Determining the Potential for Organic Material Use In Northeast Commercial Pear Production
The two principle pests of pear production in the Northeastern US are pear psylla, Cacopsylla pyricola (Foerster), and Fabraea leaf spot (FLS), Fabraea maculata were managed using alternative pest managment strategies. For a second year studies were conducted to manage these pests at Cornell University’s Hudson Valley Laboratory research pear orchard and a large commercial pear orchard in Milton, NY, demonstrating the commercial use and effectiveness of two OMRI products. Trials employed a split timing of two applications using a barrier film in early season psylla management followed by mid to late season applications of an ovipositional deterrent, resulting in product efficacy equal to and or exceeding commercial levels of control of pear psylla at reduced or comparable cost. The kaolin clay product Surround WP (anhydrous aluminum silicate) used in pre-bloom and petal fall applications followed by ‘summer’ applications of 1% highly refined horticultural oils (HRO’s) beginning at 1st cover and continuing at two week intervals provided season long maintenance of psylla populations below economic thresholds, comparable to commercial treatments of pyrethroid and AgriMek when employed at or above 100 GPA at speeds of 2.5 MPH or less. Furthermore, applications of HRO’s were observed in suppressing Fabraea leaf spotting and subsequent reduction in defoliation of HRO treated pear trees compared to commercial pear psylla treatments without fungicides and untreated trees in research plots. This demonstrated the efficacy of HRO’s at reducing the effects of Fabraea leaf spot defoliation with dilute applications of oil alone.
The study again employed airblast applications including observations of variables comparing air induction nozzles to commercial hollow disk nozzles, sprayer speed and volume, finding no dramatic difference in degrees of control and supporting the use of lower levels of drift through the use of air induction nozzles. The need for season long management of FLS reduced any additional application costs associated with bi-weekly HRO applications for post bloom pear psylla management through ‘tank mixing’ HRO’s to fungicide programs. Seasonal use of HRO’s for pear management beyond the pre-bloom stage has been adopted in commercial orchards in Pennsylvania with increasing use in commercial pear sites in NY State.
Pear production in NYS is managed on nearly 2000 acres, with yearly crop yields producing roughly 16,500 tons valued at 3.85 million dollars. In the Hudson Valley region, pears comprise about 800 acres (USDA, 2005). The principle pests of pear production in the Northeastern US are pear psylla (Image 1), Cacopsylla pyricola (Foerster), and Fabraea leaf spot (Image 2), Fabraea maculata. These two pests cause premature defoliation, reduced size, quality and yield of fruit, followed by premature decline and eventual death of susceptible pear varieties (Images 3 & 4). Insecticide resistance has resulted in lower levels of pear psylla insecticide susceptibility, reducing effectiveness of current pest management strategies.
- Fabraea leaf spot on foliage and fruit
- Secretions from nymphs of ‘honeydew’ giving rise to sootymold damage to foliage and fruit.
- Pear psylla adult and eggs on stem and foliage
- Honeydew leading to leaf scortch and defoliation.
To determine the efficacy of OMRI materials on populations of pear psylla throughout the season we conducted comparative studies on a commercial pear orchard and simultaneously on and controlled research field plots in 2010 and 2011. The components of this research fall into these two study groups. The first conducted in a a commercial pear orchard of LM Clarke, in Milton, NY (Image 5). using commercial application equipment while the latter employed research equipment and data evaluation techniques suited for small plot studies on the one-acre experimental pear orchard at Cornell University’s Hudson Valley Laboratory in Highland, NY (Image 6). The second study conducted at
From 2005 to 2011 controlled field plot studies at the Hudson Valley Laboratory were made to determine the efficacy of OMRI materials on populations of pear psylla, however only 2011 results will be reported.
Trials employing four-tree plots were replicated four times in a replicated complete block design.Data collected through the growing season was evaluated using Log10 (X + 1) transformation applied for adult and foliar evaluations. To stabilize variance, percentage data were transformed by arcsine *(square root of x) prior to analysis. Fisher’s Protected LSD (P=<0.05) was performed on all small plot data; untransformed data are presented in tables. Each plot contained four trees of alternating 30 year-old ‘Bartlett’ and ‘Bosc’ cultivars, 12’ in-row x 18’ drive-row spacing, 12 ft in height with foliar and adult psylla data taken from Bosc variety. All dilutions were based on 400 gallons/acre with plot requirements ranging from 20 to gallons increasing seasonally to 50 gallons with developing canopy. Treatments were applied using a three point hitch tractor mounted high pressure ‘Pak-Tank’ sprayer using a pecan handgun operated at 300 psi delivering >350 GPA sprayed to runoff.
One of two ‘OMRI experimental plots’ employed a single 3% HMO application at first observation of egg laying followed by a single pre-bloom (green cluster – white bud) and bi-weekly post bloom applications at a 1% dilution rate in a season long program of 4 applications using 1 nymph per leaf thresholds. This was compared to a second plot employing Surround WP at 50#/A beginning at first egg observation followed by a white bud application and a single petal fall application. Bi-weekly post bloom applications of HMO at a 1% dilution rate followed in a season long program of 3 total applications using 1 nymph per leaf as the treatment threshold.
Early applications targeted overwintering adult and first generation of pear psylla. During the period from bud burst through 1st cover, evaluations to determine treatment effects on springform adult ovipositional deterrence, including subsequent 1st generation nymph emergence were conducted. Pre-bloom evaluations for pear psylla egg and nymph populations using 25 buds on 5 perimeter 1st year shoots per tree and seasonal leaf assessments sampling 25 basal leaves of 5 shoots by removing 1 distal, 1 proximal and 3 mid-shoot leaves of 5 shoots per treatment from Bosc trees were conducted throughout the season. Samples were removed to the laboratory where target pests were counted using a binocular scope. Adult numbers were assessed using 3-minute vacuum sweeps of perimeter apical shoot foliage using a hand held vacuum and screened collection bottles. Fifty Bartlett or Bosc fruit were harvested per treatment and scored for insect damage and size in both commercial and research plots.
- Image 6. Pear Orchard; Cornell University’s Hudson Valley Laboratory, Highland, NY
- Image 5. Commercial Pear Orchard, Milton, NY
Impacts and Contributions/Outcomes
The OMRI products demonstrated for a second year that commercial levels of pest management could be achieved through their use. Given the potential of insecticide resistance of the primary insecticides used to manage pear psylla, coupled with projected costs of replacing these materials, the economic comparison of presently used commercial insecticides to the costs of Surround and HMO’s most likely will become more attractive. The relationship between the material costs for growers transitioning into using barrier film and mechanical based HMO’s for psylla management have shown the Surround & HMO program producing a 24% savings in 2010 and 33% in 2011 in material costs over the conventional program can achieve higher or comparable levels of retained foliage and less damage related to lower levels of sooty mold on foliage and fruit.
The costs of AgriMek have been reduced considerably over the past two years as the patent held by Syngenta has expired and the cost of generic abamectin based insecticide are now manufactured and sold by many smaller companies, pushing AgriMek prices down to compete. That said, the price of AgriMek applications cost approximately $14.00 per acre, compared to the $1.00 per pound or $50.00 per acre at the high labeled rate for Surround WP. Lower costs will undoubtedly continue to influence AgriMek use. Yet growers positioning to greater levels of reduced risk can achieve commercial levels of pest management and sound fruit using early season Surround WP and mid through late season 1% dilute oil strategies.
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