Proc. Fla. State Hort. Soc. 104:3-5. 1991.

MANAGEMENT OF GRAPE ROOT BORER IN FLORIDA WITH A PHEROMONE

Susan E. Webb take place, and the population then declines as the number Central Florida Research and Education Center of fertile eggs decreases. A report by Johnson et al. (1986) I FAS, University of Florida showed that the pheromone of a related moth, peachtree 5336 University Avenue borer (Synanthedon exitiosa [Say]), could beused to disrupt Leesburg, FL 34748-8203 the mating of grape root borer in commercial vineyards in Arkansas and North Carolina. Since that time, an additional Additional index words. Vitaceapolistiformis, mating disruption. pheromone component has been identified from grape root borer (Schwarz et al., 1983) which when added to the orig Abstract. Disruption of mating through use of a high concentra inal pheromone greatly increased the attractiveness of the tion of pheromone was tested as a means of controlling grape resulting blend. Research has been underway to test this root borer, Vitacea polistiformis (Harris) (Lepidoptera: more specific pheromone blend (a 99:1 ratio of (E-Z)-2,13 Sesiidae) in a vineyard in Polk County, Florida. Pheromone octadecadien-1-ol acetate/(Z, Z)-3,13 octadecadien-1-ol ace tate) in several states in the Southeast, including Florida. dispensers were attached to trellis wires at a rate of 250 per In this paper, I report the results of a three-year study ha in a 1.5 ha vineyard near Kathleen which had a history conducted in a small vineyard in Central Florida to evaluate of borer infestation. A vineyard located at the Central Florida the effectiveness of mating disruption for control of grape Research and EducationCenter in Leesburg served as a control. root borer. In 1989 none of 21 female moths caught in the treated vin eyard had mated whereas over 70% of those caught in the Leesburg vineyard had. In 1990, 11.6% of females caught in Materials and Methods the treated vineyard and 87.5% of those caught at Leesburg A 1.5 ha vineyard near Kathleen, Florida with a long were fertile. Numbers of emerging moths were estimated by history of documented grape root borer infestation was counting pupal skins beneath vines on three occasions at two- chosen as the study site. No other vineyards were nearby week intervals during peak emergence. An average of 1.13 but wild grapes were growing in the vicinity. Seventy-five pupal skins per vine were found in the treated vineyard in percent of the vines were muscadine varieties and 25% 1989 and an average of 0.79 were found in 1991. Of the 99 were bunch grapes. Four blocks of the research vineyard vines examined in the treated vineyard, 29 were of the mus at the Central Florida Research and Education Center at cadine ( Vitis rotundifolia Michx.) variety 'Fry'. Over half the Leesburg (approximately 50 miles north of Kathleen), pupal skins found in 1989 were associated with this variety. which also had a history of borer infestation (Webb and In contrast, 10 vines of the variety 'Nesbitt' accounted for Mortensen, 1990), were used as a control. Approximately fewer than 1% of the pupal skins found. half the vines were muscadine varieties and half were bunch grape hybrids. The grape root borer, Vitaceapolistiformis (Harris) is the On 2 August 1989 and on 27 July 1990 pheromone most serious insect pest of both hybrid bunch (Euvitis spp.) dispensers, which resembled "twist ties," were wrapped andmuscadine grapes (Vitis rotundifolia Michx.) in Florida. around the upper trellis wire at a rate of 250 dispensers The adult is a day-flying clearwing moth that resembles a per ha. Three monitoring traps (Pherocon® 1C wing style paper wasp, both in appearance and behavior. The larval sticky traps, Georgia Ag Chem, Swainesboro, Georgia), also stage, immediately after hatching, burrows into the soil in baited with the pheromone, were installed two weeks prior search of roots, moving to and feeding in larger roots as it to treating the vineyard with dispensers. At each site, 100 grows. It is thought that development from egg to adult vines were flagged and a circle around the base of each takes at least two years (Clark and Enns, 1964). Because of vine, approximately one meter in diameter, was cleared of the location of the feeding larvae, it is difficult to control weeds and debris to make it easier to find cast pupal skins. them with insecticides. The available chemical control meas Every two weeks during the period of peak borer activity ure (one application of chlorpyrifos [Lorsban 4E] per sea (mid September to late October) the area under flagged son) is aimed at killing newly-hatched larvae while they are vines was examined for pupal skins in order to estimate on or near the soil surface. Because the period of adult numbers of emerging moths. On alternate weeks, teams of activity is so long in Florida (Snow et al., 1991; S. E. W., three or four people spent the day capturing female grape unpublished) this treatment is only partially effective. root borers. Each activity was carried out in the sameweek The use of sex pheromones to disrupt the mating be at each location. Female grape root borers were either held havior of insects is a safe, very specific control measure, for a day in order to collect eggs and then dissected to which has been investigated for many species (Berzoa, confirm mating status or were dissected only. Dispensers 1976). A sex pheromone is a chemical message sent by the were not available in 1991 and only counts of pupal skins female that allows the male to locate her. If the atmosphere were made. Because of the two-year life cycle of the grape of the vineyard is saturated with a synthetic version of this root borer, the final effects of treatment in 1989 could not chemical, the male cannot find the female, mating does not be evaluated until 1991.

Florida Agricultural Experiment Station Journal Series No. N-00503. This project was supported in part by the Florida Viticulture Advisory Results and Discussion Council. I wish to thank J. Wendell Snow for supplying pheromone and advice, W. Colson for the useof his vineyard, and J. Harris, P. Groves, At Kathleen, in 1989, male grape root borers were K. Kelley, and D. Yadon for excellent technical assistance. caught in monitoring traps in low numbers for two weeks

Proc. Fla. State Hort. Soc. 104: 1991. prior to installing the pheromone dispensers. Once the dis eight pupal skins were found under 100 vines in 1990 and pensers were in place, catches in the sticky traps dropped four were found in 1991) although moths continued to be to zero. Lures were changed every two months for the caught in sticky traps. In recent years the vineyard has not duration of the season but no moths were ever captured. often been treated with insecticide. Ants, including im Moth activity at Leesburg began during the first week in ported fire ants (Solenopsis invicto) are common in the vin August, peaked in late September (93-95 males per week) eyard at Leesburg and have been observed attacking emerg and continued into December. In 1990, dispensers were ing grape root borer moths. It is possible that predators put in place before moth activity began in Kathleen. Again, such as ants are responsible for the low numbers of grape no moths were captured in monitoring traps during the root borers found emerging from the Leesburg vineyard. season. Some sticky traps were baited with caged virgin The lack of response by males to the lures in monitoring female moths but males were unable to locate them in the traps in the vineyard at Kathleen indicates that the vineyard treated vineyard. atmosphere was permeated with pheromone from the dis At Kathleen, 21 females were captured in 1989 and 43 pensers and that the males could no longer orient to a in 1990. None of the females caught in 1989 and only specific source. The greatly reduced number of mated 11.6% of those caught in 1990 had mated. In contrast, of females also attests to the disruption of communication. the 17 females captured in Leesburg in 1989, 12 had mated Pupal case counts from 1990 indicated, however, that fertile (70.6%) and of 16 captured in 1990, 14 produced fertile females were still ovipositing in the vineyard in 1989, al eggs (87.5%). though at somewhat reduced levels. One possible explana Because the grape root borer takes two years to develop, tion is that the two week period of moth activity before the only the pupal case counts from 1989 and 1991 were com dispensers were put in place the first year was enough to pared. A paired t-test was used to determine if the differ reduce the effectiveness of the disruption. More likely is ence between years was significant. A significance level of the possibility that mated females entered the vineyard 10% was accepted because the variability associated with from wild grapes nearby. This was found to be the case in different varieties would make it likely that a true difference a test of mating disruption of peachtree borer (Snow et al., would be overlooked otherwise. The histogram shown in 1985) and was suspected in a similar study involving codling Figure 1 gives the frequency of each category of difference moth (Moffitt and Westigard, 1984). The results of Johnson in the number of pupal skins per vine found between 1989 et al. (1986) with grape root borer in Arkansas and North and 1991 in the treated vineyard. The average number of Carolina were similar to ours except that pupal skin counts borers per vine in Kathleen was 1.13 in 1989 and 0.79 in were much lower before and after. In their study, treated 1991. The difference (0.34) was significant (T = -1.70, 98 and untreated areas were part of the same vineyard, making df, P = 0.0916). Of the 99 vines examined in Kathleen, 29 it likely that pretreatment counts would be similar but also were of the muscadine variety 'Fry'. If the pupal skin counts complicating the results because, as described below, the are calculated separately for this variety, the average pheromone can act at a considerable distance from the

number of pupal skins per vine was 2.03 in 1989 and 0.828 source. in 1991 (a significant difference of 1.206, T = -2.64, df = It is not known how far grape root borers will fly to 28, P = 0.0132). In contrast, the variety 'Nesbitt' produced reach new host plants. In 1991, four rows at one end of an average of 0.10 skins per vine (total of 10 vines) in both the vineyard in Kathleen were treated with pheromone 1989 and 1990. dispensers. Sticky, pheromone-baited traps over 120 m In Leesburg in all three years, very few grape root borers from this location caught only one or two males whereas were found emerging from the selected vines (a total of those placed nearer caught none. It is likely that females would have to have mated beyond a 100 m radius of the treated vineyard. That moths were still captured in high 50 numbers in the vineyard in Leesburg when very few ap peared to be emerging within the vineyard indicates that these moths were also coming from a distance (although, 40" in this instance, moths were flying to the pheromone). To O) reduce the number of mated females coming into the vin CD 30" eyard from wild grapes, it may be necessary to distribute § the pheromone a certain distance beyond the boundary of the vineyard. 20" Varietal differences in susceptibility to attack (Webb and W CD Mortensen, 1990) appeared to affect the results as well. .E 10" U-pick vineyards often have different varieties planted side by side. Nine bunch grape varieties and 14 muscadine vari eties were represented in the 99 vines sampled at Kathleen. Preferences for individual vines seem to exist. For example, -10-9-8-7-6-5-4-3-2-1 0 1 2 3 4 5 6 15 pupal cases were found under a vine of the variety Change in no. of GRB pupal skins 4Watergate' in 1989; 14 were found in 1991. The vineyard at Kathleen is carefully maintained and Fig. 1. Differences in pupal skin counts between 1989 and 1991 in treated with chlorpyrifos (Lorsban 4E) yearly. Grape root vineyard at Kathleen, Florida that was treated with grape root borer borer is still causing some damage to this vineyard although pheromone. Negative numbers indicate a decrease in pupal skins on a particular vine (i.e., -2 indicates that 2 fewer were found in 1991) and not to the extent that it was before chemical treatment was positive numbers indicate an increase. *No pupal skins were found as begun (W. E. Colson, personal communication). The lack sociated with 42 of 50 vines with zero differences in pupal skin counts. of a good experimental treatment control (because of the

Proc. Fla. State Hort. Soc. 104: 1991. surprisingly few root borers in the Leesburg vineyard) Johnson, D. T., J. R. Meyer, and R. L. Mayes. 1986. Evaluation of Hercon makes it difficult to draw conclusions about the effect of laminated dispensers baited with Z, Z-3,13-octadecadien-l ol acetate mating disruption on the root borer population. The differ for suppression of the grape root borer, Vitacea polistiformis (Harris), (Lepidoptera: Sesiidae), populations in grapes. J. Entomol. Sci. 21:231- ences in mating success and the differences in the numbers 236. of males attracted to pheromone traps, however, make it Moffitt, H. R. and P. H. Westigard. 1984. Suppression of the coding moth likely that the decrease in pupal skin counts at Kathleen (Lepidoptera: Tortricidae) population on pears in southern Oregon was due to the treatment. Over time mating disruption through mating disruption with sex pheromone. J. Econ. Entomol. 77:1513-1519. might reduce populations to the point where insecticide Schwarz, M., J. A. Klun, B. A. Leonhardt, and D. T.Johnson. 1983. (E, would no longer be needed. Reducing insecticide use Z)-2,13-octadecadien-l ol acetate. A new pheromone structure of sesiid should also favor the survival of natural predators of grape moths. Tetrahedron Letters 24:1007-1010. root borer. Snow, J. W., C. R. Gentry, and M. Novak. 1985. Behavior and control of the peachtree borer and lesser peachtree borer (Lepidoptera: Sesiidae) in peach orchards permeated with (Z,Z)-3,13-octadecadien-l-ol acetate. J. Econ. Entomol. 78:190-196. Literature Cited Snow, J. W., D. T. Johnson, and J. R. Meyer. 1991. The seasonal occur rence of the grape root borer, (Lepidoptera: Sesiidae) in the eastern Berzoa, M. 1976. Control of the gypsy moth and other insects with be United States. J. Entomol. Sci. 26:157-168. havior-controlling chemicals, p. 99-118. In: M. Berzoa (ed.). Pest man Webb, S. E. and J. A. Mortensen. 1990. Evaluation of bunch grape agement with insect sex attractants. Amer. Chem. Soc, Washington, rootstocks and muscadine varieties for resistance to grape root borer. D.C. Proc. Fla. State Hort. Soc. 103:310-313.

Proc. Fla. State HorL Soc. 104:5-9. 1991.

COMBINATION OF TRELLIS SYSTEMS TO OPTIMIZE THE USE OF FARM RESOURCES IN MUSCADINE GRAPE PRODUCTION

Stephen Leong and Sola Lamikanra total soluble solids were found to be equal or better for Center for Viticultural Sciences GDC than for the SW system (1). Studies in Arkansas also Florida A&M University revealed the superior performance of the GDC system for Tallahassee, Florida 32307 Concord grapes (5, 7, 10). This study was conducted to evaluate the resource pro Abstract. Muscadine grape production in Florida is commonly ductivity of the two systems under selected resource con undertaken by using the single-wire (SW) system primarily straint scenarios (Table 1) using data from the Center's because of its lower captial requirements and lower mainte vineyard as well as information provided by grape growers nance. However, research findings have shown that the and researchers in Florida and the neighboring states. The Geneva Double Curtain (GDC) system is more productive al objective was to determine which system or combination of though its investment cost and resource requirements are re systems would enable growers to maximize grape produc latively higher. The GDC is relatively more capital efficient tion under selected capital and labor constraints. while the SW is more labor efficient. Results from a linear programming model showed that growers with limited re sources will be able to maximize production by combining Table 1. Summary of muscadine grape growing scenarios under selected systems. The combination of SW:GDC in the ratio of 1:0.7 resource constraints. provided the optimum combination. Additional Grape growing is a capital intensive enterprise with es Capitol Vineyard Full-time worker Scenario Land ($1,000) est. worker Feb-Mar timates of investment capital ranging from $3,300 to $4,050 June per acre (2, 9a, 6). In Florida, muscadines are commonly la. 10 50 custom 1 0 0 grown using the single-wire (SW) or the Geneva Double lb. 10 75 custom 1 0 0 Curtain (GDC) system (1,3, 8), and each system has its own lc. 10 100 custom 1 0 0 resource requirements and level of productivity. Resource 2 a. 10 50 custom 1 0 1 productivity is a major concern for growers who want to 2 b. 10 75 custom 0 1 2 c. 10 100 custom 0 1 maximize production and net return from a given set of 3 a. 10 50 EL 2 0 resources. 3b 10 50 EL 2 1 One of many important decisions that a grower makes 3 c. 10 50 EL 3 0 is the type of trellis system to use. Some growers favor the 4 a. 10 75 EL 2 1 SW system because of its lower investment and maintenance 4 b. 10 75 EL 3 0 costs while others favor the GDC system although it is more 4 c. 10 75 EL 3 1 capital and labor intensive. Experience has shown that the 5 a. 10 100 EL 3 0 GDC often out-yields the SW system. Studies by Andersen 5 b. 10 100 EL 3 1 et al. (1), Brightwell and Austin (4), Morris et al. (7) have 5 c. 10 100 EL 4 1 shown that the yield differential between the two systems custom = establishment of vineyard to be done by contract or custom labor. could be as high as 35 percent. In addition, berry size and EL = employed labor was used to establish the vineyard.

Proc. Fla. State Hort. Soc. 104: 1991.