Evaluation of seed treatment insecticides for management of the rice water weevil,Lissorhoptrus oryzophilus Kuschel (Coleoptera: Curculionidae), in commercial rice fields in Louisiana

The rice water weevil, Lissorhoptrus oryzophilus Kuschel (Coleoptera: Curculionidae), is the most injurious insect pest in US rice production. Yield losses in excess of 25% can occur from severe infestations. Management demonstrations were conducted in the 2008, 2009, 2010, and 2011 growing seasons to evaluate the use of commercially available insecticides to control L. oryzophilus in commercial rice fields. The demonstration tests, conducted on farms throughout Louisiana, compared the efficacies of recently registered seed treatment insecticides to untreated controls and to foliar applications of pyrethroids. Efficacy was assessed by collecting root/soil core samples three to four weeks after application of permanent flood and counting numbers of larvae and pupae in core samples. Tests were replicated across locations in multiple rice-producing Louisiana parishes. Densities of larvae and pupae in core samples exceeded the larval threshold (three larvae or pupae per core sample) in over 80% of untreated plots/cuts, confirming the ubiquity and severity of this insect as a pest of rice. Use of chlorantraniliprole (Dermacor^® X-100, DuPont™ Crop Protection, Wilmington, DE), thiamethoxam (CruiserMaxx^® Rice, Syngenta^® Crop Protection, Greensboro, NC), and clothianidin (NipsIt Inside^®, Valent^® USA Corporation, Walnut Creek, CA) seed treatments significantly reduced L. oryzophilus infestation compared to untreated checks. Fewer larvae and pupae were observed in rice treated with chlorantraniliprole than in rice treated with other insecticides.     

Comparative bioactivity of selected seed extracts from Brazilian Annona species and an acetogenin-based commercial bioinsecticide against Trichoplusia ni and Myzus persicae

The acute and chronic toxicity of ethanolic seed extracts from selected Brazilian Annona species (Annona montana Macfadyen, Annona mucosa Jacquin, Annona muricata Linnaeus, and Annona sylvatica A. St.-Hil) and an acetogenin-based commercial bioinsecticide (Anosom^®) were investigated against the cabbage looper Trichoplusia ni Hübner (Lepidoptera: Noctuidae) and the green peach aphid Myzus persicae (Sulzer) (Hemiptera: Aphididae). In the laboratory, extracts of A. mucosa and A. sylvatica as well as Anosom^® were especially active through oral and topical administration. A greenhouse trial showed that a formulated A. mucosa extract and Anosom^® were highly effective (>98% mortality) against third instar T. ni larvae, and comparable to a pyrethrin-based commercial insecticide (Insect Spray^®) used as a positive control. Similar to results with T. ni, A. mucosa extract showed the greatest aphicidal activity followed by A. sylvatica extract and Anosom^®. In another greenhouse trial, aphid population reduction from the formulated A. mucosa extract was superior to that provided by other treatments including the positive control. Though inferior to the A. mucosa extract, the acetogenin-based commercial insecticide (Anosom^®) and A. sylvatica extract also reduced aphid populations in a manner comparable to the positive control. Botanical insecticides based on these Annonaceae derivatives could be useful in the framework of Brassica IPM in Brazil and elsewhere, especially for organic production.     

Insecticide control of the potato tuberworm in late-crop potato foliage

The systemic insecticides, Dasanit^®, carbofuran (Furadan^®), phorate (Thimet^®), aldicarb (Temik^®) and disulfoton (Di-Syston^®) were applied in the planting furrow at 2–3 lb actual/acre for potato tuberworm (Phthorimaea operculella (Zeller)) control in Irish potato foliage. None of these compounds gave entirely satisfactory results. Dasanit was the best with slightly over 80% decrease in the number of mines and was followed closely by carbofuran; all treatments needed to be supplemented by foliage sprays for satisfactory tuberworm protection. Azinphosmethyl (Guthion^®) gave consistently outstanding results as a foliage spray at 0.5 lb/acre with over 99% tuberworm reduction. Other foliar-applied insecticides giving at least 98% tuberworm control included: Monitor^®, monocrotophos (Azodrin^®), phosphamidon, Orthene^®, Torak^®, methomyl (Lannate^®) and Dursban^® (all at 0.5 lb/acre) and Phosvel^® (1 lb/acre).     

Use of fluorescence to determine reduction in Bemisia tabaci (Hemiptera: Aleyrodidae) nymph feeding when exposed to cyantraniliprole and imidacloprid through systemic applications

The Bemisia tabaci whitefly is an important pest of many agricultural crops. Direct feeding by this pest can cause physiological plant symptoms including irregular ripening in tomatoes and silverleaf disorder in squash. In addition, B. tabaci can transmit more than 100 plant viruses that cause severe diseases that affect crop yield and quality. Insecticides are often applied to control this pest and they may be applied to the foliage and/or to the soil. Insecticides that kill quickly or cause feeding cessation reduce the damage caused by B. tabaci on the host plant most effectively. In this study fluorescence was used to assess B. tabaci feeding and to determine the effect of systemically applied insecticides on feeding by the pest. Cyantraniliprole (Verimark™) and imidacloprid (AdmirePro^®) produced a rapid reduction in B. tabaci feeding. At 24 h after a systemic application, the percentage of whitefly nymphs still feeding in plants treated with cyantraniliprole (anthranilic diamide) and imidacloprid (neonicotinoid) were 19% and 33%, respectively. Both products showed a good reduction in insect feeding and since they have different modes of action they should be considered as rotational partners for B. tabaci control in areas where there is no resistance to neonicotinoid insecticides. While the fluorescein sodium salt cannot be used to trace the uptake of insecticides, it has been shown to reliably demonstrate feeding cessation of whitefly nymphs after foliar and systemic applications of insecticides.     

Larval survival and plant injury of Cry1F-susceptible, -resistant,and -heterozygous fall armyworm (Lepidoptera: Noctuidae) on non-Bt and Bt corn containing single or pyramided genes

The fall armyworm, Spodoptera frugiperda (J.E. Smith), is a major target of transgenic corn, Zea mays L., expressing Bacillus thuringiensis (Bt) proteins in both North and South America. A highly Cry1F-resistant strain of S. frugiperda was established from a field collection in Puerto Rico in 2011. In this study, three greenhouse trials were conducted to evaluate larval survival and leaf injury of Cry1F-susceptible, -resistant, and -heterozygous genotypes of S. frugiperda on whole plants of five non-Bt and eight Bt corn hybrids. The Bt corn products included two single-gene Bt corn hybrids containing Herculex^®I (Cry1F) and YieldGard^® (Cry1Ab) traits and six pyramided Bt corn hybrids representing four traits: Genuity^® VT Double Pro™, Genuity^®VT Triple Pro™, Genuity^® SmartStax™, and Agrisure^® Viptera™ 3111. In each trial, neonates of S. frugiperda were placed into the plant whorls at vegetative plant stages (V6–V10). Larvae of the three insect genotypes on non-Bt corn hybrids survived well and caused serious plant injury. Cry1Ab corn was ineffective against all three insect genotypes. On Cry1F corn plants, resistant larvae survived on 72.9% plants after 12–15 d and caused a leaf injury rating (Davis' 1 to 9 scales) of 5.7 after 7 d and 7.6 after 12–15 d. Both the larval survivorship and leaf injury rates of the resistant larvae on Cry1F corn plants were not significantly different from those observed on non-Bt corn hybrids. In contrast, no live larvae and little or no leaf injury were observed on the Cry1F corn plants that were infested with susceptible or heterozygous genotypes, or on the pyramided Bt plants. The results demonstrated that the Cry1F-resistant S. frugiperda was highly resistant to whole plants of Cry1F corn and the resistance was recessive. Hybrids that contained one of the four pyramided Bt traits were effective for managing the Cry1F resistance in S. frugiperda.     

Control of cotton bollworms with fenvalerate in India

The synthetic pyrethroid fenvalerate (Sumicidin^® 20E¹) has been tested in 64 field trials of the control of bollworms on rainfed and irrigated cotton in Maharashtra, Tamil Nadu, Punjab, Andhra Pradesh, Haryana, Rajasthan, Madhya Pradesh, Gujarat and Karnataka. Fenvalerate, at dose levels of 50–150 g a.i./ha, was tested on 15 varieties of cotton, with long, extra-long, short and medium staples. From two to nine sprays were applied at intervals of 7–30 days, depending on whether the insecticide was sprayed according to a calendar-based schedule or when needed. Fenvalerate was compared with conventional insecticides such as carbaryl, monocrotophos, endosulfan and phosalone, and also with the synthetic pyrethroids permethrin, cypermethrin and deltamethrin. The percentage of bollworm-infested plants in the fenvalerate-treated plots ranged from zero to 21·8% and in the untreated plots was up to 100%. With conventional pesticides the maximum level of infestation was 97·2%. Increases in yield of seed cotton from fenvalerate-treated plots over those from plots treated with conventional pesticides were 54%, 57%, 67%, 84%, and 86% over monocrotophos, carbaryl, quinalphos, phosalone and endosulfan, respectively, representing increases of 791–1046 kg/ha.     

Evaluation of chemical disinfestants in reducing Verticillium dahliae conidia in irrigation water

Irrigation water disinfestation is an unexplored option for reducing Verticillium dahliae inoculum in water and consequently for more efficiently managing Verticillium wilts in Andalusia. We assessed Suppressive Efficacy (SE; water was infested and subsequently treated) and Preventive Efficacy (PE; previously treated water was subsequently inoculated) of OX-VIRIN^®, OX-AGUA AL 25^® and Deccoklor^® in reducing water infestations by V. dahliae conidia. Five concentrations of each disinfestant, the lowest three being recommended by the manufacturer, were tested in vitro against six V. dahliae isolates. Validation assays were carried out in experiments under natural environmental conditions in spring. The four highest concentrations of OX-VIRIN^® (0.8–51.2 mL L⁻¹), the three highest of OX-AGUA AL 25^® (46.4–417.5 μL L⁻¹) and the two highest of Deccoklor^® (0.375 and 3.75 mL L⁻¹), showed an in vitro-efficacy (SE and PE) of 96.2, 80.0 and 100.0% after 30, 5 to 30 and 15 days respectively. Therefore, recommended concentrations for OX-VIRIN^® and OX-AGUA AL 25^® showed a greater in vitro-effectiveness than those recommended for Deccoklor^®. Assays in natural environmental conditions proved that OX-VIRIN^® at the recommended concentration of 3.2-mL L⁻¹, applied every 28 days to water, was the most effective treatment (SE and PE), with a 100% reduction of the average relative viability after 56 days. Other chemical treatments showing high in vitro-efficacy, such as OX-VIRIN^® at 0.8 mL L⁻¹ and OX-AGUA AL 25^® at 46.4 μL L⁻¹ showed an SE of 99.9% after 14 and 28 days when applied every 28 and 14 days, respectively. However, PE of OX-AGUA AL 25^® at 46.4 μL L⁻¹ was only 59 and 38% after 28 and 14 days respectively, depending on the experiment.     

Evaluation of adjuvants for enhanced management of Podosphaera xanthii using potassium silicate and biocontrol agents

Three adjuvants [polyether-polymethylsiloxane-copolymer (Break-Thru^®), alkoxylated fatty alkylamine polymer/ethoxylated sorbitane ester (Partner 650^®) and polyoxyethylene 20 sorbitan monooleate (Tween-80^®)] were compared for their ability to improve the efficacy of potassium silicate and biocontrol agents (BCAs) against powdery mildew of zucchini caused by Podosphaera xanthii (Castagne) U. Braun & Shishkoff. The most effective adjuvant was investigated for its direct impact on the pathogen and deposition of BCAs using electron microscopy and its compatibility with the BCAs and zucchini plant was evaluated to establish an integrated management of powdery mildew. Furthermore, effects of Si spray in accumulation of Si and K in the leaves were measured. Break-Thru^® and Partner 650^® improved the efficacy of silicate by 18–35%. The best adjuvant, Break-Thru^®, caused a collapse and degeneration of the conidia and hyphae of the pathogen, restricted growth and spread of the powdery mildew colonies by binding its propagative structures, and improved deposition of BCAs on the leaf surface and the fungus. Break-Thru^® was compatible with the plant and the BCAs at concentrations <0.4 ml l⁻¹, and can be used with selected BCAs and SiO₂ for an integrated management of powdery mildew. SiO₂ applied as a foliar spray increased the level of Si in zucchini leaves, which may contribute to systemic resistance of the plant against the disease.     

Insecticides for control of potato tuberworm and green peach aphid on potatoes in California

Six insecticides were evaluated in a replicated field experiment at Gonzales, California, for control of the potato tuberworm,Phthorimaea operculella (Zeller), and the green peach aphid,Myzus persicae (Sulzer). Azodrin^®, methomyl, Stauffer N 4543 (O-isobutyl ethylphosphonodithioate S-ester with N-(mercaptomethyl) phthalimide) and azinphosmethyl were applied as foliage sprays by ground sprayer at 2-week intervals. The systemic insecticides, aldicarb (Temik^®) and carbofuran (Furadan^®) formulated as 10% granules, were applied to the soil as side dress treatments on the same day that the spray treatments were begun. Aldicarb granules were also applied topically so that the granules fell on the young plants and on the soil surface. Azinphosmethyl, Stauffer N 4543, Azodrin^® and methomyl effectively controlled the tuberworm larvae in the foliage but effective control of tuberworms in the harvested tubers occurred only where azinphosmethyl, methomyl and Stauffer N 4543 were used. The granule applications of carbofuran and aldicarb were totally ineffective in controlling the potato tuberworm. Effective green peach aphid control was obtained with Azodrin^® spray and the two granular aldicarb treatments. The side dressed application of aldicarb appeared to provide better green peach aphid control than did the soil surface application.     

Bioactivity of Six Plant Extracts on Adults of Demotispa neivai (Coleoptera: Chrysomelidae)

Demotispa neivai Bondar (Coleoptera: Chrysomelidae) damage oil palm fruits, which makes it necessary to develop products to control this insect. The mortality, repellency, and antifeeding effects on adults of D. neivai of six plant extracts of Azadirachta indica A. Juss. (Sapindales: Meliaceae), Ricinus communis (L.) (Malpighiaes: Euphorbiaceae), Citrus sinensis Oesbek (Sapindales: Rutaceae), Nicotiana tabacum (L.) (Slanales: Solanaceae), Capsicum annuum (L.) (Solanales: Solanaceae), and Artemisia absinthium (L.) (Asterales: Asteraceae) were determined: 1) the lethal concentration LC_50-90, lethal time of D. neivai was evaluated after spraying the fruits of oil palm; 2) repellent effects of each ingredient were evaluated by calculating the index of repellency; 3) antifeeding effects with the rate of inhibition calculated between doses of 20 and 24 g/liter. The mortality of D. neivai was higher with the extracts Ci. sinensis, R. communis, N. tabacum, and Ca. annuum. The mortality of D. neivai increased in the first 72 hr in all treatments. The extracts of N. tabacum, Ca. annuum, and A. indica were more repellent to D. neivai that those of Ci. sinensis, Ar. Absinthium, and R. communis. Antifeeding effect was higher with Ci. sinensis and R. communis. The increased mortality of D. neivai by Ci. sinensis can be explained by the effect of this compound on the respiratory system of insects. Extracts of Ci. sinensis, R. communis, N. tabacum, and Ca. annuum repelled and caused mortality of D. neivai and, thus, can be used in integrate pest management programs of this pest in oil palm plantations.     

Interaction between host plant resistance and biological activity of Bacillus thuringiensis in managing the pod borer Helicoverpa armigera in chickpea

The legume pod borer Helicoverpa armigera (Hubner) (Lepidoptera: Noctuidae) has developed high levels of resistance to conventional insecticides, and therefore, efforts are being made to develop transgenic chickpea expressing toxin genes from the bacterium Bacillus thuringiensis (Bt) for controlling this pest. However, there is an apprehension that acid exudates in chickpea might interfere with the biological activity of Bt. Therefore, we studied the biological activity of Bt (Biolep^R) on four chickpea genotypes with different levels of resistance to H. armigera under field conditions, and by incorporating lyophilized leaf and pod tissue into the artificial diet with and without Bt. The pH of the acid exudates varied from 2.1 to 2.9, and malic and oxalic acids were the major components of the acid exudates in different chickpea genotypes. There was no survival of H. armigera larvae in chickpea plants sprayed with 0.1, 0.2 and 0.5% Bt. There was a significant reduction in larval survival, larval and pupal weights and fecundity, and prolongation of larval and pupal periods in chickpea plots sprayed with Bt (0.05%) as compared to the unsprayed plots. Biological activity of Bt was lower on artificial diets with leaf or pod powder of chickpea genotypes, which might be because of a low intake of Bt toxins due to the antifeedant effects of acid exudates in the chickpea or reduction in biological activity of Bt due to the interaction of biochemical constituents in chickpea with the Bt toxins. Larval survival, larval and pupal weights, pupation and adult emergence were significantly lower on diets with leaf or pod powder of the H. armigera-resistant genotypes than on the susceptible check. Chickpea genotypes with resistance to H. armigera acted in concert with Bt to cause adverse effects on the survival and development of this insect. The results suggested that development of transgenic chickpeas expressing toxin genes form Bt will be quite effective for controlling of the pod borer, H. armigera.     

Spraying potatoes to prevent leaf roll spread by the green peach aphid

Studies were made at Presque Isle, Maine, 1962–1966, to determine the suppressive effects of several materials against spread of the potato leaf roll cirus,Corium solani Holmes, transmitted by the green peach aphid,Myzus persicae (Sulzer), when applied as foliar sprays to Kennebec, Green Mountain, or Chippewa potatoes in field cages or in field plots. The early cage tests showed that spray mixtures containing 1% of the systemic plant growth regulant chlorocholine chloride (2-chloroethyltri-methylammonium chloride) or 1% of mineral oil were more effective than the insect antifeeding compound AC-24,055^® (=ENT-25,651), the aphid-repellent compounds ENT 20,430 or ENT 21,178, or the surfactants Sarkosyl-O^® (bis (2-ethylhexyl) sodium sulfosuccinate) or Aerosol-OT^® (CH₃ (CH₂)_n CON (CH₃) CH₂ COOH). Field tests disclosed that chlorocholine chloride at 5.2 lb or 2.6 lb/a/a was more effective when healthy green peach aphids were placed on infector plants in the plots soon after the plants were sprayed, 1 week later, or soon after the 2nd of 2 weekly applications than when the aphids were introduced before spraying. The difference in leaf roll suppression at these two dosages was not significant at the 5% level; as high as 90% control of leaf-roll spread was obtained. When only natural infestations of aphids were involved and field spread of the virus was light, the 86% control of leaf roll spread that was obtained from 4 weekly applications made in late June and in July was not significantly different (P=0.05) from the 79% control obtained from 2 biweekly applications made during the same period of time. The potato plants soon recovered from the slight chlorosis resulting from the spray treatment and there was no reduction in weight of US 1 tubers at harvest. Aphid population trends in treated plots were not affected.     

Insecticides applied to soil of transplant plugs for Bagrada hilaris (Burmeister) (Hemiptera: Pentatomidae) management in broccoli

Chemical control with insecticides, typically applied as foliar sprays or chemigation, is the primary tactic used to manage Bagrada hilaris (Burmeister) (Hemiptera: Pentatomidae). We evaluated the efficacy of 14 insecticides, including both systemic and non-systemic insecticides, against B. hilaris applied as a seedling tray drench. Experiments were conducted in both greenhouse and field settings. In all experiments, we used the maximum label rate of insecticides and calculated dose per seedling based on this rate and standard plant density per hectare. Each seedling in the tray received 2-mL insecticide solution, and the seedlings were then exposed to B. hilaris adults after transplanting in cages for greenhouse experiments or natural B. hilaris populations in the field experiments. A scale system (0–4) was used to evaluate the severity of B. hilaris feeding injury on leaves where 0 = no injury and 4 = >75% of the leaf margins with B. hilaris feeding injury. We evaluated damage using the rating system, percentage of damaged leaves, number of feeding injury sites, as well as plant height, leaf width, and fresh and dry weight. In the greenhouse experiment, percentage of injured leaves, number of injury sites, and damage rating were significantly lower for transplants treated with acetamiprid, clothianidin, dinotefuran, imidacloprid, and thiamethoxam, and cyclaniliprole compared with the untreated. There was a relationship between feeding injury sites and plant height, leaf width, fresh and dry weight (R² > 0.5) in both 2015 field experiments. Similarly, the transplants treated with acetamiprid, clothianidin, dinotefuran, imidacloprid, thiamethoxam, thiamethoxam + chlorantraniliprole, imidacloprid + β-cyfluthrin and cyclaniliprole had significantly lower damage ratings than those treated with chlorpyrifos, bifenthrin, tolfenpyrad, flonicamid, cyantraniliprole, spinetoram and the untreated control. For transplanted broccoli, treatment of transplant plugs with neonicotinoid insecticides prior to planting can be an effective method for controlling B. hilaris.     

The potential of mineral oils alone and with reduced rates of insecticides for the control of light brown apple moth,Epiphyas postvittana (Walker) (Lepidoptera: Tortricidae), on nursery plants

The aim of the research was to identify alternatives to chlorpyrifos for the control of light brown apple moth, Epiphyas postvittana, on nursery and ornamental plants. Viburnum tinus L., a commonly grown nursery plant, were infested with E. postvittana eggs, sprayed to run-off and mortality recorded. Several treatments were identified as equally efficacious as the standard chlorpyrifos spray (500 μg/l). The insecticides that compared most favorably with chlorpyrifos were λ-cyhalothrin and γ-cyhalothrin. Four horticultural mineral oils demonstrated good ovicidal properties when evaluated alone versus when combined with reduced rates of the above insecticides or spinosad, imidacloprid or thiacloprid. The response of some insecticide and horticultural mineral oil combinations varied, suggesting that the oil selected may be important. Chlorpyrifos, λ-cyhalothrin, γ-cyhalothrin and spinosad provided similarly high levels of residual control of neonates for up to 10 d from application. Mixtures of UltraPure, an nC21 horticultural mineral oil, with reduced rates of the above insecticides maintained residual efficacy. Alternative treatments evaluated in this study may provide a high level of E. postvittana control through egg mortality and residual effects on emerging neonates over the hatching period. Field trials are required to verify the potential of these alternatives for commercial application.     

The impact of the locust control insecticide fipronil on termites and ants in two contrasting habitats in northern Australia

Termites and ants are key ecosystem engineers and nutrient re-cyclers. Extensive spraying of insecticides presents a hazard to these insects. Using a control-treatment paired design comprising 3 replicate pairs of plots per soil type, we quantified the impact of fipronil on termite consumption of cardboard and wood baits, termite repair of deliberately damaged mounds as well as ant community composition and abundance in two different habitats (black vertisol and red kandosol soil) when applied aerially at a dose rate recommended for locust control in Australia. The study was conducted from 2006 to 2008. The diversity of termites and ants was higher and side-effects were more pronounced on kandosol than on vertisol soil. Overall termite consumption of cardboard baits was significantly greater in unsprayed than in sprayed plots while losses were significantly greater in only one (vertisol) or two (kandosol) sprayed plots, respectively, compared to paired unsprayed plots. In the first year, termite consumption of wood baits was generally significantly greater on unsprayed than on sprayed kandosol while only marginally significant on unsprayed vertisol. Again, losses were significantly greater in one (vertisol) and two (kandosol) sprayed plots, respectively, compared to paired unsprayed plots. Overall termite consumption of wood baits was similar among plots in the second year post-spray although consumption remained significantly depressed in one pair of sprayed plots in each habitat. The capacity of the mound-building termite, Drepanotermes rubriceps (Froggatt) unique to kandosol, to repair damaged mounds was significantly reduced by fipronil. Furthermore, colonies of Iridomyrmex greensladei Shattuck, an ant species associated with mounds of D. rubriceps, were not re-located five months post-spray. Ant communities were also adversely affected. On vertisol, species richness and relative abundance were similar among treatments, but significantly fewer species were caught in one individual sprayed plot. In contrast on kandosol, species richness and relative abundance were significantly reduced by fipronil. A drop in species richness was observed in all and a drop in relative abundance in two sprayed plots. On vertisol, abundances of two species were significantly lower in sprayed than in paired unsprayed plots. Likewise on kandosol, abundances of five species were significantly reduced in sprayed plots, and one species was not caught at all. The weight of evidence of our findings indicate that fipronil, even at a low rate, will have substantial adverse impacts on the diversity and activity of termites and ants, especially if applied within one to two years of earlier applications.     

Repellency of selected biorational insecticides to potato psyllid, Bactericera cockerelli (Hemiptera: Psyllidae)

Bactericera cockerelli has recently become a major concern because of its direct feeding and vectoring of bacterial diseases in many solanaceous crops. The repellency of four biorational insecticides, MOI-201 (a Chinese medicine plant extract), Requiem (a plant extract of Chenopodium ambrosioides), BugOil (a mixture of four plant essential oils), and SunSpray oil (a mineral oil), to B. cockerelli adults was tested on tomato. In a no-choice test, all the insecticides had significant repellency to adults and deterred oviposition as compared with untreated controls. Of the four insecticides, the two oils showed a stronger repellency to adults and deterred oviposition more strongly than Requiem or MOI-201. In a choice test, all insecticides had significant repellency to adults and deterred oviposition compared to untreated controls. Of the four tested insecticides, <1 adults and no eggs were found on the leaves treated with SunSpray Oil, BugOil or Requiem 3 d after treatment. The repellency rates of these three insecticides were 77.2–95.4%. MOI-201 also repelled adults significantly and deterred oviposition compared to untreated controls even though it was the least effective insecticide among the four evaluated. In conclusion, all four insecticides tested showed significant repellency to B. cockerelli adults and deterred oviposition, especially the two oils. The overall repellency to potato psyllid adults can be arranged in a descending order of SunSpray oil > BugOil > Requiem > MOI-201. These insecticides could be used in integrated pest management programs targeted against the potato psyllid on solanaceous crops.     

Characterization of fungicide resistant isolates of Phaeoacremonium aleophilum infecting grapevines in Spain

Fungicide resistance in Phaeoacremonium aleophilum, one of the most frequent fungal pathogens associated with grapevine trunk diseases, was investigated and found to exist in some isolates of the pathogen against a commercial formulation, Escudo^®. The effect of this compound and its two active substances, carbendazim and flusilazole, was first evaluated on the mycelial growth of P. aleophilum. Escudo^®-resistant isolates were estimated at a frequency of 24% in Spanish vineyards. Then, the two active substances were used individually to test their effect on mycelia growth of twelve single-spore cultures originating from six Escudo^®-resistant isolates. Flusilazole (DMI-triazole) did not inhibit mycelia growth of any single-spore cultures of P. aleophilum. Carbendazim (benzimidazole) used alone allowed the growth of the same single-spore cultures that were also resistant to Escudo^®. AFLP characterization of sensitive and resistant single-spore cultures showed genetic diversity within P. aleophilum isolates but no AFLP markers were associated with resistance. New primers set (L2/R1) were designed to partially amplify the exon 6 of the beta-tubulin gene of P. aleophilum. Two different point mutations resulted in glycine (GGC) or lysine (AAA) replacing the glutamic acid (GAG) at codon 198 of the beta-tubulin gene in some of the resistant single-spore cultures studied. Resistant single-spore cultures of P. aleophilum were shown to have different aggressiveness levels as sensitive single-spore cultures by inoculation of wood segments of Vitis vinifera in the presence and absence of fungicide.     

Effect of Tithonia diversifolia Mulch on Atta cephalotes (Hymenoptera: Formicidae) Nests

Recent studies have shown an insecticidal effect of Tithonia diversifolia (Hemsl.) Gray (Asterales: Asteraceae) foliage on workers of Atta cephalotes L. and inhibitory effects of this plant on the growth of the symbiotic fungus Leucoagaricus gongylophorus (A. Müler) Singer. To evaluate the potential of T. diversifolia as a biological control treatment of this important pest, we assessed the effect of green manure (mulch) of this plant on natural nests of A. cephalotes, in Cali, Colombia. Three treatments were randomly assigned to 30 nests: 1) green mulch of T. diversifolia, 2) green mulch of Miconia sp., Ruiz & Pav. and 3) unmulched control. Every 2 wk for 6 mo, the surface of the nests was completely covered with leaves. Physical and chemical parameters of nest soil were assessed before the first and after the last application of the mulch. Ant foraging in T. diversifolia-treated nests decreased by 60% after the initial applications of the mulch, while nest surface area decreased by 40%. When the nests covered with T. diversifolia were opened, it was observed that the superficial fungus chambers had been relocated at a greater depth. In addition, microbial activity and soil pH increased by 84% and 12%, respectively, in nests covered with plant residues. In conclusion, the continued use of T. diversifolia mulch reduces foraging activity and negatively affects the internal conditions of the colonies, thereby inducing the ants to relocate the fungus chambers within the nests.     

Model of stripe rust infection and control on irrigated wheat in the murrumbidgee irrigation areas of new South Wales

A well-developed epidemic of stripe rust on a field crop of a susceptible wheat cultivar (cv. Avocet) led to significant yield reductions compared to plots which were protected with regular applications of the fungicide triadimefon (Bayleton®). A modified logistic transformation of the leaf infection data provided values of apparent infection rate, r, which are required for use in simulation models of disease progress and predicted yield loss, such as epidemic and epipre. Flagleaf area at early water stage of the kernels (86 days following sowing, DFS; Zadoks growth stage 70), afforded a good prediction of grain yield. Stripe rust infection of the flag leaf had a strong negative effect on final grain yields larger than would have been predicted solely from a loss of photosynthetic area. Flood irrigation did not affect the level of disease on the flag leaf at 86 DFS nor the apparent infection rate of stripe rust on the flag leaf. Irrigation gave increased grain yield only in sprayed treatments. Conversely, while there was a yield response due to fungicide application to cv. Avocet in both irrigated and non-irrigated plots, the cost benefit of spraying the latter was marginal.     

Effects of nitrogen rate on nitrate–nitrogen accumulation in forage kale and rape crops

Nitrogen fertilizer is applied to supplement soil nitrogen supply to maximize forage brassica crop dry-matter production. However, nitrogen fertilizer applications in excess of that required to maximize growth result in potentially toxic nitrate–nitrogen (NO₃–N) concentrations in grazeable plant tissues. Three experiments, two for forage kale at Lincoln (Canterbury) and one for forage rape at Hastings (Hawke's Bay) in New Zealand were grown under different rates of nitrogen (0–500 kg N ha⁻¹) to determine the effect of different rates of nitrogen on NO₃–N content of different plant parts of the crops. One of the kale experiments was grown with either full irrigation or no rain and no irrigation over summer, hereafter referred to as summer drought. The NO₃–N concentration on a whole plant (weighted average) basis increased from 0·1 mg g⁻¹ dry matter for the control plots to 2·30 mg g⁻¹ for the 500 kg N ha⁻¹ plots for forage kale. It increased from 0·99 for the control plots to 3·37 mg g⁻¹ for the 200 kg N ha⁻¹ plots for forage rape crops. However, NO₃–N concentration increased with N supply under the summer-drought plots from an average of 0·33 mg g⁻¹ when ≤120 kg N ha⁻¹ was applied to 2·30 mg g⁻¹ for the 240 kg N ha⁻¹ treatments but was unaffected by N supply under irrigation. The NO₃–N concentrations were higher in the stems and the petiole (which included the midrib of the leaf) than leaves in all three experiments. The NO₃–N concentration was highest at the bottom of the kale stem and decreased towards the top. We recommend N application rates based on soil tests results, and for conditions similar to the current studies up to 300 kg N ha⁻¹ under irrigation and adjusted lower N rates for regions prone to dry summers.