Effect of the width of the herbicide strip on mite dynamics in apple orchards.

Herbicide strips are used in apple orchards to promote tree growth and survival, to increase yield and to reduce the risk of rodent damage to tree bark. However, herbicide strips, particularly wider ones, may cause problems including soil erosion, reduced organic matter, leaching of nitrates into ground water and increased incidence of plant diseases and pests, including two-spotted spider mites, Tetranychus urticae Koch. In this 2 year study we monitored mite dynamics in apple trees and used sticky bands on tree trunks to determine rates of T. urticae immigration into Nova Spy apple trees in plots with wide (2 m) or narrow (0.5 m) herbicide strips. Use of wider herbicide strips promoted two risk factors that could trigger outbreaks of tetranychid mites. First, concentrations of leaf N in apple trees were higher and those of P and K were lower with the wide strips. Such changes in nutritional quality of leaves would increase the potential for more rapid population growth of T. urticae, and to a lesser extent, the European red mite, Panonychus ulmi (Koch). Second, there were higher rates of T. urticae immigration from the ground cover vegetation into the trees. In 2006, and for most of 2007, densities of T. urticae were higher with wide herbicide strips, whereas densities of P. ulmi were not enhanced. However, by late August to early September in 2007, densities of both tetranychids were lower with wide herbicide strips. This is because both risk factors were counterbalanced, and eventually negated, by the enhanced action of phytoseiid predators, mostly Typhlodromus pyri Scheuten. From July through September 2006, ratios of phytoseiids to tetranychids were always several-fold lower with wide herbicide strips but in 2007, from mid-July onwards, predator-prey ratios were usually several-fold higher with wide strips. However, this numerical response of phytoseiids to prey density can only occur where the pesticide program in orchards is not too harsh on phytoseiids. Hence the impact of width of herbicide strip is contingent on the composition and size of the phytoseiid complex and the impact of pesticides on predation.

Particle films for managing arthropod pests of apple.

A two-season study showed that a calendar-based spray program to manage arthropod pests with kaolin (60 g/liter) applied at the rate of 450 liters/ha was effective against European apple sawfly, Hoplocampa testudinea (Klug) (Hymenoptera: Tenthredinidae); white apple leafhopper, Typhlocyba pomaria McAtee (Homoptera: Cicadellidae); apple red bug, Lygidea mendax Reuter (Heteroptera: Miridae); pear plant bug, Lygocoris communis (Knight) (Heteroptera: Miridae); and the apple rust mite, Aculus schlechtendali (Nalepa) (Acari: Eriophyidae). Although it reduced Curculionidae damage, the level of damage was still too high. It had no effect on apple maggot, Rhagoletis pomonella (Walsh) (Diptera: Tephritidae); codling moth, Cydia pomonella (L.) (Lepidoptera: Tortricidae); and tarnished plant bug, Lygus lineolaris (Palisot de Beauvois) (Heteroptera: Miridae). Laboratory studies showed fewer gravid twospotted spider mites, Tetranychus urticae Koch (Acari: Tetranychidae), and fewer eggs laid by these females. The study also showed no effect of kaolin on Neoseiulus fallacis (Garman) (Acari: Phytoseiidae).

Effects of acaricides, pyrethroids and predator distributions on populations of Tetranychus urticae in apple orchards.

We sampled mites in three apple orchards in Nova Scotia, Canada, that had been inoculated with pyrethroid-resistant Typhlodromus pyri and had a history of Tetranychus urticae outbreaks. The objective of this study was to monitor populations of T. urticae and phytoseiid predators on the ground and in trees and to track dispersal between the two habitats. Pesticides were the chief cause of differences in mite dynamics between orchards. In two orchards, application of favourably selective acaricides (abamectin, clofentezine) in 2002, coupled with predation by T. pyri in trees and Neoseiulus fallacis in ground cover, decreased high T. urticae counts and suppressed Panonychus ulmi. By 2003 phytoseiids kept the tetranychids at low levels. In a third orchard, application of pyrethroids (cypermethrin, lambda-cyhalothrin), plus an unfavourably selective acaricide (pyridaben) in 2003, suppressed phytoseiids, allowing exponential increases of T. urticae in the ground cover and in tree canopies. By 2004 however, increasing numbers of T. pyri and application of clofentezine strongly reduced densities of T. urticae in tree canopies despite high numbers crawling up from the ground cover. Another influence on T. urticae dynamics was the distribution of the phytoseiids, T. pyri and N. fallacis. When harsh pesticides were avoided, T. pyri were numerous in tree canopies. Conversely, only a few N. fallacis were found there, even when they were present in the ground cover and on tree trunks. Low numbers were sometimes due to pyrethroid applications or to scarcity of prey. Another factor was likely the abundance of T. pyri, which not only competes with N. fallacis, but also feeds on its larvae and nymphs. The scarcity of a specialist predator of spider mites in trees means that control of T. urticae largely depends on T. pyri, a generalist predator that is not particularly effective in regulating T. urticae.

Acaricidal properties of a Chenopodium-based botanical.

The emulsifiable concentrate UDA-245 [25% EC (vol:vol)], based on an essential oil extract from Chenopodium ambrosioides variety ambrosioides, a North American herbaceous plant, was compared with commercially available pesticides for their effectiveness to control the adult stage and egg hatch of the twospotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae) and the European red mite, Panonychus ulmi (Koch) (Acari: Tetranychidae). After a laboratory bioassay with adult twospotted spider mites, a 0.5% concentration of UDA-245 was more effective than 0.7% (AI) of neem oil (Neem Rose Defense). After a similar bioassay with the European red mite, a 0.5% concentration UDA-245 was as effective as 0.006% (AI) of abamectin (Avid). UDA-245 at 0.5% significantly reduced egg hatch of the twospotted spider mite, 5 and 9 d after treatment and of the European red mite 6 d after treatment. Egg hatch was significantly lower using 0.006% (AI) of abamectin, 0.7% of neem oil, and 1.0% insecticidal soap than UDA-245. Residual tests indicated that UDA-245 may be persistent in the environment only for a few hours. Only 23% mortality was noted when mites were introduced on bean leaves 1 h after treatment with a 2% concentration of UDA-245. At the recommended dose of 0.5%, UDA-245 was not considered phytotoxic for most plants tested, i.e., lettuce, roses, and tomatoes. Results suggest that a greenhouse integrated pest management program using UDA-245 could effectively and selectively control mite infestations by treating "hot spots" with negligible effect on biological control agents when treating before introduction or when natural enemies are absent.

Insecticidal properties of a Chenopodium-based botanical.

The emulsifiable concentrate UDA-245 based on an essential oil extract from Chenopodium ambrosioides variety near ambrosioides, a North American herbaceous plant, was compared with commercially available pesticides for their effectiveness to control green peach aphid, Myzus persicae (Sulzer) (Homoptera: Aphididae), western flower thrips, Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae), and greenhouse whitefly, Trialeurodes vaporariorium (Westwood) (Homoptera: Aleyrodidae). Side effects on the whitefly parasitoid Encarsia formosa Gahan (Hymenoptera: Aphelinidae) also were determined. With green peach aphid, UDA-245 at 0.5% concentration was significantly more effective than the control (water) treatment in a laboratory bioassay and significantly more effective than neem oil and the control treatment and as effective as insecticidal soap in a greenhouse assay. With the western flower thrips, UDA-245 at 0.5% was significantly more effective than neem oil, insecticidal soap and the control treatment in a laboratory bioassay, whereas in a greenhouse assay, UDA-245 at 1.0% was the only treatment that maintained control of the western flower thrips 2 wk after the last treatment period. UDA-245 at 0.5% (laboratory bioassay) was significantly more effective in managing greenhouse whitefly than neem oil, endosulfan, and the control treatment and as effective as insecticidal soap. Insecticidal soap proved to be toxic to the parasitoid E. formosa (71.9% mortality), whereas UDA-245 at 0.5% was not significantly more toxic than the control (11.2 and 4.6% mortality, respectively). Our results suggest that a greenhouse integrated pest management (IPM) program using a botanical such as UDA-245 could effectively control infestations of major pests present while having a negligible effect on biological control agents.

Baseline toxicity of several pesticides to Hyaliodes vitripennis (Say) (Hemiptera: Miridae).

Hyaliodes vitripennis (Say) is a univoltine indigenous predacious mirid. It has been reported in several orchards where IPM programmes are used. It is a generalist, and feeds on phytophagous mites in addition to other arthropods. In Quebec, a foliar application of imidacloprid, deltamethrin or lambda-cyhalothrin is used at least once per season to manage arthropod pests such as leafhoppers and leaf-eating caterpillars. Meanwhile, several applications of metiram, flusilazole, myclobutanil and mancozeb are made to control apple scab [Venturia inaequalis (Cooke) Winter]. In laboratory trials, comparison of lethal concentrations of the three insecticides against H vitripennis nymphs and adults showed no significant difference. However, when lethal concentrations were compared between two growth stages for each insecticide, a significant difference was noted between adults and nymphs treated with lambda-cyhalothrin, adults being more susceptible than nymphs. No such difference could be detected for imidacloprid or deltamethrin. When LC50 values were compared with the manufacturer's label rates, deltamethrin and imidacloprid were toxic to the nymphs and adults, and lambda-cyhalothrin was slightly toxic to the nymphs and moderately toxic to the adults. Among the fungicides evaluated in the laboratory, myclobutanil showed moderate toxicity to adults at the manufacturer's label rate. The remaining fungicides had no toxic effects to adults or nymphs, even at four times the manufacturer's label rate.

Effects of five insecticides used in apple orchards on Hyaliodes vitripennis (Say) (Hemiptera: Miridae).

Azinphos-methyl, carbaryl, dimethoate, phosmet and phosalone were used in apple orchards to manage apple aphid, apple maggot, woolly apple aphid and leaf eating caterpillars. Among the five insecticides evaluated, dimethoate, carbaryl and azinphosmethyl were the most toxic to the nymphs and adults of Hyaliodes vitripennis (Say) from two regions. Phosalone was the least toxic. Nymphs were more resistant than the adults. While the LC50 for dimethoate was 130 ppm for nymphs, it was 3 ppm for adults from St. Jean-Baptiste-de-Rouville. There were also significant differences in the level of resistance between the two regions where the H. vitripennis were collected. At St. Alexandre the LC50 for phosalone on nymphs was 19,250 ppm whereas, at St. Jean-Baptiste-de-Rouville it was 160,000 ppm.

Azinphos-methyl residues in apples and spatial distribution of fluorescein in vase-shaped apple trees.

Vase-shaped standard apple trees cv. McIntosh were sprayed with azinphos-methyl at pink, pink and 1st cover and 1st cover only. Residue analyses by gas chromatography revealed detectable residues on foliage until mid summer. At harvest, negligible residue levels were found on the peel and the whole apple. On four trees, fluorescein was sprayed in the same manner as the insecticide and maximum levels of the dye were detected on the outside lower canopy along the row. Minimal concentration of fluorescein was detected on the inner upper canopy away from the direction of the row.