Impact of Planting Dates and Insecticide Strategies for Managing Crucifer Flea Beetles (Coleoptera: Chrysomelidae) in Spring-Planted Canola

Abstract

Integration of cultural practices, such as planting date with insecticide-based strategies, was investigated to determine best management strategy for flea beetles (Phyllotreta spp.) (Coleoptera: Chrysomelidae) in canola (Brassica napus L.). We studied the effect of two spring planting dates of B. napus and different insecticide-based management strategies on the feeding injury caused by fleabeetles in North Dakota during 2002-2003. Adult beetle peak emergence usually coincided with the emergence of the early planted canola, and this resulted in greater feeding injury in the early planted canola than later planted canola. Use of late-planted canola may have limited potential for cultural control of flea beetle, because late-planted canola is at risk for yield loss due to heat stress during flowering. Flea beetle injury ratings declined when 1) the high rate of insecticide seed treatment plus a foliar insecticide applied 21 d after planting was used, 2) the high rate of insecticide seed treatment only was used, or 3) two foliar insecticide sprays were applied. These insecticide strategies provided better protection than the low rates of insecticide seed treatments or a single foliar spray, especially in areas with moderate-to-high flea beetle populations. The foliar spray on top of the seed treatment controlled later-emerging flea beetles as the seed treatment residual was diminishing and the crop became vulnerable to feeding injury. The best insecticide strategy for management of flea beetle was the high rate of insecticide seed treatment plus a foliar insecticide applied at 21 d after planting, regardless of planting date.

Bioclimatic approach to assessing the potential impact of climate change on two flea beetle (Coleoptera: Chrysomelidae) species in Canada

“…For example, seeding date influences the extent of flea beetle damage to canola to varying degrees in different regions of the Prairie Ecozone. In North Dakota, United States of America, flea beetle damage to canola was reported to be greater when crops were planted in late April to early May as opposed to those planted in late May (Milbrath et al 1995;Knodel et al 2008). Cárcamo et al (2008) found that canola planted in April in southern Alberta had lower flea beetle populations and less plant damage than crops planted in May, while the opposite occurred in more northern regions of Alberta.…”

Biology, Ecology, and Management of Flea Beetles in Brassica Crops

“…In general, earlier SOSR planting dates resulted in lower flea beetle abundance in Manitoba, Canada (73) and a reduction in damage in southern Alberta, Canada (36) and in Sweden, even with measurable yield gains (86,87). However, more flea beetles (90) and higher damage were observed with early planting dates in North Dakota (72) and in central and northern Alberta (36). These variable effects have been attributed to different species assemblages among regions, which could result in different responses to environmental conditions that affect flea beetle feeding and plant growth (36,87).…”

“…Adult flea beetle damage to oilseed rape (OSR) is very fast and difficult to monitor in large fields (120), and there is currently a lack of forecasting models that allow growers to predict economically damaging populations that require treatment (99,113). Therefore, farmers in North America and Europe traditionally used prophylactic applications of in-furrow granules or seed-coated systemic insecticides to control flea beetles in OSR (72,74,85,118,120,134). Since the mid-1990s, nearly all OSR seeds planted in Canada have been treated with systemic neonicotinoid insecticides, which are effective in reducing flea beetle damage to seedlings, usually for up to three weeks (72,113).…”

“…Therefore, farmers in North America and Europe traditionally used prophylactic applications of in-furrow granules or seed-coated systemic insecticides to control flea beetles in OSR (72,74,85,118,120,134). Since the mid-1990s, nearly all OSR seeds planted in Canada have been treated with systemic neonicotinoid insecticides, which are effective in reducing flea beetle damage to seedlings, usually for up to three weeks (72,113). Thus, protection against late-emerging flea beetles often requires 2-3 foliar insecticide applications or replanting of the field (72,113).…”

“…Since the mid-1990s, nearly all OSR seeds planted in Canada have been treated with systemic neonicotinoid insecticides, which are effective in reducing flea beetle damage to seedlings, usually for up to three weeks (72,113). Thus, protection against late-emerging flea beetles often requires 2-3 foliar insecticide applications or replanting of the field (72,113). In China, seed treatments began after 2000 and are preferred by local growers over conventional foliar sprays because they provide extended protection of SOSR seedlings over three weeks and reduce labor costs (40).…”