Field Evaluation of Insecticides for Control of Cabbage Maggot (Diptera: Anthomyiidae) in Rutabaga in Canada.

At the time of this research, there were only two insecticides registered for control of cabbage maggot, Delia radicum L., in rutabaga in Canada, one of which (diazinon) will be deregistered by 2017, and resistance having been reported in some areas for the other (chlorpyrifos). To screen for chemistries to replace these organophosphates, and obtain efficacy data comparable between key vegetable brassica production areas in Canada, four small plot field studies were conducted concurrently in British Columbia, Saskatchewan, Ontario, and Quebec in 2009. These studies followed standardized protocols for seeding, application of insecticide drenches, sampling and damage assessment, and generally tested the same products. Of the insecticides evaluated, none provided maggot control comparable with the industry standard, chlorpyrifos. However, cyantraniliprole (Cyazypyr 200SC; registered in 2015 as Verimark) applied at 3 g AI (15.0 ml product)/100 m row of seeded rutabagas consistently provided the next highest reduction in % culls, suggesting the efficacy of this chemical may be improved if used at higher rates. The results of these studies are discussed in the context of current literature on D. radicum management in rutabaga. Future management strategies are also discussed, including a transplant plug treatment approach for increasing the dosage per plant and efficacy of chemistries such as Cyazypyr 200SC in the field.

Mortality of a wireworm, Agriotes obscurus (Coleoptera: Elateridae), after topical application of various insecticides.

Ten insecticides representing seven chemical groups were applied at various concentrations topically by using a Potter Spray Tower to evaluate their relative toxicities on the European wireworm Agriotes obscurus L. (Coleoptera: Elateridae). Wireworms were stored at 15 degrees C after exposure to organophosphate (OP) (chlorpyrifos, diazinon), pyrethroid (tefluthrin), thianicotinoid (thiamethoxam, clothianidin), chloronicotinoid (imidacloprid, acetamiprid), phenyl pyrazole (fipronil), organochlorine (lindane), and spinosyn (spinosad) insecticides, and their postapplication health was evaluated weekly for up to 301 d. LC50, LC90, LT50, and LT90 values were calculated for each chemical except acetamiprid, and compared with those of lindane, clothianidin, and chlorpyrifos. Wireworms exposed to OPs died or recovered more quickly (LT50 < 20 d, LT90 < 50 d), than those exposed to all other insecticides tested except tefluthrin (LT50 = 25.5 d, LT90 = 66.5 d). Wireworms exposed to sublethal concentrations of all neonicotinoids quickly became moribund after application but made a full recovery. Wireworms exposed to fipronil at concentrations near the LC90 value showed no intoxication symptoms for up to 35 d, and they did not recover after symptoms developed. For each chemical, increasing the concentration increased the time required for wireworms to recover but decreased the time required to kill wireworms. Fipronil was highly toxic to wireworms (LC50 = 0.0001%), but acetamiprid (LC50 = 1.82%), imidacloprid (LC50 = 0.83%), tefluthrin (LC50 = 0.23%), diazinon (LC50 = 0.54%), and spinosad (LC50 = 0.51%) were not. The toxicity of both clothianidin (LC50 = 0.07%) and thiamethoxam (LC50 = 0.17%) were similar to those oflindane (LC50 = 0.06%) and chlorpyrifos (LC50 = 0.10%).

Evaluation of sampling methodology for determining the population dynamics of onion thrips (Thysanoptera: Thripidae) in Ontario onion fields.

Onion thrips, Thrips tabaci Lindeman, are an economic pest of alliums worldwide. In Ontario onion-growing regions, seasonal abundance and population trends of onion thrips are not well known. The objectives of this research were to investigate onion thrips population dynamics by using both white sticky traps and plant counts, to gain insight into flight height, and to determine the genus and sex of thrips fauna present in monitored fields. Adult thrips were captured on white sticky traps placed in two commercial onion fields in the Thedford-Grand Bend Marsh region as early as mid-May in 2001, 2002, and 2003. Thrips were not recorded on onion plants in these fields until late June and early July. A comparison of sticky trap captures to plant counts revealed a strong, positive correlation, indicating that sticky traps, which consistently detected thrips earlier than plant counts, could be used instead of plant counts early in the season to monitor onion thrips populations. Pole traps placed in onion and an adjacent soybean, Glycine max (L.) Merr., field revealed that regardless of crop type, most thrips were captured 0.7-0.95 m above the soil surface. During this study, 70% of 137,000 thrips captured on sticky traps and 89% of 1,482 thrips captured in pan traps were female onion thrips. No male onion thrips were identified in this study: most of the remaining thrips were Frankliniella spp.

The effect of multiple soil applications of disulfoton on enhanced microbial degradation in soil and subsequent uptake of insecticidal chemicals by potato plants.

Potatoes were grown during 1992 in 2 m2 plots of loam which had received 1, 2 or 3 annual treatments of Di-Syston 15G, equivalent to 3.36 kg AI/ha, in furrow at planting. The presence of enhanced degradative activity to the sulfoxide and sulfone metabolites of disulfoton in the soil treated in the previous two years was confirmed by laboratory tests prior to the 1992 treatments. Soil, seed potato and foliage from the three treatments were analyzed for disulfoton and its sulfoxide and sulfone metabolites for 12 wk following planting/treatment. Disulfoton was the major insecticidal component of the soil, a minor component of the seed piece and was not detected (< 0.02 ppm) in potato foliage. Disulfoton concentrations in each of the three substrates sampled were similar for the three treatments. Disulfoton sulfoxide and sulfone were the major insecticidal components of the seed piece and foliage. Their maximum concentrations in 1st year soil, seed pieces and foliage were ca. 2x, 2x and 6x, respectively, those measured in the 2nd and 3rd year treatments. The results demonstrate that enhanced microbial degradation of relatively minor insecticidal compounds in the soil can profoundly affect insecticide levels in the plant when these compounds are the major insecticidal components accumulated. The broader implications for crop protection using soil-applied systemic insecticides are discussed.

The persistence of insecticidal chemicals in soils treated with granular formulations of disulfoton and their uptake by potato plants.

Potatoes were grown from cut seed in Plainfield sand treated in-furrow with disulfoton (Di-Syston 15G, 3.36 kg AI/ha) in 1983 and from whole seed in similarly treated loam in 1991. Soils were contained in 2 m2 field plots. Soil, seed potato and foliage were analyzed for the insecticide and its sulfoxide and sulfone metabolites during the 8-12 wk following planting. Disulfoton disappeared at different rates from the two soils (ksand = 0.024 day-1, kloam = 0.056 day-1) with partial conversion to the sulfoxide and sulfone in both. Larger quantities of the three insecticidal components were absorbed by the seed potato in the cut-seed/sand combination. The relative amounts of these components in the seed potato also differed between treatments with disulfoton being the largest component of the cut-seed/sand and smallest in the whole-seed/loam. Disulfoton sulfoxide and sulfone were the major insecticidal components of the foliage and concentrations in the initial foliage (each ca. 10 ppm) were similar for both treatments. Sulfoxide concentrations in the foliage decreased more rapidly than the sulfone and the decrease in concentration of each of the components was similar for the two treatments.

A comparison of the persistence in a clay loam of single and repeated annual applications of seven granular insecticides used for corn rootworm control.

In May 1983, granular formulations of carbofuran, chlorpyrifos, disulfoton, fonofos, isofenphos, phorate, and terbufos were applied in incorporated bands to duplicate 2 m2 field plots of clay loam. Insecticide concentrations were determined in the bands at 0,1,2,3,4,6,8,10,12,16, and 20 wk. Following spring cultivation, the insecticides were applied to the same plots in 1984 and 1985. In addition, carbofuran was applied to previously untreated plots in 1984 and all 7 materials were applied to previously untreated plots in 1985. Sampling and analysis were carried out as in 1983. Persistence was assessed on the basis of the disappearance rates measured for the 1st 8 wk and of a calculated Effectiveness Potential (the ratio of the average residue in the upper 5 cm of the band at 8, 10 and 12 wk and the published LC95 for western corn rootworm in clay loam soil). Soils treated with carbofuran and isofenphos in 1984 and all soils treated in 1985 were tested for anti-insecticide activity. Soil cores from some carbofuran, chlorpyrifos and terbufos treated plots were sectioned vertically to establish the distribution of the insecticides during 1985. In addition, granular and pure chemical forms of isofenphos and carbofuran were applied at 10 ppm to anti-isofenphos and anti-carbofuran active and control soils (from field plots) maintained at 10 and 20% moisture in the laboratory to assess the effect of formulation and moisture on persistence in active soils. Insecticide concentrations were determined at 0,1,3,7, 10,14,21,28, and 35 days. The persistence of chlorpyrifos, terbufos and phorate was relatively constant over the 3 years and between plots receiving single and multiple treatments. Disulfoton and fonofos behavior was more variable and that of carbofuran and isofenphos was extremely variable. Anti-insecticide activity against carbofuran and isofenphos was detectable 2 wk after an initial application and was still present the following spring. Anti-insecticide activity against fonofos, terbufos sulfoxide, phorate sulfone and disulfoton sulfone was also generated in this soil. Anti-insecticide activity against chlorpyrifos, disulfoton, terbufos and phorate was not present. Carbofuran, chlorpyrifos and terbufos (+ metabolites) present in the upper 5 cm of soil averaged 93, 94 and 94%, respectively, of the total core contents over 12 wk. Significant moisture dependent differences were observed between the behavior of granular carbofuran and granular isofenphos in anti-insecticide active soils.(ABSTRACT TRUNCATED AT 400 WORDS)