Comparative evaluation and economic potential of ecorational versus chemical insecticides for crucifer flea beetle (Coleoptera: Chrysomelidae) management in Canola

From 2001 to 2004, field studies were conducted to evaluate the effect of the ecorational insecticides SpinTor (spinosad), BotaniGard (Beauveria bassiana), Neemix (azadirachtin), and Surround (kaolin) against crucifer flea beetle on canola, Brassica napus L., at the cotyledon stage. The ecorational treatments were compared with a standard foliar chemical insecticide, Capture (bifenthrin), and the chemical seed treatment insecticide Helix XTra (thiamethoxam). This study indicated that flea beetle injury was lower for Helix XTra, Capture, and the ecorational insecticide SpinTor. SpinTor was less effective when flea beetle populations were relatively high (200-300 per trap-week). Yields for chemical insecticide treatments were always greater than SpinTor, with differences being the smallest (68-374 kg/ha) at low levels of flea beetle feeding injury. Differences were greatest when canola seedling injury was high (775-1,364 kg/ha). Yield differences between the conventional insecticides and BotaniGard, Neemix, and Surround were 119-439 and 61-2,248 kg/ha at low and high flea beetle feeding injury, respectively. Although yield differences between SpinTor and chemical insecticides were relatively small at lower levels of flea beetle injury, net losses ranged from $47 to $151/ha when SpinTor was used as an alternative to a standard chemical seed treatment, Helix XTra. This suggests that SpinTor would not be a viable alternative to the chemical insecticide. Net losses ranged from $30 to $266/ha when BotaniGard, Neemix, and Surround were used as alternatives to the seed treatment.     

Field tests with insecticides and insect growth regulators to control insect pests of cowpea and its effects on certain beneficial insects

A small‐plot tests were conducted on cowpea, Vigna ungiculata (L.) Walp, to determine the effectiveness of 14 selected insecticides representing four insecticide classes (organophosphates, carbamates, pyrethroids, and insect growth regulators, IGRs), and four insecticide/IGR mixtures on cowpea insect pests and its effects on certain beneficial insects. By day 3 after treatement, the insecticides phenthoate, isoxathion, cyanophos, carbaryl, and cypermethrin used at sub‐recommended rates reduced the leafhopper, Empoasca spp., populations by >83% than those in the control. On that day, all insecticide treatments significantly reduced the cowpea aphid, Aphis craccivora, numbers below that of the control. The prothiofos, isoxathion, pirimicarb, and fenpropathrin treatments provided continuing control to both leafhoppers and aphids through day 21 after spraying. It seems that most insecticide treatments were not effective in whitefly, Bemisia tabaci, control. The best control of the whitefly immatures was obtained by day 3 after spraying in plots received thiodicarb (76%) and fenpropathrin (60%). All selected insecticides and rates used had very low residual effect against B. tabaci immatures. By day 3 posttreatment, the carbaryl (2.02 kg/ha) caused completely protection for cowpea pods frMw blue pea butterfly, Lampides boeticus, larvae. The IGRs, flufenoxuron and Dowco‐439, applied alone and those applied in mixtures with insecticides, carbaryl/teflubenzuron, chlorpyrifos/XRD‐473, and methomyl/ flufenoxuron, exhibited satisfactory control (>81%) to butterfly larvae on day 7 posttreatment. All treatments did not exhibit a considerable residual activity against L. boeticus larvae through 2–3 weeks followed spray. Most insecticides applied at the higher rates used significantly reduced the numbers of limabean pod borer, Etiella zinckenella, larvae found in cowpea pods collected on day 7 after application. The IGRs, flufenoxuron and Dowco‐439, applied alone, at 0.119 kg/ha, or in mixtures, methomyl/flufenoxuron (0.167 kg/ha) and chlorpyrifos/Dowco‐439 (0.911 kg/ha) caused >73% control of E. zinckenella larvae through day 21 posttreatment. The best control of cowpea weevil, Callosobru‐chus spp., adults (>83%), on day 3 after spraying, was obtained in treatments of cyanophos (1.19 kg/ha), prothiofos (1.43 kg/ha), flufenoxuron (0.119 kg/ha), and chlorpyrifos/Dowco‐439 (0.911 kg/ha). The IGR flufenoxuron applied alone or in mixture, methomyl/flufenoxuron (0.164 kg/ ha) exhibited satisfactory residual activity against Callosobruchus adults through day 21 posttreatment. Percentage seed damage by the larvae of cowpea weevils was significantly lower in most treatments than that of control. Populations of insect predators found in all treated plots were extremely reduced than those found in untreated plots. By day 21 after spraying, the IGRs flufenoxuron, XRD‐473, and Dowco‐439, applied at the low rate of 0.071 kg/ha, seemed to be less effect against insect predators than other insecticides used.     

Economic injury level and sequential sampling plan for Bemisia tabaci in outdoor tomato

Abstract:  This work aimed to determine the economic injury levels and to establish sequential sampling plans for nymphs and adults of the whitefly Bemisia tabaci Genn. (Sternorrhyncha: Aleyrodidae) in tomato fields. Densities of nymphs and adults, as well as crop yield were evaluated in 13 commercial tomato fields to determine the economic injury levels. The whitefly nymphs were sampled by direct counting in a leaf from the lower part of the canopy and the adults were sampled by beating an apical leaf against a white plastic tray. The sequential sampling plan was based on data collected in eight commercial tomato fields. The validation of the sequential sampling plan was carried out based on the curves of operational characteristics and average sample numbers. The decisions reached with the conventional and the sequential sampling plans in 21 commercial fields were compared for the intended validation of the sequential plan. The economic injury levels were four nymphs per leaf and one adult per tray. The decisions taken based on the sequential sampling plan were similar to those obtained through the conventional sampling plan. Most of the decisions taken with the sequential sampling plan were obtained through the minimum number of seven samples per field for nymphs and 11 samples per field for adults, with reductions of 84.44% and 54.17% in the number of samples required to reach a decision with the sequential sampling plan compared with the conventional sampling plan.     

Use of a gut content ELISA to detect whitefly predator feeding activity after field exposure to different insecticide treatments

A 2-year commercial-scale study was conducted to qualitatively evaluate the effect of different insecticide treatment regimes on the predator complex attacking Bemisia tabaci (Gennadius) in cotton. In 1996 three insecticide regimes were compared: a rotation of conventional broad-spectrum insecticides or one of two different regimes based on the initial use of the insect growth regulators (IGRs), buprofezin and pyriproxyfen. In 1997 the same three regimes plus an untreated control were compared; split-plots were sprayed once for Lygus hesperus Knight control using a broad-spectrum insecticide. Relative feeding activity for each predator species was compared between treatment regimes by analyzing the gut contents of predators for the presence of whitefly remains using a whitefly-specific enzyme-linked immunosorbent assay (ELISA). The ELISA results were combined with predator density data to obtain a qualitative pesticide impact index for each predator group. In total, we analyzed the gut contents of 32 262 field-collected predators, representing nine different taxa. Of these, Pseudatomocelis seriatus (Reuter), Spanagonicus albofasciatus (Reuter), and spiders consisting primarily of Misumenops celer (Hentz) are shown to be whitefly predators for the first time. Predator populations were usually reduced in plots that received applications of broad-spectrum insecticides for B. tabaci and L. hesperus control, but there were few treatment differences in the proportions of predators containing whitefly remains in their guts. However, the feeding activity of certain predator species in fields sprayed with broad spectrum insecticides was significantly reduced compared with those in IGR-based and control treatments. Overall, insecticide regimes using IGRs were less lethal to the whitefly predator complex than regimes consisting of only conventional, broad-spectrum insecticides, but differences in predator feeding activity on whitefly between the various insecticide treatment regimes were minimal.     

Impact of greenhouse whitefly management on strawberry fruit quality

The greenhouse whitefly, Trialeurodes vaporariorum （Westwood）, is an important pest of strawberries in California, USA. The adults and nymphs feed on phloem sap of leaves to remove the photo-assimilates. The objective of this study is to test the impact of whitefly management with insecticides on strawberry fruit quality. Applications of imidacloprid, thiamethoxam, buprofezin and pyriproxyfen decreased the mean adult whitefly numbers by 2.80-, 2.17-, 1.69- and 1.39-fold, respectively, compared to the untreated control, Similarly, the mean numbers of first and second instar whiteflies were reduced 4.36-, 2.20-, 1.90- and 2.02-fold, respectively, while the mean numbers of third and fourth instars were reduced 5.48-, 2.28-, 2.71- and 1.43-fold, respectively, in plants treated with imidacloprid, thiamethoxam, buprofezin and pyriproxyfen. The mean soluble solids content in imidacloprid, thiamethoxam, buprofezin and pyriproxyfen treatments was 1.04-, 1.06-, 1.03- and 1.04-fold greater, respectively, than that in the control. The whitefly reduction enhanced the mean fruit titratable acidity by 4%-6%. Mean glucose levels in imidacloprid and thiamethoxam treatments were significantly higher than in other treatments. However, the whitefly management did not affect the mean fructose levels, lmidacloprid, thiamethoxam and pyriproxyfen treatments boosted the ascorbic acid levels by up to 4%. The impact of whitefly management on strawberry fruit nutrition and antioxidant capacity is discussed.     

Comparison of management strategies for squash bugs (Hemiptera: Coreidae) in watermelon

Two watermelon pest management practices, a squash trap crop and a standard recommendation using soil-applied carbofuran, were compared using large-scale field plots to assess trap crop suitability as a replacement for the standard in 2000, 2001, and 2002. In both systems, foliar insecticide applications were used to control squash bugs when populations exceeded threshold levels. During 2001 and 2002, a treatment of untreated watermelon was used. Early season adult insects, from seedling to fruit set, are most critical for watermelon. Significantly fewer early adult bugs were found on watermelon in the trap crop than in the standard recommended practice in 1 of 3 yr. In both years, significantly fewer adult squash bugs were found in watermelon in the trap crop than in untreated fields. The standard recommended practice significantly reduced adult squash bugs in watermelon compared with the untreated in 1 of 2 yr. There was no significant correlation of watermelon yield and squash bug density, indicating that squash bug densities were too low to impact yield. Although squash bugs were reduced significantly by the trap crop, marketable watermelon yields were lower in the squash trap crop than in untreated watermelon, suggesting that pest management treatments may interfere with crop productivity factors other than squash bug colonization. Results suggest that mid-season production squash bug should be managed by monitoring populations and using insecticides as needed rather than using at-plant treatment. Further research is needed to compare treatments during early-season production.     

Nematicide Efficacy,Root Growth,and Fruit Yield in Drip-irrigated Pineapple Parasitized by Rotylenchulus reniformis

A 3-year field trial near Kunia, Oahu, Hawaii, was conducted to evaluate four nematicide treatments for efficacy against Rotylenchulus reniformis in drip-irrigated pineapple (Ananas comosus L. (Merr.)). The treatments were (A) preplant fumigation with 1,3-dichloropropene (1,3-D) (336 liter/ ha) and postplant drip application of fenamiphos (3.4 kg/ha) with restricted irrigation, (B) preplant 1,3-D only, weekly irrigation, (C) 1,3-D fenamiphos, weekly irrigation, and (D) postplant fenamiphos only, weekly irrigation. Fenamiphos was applied at 3-month intervals for 1 year after planting in three treatments. Although nematode populations increased in all treatments 1 year after planting, no differences in fruit yield were detected among treatments in the first (plant crop) harvest 19 months after planting. In the second (ratoon) crop (33 months after planting) significant yield differences, larger fruit size, and greater root biomass were obtained in the dual nematicide treatments. Root biomass increased continuously throughout the crop cycle, was greatest near the drip line, and showed a shallow depth distribution (30-40 cm). Rotylenchulus reniformis populations and fenamiphos concentrations were negatively correlated in soil profiles taken 13 months after planting. In the absence of postplant fenamiphos applications, nematode numbers were positively correlated with root biomass.     

Management of Meloidogyne incognita with Chemicals and Cultivars in Cotton in a Semi-Arid Environment

Management of Meloidogyne incognita (root-knot nematode) in cotton in the United States was substantially affected by the decision to stop production of aldicarb by its principle manufacturer in 2011. The remaining commercially available tools to manage M. incognita included soil fumigation, nematicide seed treatments, postemergence nematicide application, and cultivars partially resistant to M. incognita. Small plot field studies were conducted on a total of nine sites from 2011–2013 to examine the effects of each of these tools alone or in combinations, on early season galling, late-season nematode density in soil, yield, and value ($/ha = lint value minus chemical costs/ha). The use of a partially resistant cultivar resulted in fewer galls/root system at 35 d after planting in eight of nine tests, lower root-knot nematode density late in the growing season for all test sites, higher lint yield in eight of nine sites, and higher value/ha in six of nine sites. Galls per root were reduced by aldicarb in three of nine sites and by 1,3-dichloropropene (1,3-D) in two of eight sites, relative to the nontreated control (no insecticide or nematicide treatment). Soil fumigation reduced M. incognita density late in the season in three of nine sites. Value/ha was not affected by chemical treatment in four of nine sites, but there was a cultivar × chemical interaction in four of nine sites. When value/ha was affected by chemical treatment, the nontreated control had a similar value to the treatment with the highest value/ha in seven of eight cultivar-site combinations. The next “best” value/ha were associated with seed treatment insecticide (STI) + oxamyl and aldicarb (similar value to the highest value/ha in six of eight cultivar-site combinations). The lowest valued treatment was STI + 1,3-D. In a semi-arid region, where rainfall was low during the spring for all three years, cultivars with partial resistance to M. incognita was the most profitable method of managing root-knot nematode in cotton.     

Effects of Application Strategies of Fumigant and Nonfumigant Nematicides on Cantaloupe Grown in Deep Sand Soils in Florida

A 2-year study was conducted in which three treatment tactics of oxamyl (at planting application, application every 2 weeks, and rescue applications, as determined by crop symptoms) were compared to fumigant treatments with methyl bromide, 1,3-dichloropropene (1,3-D), and 1,3-D plus chloropicrin for management of Meloidogyne spp. In 2002, treatments that included 1,3-D produced higher yields as determined both by number and weight of marketable fruit. All treatment tactics relying solely on oxamyl, at planting, scheduled treatments, and rescue, were not different from untreated controls for both marketable yield and number of fruit. Gall ratings in 2002 were lowest for 1,3-D at the 112-liters/ha rate, followed by 1,3-D at 84 liters/ha with and without oxamyl. All treatments of oxamyl, except when combined with 1,3-D, had gall ratings not different from untreated plots. In 2004, treatments of methyl bromide and 1,3-D plus chloropicrin had the highest total number of both marketable fruit and highest marketable yields. All treatment strategies relying solely on oxamyl had yields equivalent to the untreated controls. Mean root-gall ratings were lowest for methyl bromide plus chloropicrin and 1,3-D plus chloropicrin treatments. Root-gall ratings for all treatment tactics relying solely on oxamyl were not different from untreated controls.     

Contextualising pollination benefits: effect of insecticide and fungicide use on fruit set and weight from bee pollination in lowbush blueberry

Current approaches to determining the value of insect pollinators to crop yield assume that plants are primarily pollen limited. This is particularly relevant in a crop such as lowbush blueberry, Vaccinium angustifolium, where no fruit will set without insect‐mediated cross‐pollination. However, such valuations usually ignore other factors that are necessary to maximise crop yields. We conducted an experiment to test whether yields of lowbush blueberry attributed to pollinator activity increased independently of pest management. The experiment was a 2 × 2 factorial design, incorporating two intensities of pollination (25% or 100% of flowers), and two levels of insect and disease management with recommended fungicide and insecticide sprays (‘full inputs’ or ‘no inputs’). We demonstrated an interaction between these two factors, such that increased fruit set at harvest was only possible if 100% pollination was combined with the ‘full input’ treatment. Furthermore, increases in fruit weight among the remaining treatments were only realised in the ‘full input’ plots. These results suggest that the value accorded to pollinator activity in blueberries is strongly dependent upon pest and disease management of the crop.     

Female sex pheromone of brinjal fruit and shoot borer,Leucinodes orbonalis (Lepidoptera: Pyralidae): trap optimization and application in IPM trials

Delta and wing traps baited with synthetic female sex pheromone of Leucinodes orbonalis Guenée were found to catch and retain ten times more moths than either Spodoptera or uni-trap designs. Locally-produced water and funnel traps were as effective as delta traps, although 'windows' cut in the side panels of delta traps significantly increased trap catch from 0.4 to 2.3 moths per trap per night. Trap catch was found to be proportional to the radius of sticky disc traps in the range 5-20 cm radius, discs with a 2.5 cm radius caught no moths. Wing traps placed at crop height caught significantly more moths than traps placed 0.5 m above or below the crop canopy. Replicated integrated pest management (IPM) trials (3 x 0.5 ha per treatment) were conducted in farmers fields with young and mature eggplant crops. Farmers applied insecticides at least three times a week in all check and IPM plots. In addition pheromone traps were placed out at a density of 100 per ha and infested shoots removed weekly in the 0.5 ha IPM plots. Pheromone trap catches were reduced significantly from 2.0 to 0.4 moths per trap per night respectively in check and IPM plots in a young crop and 1.1 to 0.3 moths per trap per night in check and IPM plots respectively in a mature crop. Fruit damage was significantly reduced from an average of 41.8% and 51.2% in check plots of young and mature crops respectively to 22% and 26.4 respectively in the associated IPM plots. Significant differences in pheromone trap catches and fruit damage were attained four and two weeks respectively after IPM treatments began in the mature crop whereas in the immature crop significant differences were not observed for the first eight to nine weeks respectively. The relative impact of removing infested shoots and mass trapping on L. orbonalis larval populations was not established in these trials but in both cases there was an estimated increase of approximately 50% in marketable fruit obtained by the combination of control techniques compared to insecticide treatment alone.     

Vegetative and reproductive responses,oil yield and composition from olive trees (Olea europaea) under contrasting water availability during the dry winter‐spring period in central Argentina

In Argentina, the climatic pattern of the olive production areas is characterised by a marked water deficit during winter and spring months. A field experiment was carried out to evaluate the effect of water availability during the pre‐flowering–flowering period on vegetative, reproductive and yield responses of olive trees grown in central Argentina. From the end of autumn to mid‐spring, four irrigation treatments were imposed to olive trees (Olea europaea, cv. Arbequina and Manzanilla) at 0, 25, 50 and 75% estimated crop evapotranspiration (ETc). Also, a control treatment was kept at 100% ETc for the entire year. For the first crop year evaluated, water deficit applied at early June, approximately 4 months prior to bloom, reduced the vegetative shoot growth and delayed the flowering time, resulting in shortening of the fruit maturation period and, ultimately, decreased fructification. Trees irrigated with high (75% of ETc) and full (100% of ETc) winter‐spring water supply presented significantly higher values of flower density, fruit density and final fruit yield which resulted in water productivity (kg fruits mm^?1 of irrigation/ha) enhancements of about 500% (cv. Arbequina) and 330% (cv. Manzanilla) with respect to those obtained from the corresponding unirrigated treatments. Differences between treatments in oil content and composition were primarily attributed to variations in fruit maturity. Differences in fatty acid composition were stronger in cv. Arbequina where a gradual increase in oleic acid content was registered in parallel to the increase in irrigation water supply. From a practical stand point, results obtained from most of the analysed parameters were quite similar for both T75 and T100 treatments. Thus, the possible convenience of irrigation at T75% ETc should be considered since it may warrant profitable olive production while saving a considerably quantity of irrigation water in the olive production area in central Argentina.     

Reduction of sooty mold damage through biocontrol of the greenhouse whitefly <Emphasis Type="Italic">Trialeurodes vaporariorum</Emphasis> (Hemiptera: Aleyrodidae) using selective insecticides in tomato cultivation greenhouses

The proliferation of sooty mold on tomato fruit, Solanum lycopersicum L.—as caused by the secretion of honeydew on the fruit by greenhouse whitefly, Trialeurodes vaporariorum (Westwood) (Hemiptera: Aleyrodidae)—has recently become a serious problem in estivo-autumnal greenhouse tomato cultivation in Japan. It is becoming increasingly difficult to control T. vaporariorum using insecticides because whiteflies have developed resistance to a variety of insecticides. As the first step towards integrated pest management, we examined whether the use of selective insecticides could prompt a cascade process in which an increase in parasitoids is followed by a decrease in whitefly occurrence and then a reduction in sooty mold damage. We compared greenhouses in which nonselective insecticides effective against T. vaporariorum and its parasitoids were used (hereafter denoted “nonselective insecticide greenhouses”) with greenhouses in which selective insecticides for T. vaporariorum were used (hereafter denoted “selective insecticide greenhouses”) in terms of the density and level of parasitism of T. vaporariorum as well as the degree of damage from sooty mold. The number of parasitized whiteflies increased with the number of whiteflies in the selective insecticide greenhouses, whereas it remained at low levels regardless of the number of whiteflies in the nonselective insecticide greenhouses. Furthermore, the selective insecticide greenhouses showed significantly higher parasitism levels, fewer whiteflies, and reduced sooty mold damage compared to the nonselective insecticide greenhouses. These results suggest that the use of selective insecticides causes an increase in parasitism, which in turn suppresses the number of greenhouse whiteflies and, eventually, sooty mold.     

Relative Efficacy of Some Insecticides Against Brinjal Fruit and Shoot Borer,Leucinodes orbonalis Guen., and Their Impact on Fruit Yield

Six insecticides and their eight combinations were tested for their efficacy against brinjal fruit and shoot borer, Leucinodes orbonalis. Endosulfan + deltamethrin (0.07%, 0.0025%) and endosulfan + fenvalerate (0.07% + 0.005%) were highly effective against fruit borer that recorded only 13.3% damage as compared to 69.8% in control. The other promising treatments which significantly reduced the fruit damage over the control were in the order: carbaryl + fenvalerate = dichlorvos + fenvalerate (14.9%) > malathion + fenvalerate (16.4%) > fenvalerate + deltamethrin (16.6%) > dichlorvos = carbaryl + deltamethrin = malathion = dichlorvos + deltamethrin = malathion + deltamethrin (18.3%) > endosulfan (20.0%) > carbaryl (21.6%) with mean percentage of damage 14.9, 16.4, 18.3, 20.0, 21.6 and 69.8%, respectively. Carbaryl was least effective, but its combinations with pyrethroids were proved superior over carbaryl alone. Cost - benefit ratio ranged from a minimum of 1: 5.10 (carbaryl) to a maximum of 1: 20.44 (fenvalerate). Dichlorvos + fenvalerate combination gave the highest yield of 263.45 q/ha, whereas carbaryl was least effective giving 225.7 q/ha. with a net gain of Rupees 42,443.00 (US$ 886.00) and 28,141.00 (US$ 587.49), respectively. The other treatments were intermediate between the two insecticide regimes. However, all the treatments were superior over the control which produced 113.58 q/ha with a net gain of Rupees 340.00 only.     

Tactics for management of thrips (Thysanoptera: Thripidae) and tomato spotted wilt virus in tomato

Four studies were conducted in Georgia during spring 1999, 2000, 2001, and 2002 to evaluate various management tactics for reducing thrips and thrips-vectored tomato spotted wilt virus (TSWV) in tomato and their interactions relative to fruit yield. Populations of thrips vectors of TSWV, Frankliniella occidentalis (Pergande) and Frankliniella fusca (Hinds), were determined using flower and sticky trap samples. The management practices evaluated were host plant resistance, insecticide treatments, and silver or metallic reflective mulch. Averaged over all tests, the TSWV-resistant tomato 'BHN444' on silver mulch treatment had the largest effect in terms of reducing thrips and spotted wilt and increasing marketable yield. Of the insecticide treatments tested, the imidacloprid soil treatment followed by early applications of a thrips-effective foliar insecticide treatment provided significant increase in yield over other treatments. Tomato yield was negatively correlated with the number of F. fusca and percentage of TSWV incidence. F. occidentalis per blossom was positively correlated with percentage of TSWV incidence, but not with yield. No significant interactions were observed between cultivar reflective mulch main plot treatments and insecticide subplot treatments; thus, treatment seemed to be additive in reducing the economic impact of thrips-vectored TSWV. Control tactics that manage thrips early in the growing season significantly increased tomato yield in years when the incidence of TSWV was high (>17%).     

Pyriproxyfen controls silverleaf whitefly, Bemisia tabaci (Gennadius), biotype B (Homoptera: Aleyrodidae) (SLW) better than buprofezin in bitter melons Momordica charantia L. (Cucurbitaceae)

To improve compatibility between chemical and biological controls, the use of selective insecticides such as insect growth regulators (IGRs) is crucial. In cucurbits, the use of pyriproxyfen (an IGR) has been shown by others to be an effective method of reducing the number of sap-sucking insects, especially silverleaf whitefly, Bemisia tabaci (Gennadius) Biotype B (SLW). Therefore, we compared pyriproxyfen and buprofezin (an IGR) with that of no treatment (control) in a bitter melon crop for the control of populations of SLW and for their effects on fruit production. Pyriproxyfen controlled SLW and tended to have heavier fruits than the control treatment and reduced the abundance of nymphs and exuvia. Buprofezin showed no evidence in controlling SLW compared with the pyriproxyfen and control treatments. Neither pyriproxyfen nor buprofezin had any effect on the number of harvested fruit or overall fruit yield, but the average weight per fruit was higher than the control treatment. Pyriproxyfen was effective in controlling whitefly populations in bitter melons, and both pyriproxyfen and buprofezin may have the potential to increase yield. Their longer-term use may increase predation by natural enemies as they are species-specific and could favour build up of natural enemies of SLW. Thus, the judicious use of pyriproxyfen may provide an effective alternative to broad-spectrum insecticides in small-scale cucurbit production.     

Threecornered alfalfa hopper (Hemiptera: Membracidae): seasonal occurrence, girdle distribution, and response to insecticide treatment on peanut in South Carolina

A survey of threecornered alfalfa hopper, Spissistilus festinus (Say) (Hemiptera: Membracidae), damage in 60 South Carolina peanut, Arachis hypogaea L., fields showed that 89 and 58% of plants had feeding girdles during 2003 and 2004, respectively. Use of a foliar insecticide for other target pests reduced hopper damage. Hopper damage was not affected by sampling distance from the field edge; therefore, injury was adequately assessed at 10 m from field borders. In-furrow insecticide choice, planting date, soil texture, previous crop, or tillage did not measurably affect girdling. Subsequent field experiments demonstrated a cultivar effect on threecornered alfalfa hopper injury, with the standard runner-type cultivar ('Georgia Green') more susceptible than the standard Virginia-type ('NC-V11'). More than 50% of stem girdling occurred on the basal quarter (first five internodes) of the plant. Most feeding occurred on secondary branches of main and lateral stems. Weekly sampling of seven grower fields showed that adult hoppers colonize peanut during June and produce two generations on peanut. Only low levels of plant girding were observed in June, but plant girdling increased gradually through late July, when girdling markedly increased contemporary with peak populations of first generation nymphs and adults. A second increase in plant girdling, observed in early September, coincided with the second generation of nymphs on peanut. Foliar treatments at 45- 60 d after planting (DAP) were most effective in suppressing injury. Granular chlorpyrifos treatment also suppressed hopper injury. There was no yield response to insecticide treatments at the hopper injury levels in these tests (up to six girdles per plant). Although the economic injury level (EIL) for this pest has not been defined, our data indicate that a critical interval for monitoring hopper activity is the first 3 wk of July, before the occurrence of significant injury. Where growers have a consistent risk of economic injury, applying foliar treatment in mid-July would be most effective in suppressing damage.     

Economic injury levels for western flower thrips (Thysanoptera: Thripidae) on greenhouse cucumber

Low, medium and high densities of western flower thrips, Frankliniella occidentalis (Pergande), were established in three greenhouses at the Greenhouse and Processing Crops Research Centre, Ontario, Canada, in 1996 and 1998 to develop economic injury levels for thrips on greenhouse cucumber. Thrips densities were monitored weekly using yellow sticky traps and flower counts. Fruit was harvested twice a week, graded for size, weighed, and rated for thrips damage using three damage categories. Significant yield reduction was detected 4 wk after severe fruit damage was observed in the high and medium thrips density treatments in 1996 and 7 wk in 1998. Percentage of severe damaged fruit (P(F3)) has significant linear relationships with the adult thrips density (x) that was sampled by sticky traps 1 wk before harvest (P(F3) = -0.2533 + 0.0828x) and that was sampled by flower counts 2 wk before harvest (P(F3) = -0.2025 + 0.5490x). Based on the regression equations, economic injury levels, expressed as adult thrips per sticky trap per day or adult thrips per flower, were calculated for various combinations of control costs, yield potential and fruit prices. The economic injury levels for F. occidentalis ranged from 20 to 50 adults per sticky trap per day or 3 to 7.5 per flower as determined under average greenhouse production conditions in Ontario, Canada.     

Fruit Yield,not DBH or Fruit Crown Volume,Correlates with Time Spent Feeding on Fruits by Wild Leontopithecus rosalia

Assessing fruit availability is a critical element in testing hypotheses concerning resource use by frugivores. One method to estimate fruit availability is to measure tree diameter at breast height (DBH) and assume a positive correlation with fruit tree productivity. Our first objective was to test the relationship between DBH and tree productivity. We used as our measures of tree productivity: volume of the fruit bearing region of the tree crown (FBRv) and fruit yield measured as grams of dry fruit matter per fruit bearing region (FBR). Our second objective was to determine if time spent feeding on fruits by golden lion tamarins was correlated with 3 measures of tree productivity within their territories. We define tree productivity within a territory as tree productivity × tree density (fruit tree productivity/ha). We used as our measures of tree productivity/ha: (1) DBH × tree density, (2) fruit yield × tree density, and (3) FBRv × tree density. We measured DBH and FBRv for 17 fruit species commonly eaten by golden lion tamarins in Poço das Antas Reserve, Brazil. We counted fruits in trees and collected fruits to calculate fruit yield. We used measures of tree densities to calculate tree productivity/ha. We found that DBH correlated with fruit yield. The time tamarins spent feeding did not correlate with DBH ( × tree density) or FBRv ( × tree density), but it correlated with fruit yield ( × tree density). Our results emphasize the importance of recording temporal and spatial measures of fruit productivity that are meaningful to the frugivore studied.     

Corn Residue Supply in the Irrigated Corn Belt

The present study quantifies the profit-maximizing supply of corn stover per unit of land under alternative crop rotations in irrigated cropland with and without limits to irrigation. The model is parameterized based on growing conditions in Nebraska, USA. Our analysis quantifies a trilemma between stover supply, groundwater consumption, and food/feed supply per unit of land. In the absence of water conservation policies, higher stover prices are associated with higher supply and increased irrigation application. If an upper limit is imposed on irrigation at the baseline level (for groundwater conservation purposes), an increase in net revenue from stover sale from $15 to $25/metric ton is associated with an increase in stover supply of 5 metric tons/ha and a 2-metric ton reduction in corn yield under continuous corn. Under corn/soybean rotation, such an increase in net revenue is associated with an increase in stover supply of 10 metric tons/ha, and reductions of 0.5 metric tons in corn yield and 0.7 metric tons in soybean yield.