The Canadian spring wheat (Triticum aestivum L.; Poaceae) cultivar 'Superb' was less susceptible to damage by Hessian fly, Mayetiola destructor (Say), than the spring wheat cultivars 'AC Barrie', 'AC Foremost', 'McKenzie', 'AC Domain', and 'Glenlea' in Manitoba. The partial resistance of 'Superb' was similar, at the seedling stage, to that of 'Guard', which possesses the resistance gene H18. Females laid eggs readily on all cultivars, providing no evidence for antixenosis, but few larvae developed on seedlings of 'Superb' and 'Guard', showing that antibiosis against larvae is the mechanism of resistance in these seedlings. In the field, where infestation of spring wheat takes place about 4 weeks after the seedling stage, 'Guard' continued to show high levels of resistance, but 'Superb' was less resistant, although still more resistant than highly susceptible cultivars. Infested stems of 'Superb' and 'Nordic' were less likely to break than infested steins of other cultivars, showing that these two cultivars are partially tolerant to infestation. Infested stems of 'Guard' and other cultivars showed high levels of stem breakage and are intolerant. Yield losses due to infestation by Hessian fly were mostly caused by the breakage and falling over of infested stems, which prevented the seeds on these stems from being harvested. Infested stems of all susceptible cultivars that remained standing at harvest had lower seed masses and fewer seeds per spike than uninfested stems, which contributed to yield loss. 'Grandin', a parent of 'Superb', is the probable source of resistance in 'Superb', but the pedigree of 'Grandin' provides no clue as to the gene(s) involved. The partial antibiosis and tolerance expressed by 'Superb' is sufficient to reduce losses to Hessian fly by 65% in comparison with a susceptible cultivar such as 'AC Barrie'. 'Superb' is the first Canadian spring wheat cultivar identified to have an agronomically useful level of resistance to Hessian fly.

This paper describes a comparative analysis of the suitability of three artificial diets for the development of the cherry bark tortrix ( CBT), Enarmonia formosana Scopoli ( Lepidoptera: Tortricidae), to simplify the rearing process for this species and its potential classical biological control agents. The three diets tested included ( 1) a pinto bean- based diet modified specifically for the CBT, ( 2) the diet for codling moth, Cydia pomonella Linnaeus ( Lepidoptera: Tortricidae), and ( 3) the Singh general- purpose diet. Survival from first instar to the pupal stage was very low on the pinto bean, codling moth, and Singh general- purpose diets ( 29, 0, and 0%, respectively). Survival was consistently greater, yet still low, for larvae that were reared through the first instar on bark and subsequently transferred to the codling moth or Singh general- purpose diets ( 5 and 32%, respectively). In comparison, larvae started on the pinto bean diet as second instars had a survival rate of 90%, only slightly below that of sibling larvae from the cherry bark control group ( 100%). Larval development time was fastest on cherry bark ( 36 +/- 2 days), differing significantly from that on the pinto bean diet ( started as first instars: 58 +/- 2 days; started as second instars: 46 +/- 2 days), but not from the development time of larvae on the Singh general- purpose diet ( 44 +/- 3 days). Pupal weights were greatest for specimens from the Singh general- purpose diet ( 14.9 +/- 0.5 mg) and lowest for those from the pinto bean diet ( started as first instar: 12.3 +/- 0.6 mg; started as second instar: 12.1 +/- 0.4 mg). Pupal weights from cherry bark were intermediate ( 13.5 +/- 0.6 mg). Early mortality, resulting primarily from rejection of the diet, remains to be the critical impediment in CBT rearing. It is therefore suggested that a phagostimulant from cherry bark be identified and included in an artificial diet shown to be nutritionally suitable, such as the Singh general- purpose diet or the pinto bean diet.

Peristenus digoneutis Loan and Peristenus stygicus Loan, parasitoids of the European tarnished plant bug Lygus rugulipennis Poppius, are established in the United States for biological control of native North American Lygus species, and are being considered for deliberate release in Canada. High lifetime fecundity of parasitoids is considered a desirable attribute of biological control agents and therefore, an understanding of parasitoid reproductive biology is required. In the present study, the potential lifetime fecundity of both agents was compared under laboratory conditions to estimate the potential impact of Peristenus species on Lygus. Synovigenic P. digoneutis and P. stygicus females oviposited most actively in the first two weeks of their lifetime, with a maximum average daily oviposition rate after five days. The maximum number of eggs laid per day was 83 eggs for P. stygicus, and 36 eggs for P. digoneutis. P. digoneutis has an average potential lifetime fecundity of 385 ± 35 SE eggs produced over 22 ± 3 SE days. In contrast, P. stygicus females have a 50% higher mean potential lifetime fecundity reaching 782 ± 65 SE eggs over 28 ± 1 SE days. A positive correlation between lifetime fecundity and body size was found only for P. stygicus, and both species showed a significant relationship between lifetime fecundity and oviposition period. The present study demonstrates that the fecundity of P. digoneutis and P. stygicus is considerably higher than previously reported. Based on these findings, P. stygicus appears to be the most effective biological control agent for Lygus lineolaris (Palisot de Beauvois) when only fecundity is taken into consideration.

To ascertain the reasons for the Hessian fly (Mayetiola destructor (Say)) survival in previous field tests, confirmatory studies were conducted in the laboratory. Investigations were conducted to verify the effect of different types of test cages (designated as types A, B and C) containing different quantities of infested wheat seedlings on thermal death of the Hessian fly puparia. Calibrated thermocouple probes were inserted into the bales and the test cages containing the bulk of the infested wheat seedlings. Four mesh bags were inserted into a bale. The instrumented bale was placed in the heating chamber. The bale was heated for 18 min: 6 min heating from top to bottom, 6 min from bottom to top, and 6 min from top to bottom. Ambient air (20 - 27 o C) was circulated through the control bales. Results indicated that the moisture content of the infested wheat seedlings ranged from 18.7 to 19.9% for the type A test cages, 15.1 to 29.0% for type B and 15.9 to 18.5% for type C. The moisture contents of the infested wheat seedlings (15.1 to 29.0%) were relatively higher than the moisture contents of the hay bales used in previous field trials (12.6 to 14.7%) and the present tests (11.1 to 12.8%). The temperature profiles within the infested wheat seedlings for types A and B test cages lagged behind the temperature profiles within the bales. The temperature within the bulk of the infested wheat seedlings for some of types A and B test cages never reached 60 o C. There were more type A cages that did not reach 60 o C compared to type B cages. Temperatures measured within the infested wheat seedlings for the type C test cages followed closely the temperatures within the bales. All temperatures within the bulk of the wheat seedlings for type C cages reached 60 o C for more than 3 min. There were Hessian fly survivors in the infested wheat seedlings contained in types A and B test cages during the heat disinfestation tests. The total Hessian fly survivors ranged from 107 to 131 for type A test cages and 129 to 163 for type B. There were no Hessian fly survivors during the heat disinfestation tests for the infested wheat seedlings contained in the type C test cages. The total Hessian fly survivors in the unheated control tests were 461 for type A test cages, 350 for type B and 648 for type C.