Mating Disruption for Oriental Fruit Moth in Peaches on a State Wide Basis

Dean F. Polk, Peter Winkler, David Schmitt, Meredith Peters, Eugene Rizio

Rutgers Fruit Research & Extension Center

283, Rt. 539, Cream Ridge, NJ 08515

    New Jersey peach production is often ranked 3rd or 4th in the US, depending on the season's growing conditions. Peaches and nectarines are produced on about 10,500 acres (4,251 ha.), most of which is located in the southern half of the state and grown for wholesale markets. Farm size varies between 70 acres (28 ha.) to just over 1,000 acres (405 ha.). Farms in the northern half of the state are smaller (5 to 50 acres or 2 to 20 ha.), where fruit is produced for direct market outlets.
    New Jersey peach growers may spend up to $600 or more per acre for pesticides, but average just over $200 per acre. Insecticide use averages just over $70 per acre ($173 per ha.) or an average use of 6.5-7.0 lb ai per acre per season (16-17 lb ai per ha). Peach and nectarine growers may apply 10 full cover sprays of insecticide per season, or up to 20 alternate row middle applications on late ripening cultivars. Pre-harvest target pests that drive the spray program include oriental fruit moth (OFM), and tarnished plant bug and stink bugs. Other targets often include Japanese beetle, tufted apple budmoth, flower thrips, and green peach aphid.
    In recent years, a number of factors have encouraged us to explore the use of mating disruption for various peach pests. These include the occurrence of organophosphate resistant OFM populations, issues brought on by the Food Quality Protection Act (FQPA), and buyer awareness and public opinion regarding pesticide use. Mating disruption may also help in labor management by reducing reentry interval times during thinning and reduce farmworker exposure to pesticide residues.
    We view mating disruption as another tool to be used in our IPM practices. In order to be successfully adopted, mating disruption will need to fit in with existing horticultural, labor management, and other production practices. If targeting OFM, other key pests also need to be well managed under an IPM program.

Objectives in the New Jersey program:

Methods:

    Small scale trials (5-10 acres or 2 to 4 ha.) for mating disruption of oriental fruit moth had been demonstrated to New Jersey peach growers since 1994. Based on the promising results obtained from small scale plots, a larger area-wide program was started in 1998. In 1998 most of the project was focused on just over 500 acres in one area near Richwood, Gloucester County plus 2 farms in northern counties. While most blocks yielded clean fruit, OFM from abandoned orchards and resistant populations were problematic. In 1999 our project worked with growers in 3 southern and 2 northern counties. OFM mating disruption was employed on 13 farms with 544 acres (220 ha.) under treatment. This included 91 blocks of fruit planted with 37 cultivars that ripened from early July through mid September. Nine farms with OFM mating disruption treatments were in southern counties, and 4 were in northern counties.
    All dispensers were supplied by from Shin Etsu Chemical Co. except for 100 acres treated with Hercon Disrupt for OFM. Isomate M-100 dispensers were applied at the rate of 100 dispensers per acre, while M Rosso units were applied at the rate of 200 per acre. All blocks with outside borders had an additional dispenser applied on the border tree or on neighboring apples or woods if present. Hercon material was used in three blocks on one farm and for border applications on a number of other blocks. Most Shin Etsu OFM material consisted of Isomate M-100. Approximately 20 acres (8.1 ha.) was treated with Isomate-M Rosso. Treatments were split with 10 acres receiving treatment prior to first OFM emergence on 4/5-6, and 10 acres being treated close to first peak adult flight. All Isomate M-100 and Hercon Disrupt were placed between 5/4-10 or just after the first flight peaked.
    Farms were monitored once per week by using pheromone traps and a full scouting procedure for arthropods and diseases. In most cases, blocks under standard (Std) IPM pesticide programs were compared to blocks under mating disruption (MD) treatment. Blocks of the same variety or if not available, blocks that ripened during the same time period, were compared between treatments on the same farm. Peach cultivars were divided into early/mid season varieties and late season varieties for the purpose of data analysis. Early/mid cultivars are defined as those ripening from the last week of July through about August 10, or those varieties that should have been protected by the expected life of the M-100 dispensers. Late season cultivars are those that ripened after August 25, and therefore required additional late season insecticides. In season pest and fruit quality data was pooled from those farms that had both management systems and compared using an unpaired T test. On some farms either all or most of the acreage was treated with pheromone leaving no comparison blocks with standard insecticide sprays. A total of 57 OFM traps were used in MD blocks to measure the extent of trap shut-down, and baited with .1 mg ai Z,8 and E,8 dodecenyl acetate, and Z,8 dodecenol (Scenturian). Traps were also placed in standard blocks to monitor normal OFM flight patterns, and baited the same amount of active ingredient. Post harvest fruit quality data was collected in 307, 100 fruit samples from mating disruption blocks and 195, 100 fruit samples from standard blocks. A total of 50,200 fruit was examined from monitored blocks for pest injury. While a complete insect and disease scouting was done each week, the data relative to this demonstration includes:

                1) In-season monitoring that measured:
                                a) Trap counts or trap shut down.
                                b) OFM flags per tree - averaged across a 10 tree sample site.
                                c) Catfacing insect counts, or the number of tarnished plant bugs and stink bugs per 50 sweeps in the ground cover.

2) Post harvest evaluations taken in 100 fruit samples, with at least three samples taken in each block at harvest. While all pest and non-pest injury was recorded, the most common insect injuries were summarized, and include oriental fruit moth, catfacing insects, Japanese beetle, and tufted apple budmoth and leafrollers (TABM/LR).

3) Grower pesticide use records. Spray records were analyzed by block for the types and amounts of all pesticides used, along with estimated retail costs run from a standard price list within our IPM database.

     Since trees are pruned during March through May, or during the first OFM flight, insecticide sprays were applied using a degree model for the first generation. These were made in four alternate middle applications, which also controlled plum curculio and most of the early season catfacing insect complex. Treatments for green peach aphid and flower thrips were made on an as needed basis, primarily on nectarines.

    Isomate M-100 and Hercon Disrupt dispensers last about 90 days in the field, or through the end of July. Therefore, insecticide treatments were resumed on late varieties through early September. The only exception to this was where M Rosso (lasts 125 to 150 days) was used in a block of Encore (ripening during the first week of September), where no additional insecticides were used.

Results:

    Trap shut-down was achieved on all farms, but insect pressure varied greatly from farm to farm. Counts taken of OFM flagging throughout the season showed little to no difference between mating disruption vs. standard blocks. There were no significant differences in either early/mid or late season varieties in the number of flags per tree or the number of catfacing insects found in the ground cover (Figures 1 & 2 for late season varieties). There were also no differences in the overall percentage of clean fruit. There were no significant differences in OFM injury across all farms in either early/mid season varieties or late season varieties. There were no differences in other pest injury on late season varieties, (Figures 5 & 6 , 7-9) but there were higher levels of catfacing insect and Japanese beetle injury in the early/mid season mating disruption blocks (Figures 3 & 4). This is reasonable, since: A) Most catfacing pressure is often early in the season when the fruit was not being sprayed; and B) Most Japanese beetle pressure comes during the final 10 days preharvest on varieties that ripen from mid July through early August, again when many of these varieties were not being sprayed. It should be noted that all blocks had a high percentage of clean, marketable fruit.

    Insecticide use was reduced in most cases, on some farms up to 60+%. Insecticide cost savings also varied, and were close to $30 per acre on some late season blocks, but averaged close to $20 per acre on late season varieties. Some growers used as much as 66% less insecticide on late season varieties, but averaged 36% less ai used in MD blocks (Tables 1,2 and 3). Greater differences were seen when heavier amounts of insecticide were used in the standard program, or where well managed ground covers minimized populations of tarnished plant bugs and other cat-facing insects. The single greatest factor that affected the use of supplemental insecticides were populations of tarnished plant bugs and stink bugs. The 1999 season was a year of very light insect pressure. Therefore the a.i. use in standard insecticide treated blocks was reduced about 1/3 from a "normal" season.

    The use of mating disruption for OFM was shown to be a promising tool for IPM. Challenges in further adoption include the management of other insects such as Japanese beetle and various catfacing insects. Cost may also be a factor, but will also be influenced by pest pressure and the costs of insecticides.