The two principle pests of pear production in the Northeastern US are pear psylla, Cacopsylla pyricola (Foerster), and Fabraea leaf spot (FLS), Fabraea maculate 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 or combination of Delegate and Movento when employed at or above 100 GPA at speeds of 2.5 MPH or less. In our 2010-2011 Cornell’s Hudson Valley small plot study we again observed applications of HRO’s effective 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 (PDMR Abstract). 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 (Image 3 & 4), followed by premature decline and eventual death of susceptible pear varieties. Bosc being a very susceptible variety used in fresh fruit marketing. Insecticide resistance has resulted in lower levels of pear psylla insecticide susceptibility, reducing effectiveness of current pest management strategies to reduce insect populations.
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 replicated 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 using commercial application equipment at the LM Clarke orchard, in Milton, NY (Doc. 1). 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. The second study conducted at HVL employed handgun applications of 4 tree plots using 30 year old Bartlett and Bosc trees.
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 ‘HVL 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 (employed as an ovipositional deterrent, to reduce egg viability, to smother early instar nymphs) 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.
Results from our data taken in both commercial large block and small plot research studies in 2010 and 2011 demonstrate and confirm the efficacy of using the combination of early season Surround and post petal fall applications of 1% oil in seasonal control for pear psylla compared to commercial standards. In 2011 we used fewer applications then in 2010 to reduce costs further. We did see lower levels of control in some of our treatments due to the reduction in applications during the latter part of the season. It is likely an application on 1 June would have optimized the results in program by reducing oviposition of the 2nd generation eggs.
Plots with lower volume rates and increased ground speed appeared to have increased injury compared to plots with decreased speed and increased volume. The pear psylla evaluations in the Surround and oil combinations across the trial using 1.25, 2.5 or 3.5 mph applications appeared to have a ‘rate response’ based on output volume of 75, 148.9 or 250 GPA. Slower speed and higher output volume appeared to have better control with little difference between hollow cone nozzles or air induction nozzles. The grower standards varied considerably between the AgriMek program and Delegate program with better results being obtained using AgriMek at the onset of the 2nd generation nymph hatch.
The impact of this study on the results will speak to the topic of toxicology regarding chemical efficacy. The study provides very strong data to demonstrate the efficacy of barrier films and ovipositional deterrence with relatively little toxicity to target pest or beneficial population complex. The use of Kaolin clay during the early season will have no detrimental effect on tree physiology to cause lenticel enlargement, observed in 2-3% early season oil applications. The use of oil late in the season will allow the tree to ‘harden off’, becoming less susceptible to oil injury at the 1% dilute use rate.
Although the materials are themselves more expensive, the judicious use of these products in limited applications would be applied when control of Fabraea maculate is required, reducing the costs of additional applications in NY and Connecticut where Fabraea is a pest disease.
Education & Outreach Activities and Participation Summary
A video available for on-demand viewing of this project up through 2010 data collection is available on the Hudson Valley Regional Fruit Program web site at:
Insect pest management guidelines were incorporated into the organic tree fruit In-Depth workshop in March of 2011; Tree Fruit Workshops in Hudson and Milton, NY in May and June, 2011-12 were conducted to grower audiences with 55 and 75 attendees respectively.
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 with newly developed products such as Movento and Delegate. 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. Increased market share may be obtained if growers employ marketing strategies that include the advertisement of organic (OMRI) product use.
A grower standard program consisting of a single pre-bloom oil application at 3% (3 gallons/A), followed by a pyrethroid (Asana XL (esfenvalarate) at 15 oz./A) at the white bud stage are used to manage the overwintering adult psylla. Two applications of AgriMek ((abamectin) at 20 oz./A+ 0.25% HMO) beginning at 10 days post petal fall (10dpPF) and again at a 21 day interval, are now the standard control measure to manage 2nd generation pear psylla in the Hudson Valley. In 2011 a mid-season application of Delegate ((Spinetoram) WG + 0.25% HMO at 7.0 oz./A) in one plot was compared to the Movento 240SC ((Spirotetramat) + 0.25% HMO 9.0 fl oz/A) in the second growers standard plot.
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 &amp;amp; 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.
No less than four regional pear growers have adopted this program in part or in its entirety since 2010 with a number of large Pennsylvania state growers using this strategy. Many growers are reluctant to use oil late in the season and further outreach will need to be continued to increase adoption to this approach.
Given the reduced cost of this program and lackluster performance of newer more expensive insecticides employed to manage pear psylla , it is likely this program will gain in popularity as long as it is used correctly. Use of oil in a dilute NOT A CONCENTRATE application is critical for this program to be successful. In other words, 1 gallon in mixed in 100 gallons of spray solution to achieve the needed 1%.
Areas needing additional study
As with any new pest management program, the adoption of these strategies will need to be replicated on a number of commercial farms over yearly climatic variables to discern if the 2010-11 results are effective and confirm to producers that this approach is effective and profitable.