Richard E. Rice, Cynthia A. Atterholt,1 Michael J. Delwiche1 and Richard A. Jones
Kearney Agricultural Center, University of California, Parlier, California 93648, USA
Abstract - Pheromones of Oriental fruit moth (OFM), Grapholita molesta, peach twig borer (PTB), Anarsia lineatella, and San Jose scale (SJS), Quadraspidiotus perniciosus, were mixed into sprayable emulsions of water and paraffin and applied to stone fruit trees for mating disruption of these pests. Pheromone/emulsion blends were applied twice for OFM and PTB during the 1995 season, using 49.4 to 76.6 g active ingredient/ha/application; SJS pheromone was applied only once at 74 g active ingredient/ha. Efficacy of mating disruption was measured by pheromone trap (OFM, PTB) or sticky tape (SJS) collections and infested fruit. Results of these field trials showed that treatments using OFM pheromone were comparable to commercial mating disruption dispensers, with monitoring trap shutdown for 8 to 12 weeks, and reduction of fruit infestation of 80 to 90 percent. The PTB pheromone treatments were less effective, with increased collections of PTB moths in monitoring traps and no differences in infested fruit compared to untreated checks. Mating disruption of SJS using pheromone in paraffin emulsions showed some reduction in crawler populations for two generations after treatment, but the cost of pheromone is prohibitive for commercial use.
Key words - sex pheromone, mating disruption, sprayable dispenser, Grapholita molesta, Anarsia lineatella, Quadraspidiotus perniciosus
Mating disruption as a control strategy for insect pests has been the subject of considerable research and commercial interest in recent time (Ridgway et al. 1990). In these efforts, control of the Oriental fruit moth (OFM), Grapholita molesta Busck, in peaches and nectarines has been one of the more successful applications of this technique (Rice & Kirsch 1990: Vickers 1990; Pree et al. 1994). More recently, mating disruption of the peach twig borer (PTB), Anarsia lineatella Zeller, has been demonstrated in California (Rice & Millar 1992).
Although successful, these and other mating disruption programs have primarily used hand-applied plastic or polymer pheromone dispensers of various types and designs. Over time, it has become apparent that development of sprayable or other mechanical application system for disruption pheromones could lead to decreased application costs, improved placement of pheromones in tree crops, and possibly less environmental contamination from depleted plastic dispensers. In this report, we describe the development and application of a prototype sprayable, mechanically applied pheromone dispensing system for mating disruption of Oriental fruit moth and peach twig borer in orchard crops that is easy and potentially less costly to apply, and is biodegradable over a period of months.
Oriental fruit moth and peach twig borer emulsions
Synthetic Oriental fruit moth pheromone (Biwer et al. 1979; Cardé et al. 1980) (93% (Z)-8-dodecenyl acetate, 6% (E)-8-dodecenyl acetate, 1% (Z)-8-dodecenol), and peach twig borer pheromone (Roelofs et al. 1975) (75% (E)-5-decenyl acetate, 18.7% (E)-5-decen-1-ol, 6.3% inerts) were obtained from Bedoukian Research Inc. (Danbury, CT, USA). The pheromones were mixed in water emulsions of paraffin and two different emulsifiers. The two emulsifiers used in the respective pheromone formulations were triethylamine (TEA) stearate or Span 60® (sorbitan monostearate), a commercial emulsifier used in cosmetic products. Paraffin (ParoWax®) blocks were melted on a laboratory heater and emulsifier was added. OFM or PTB pheromone was then added to the paraffin/emulsifier blend along with small amounts of soy oil and vitamin E. The liquid paraffin-pheromone blend was mixed during this process with a handheld kitchen blender. After mixing the pheromone and other materials into the paraffin, the emulsion was formed by adding water in a 60% water - 40% paraffin/emulsifier/pheromone ratio.
The finished paraffin emulsions were applied to peach, nectarine, plum, and almond trees using an Idico® stainless steel one-quart tree-marking paint gun (Forestry Suppliers; Jackson, MS, USA). It was calculated that each squirt from the paint gun would deliver approximately 1.26 ml of emulsion. In field applications, a portion of this amount was lost due to splatter from the target site on the tree (large scaffold limbs) or dripping from the nozzle of the gun. This loss was estimated at ca. 0.26 ml per shot, thus leaving approximately 1 ml of emulsion per shot on the tree, or 62.5 mg of pheromone per shot. Four squirts of pheromone emulsion would deliver 250 mg pheromone to each target tree. Emulsions formulated with TEA stearate were less viscous than emulsions using Span 60, which were creamier, more viscous, and formed a more compact deposit when applied to scaffold limb surfaces. In addition, different batches of emulsion blends tended to have somewhat variable viscosities, making it difficult to control precisely the actual amount of pheromone applied.
The target rate of pheromone application for OFM disruption was set at 75 g pheromone/ha. Using this as a base application rate, the actual number of squirts and amount of pheromone needed per tree was then calculated based on the planting density and number of trees/ha. The target rate of PTB pheromone was targeted at 50 to 63 g/ha, comparable to the rate registered for commercial use.
After first emergence of Oriental fruit moth at the Kearney Agricultural Center in 1995, OFM pheromone in paraffin emulsion was applied to the south (downwind) 0.8 ha of a 1.6-ha plum orchard. OFM pheromone-paraffin emulsions were also applied to a 0.8-ha block of Fantasia nectarines and a 0.58-ha block of mixed stone fruits at Kearney. The plums received emulsion mixed with Span 60 emulsifier. The nectarines and mixed stone fruit orchards were initially treated with emulsions using the TEA stearate emulsifier; second applications used Span 60 emulsifier.
On March 6, 1995, OFM pheromone emulsion using Span 60 emulsifier was applied to a 0.8-ha portion of a large almond orchard. Pheromone monitoring traps were placed in the treated area, and in the same orchard 0.7 km from the treated area. Following applications of the pheromones to these four test plots, the emulsion deposits were subjected to unseasonably heavy amounts of rain and wind over the following three weeks, but these conditions appeared to have little or no effect on the emulsion deposits. OFM pheromone-emulsion blends were reapplied to the plums on June 7; to the nectarines on May 17, and to the mixed stone fruit block on May 16, 1995. A second application was applied in the almond orchard on June 3.
Peach twig borer pheromone in the paraffin emulsion blends was applied at ca. 25 g active ingredient/ha to the nectarines at Kearney on April 3, with a second application on May 10. The mixed stone fruit planting was treated with PTB pheromone emulsions on March 30 and May 10, and the almonds were treated for PTB mating disruption with pheromone emulsions on April 4 and May 10.
In all orchards, second applications of OFM and PTB pheromone-emulsion blends were mixed using Span 60 emulsifier.
San Jose scale pheromone emulsions
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Synthetic San Jose scale pheromone (Gieselmann et al. 1979) was obtained from PheroTech Inc. (Delta, B. C., Canada), in a blend of 22.8% (Z)-3,7-dimethyl-2,7-octadien-l-yl propanoate, 73.9% 3-methylene-7-methyl-7-octen-1-yl propanoate, and 3.3% impurities including 0.6% neryl propanoate. This pheromone blend was mixed in paraffin emulsion using Span 60 emulsifier with 312.5 mg pheromone/g emulsion. Delivered application rate of the SJS pheromone was targeted to be 75 g pheromone/ ha as with the OFM pheromones. However, the delivered volume of pheromone emulsion was eight shots per tree (to deliver 0.25 g pheromone/tree) rather than the four shots per tree with the OFM and PTB pheromones. The reason for the additional amount of emulsion per tree was to attempt greater dispersal of the SJS pheromone over a larger portion of the scaffold limbs because of the thought that the pheromone must be more widely distributed throughout the tree to disrupt orientation of walking males on tree bark in addition to males flying within the tree canopy.
On March 6, 1995, San Jose scale pheromone paraffin emulsion was applied to twelve contiguous Fantasia nectarine trees in a three-row by four-tree block. A similar block of untreated Fantasia check trees was located approximately 90 m crosswind from the twelve pheromone-treated trees. Within each treatment (pheromone and untreated check), five trees were randomly selected for monitoring with a SJS pheromone trap (Trécé Inc., Salinas, CA, USA) and two sticky tapes for collection of flying and walking male scale, and crawlers resulting from mating of virgin females.
The first detected SJS male emergence occurred on March 7, 1995. This male biofix was established by collection of males on the sticky tapes rather than flying males collected on the pheromone traps. Thus it appears that the SJS pheromone emulsion was applied at the optimum time for disruption of male scale emergence and mating. The first male scale was collected on a pheromone trap in the untreated check trees on March 10. As in the OFM applications, the Span 60 deposits on nectarines showed no apparent affect from over 7.6 cm of rain on March 9 and 10, e.g. there was no loss of emulsion deposit from the tree limbs.
Following application, emulsion deposits on the trees would usually dry within one to four hours. Pheromone emulsion using the TEA stearate emulsifier produced a thinner deposit on the tree bark and also tended to discolor after application to the bark, taking on an oily, light brown appearance. Emulsions using the Span 60 emulsifier dried somewhat slower, but produced a more uniform deposit that tended to clump rather than run and spread on the bark. The Span 60 emulsifier blend held its form in a “toothpaste” blob, whereas the stearate emulsifier mix was too thin to form a thick paste and would run and drip readily if applied in only one small spot. The characteristics of the Span 60 emulsifier may be advantageous by slowing release of the pheromone from a more compact deposit rather than a thin, dispersed deposit as produced by the stearate emulsifier.
Oriental fruit moth mating disruption
The effects of two applications of Oriental fruit moth pheromone mixed in the paraffin-emulsion blends applied in the 0.8-ha plum block are shown in Figure 1. Although only twelve OFM male moths were captured in the two pheromone monitoring traps in the untreated (north) portion of this orchard during the first flight in mid-March through late April, no moths were captured in the treated 0.8 ha of this block. During the second flight, from late May through late June, 21 moths were captured in the un-
Figure 1 Pheromone trap collections of Oriental fruit moth in a 0.8-ha plum orchard treated with OFM pheromone/paraffin emulsion. Span 60 emulsifier used in both applications; 76.0 g and 76.3 g OFM pheromone/ha in first and second applications, respectively (Kearney Agricultural Center, Parlier, CA, 1995)
Figure 2 Pheromone trap collections of Oriental fruit moth in a 0.8-ha nectarine orchard treated with OFM pheromone/paraffin emulsion TEA stearate emulsion with 50.0 g pheromone/ha used in first application; Span 60 emulsion with 75.3 g pheromone/ha in second application (Kearney Agricultural Center, Parlier, CA, 1995)
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treated check area and five moths were caught in the treatment on June 2 and 6. This triggered the second application of pheromone on June 7. As a result, only one moth was captured in the treatment on July 14 during the third flight, while significant increase was seen in the untreated check. This trend with higher populations in the check was also seen in the fourth and fifth flights in August and September, while the populations in the paraffin-emulsion treatments remained relatively low in the treated area. Evaluations for OFM larvae in fruit at harvest were not taken in this orchard due to the extremely low or nonexistent incidence of OFM larvae in plum fruit.
The results of mating disruption with OFM pheromones in paraffin emulsions in the 0.8-ha block of nectarines are shown in Figure 2. Applications of the disruption pheromones on March 2 at the beginning of the OFM flight and again on May 17 at the beginning of the second flight resulted in complete trap shutdown in this orchard until July 14 at the peak of the third OFM flight. Oriental fruit moth population pressure in this orchard was considered relatively high for a commercial orchard with populations peaking at over 30 in the second flight, over 120 moths/trap/week in the third flight, and approaching 180 moths/trap/week in the fourth flight. Even under these conditions moth populations in the treated block remained acceptably low through the end of the fifth flight in late September and early October.
OFM infestation levels in mature nectarines in this orchard were determined at harvest dates of July 14 and July 21 and were compared to fruit taken from an untreated Fantasia block approximately 0.8 km upwind. One thousand fruit were taken from each orchard and examined for both OFM and PTB damage. Fruit in the mating disruption block showed 0.4% OFM infestation while fruit from the untreated check orchard showed 2.4% OFM infestation (Table).
| Location | Crop | Treatment a | % Infested Fruit | |
| OFM | PTB | |||
| KAC 36 | Peach | Check | 3.5 | 3.1 |
| MD | 0.3 | 3.5 | ||
| Almond | Check | - | 2.7 | |
| MD | - | 3.8 | ||
| KAC 74 | Nectarine | Check | 2.4 | 19.8 |
| MD | 0.4 | 15.0 | ||
| SJS | ||||
| KAC 32 | Nectarine | Check | 19.8 | |
| MD | 26.1 | |||
a Two applications per season for Oriental fruit moth (OFM) and peach twig borer (PTB) (50.0 to 77.5 g a.i./ha/application). One application for San Jose scale (SJS) (75.0 g a.i./ha; March 6, 1995)
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Pheromone monitoring traps in the mixed stone fruit orchard also showed extremely good monitoring trap shutdown in the mating disruption treatments following applications of pheromone on March 2 and May 16. No OFM moths were caught in either of the first two flights in this orchard and only a small number were collected in the disrupted orchard during the third flight in comparison to the upwind untreated check. Male moth collections in the fourth and fifth flights increased to much higher numbers in relation to the untreated checks but this is thought to be due to the small size of the pheromone-treated block and possible inflights of male moths from adjacent untreated almonds. One thousand Flamecrest peaches were harvested in this block on June 26 for evaluation of OFM and PTB damage and compared to 1 000 fruit taken from the nearby untreated check orchard. The OFM infestation level in the mating disruption block was 0.3% compared to 3.5% in the untreated check (Table).
The two applications of OFM mating disruption pheromones in paraffin emulsions applied to almonds also showed excellent trap shutdown through the first three flights. OFM is not usually considered a pest in almonds but populations can often be high enough to allow evaluation of various types of OFM treatments and controls. Because trap shutdown in the almonds following the first application of pheromone on March 6 was so good, it was determined not to apply the second application until the first moth was captured in monitoring traps in the pheromone-treated 0.8-ha block of this orchard. A single male OFM was captured in the pheromone treatment on June 2, resulting in the second application the following day. After this application, the monitoring traps in the pheromone treatment were again completely shut down through the third OFM flight and no moths were captured in the treatment until mid-August, during the major portion of the fourth OFM flight. Monitoring for OFM in almonds was terminated in early September due to the drying-down of the orchard and preparations for harvest. However, it was apparent that the pheromone treatments in this orchard had a significant effect on the ability of male OFM moths to orient to monitoring traps, compared to the untreated portion of this 50-ha orchard.
The efficacy of the pheromone-paraffin emulsion blends for mating disruption of Oriental fruit moth in these several orchards in 1995 indicate that the pheromone treatments were capable of shutting down the monitoring traps for at least the entire first OFM flight and perhaps a significant portion of the second flight as well. This period of trap shutdown of approximately 60 to 75 days is comparable to that observed with the plastic hand-applied mating disruption dispensers currently available. OFM trap shutdown for approximately 7 to 10 weeks following the second application of disruption pheromone in mid-May to early June was also quite encouraging, given the absence of prior history and experience with this pheromone-dispensing system. In addition, the reduction in fruit damage from OFM in the nectarines and peaches was also encouraging for the first evaluation of control of OFM with this pheromone system. These data show results comparable to what would be expected from the commercial mating disruption pheromone products presently available to growers.
Peach twig borer mating disruption
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The first applications of PTB pheromones in paraffin emulsions were made at the Kearney Agricultural Center during the first week of April 1995. In nectarines the emulsions were applied on April 3 but within three weeks moths were being trapped in the pheromone treatment as well as in the untreated nearby check orchard (Figure 3). The second application of PTB pheromone was applied in this orchard on May 10, resulting in PTB collections in monitoring traps being brought down to zero levels during the latter portion of the first PTB flight. With the onset of the second flight in early June, however, monitoring traps in the pheromone-treated orchard again showed increasing collections comparable to those in the untreated check orchard. These collections indicated that the field residual and longevity of the PTB pheromone in either the TEA stearate or Span 60 paraffin-emulsion formulations was relatively short compared to OFM pheromones in the same formulations. PTB infestations in fruit harvested on July 14 and 21 showed an infestation level of 15% in the mating disruption pheromone treatment, which compared to a 19.8% infestation level in the untreated check orchard (Table).
Figure 3 Pheromone trap collections of peach twig borer in a 0.8-ha nectarine orchard treated with PTB pheromone in paraffin emulsion. Span 60 emulsifier used in both applications; 59.8 g and 62.0 g pheromone/ha in first and second applications, respectively (Kearney Agricultural Center, Parlier, CA, 1995)
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Pheromone trap data from the mixed stone fruit block again showed an unacceptably short residual of PTB pheromone in the paraffin emulsions resulting in breakdown of the disruption treatment within three to four weeks after pheromone application. Male PTB moth collections in this orchard during the second and third flights in July through August showed monitoring trap collections higher in the pheromone treatment than in the untreated check orchard traps. Fruit harvested on June 26 showed a PTB infestation level of 3.5% compared to 3.1% in fruit harvested from the untreated check orchard on the same date (Table).
Data from pheromone monitoring traps in the almond orchard also showed rapid breakthrough of male PTB moths to monitoring traps in the disruption treatment following the first application on April 4. This occurred only three weeks following the first application. Following a second application of pheromone on May 10, PTB moth collections were reduced in the pheromone treatment for a period of approximately five weeks compared to the untreated check portion of the orchard. However, with the onset of the second flight in late June, moth collections in the pheromone treatment were similar to the untreated check and continued at high levels in both treatments through the remainder of the season.
Peach twig borer infestation levels in the almonds were evaluated by harvesting 1 000 nuts at random from within both the 0.8-ha pheromone-treated block and the area of the untreated orchard containing monitoring traps. These nuts were collected immediately following commercial shaking of the nuts to the ground in the respective treatment areas. Because these almonds were a hard-shell cultivar, PTB presence was evaluated only on the basis of hull infestation and showed a 3.8% infestation level in the mating disruption treatment compared to a 2.7% infestation in the untreated check portion of the orchard (Table). PTB pheromone was not applied to the plum orchard at Kearney because this orchard had been treated prior to bloom with dormant sprays for PTB and SJS control. Consequently it was felt that pheromone application and monitoring for PTB in this block would not yield useful data for PTB mating disruption.
The results of the treatments with PTB pheromone in paraffin emulsion indicate that acceptable mating disruption was not achieved with the paraffin-emulsion formulations used in field trials in 1995. Both the pheromone trap data and fruit infestation data indicate relatively low or no mating reduction in these several treatments. This is in contrast, however, to the results observed with the OFM mating disruption formulations used in the same orchards in 1995.
San Jose scale mating disruption
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Pheromone treatments in paraffin emulsions for SJS in Fantasia nectarines were evaluated by counting crawlers trapped on sticky tapes on treated trees versus untreated trees and by evaluation of scale infesting mature fruit. Following the single application of pheromone to these trees on March 6 (beginning of male scale emergence and potential disruption) crawler collections on sticky tapes during the first generation of crawler emergence showed a considerable reduction in populations on treated trees versus untreated trees (Figure 4). The small initial peak of crawler collections on April 6, showing no difference between the check and mating disruption treatment, is believed due to crawler emergence from mated, overwintered females that were not affected by the pheromone treatment.
Figure 4 Sticky tape trap collections of San Jose scale crawlers in untreated check nectarine trees compared to trees treated with 75.0 g SJS pheromone/ha in paraffin emulsion (Span 60 emulsifier) (Kearney Agricultural Center, Parlier, CA, 1995)
The lower collections of crawlers from April 13 through June 22 are thought to be a result of reduced male orientation to calling virgin female scale and less mating during the first male flight. This initial reduction of scale crawlers seemed to carry over into the second adult generation in June and early July, again resulting in a lower population of crawlers in the mating disruption treatment during the second generation in July and August. However, this difference in populations disappeared during the third crawler generation in late August and early September.
Fruit harvested in mid-July from both the pheromone treated trees and the untreated check trees showed no significant difference in infestation levels on fruit, with the mating disruption treatment having 26.1% infested fruit and the check trees showing 19.8% infested fruit. The fruit infestation data is contradictory to the data collected on the sticky tapes for total crawler populations. The fruit data, however, may be somewhat misleading as no attempt was made during the harvest evaluation to distinguish between only a single crawler per fruit versus several or more crawlers per fruit.
The results of the single application of SJS pheromone to nectarines suggest that there may be some potential for mating disruption and control of SJS using pheromones in paraffin-emulsion formulations. Based on the single trial in 1995, however, it would be premature to either reject or accept the potential for mating disruption of scale using synthetic pheromones on tree fruit. The crawler collection data on sticky tapes suggest that further trials for mating disruption of SJS are warranted, but this will depend upon both availability and cost of the synthetic SJS pheromones.
Biwer G, Descoins C, Gallois M (1979) Etude des constituants volatils presents dans la glande productrice de pheromone de la femelle vierge de Grapholitha molesta (Busck), Lepidoptera: Tortricidae (Olethreutinae). C r Acad Sci Ser. D 288, 413
Cardé AM, Baker TC, Cardé RT (1980) Identification of a four-component sex pheromone of the Oriental fruit moth, Grapholitha molesta (Lepidoptera: Tortricidae). J chem Ecol 5, 423-427
Gieselmann MJ, Rice RE, Jones RA, Roelofs WL (1979) Sex pheromone of the San Jose scale. J chem Ecol 5, 891-900
Pree D, Trimble R, Whitty K, Vickers P (1994) Control of Oriental fruit moth by mating disruption using sex pheromone in the Niagara Peninsula, Ontario. Can Entomol 126, 1287-1299
Rice RE, Kirsch P (1990) Mating disruption of Oriental fruit moth in the United States, pp. 193-211 in Ridgway RL, Silverstein RM, Inscoe MN (eds.) Behavior-Modifying Chemicals for Insect Management. Marcel Dekker, New York
Rice RE, Millar JG (1992) Mating disruption of peach twig borer, Anarsia lineatella Zeller: progress and problems. IOBC wprs Bulletin 15(5), 56-60
Ridgway RL, Silverstein RM, Inscoe MN (1990) Behavior-modifying chemicals for insect management. Marcel Dekker, New York
Roelofs W, Kochansky J, Anthon E, Rice R, Cardé R (1975) Sex pheromone of the peach twig borer moth (Anarsia lineatella). Environ Entomol 4, 580-582
Vickers RA (1990) Oriental fruit moth in Australia and Canada, pp. 183-192 in Ridgway RL, Silverstein RM, Inscoe MN (eds.) Behavior-Modifying Chemicals for Insect Management. Marcel Dekker, New York
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