, cranberry tipworm eggs were only detected by carefully dissecting infested buds. For flower thrips, four monitoring techniques were evaluated for their effectiveness in detecting thrips populations. These techniques included
white sticky boards, dipping flower clusters into alcohol, tapping floral clusters onto a white surface, and collection of floral clusters for dissection. White boards proved to be the most effective technique for sampling thrips in our rabbiteye and southern highbush plantings, regardless of sampling dates. In the Rabbiteye blueberry planting, the alcohol dip technique performed better than the floral tap samples. Tapping floral clusters over a flat white surface was the least effective in Rabbiteye planting. For blueberry maggot, Rhagoletis mendax Curran, high populations of adults were caught on Pherocon AM yellow sticky boards in several rabbiteye varieties in north-central Georgia. In southeastern Georgia, blueberry maggot adults were only caught in the woodlands adjacent to Rabbiteye blueberries. There were no blueberry maggots caught in any of the Florida Counties that we monitored. With respect to parasitism by cranberry tipworm, greater host availability resulted in higher %
parasitism among four parasitoid species that included, Aprostocetus (Eulophidae), Inostemma, Platygaster, and Synopeas (Platygasteridae). Percent parasitism for Aprostocetus was low (5 %) when platygasterid competitors were present. For flower thrips, very few natural enemies were recorded in rabbiteye and southern highbush blueberries. The presence of minute pirate bugs, Orius insidiosus (Anthocoridae) was common in a few blueberry plantings but their effects on regulating thrips populations needs further evaluation. The effectiveness of several reduced-risk insecticides for controlling cranberry tipworm and flower thrips were evaluated. None of the reduced-risk insecticides, applied as foliar sprays, were effective in reducing populations of cranberry tipworm. For conventional insecticides, Diazinon-treated blueberry bushes had significantly fewer cranberry tipworm larvae compared with bushes treated with other insecticides. For flower thrips, the only insecticide that
significantly reduced thrips populations below the control was Assail (Acetamiprid). More screening of insecticides is necessary before an effective reduced-risk insecticide is identified for cranberry tipworm and thrips.
Impacts
Developing an effective monitoring technique will allow growers to detect the presence of gall midge and thrips early in the season. This will allow growers to make management decision, which may minimize the use of pesticides. The use of reduced-risk pesticides will enable growers to use less toxic compounds for managing key pests; thereby minimizing the negative effects on the environment.
Publications
- Liburd, O. E., Sarzynski, E. M. and Gerard Krewer. 2004. Results of gall midge control experiments in Bacon Co. and recommendations for control. Proceedings of the Southeastern Regional Fruit and Vegetable Conference. January 9-11. Savannah, Georgia. 5 pp.
- Liburd, O. E. 2004. The effectiveness of various insecticides to control blueberry gall midge. March issue, Berry/Vegetable Times 4:2-4.
- Liburd, O. E., and E. M. Finn. 2003. Evaluation of conventional and reduced-risk insecticides for control of flower thrips in blueberries. June-July issue, Berry/Vegetable Times 3:1-2.
- Liburd, O. E. 2003. Cold wintry conditions impacted thrips abundance in Florida blueberries during 2003. May issue, Berry/Vegetable Times 3:3
- Liburd, O. E., and E. M. Finn. 2002. Blueberry gall midge: A key pest of blueberries in the southeast. Fruit Grower News 40: 18-19.
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Progress 10/01/02 to 10/01/03
Outputs
Experiments to evaluate different sampling techniques for detecting various life stages of blueberry gall midge (cranberry tipworm) and thrips were conducted in both rabbiteye and southern highbush plantings. In our gall midge study three monitoring techniques were evaluated: 1) use of unbaited yellow sticky boards, 2) collection of bud samples for emergence, 3) collection of bud samples for dissection. In our bud sampling techniques, 140 buds (35 buds from each replicate) were collected at random each week for larval emergence and dissection techniques. In our rabbiteye planting, the emergence technique was significantly more effective in detecting blueberry gall midge adults in floral buds compared with either yellow boards or dissection techniques. In our leaf bud analysis, yellow sticky boards were more effective in detecting adults compared with emergence or dissection techniques. Similar numbers of blueberry gall midge larvae were detected using emergence and
dissection techniques in floral and leaf buds. Blueberry gall midge eggs were only detected with the dissection technique. In the southern highbush planting, the emergence technique was significantly better in detecting blueberry gall midge adults in floral and leaf buds compared with yellow sticky boards or dissection techniques. No blueberry gall midge eggs were found in southern highbush floral buds. Various colors of unbaited sticky board traps were used to monitor flower thrips. Four treatments were evaluated: 1) standard pantone yellow, 2) safety white, 3) walnut husk green and 4) thrips blue. The results indicated that white, blue, and yellow sticky traps captured significantly more thrips than green in rabbiteye and southern highbush plantings. In addition to unbaited colored sticky boards, three other techniques were evaluated for their ability to detect flower thrips population in blueberry plantings: These techniques included: dipping flower clusters into alcohol, tapping
floral clusters onto a white surface and collecting floral clusters for dissection. In rabbiteye plantings, white sticky boards were significantly more effective in detecting flower thrips than the other techniques evaluated. Frankliniella bispinosa was the most abundant species of flower thrips encountered, comprising more than 95% of the total thrips in our samples. Other species recorded were F. tritici and F. occidentalis. In our blueberry maggot surveillance studies, we recorded Rhagoletis mendax adults in 3 of the 4 counties that were monitored in Georgia. We found no blueberry maggot in our surveillance studies in Florida. Seven insecticides treatments were evaluated for control of gall midge and flower thrips. Treatments included Diazinon, Malathion, Thiamethoxam, Spinosad, Azadirachtin, Surround and an untreated control. Overall, diazinon-treated blueberry bushes had significantly fewer blueberry gall midge larvae compared with buds treated with other compounds. In Florida,
Surround was the only insecticide that significantly reduced flower thrips population where as in Georgia, Malathion and Ecozin were the most promising compounds for suppressing flower thrips population.
Impacts
Developing an effective monitoring technique will allow growers to detect the presence of gall midge and thrips early in the season. This will allow growers to make management decision, which may minimize the use of pesticides. The use of reduced-risk pesticides will enable growers to use less toxic compounds for managing key pests; thereby minimizing the negative effects on the environment.
Publications
- Sarzynski, E. M. and O. E. Liburd. 2003. Techniques for monitoring cranberry Tipworm (Diptera: Cecidomyiidae) in Rabbiteye and Southern highbush blueberries. J. Econ. Entomol. 96: 1821-1827.
- Liburd, O. E., and E. M. Finn. 2003. Evaluating techniques for detecting blueberry gall midge in southern highbush and rabbiteye blueberry plantings. Dixie blueberry News. 1: 1-3.
- Liburd, O.E. 2003. Cold wintery conditions impacted thrips abundance in Florida Blueberries during Berry/Vegetable Times 3: 3-4.
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Progress 10/01/01 to 10/01/02
Outputs
We evaluated several monitoring techniques for their ability to detect blueberry midge, Dasineura oxycoccana (Johnson) in rabbiteye and southern highbush blueberry plantings. Four colors of unbaited sticky boards, including yellow, white, green, and blue. The results indicated that blueberry gall midge (adults) did not show a preference for colors and that monitoring boards were largely ineffective in detecting adults. In a follow-up study, two other sampling techniques, 1) emergence and 2) bud dissection, were compared with sticky boards for their effectiveness in detecting blueberry gall midge. Preliminary results suggest that emergence methods are more reliable for detecting blueberry gall midge (adults) compared with monitoring boards. Generally, emergence and dissection methods performed equally well for detecting larvae in buds. In our thrips survey we found that Frankliniella bispinosa (Morgan) was the principal pest affecting southern highbush blueberry
plantings in north-central Florida. In northern Florida, Frankliniella tritici (Fitch) was the most abundant species, composing 72.8% of the adult thrips found in our sample. In our monitoring studies blue and white sticky boards were significantly more attractive to flower thrips compared with yellow, which was significantly more attractive than green boards. Because counting the total number of thrips on individual boards was difficult during peak flight, we developed a sampling protocol using a mathematical model whereby only a subset of the total number of quadrats on the boards was sampled. The results from sampling this subset of "quadrat" yielded identical treatment separation as counting the total surface area of the board. For blueberry maggot, Rhagoletis mendax Curran, no flies were caught on Pherocon A.M yellow sticky boards in Florida but high numbers were trapped in Georgia. In other studies, a survey of natural enemies for potential biological control agents for thrips
was conducted at one rabbiteye and one southern highbush blueberry planting. Natural enemies, if present, were rare and no predators were collected in these samples. None of the inspected thrips showed signs of parasitism. In our insecticide evaluation trials, four chemical insecticide treatments including SpinTor 2SC (4 and 6 oz of product per acre), Provado 1.6F (4 oz of product per acre), Imidanr 70W (1 1/3 lbs product per acre) and control was evaluated for control of flower thrips Frankliniella spp. Significantly more thrips were found on un-treated bushes compared with all other treatments evaluated. The lowest numbers of thrips were found on Provado-treated blueberry bushes. However, thrips counts on Provado-treated bushes were not significantly different to SpinTor-treated bushes.
Impacts
Growers will be able to carry out effective monitoring for blueberry gall midge, flower thrips and blueberry maggot. As a result of better monitoring protocols for these pests, growers will be better able to accurately time their insecticide applications; consequently reducing the number of sprays. In addition, growers will have at their disposal more reduced risk insectcides for control of key pests in blueberries.
Publications
- O. E. Liburd and E. M. Finn. 2002. Blueberry gall midge: key pest of blueberries in the southeast. 40:18-19
- O. E. Liburd and E. M. Finn. 2002. The status of blueberry gall midge in the southeastern United States, Edis Extension Publication ENY-825, University of Florida, Gainesville, F.L.
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