The Effects of Alfalfa Plant Bug (Hemiptera: Miridae) Feeding Late in the Season on Alfalfa Seed Yield in Northern Saskatchewan

Abstract

A 4-year field cage study was conducted to determine what effects feeding of alfalfa plant bug, Adelphocoris lineolatus (Goeze), late in the season had on alfalfa seed yields. When zero, one, two, or four alfalfa plant bugs were placed in sleeve cages containing stems of alfalfa at the green pod stage of growth, there was a significant decrease in the number of pods per cage and per raceme, the number of healthy seeds, and the weight of seeds with two or four bugs per cage. Increasing the duration of infestation resulted in significant increases in the number of damaged seeds per cage. An insecticide field trial was conducted in north central Saskatchewan in 1988 to determine what effects the occurrence of plant bugs had on seed yields of alfalfa. Alfalfa plant bug, lygus bug (Lygus spp.), pea aphid [Acyrthosiphon pisum (Harris)], and beneficial arthropod populations were monitored from 23 June to 1 September 1988. Seed yields were significantly greater in plots that were treated with trichlorfon in June and in June and August than in plots that were treated in August alone. The implications of a large alfalfa plant bug population late in the season to alfalfa seed production in the area are discussed.

Plant bugs (Hemiptera: Miridae) on field beans and soybeans in Manitoba, Canada: species composition and seasonal occurrence

“…The numbers of alfalfa plant bug, A. lineolatus , in field beans and soybeans in our study were too low for conclusions to be drawn about reproduction or development in these crops. Adelphocoris lineolatus is primarily a herbivore of alfalfa and red clover, and occurs in low numbers in other crops (Hughes 1943; Craig 1963; Soroka and Murrell 1993; Mostafa 2007). At least some cultivars of Phaseolus vulgaris are poor hosts for A. lineolatus : relative to insects reared on alfalfa, fewer nymphs survive to adulthood and the durations of the oviposition period and adult life are reduced (Qiaosi et al 1994).…”

“…Plant bugs (Heteroptera: Miridae) of the genera Lygus Hahn and Adelphocoris Reuter are important crop pests in the Canadian Prairie Provinces (Kelton 1980), where they attack a wide range of crops including canola (Butts and Lamb 1990; Gerber and Wise 1995), alfalfa (Craig 1983; Soroka and Murrell 1993; Gerber and Wise 1995; Mostafa and Holliday 2008), and buckwheat (Wise et al 2005). The most common Lygus species present in Manitoba crops are Lygus lineolaris (Palisot de Beauvois), Lygus borealis (Knight), and Lygus elisus (Van Duzee) (Timlick et al 1993; Gerber and Wise 1995; Mostafa 2007).…”

Insecticidal control of late-season plant bug (Hemiptera: Miridae) infestations in Manitoba has no effect on alfalfa seed quantity and quality

“…A threshold of 12Á16 plant bugs per sweep at this time is suggested in Saskatchewan (Harris 1992), but the basis for these numbers is unclear. In cages, seed yield loss from alfalfa plant bugs does not occur until well above this threshold (Soroka and Murrell 1993). Although some growers in Manitoba use the early-season threshold to justify a late-season insecticide application, there is no evidence that the early-season threshold is applicable in August.…”

“…Although some growers in Manitoba use the early-season threshold to justify a late-season insecticide application, there is no evidence that the early-season threshold is applicable in August. It is likely that thresholds for August differ from early-season thresholds because of differences in insect population structure (Murrell 1987;Soroka and Murrell 1993;Uddin 2005) and plant physiological stage (Goplen et al 1987). The objective of this research was to assess the effect of late-season plant bugs on quantity and quality of alfalfa seed yield in Manitoba, and if possible to derive an economic injury level (Stern et al 1959) for plant bugs at that time.…”