Adult Pear Research Articles

Predation risk can modify the foraging behaviour of frugivorous carnivores: Implications of rewilding apex predators for plant-animal mutualisms.

Apex predators play key roles in food webs and their recovery can trigger trophic cascades in some ecosystems. Intra‐guild competition can reduce the abundances of smaller predators and perceived predation risk can alter their foraging behaviour thereby limiting seed dispersal by frugivorous carnivores. However, little is known about how plant–frugivore mutualisms could be disturbed in the presence of larger predators.We evaluated the top‐down effect of the regional superpredator, the Iberian lynx Lynx pardinus, on the number of visits and fruits consumed by medium‐sized frugivorous carnivores, as well as the foraging behaviour of identified individuals, by examining the consumption likelihood and the foraging time.We carried out a field experiment in which we placed Iberian pear Pyrus bourgaeana fruits beneath fruiting trees and monitored pear removal by frugivorous carnivores, both inside and outside lynx ranges. Using camera traps, we recorded the presence of the red fox Vulpes vulpes, the Eurasian badger Meles meles and the stone marten Martes foina, as well as the number of fruits they consumed and their time spent foraging.Red fox was the most frequent fruit consumer carnivore. We found there were fewer visits and less fruit consumed by foxes inside lynx ranges, but lynx presence did not seem to affect badgers. We did not observe any stone marten visits inside lynx territories. The foraging behaviour of red foxes was also altered inside lynx ranges whereby foxes were less efficient, consuming less fruit per unit of time and having shorter visits. Local availability of fruit resources, forest coverage and individual personality also were important variables to understand visitation and foraging in a landscape of fear.Our results show a potential trophic cascade from apex predators to primary producers. The presence of lynx can reduce frugivorous carnivore numbers and induce shifts in their feeding behaviour that may modify the seed dispersal patterns with likely consequences for the demography of many fleshy‐fruited plant species. We conclude that knowledge of the ecological interactions making up trophic webs is an asset to design effective conservation strategies, particularly in rewilding programs.

Efficacy evaluation of horticultural oil based thermotherapy for pear psylla management

The goal of this study was to improve techniques for pear psylla, Cacopsylla pyricola (Föerster) control, one of the major pests in pear orchards worldwide and in the United States. Mortality of adult pear psylla was determined after its exposure to horticultural oil (HO) combined with high temperature (thermotherapy) treatments. A laboratory–scale application technology unit was developed to apply HO–based thermotherapy. Spray treatments included four variables namely heat–condition (i.e., heat and no–heat), HO concentration (i.e., 0.5 and 1.0%), nozzle types (i.e., N1: Conejet nozzle, N2: D2/DC13 disc–core nozzle) and application pressure (i.e., 344.7 [50] and 689.5 [100] kPa [psi]). Each treatment was replicated four times on pear psylla bioassays. Mortality was evaluated at 3, 6, 12, 24 and 48 h after spray application. HO combined with thermotherapy achieved as high as 100% pear psylla mortality during early hours after spray application. The overall mean pear psylla mortality using HO under heat condition (63.7 ± 2.4% [mean ± std. error]) was significantly higher compared to no–heat condition (43.6 ± 1.8%). Higher HO concentration (i.e., 1.0%) under heat condition had significantly higher mortality (60.2 ± 2.3%) compared to similar applications at lower concentration (47.1 ± 2.0%). Pear psylla mortality was significantly affected by nozzle type under heat conditions, and nozzle N1 (with comparatively higher spray coverage on water sensitive papers) had significantly higher (74.4 ± 3.1%) pear psylla mortality compared to nozzle N2 (52.9 ± 3.3%). The interaction between thermotherapy and each of the HO concentrations and nozzles on psylla mortality was significant at α = 0.05. Overall, HO combined with thermotherapy caused a rapid kill of pear psylla. Future field studies are warranted to evaluate efficacy of HO–based thermotherapy at reduced HO concentrations and pertinent effects on smothering of eggs and pear psylla mortality.

Liming and Manganese Foliar Levels in Orange

ABSTRACT Citrus cultures have a fundamental importance to the Brazilian economy; certain aspects such as plant nutrition, yield, and fruit quality are vital for the citrus industry sustainability. The present study evaluated the nutritional status of manganese in adult Pear orange trees using different lime rates topically applied to the soil. The direct evaluation of lime rates effects on leaf manganese (Mn) levels revealed a decrease of the nutrient correlated to its increased, as well as passage of time between application and measurement. Foliar sampling 30 months after surface lime application evidenced a high correlation of foliar manganese levels with soil base saturation of 10–20 cm. Leaf manganese levels which showed a great probability of high productivity were between 33 and 70 mg kg−1.

An Inexpensive Immunomarking Technique for Studying Movement Patterns of Naturally Occurring Insect Populations

An immunomarking system useful for determining insect movement patterns was developed that allows the marking of naturally occurring populations of insects within large areas with inexpensive and readily available proteins that can be applied using standard spray equipment. Enzyme-linked immunosorbent assay (ELISA) protocols were developed to detect chicken egg albumin (as egg whites), bovine casein (as cows’ milk), and soy protein (as soy milk) at levels ≤30 ppb. Field applications showed that all of the proteins were stable and detectable at high levels on apple leaves at least 19 d after application. When adult pear psylla (Cacopsylla pyricola Foerster, Homoptera: Psyllidae) walked across apple leaves with field-aged residues of the marker proteins plus either Sylgard 309, EDTA, or both, they acquired the mark over the 19-d test period an average of 78.9, 19.4, and 2.1% of the time for egg whites, milk, and soy milk, respectively. Two field applications of the three markers were applied to an apple orchard during the first generation flight of codling moth (Cydia pomonella L., Lepidoptera: Tortricidae). We found that 46.5% of moths captured within a 2.8-ha area (including 1.6-ha surrounding the treated areas) tested positive for at least one of the three proteins. The marker systems developed cost between $0.12 and $0.26liter versus older immunomarkers (using purified vertebrate IgG) that cost roughly $500/liter.

(214) Adult Pear Response to Integrated Nitrogen Fertigation and Drip Irrigation System

Responses of adult pear to the integrated N fertigation and drip irrigation system have not been documented in Oregon. A field trial was conducted on adult pear at the Mid-Columbia Agricultural Research and Extension Center, Hood River, Ore., in 2005. Two N and water management systems (integrated N fertigation and drip irrigation system; and broadcast application of dry N fertilizer to the soil surface and microsprinkler irrigation system) were compared on pear cultivars of Bartlett and Golden Russet Bosc, and rootstocks of OH×F97 and OH×F87. The responses of these cultivars and rootstocks to the integrated N fertigation and drip irrigation system were similar. The integrated N fertigation and drip irrigation system consumed 1450 m3·ha-1 of irrigation water during the entire season from May to September, reducing irrigation water use by 73% compared with 5297 m3·ha-1 under the current system—broadcast application of dry N fertilizer to the soil surface and microsprinkler irrigation system averaged over the four cultivar and rootstock combinations. The fruit yield was statistically similar for the integrated N fertigation and drip irrigation system and the broadcast application of dry N fertilizer and microsprinkler irrigation system on the average of the four cultivars and rootstocks. Differences in fruit size and color were negligible between the two N and irrigation management systems. Overall, our results suggest that adopting the integrated N fertigation and drip irrigation system does not cause significant reduction in yield or quality of adult pear; the integrated N fertigation and drip irrigation system could be a profitable and environmentally sound management alternative for pear production.

Quantitative Relationship Between Sticky Trap Catch and Beat Tray Counts of Pear Psylla (Homoptera: Psyllidae): Seasonal, Sex, and Morphotypic Effects

Adult pear psylla, Cacopsylla pyricola (Foerster), were monitored with beat trays, yellow sticky traps, and clear sticky traps for 2 yr at 3 orchards to determine whether a general relationship exists between tray counts and sticky trap catch. Samples were also categorized according to morphotype of the insect (summerform versus winterform), diapause status of winterforms (diapausing versus postdiapause and reproductive), and sex of the insect. Most (42 of 48) of the samples indicated that trap catch varied significantly with tray count (by linear regression analysis). However, aside from the fall winterform generation, no general relationship between trap catch and tray count was noted. Results suggest that sticky trap counts often had a large behavioral or activity component that obscured density effects. These effects were especially noticeable in the spring winterform generation and the summerform generation. Factors affecting sticky trap catch included sex of the insect, reproductive status, trap color, insect age, and leaf fall. We suggest that these factors, as well as others not explored here (e.g., weather), contributed to the lack of a general relationship between tray and trap counts. Previous work indicates that either method predicts damage to the tree; thus, for pest-management decisions, both sampling methods are useful. However, for more precise questions about absolute densities of adults, we suggest that beat trays should be preferred.

INFLUENCE OF SUGAR MAPLE HEALTH ON FECUNDITY OF PEAR THRIPS IN MASSACHUSETTS

AbstractWidespread defoliation of sugar maple stands due to pear thrips,Taeniothrips inconsequens(Uzel), feeding occurred in Massachusetts in 1987 and 1988. To assess the role of tree health as a possible cause of these outbreaks, an experiment was conducted in sugar maple stands in Massachusetts in 1990. Sleeve cages were placed on mature sugar maples and stocked with adult female pear thrips to determine the relation between root starch reserves (an index of tree health) and thrips fecundity. The experiment was run at four sites, assessing both root starch levels and thrips fecundity on individual trees. Each stand showed a range from high to low starch values and trees at each end of the root starch index spectrum were selected for use in the experiment at each site. Analysis of data showed no differences between sites, apart from those linked to starch levels, and found thrips fecundity to be positively correlated with higher starch reserves. The results of this experiment do not support the original hypothesis that declining tree health was a causal factor in pear thrips outbreaks on sugar maple in Massachusetts.

Traps for Monitoring Pear Thrips (Thysanoptera: Thripidae) in Maple Stands and Apple Orchards

The effect of trap color and orientation on capture of adult pear thrips, Taeniothrips inconsequens (Uzel), was tested in Connecticut and Massachusetts. In single degree-of-freedom comparisons, vertically positioned fluorescent yellow rectangles caught the greatest numbers of thrips compared with all other vertically positioned hues tested, but numbers captured on fluorescent yellow did not differ significantly from captures on commercially available yellow, dark red, or white traps. Dark green and dark blue traps were least attractive to adults. In season-long trials of commercially available yellow, red, and white traps alone in apple and maple, yellow traps captured the most thrips. Fluorescent yellow traps in horizontal adhesive-down and 45°-adhesive-down orientations caught significantly fewer adult thrips than cylindrical, vertical, horizontal adhesive-up, or 45° adhesive-up orientations of the same hue. Upward-facing 45° orientations caught significantly more thrips than vertical rectangles of the same hue. Captures on vertical rectangles and on vertical cylinders did not differ significantly. We found that the most practical visual trap to estimate relative density and activity of pear thrips was a commercially available, nonbaited vertical yellow rectangle (16 by 19.5 em).

Effects of temperature during bud burst on pear thrips damage to sugar maple

Sugar maple (Acersaccharum Marsh.) seedlings were exposed to either cool (11.9 °C) or warm (18.2 °C) temperatures in the presence or absence of adult pear thrips (Taeniothripsinconsequens Uzel) during bud burst and early spring growth. Time required for spring stem elongation was shorter at the warm temperature than at the cool temperature. Thrips feeding reduced height, leaf area, and seedling dry weight at both temperatures, and reductions were greater at the cool temperature than at the warm temperature. The results indicate that cool temperatures that slow bud burst promote pear thrips damage to sugar maple leaves.

OVI POSITIONAL ANTIXENOSIS-BASED HOST RESISTANCE TO THE PEAR PSYLLA IN PYRUS GERMPLASM OF EAST EUROPEAN ORIGIN

A collection of 60 genotypes-of pear (Pyrus sp.) from East Europe were assayed for ovipositional antixenosis in no-choice cage tests. Five single plant replicates of each genotype, 'Bartlett' (P. communis L.), a susceptible and NY10352 (P. ussuriensis × P. communis BC1 hybrid)' as a resistant control, were stripped to the 6 youngest, but fully expanded leaves, and enclosed in single-plant cages. Four mating pairs of summer-morph adult pear psylla were introduced into each cage. The number of eggs laid on each plant was counted after 5 days. Egg hatch was determined 7 days later, and leaf area was measured. Twelve genotypes, 8 of which are P. communis, were found to be highly resistant to oviposition. These same genotypes had previously been found to exhibit high levels of nymphal feeding antixenosis and antibiosis. The results will be discussed in light of ovipositional cues and host acceptance-related behavior of the pear psylla.

Laboratory Tests with Insect Growth Regulators on Pear Psylla, 1990

Abstract Winter form adult pear psylla collected from a commercial pear orchard were treated with topical sprays in a Potter Spray Tower. After sprays dried lots of 25 treated adults were caged on seedling pear trees until they deposited 100-300 eggs/seedling. Seedlings with PP eggs were held in a growth room at 22°C, 16L:8D until most eggs on controls had hatched. Seedlings were then examined under magnification and remaining eggs, dead and live nymphs were counted. Percent survival was calculated as (100 × live nymphs/total eggs). There were 5 replications of each treatment on each test date.

Occurrence of Pyrethroid Resistance in Pear Psylla (Homoptera: Psyllidae) Populations from Southern Ontario

Adult pear psylla, Cacopsylla pyricola Foerster, from the Niagara peninsula of Ontario were tested for susceptibility to pyrethroid insecticides from 1980 to 1989. A Potter spray tower was used. Results of tests at IS, 22, and 30°C indicated a negative temperature-toxicity relationship for permethrin and fen vale rate. Resistance to pyrethroids (first discovered in 1986 at levels of approximately 50-fold for permethrin at the LC50) has become widespread in the Niagara region. Resistance extends to all types of pyrethroids but is highest to fenvalerate (approximately 140-fold). Combinations of permethrin and potential synergists piper only but oxide or DEF did not increase the toxicity to resistant populations, suggesting that resistance was due to an insensitive target site or kdr-like mechanism. In one resistant population studied over 4 yr without further selection with pyrethroids, resistance declined from 54-fold to approximately 3D-fold after 1 yr and stabilized at 20-30-fold.

Use of Sticky Traps and Limb Jarring to Aid in Pest Management Decisions for Summer Populations of the Pear Psylla (Homoptera: Psyllidae) in Connecticut

Effectiveness of Lightning Yellow sticky traps for monitoring summer populations of adult pear psylla, Psylla pyricola Foerster, was evaluated at three heights, three orientations, and in four quadrants of pear trees. Traps placed at a height of 1.2 to 1.8 m aboveground in the south quadrant of pear trees were more significantly correlated with pear psylla egg and nymph infestations than other trap positions tested. Vertically positioned traps captured significantly more pear psylla than horizontal traps. Trap captures from all orientations were significantly correlated with egg and nymph infestations. Relationships between trap and limb jarring counts of adults and infestations of eggs and nymphs were determined by regression analyses. Both adult monitoring methods were equally effective in predicting shoot infestations of eggs and nymphs. The action thresholds for either eggs or nymphs were very similar. Based on the nymph data, action thresholds of 4.4 to 6.9 pear psylla per trap per day or 1.0 to 1.2 per limb jar are suggested for adult monitoring.

Natural Control of the Pear Psylla (Homoptera: Psyllidae): Impact of Mating Disruption with the Sex Pheromone for Control of the Codling Moth (Lepidoptera: Tortricidae)

When mating disruption with the sex pheromone was substituted for the standard organophosphorous insecticide program for control of the codling moth, Cydia pomonella (L.), in southern Oregon pear orchards, natural control of the pear psylla was enhanced through increased populations of predators, primarily Demeocorus brevis piceatus Knight and Chrysopa carnea Stephens. In pheromone-treated or untreated control plots, the number of adult pear psylla per tap averaged 1.9 and 2.0, respectively, compared with 11.6 in the plot treated with insecticides for control of the codling moth. Peak adult population levels were greater than 60 per tap in the insecticide-treated plot versus 16 per tap in the plots not treated with insecticide. The levels of immature stages of pear psylla followed the same trends throughout the 2-year study. Direct damage to the fruit, caused by pear psylla honeydew, averaged 1.5, 0.3, and 9.7%, respectively, in the pheromone-treated, untreated control, and insecticide-treated plots.

Visual Trap for Monitoring Pear Psylla (Homoptera: Psyllidae) Adults on Pears 1

Several daylight fluorescent-painted rectangles, 15 by 20 cm, effectively monitored pear psylla adults on pears. Both hue and intensity of reflection appear to be important for eliciting positive response by pear psylla adults to visual traps. The greatest captures occurred for hues with reflection peaks in the 520 to 600-nm range of the spectrum, which is the same range of pear foliage itself. Captures of adult pear psylla on visual traps of most hues or shades were significantly greater than those obtained by standard limb-jarring methods. In addition, captures of pear psylla adults on lightning yellow and arc yellow traps were beller correlated with the occurrence of eggs and nymphs on pear spurs and sooty-mold blemishing on fruits than counts obtained by limb jarring.

Dispersion Statistics and Sequential Sampling Plan for Adult Pear Psylla12

Reported here are dispersion statistics associated with a beating-tray method of sampling and sequential sampling procedures which optimize time spent estimating adult pear psylla densities. Psylla pyricola Foerster adults do not form cohesive groups or colonies such as aphids, but they do show a definite contagious distribution. Beating-tray samples taken during the early growing season, before foliage had developed, were slightly more variable, suggesting they were less efficient in estimating density than those taken after foliage developed. Insecticide applications did not affect the dispersion of pear psylla adults. Calculated stop lines for estimating adult pear psylla densities within 50% of the mean indicate minimum samples of 5, 8, and 12 trays at error levels of P = 0.2, 0.1, and 0.05.

Pear, Evaluation of Several Experimental Insecticid Es in Seasonal Control Programs, 1979

Abstract Tests were carried out in a 2.2-acre pear block at the University of California Deciduous Fruit Field Station in San Jose, California, to compare spray programs with synthetic pyrethroids and an insect growth regulator to standard chemicals and assess their effect on target and nontarget arthropods. Five treatments (including the check) each consisting of three 64-tree (8 × 8) replicates were arranged in a completely randomized design. Three of the 5 treatments were later split to accommodate additional variations in spray programs. Each program consisted of a delayed dormant application followed by a cluster bud spray (oil treatments only) and 2 or 3 cover sprays. Sprays were applied until run-off with a hydraulic handgun sprayer operating at 300 psi. Leaf samples (300/treatment) were taken at ca. 2-wk intervals to record pear psylla eggs and nymphs, spider mites, and phytoseiid predators. Leaves were brushed for rust mites. The limb-tap method was used to assess populations of adult pear psylla and macropredators (60 trays/treatment). Fruit was inspected for codling moth damage at midseason and at harvest (300/treatment) and was rated for russet (75/treatment, at harvest only).

Pear, Pear Psylla Control, 1978

Abstract Experiments were conducted in a 1.5-acre planting of 6-yr-old ‘d-Anjou’ pear trees. Dilute sprays were applied to single-tree plots with a hand gun and hydraulic sprayer operating at 400 psi. Unsprayed trees were alternated with treated trees within rows. Experiment 1 (Table 1) consisted of 6 prebloom treatments, 5 of which were miscible oil-insecticide combinations, applied Apr 18 (budburst) and Apr 25 (clusterbud). Single-tree plots were replicated 6 times in a complete randomized-block design. Effects of the treatments on pear psylla were evaluated by taking 5 spur leaf clusters at random from each plot and examining them with a stereo microscope. The numbers of eggs and nymphs per sample were recorded. Experiment 2 (Table 2) consisted of 4 treatments applied at petal fall (May 19). Single-tree plots were replicated 6 times in a complete randomized-block design. The plots which received prebloom treatments of Perthane + oil and mancozeb on Apr 18 and 25 were also included in this evaluation. May 18 and 24 counts of psylla eggs and nymps again were made by removing 5 spur leaf clusters from each plot and examining them with a stereo microscope. Counts of eggs and nymphs on Jun 6 were made from 10 leaves taken at random from growing terminal shoots of each plot. Adult pear psylla were sampled Jun 7 by counting the number that were jarred from 3 branches/tree onto an 18-inch square cloth-covered tray. Experiment 3: (Cover spray treatments) Fourteen treatments were applied to single-tree plots replicated 5 times each in a complete randomized-block design. Treatmgits were applied Jun 20 (Table 3), Jul 6 (Table 4), and Aug 17 (Table 5), with the exception of the two Pydrin treatments which were not reapplied on Aug 17. Counts of psylla eggs and nymphs were made from 10 leaves collected randomly from 10 shoot terminals/per plot. Adults were again sampled with an 18-inch square beating tray. All data were subjected to analysis of variance and were grouped using the Waller-Duncan K-ratio t test or DMRT.

Longevity, Fecundity, and Fertility of Adult Pear Psylla Chemosterilized with Tepa123

When winterform pear psylla, psylla pyricola Foerster, were reared in the laboratory through diapause and treated with 0.7. 2.1, or 4.6% aqueous solutions of tepa, egg hatch of treated females ranged from 0 to 22% and of untreated females caged with treated males was 0-8%. Longevity and fecundity were adversely affected only by the higher dose. The fecundity of unmated females (treated or untreated) was 3-6 times less than that of mated females (treated or untreated), but the fecundity of untreated females exposed to treated males was usually suppressed less than 50%. Females mated with normal males and then mated with treated males continued to lay fertile eggs. Both sexes showed some recovery from the effects of the chemosterilant 10-17 days posttreatment. Transfer of tepa from treated males to normal females and vice versa was negligible, and any that occurred had no effect on the untreated insects.

Precocity and productivity of propagated apple and pear seedlings as dependent on the juvenile period

Adult apple and pear seedlings varying in juvenile period were propagated on rootstocks. They were subsequently found to be more precocious and more productive when the juvenile period had been shorter. In view of the significant relation between vigour measured by stem diameter) and precocity of both seedlings and propagated trees, it is possible to pre-select for the potentially more precocious seedlings on the basis of vigour.