In 1997, farmers in Ontario, Canada, reported failure of some ALS-inhibiting herbicides to provide adequate control of pigweed species. Growth room experiments were conducted to confirm resistance to ALS inhibitors in populations of Powell amaranth and redroot pigweed. Twenty-two out of 35 collected seed samples were able to grow in the presence of soil-applied imazethapyr or flumetsulam. Dose–response curves were generated for 11 and 9 populations of Powell amaranth and redroot pigweed, respectively, using foliar-applied imazethapyr and thifensulfuron. Resistance to ALS inhibitors was confirmed in nine and five populations of Powell amaranth and redroot pigweed, respectively. Within each species, comparison of the herbicide rate required to reduce plant dry weight 50% (GR50) between the resistant populations and a susceptible population was conducted to obtain resistance factors. For imazethapyr, resistance factors ranged from 4.2 to 3,438 and from 33 to 168 for Powell amaranth and redroot pigweed, respectively. High-level cross-resistance to thifensulfuron was found in two populations of each species, with resistance factors ranging from 270 to 2,416. In both species, populations could be grouped according to their cross-resistance patterns: some populations were resistant to imazethapyr only, whereas others expressed resistance to both imazethapyr and thifensulfuron. The observed patterns of cross-resistance were not correlated with known herbicide exposure history of the fields where these populations originated.
We conclude that the new reduced risk insecticides metaflumizone and chlorantraniliprole and the fungicides myclobutanil, potassium bicarbonate and cyprodinil + fludioxonil are safe for greenhouse use in the presence of bumble bees. This information can be used preserve greenhouse pollination programs while maintaining acceptable pest management.
This study investigated the inßuence of different humidity levels on percentage of infection by Beauveria bassiana (Balsamo) Vuillemin (Hyphomycetes) (Botanigard EmulsiÞable Suspension formulation) on greenhouse insect and mite pests, and their commercially available biological control agents. The target insect and mite species were sprayed with B. bassiana and evaluated in petri dish trials under controlled environment conditions, on cucumber leaves under greenhouse crop conditions, and under fully sprayed greenhouse conditions. Results of this study showed that in petri dish trials, a humidity of 97.5% RH resulted in signiÞcantly higher percentage of infection (60 Ð 88.8%), while at 75 and 80% RH only 15.3Ð 43.9% of the pest insects were infected. On leaf surfaces, the differences in ambient humidity did not cause as great of variations in percentage of infection as in the petri dish trials. Increasing greenhouse humidity by 15% RH caused an increase of 17Ð25% in percentage of infection. Under high humidity conditions, whole greenhouse sprays with B. bassiana successfully suppressed populations of Frankliniella occidentalis (Pergande) and Trialeurodes vaporariorum (Westwood). Tetranychus urticae Koch was not infected by B. bassiana at sig-niÞcant levels in any of the trials. Predatory mites can be used with B. bassiana, while adult Orius insidiosus (Say), Aphidius colemani Viereck, and Dacnusa sibirica Telenga are not recommended to be introduced during the application of B. bassiana. Encarsia formosa Gahan, Eretmocerus eremicus (Rose and Zolnerowich), and Aphidoletes aphidimyza (Rondani) need to be used with caution when B. bassiana is applied.
Pepino mosaic virus (PepMV) has become an important viral disease of greenhouse tomatoes worldwide. The ability of bumble-bees (Bombus impatiens), used for pollination, to acquire and transmit PepMV was investigated, and the prevalence of PepMV in plants and bumble-bees in commercial tomato greenhouses was determined. PepMV infection in plants was determined using enzymelinked immunosorbent assay, while in bumble-bees direct real-time PCR was used. In the first experiment, the bumble-bees were exposed for 14 days to PepMV-infected plants. After 14 days, almost all bumble-bees were PepMV positive both in the hive (78.5 AE 17.5%) and in the flowers (96.3 AE 3.6%). In the second experiment, bumble-bees were released into a greenhouse with both PepMV-infected source plants and healthy non-infected target plants for 14 days. At the end of the experiment, 61.0 AE 19.5% of the bees collected from the hive and 83.3 AE 16.7% of the bees sampled from the flowers were PepMV positive. Bumble-bees transmitted PepMV from the infected to the healthy noninfected tomato plants. Two weeks after bumble-bee release, the virus was detected in leaf, fruit and flower samples of formerly healthy plants. After 6 weeks, the percentage of PepMV positive samples from the target plants increased to 52.8 AE 2.8% of the leaves and 80.6 AE 8.4% of the fruits. In the control greenhouse without bumble-bees, the target plants did not become infected. Based on the infection levels in flowers, fruits and leaves, the PepMV infection occurred possibly first in the pollinated flowers, and then spread from the fruit that developed from the flowers to other parts of the plant. In commercial greenhouses where PepMV was present, 92-100% of the plants and 88-100% of the bumble-bees were PepMV positive. No infected plant samples were found in the control commercial greenhouse, but a small number of bumble-bees (10%) tested PepMV positive.
BACKGROUND: Arthropod biological control agents (BCAs) are commonly released for greenhouse vegetable insect pest management. Nevertheless, chemicals remain a necessary control tactic for certain insect pests and diseases and they can have negative impacts on BCAs. The compatibility of some formulated reduced risk insecticides (abamectin, metaflumizone and chlorantraniliprole) and fungicides (myclobutanil, potassium bicarbonate and cyprodinil + fludioxonil) used, or with promise for use, in Canadian greenhouses with Orius insidiosus (Say), Amblyseius swirskii (Athias-Henriot) and Eretmocerus eremicus (Rose & Zolnerovich) was determined through laboratory and greenhouse bioassays. RESULTS: Overall, the insecticides and fungicides were harmless as residues to adult BCAs. However, abamectin was slightly to moderately harmful to O. insidiosus and A. swirskii in laboratory bioassays, whereas metaflumizone was slightly harmful to E. eremicus. CONCLUSIONS:In general, these products appear safe to use prior to establishment/release of these adult BCAs.
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