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Mortality to the egg stage of Colorado potato beetle, Leptinotarsa decemlineata(Say), from endemic predators was assessed in unsprayed plots within commercial potato fields in western Massacusetts in 1986 and 1987. Direct measurement of recruitment into the egg stage and of lossesto predation gave estimates of total stage-specific mortality for each generation of Colorado potato beetle and daily mortality rates. Abundance of endemic egg predators was measured through direct observation and trapping. Coleomegilla maculata (DeGeer), a coccinellid, was the most abundant predator and the only one consistently present whenever Colorado potato beetle eggs were in the field. Total mortality to eggs from predation was 39.9% in the second generation of 1986 and 37.8% and 58.1% in the first and second generations of 1987, respectively. Daily mortality rate did not change significantly during large fluctuations in prey density. Results suggest that C. maculata can contribute to the control of both early and late generations of Colorado potato beetle and efforts to conserve this natural enemy will help reduc;:ethe need for chemical control.

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Attraction and feeding responses of oriental fruit ßy, Bactrocera dorsalis (Hendel), and melon ßy, Bactrocera cucurbitae (Coquillett), were determined for different protein baits. In separate choice attraction assays for each species, signiÞcantly more ßies arrived at stations with bait than water, but no differences existed among baits of GF-120 Fruit Fly Bait, GF-120 NF Naturalyte Fruit Fly Bait, Provesta 621 autolyzed yeast extract, and Mazoferm E802. In comparison with B. dorsalis, B. cucurbitae had 2.8 times more responders and a 4.8 times better discrimination between baits and water. In a second attraction assay with only B. dorsalis, volume of bait was negatively correlated to numbers of ßies alighting on the bait. Feeding assays for both species demonstrated that time spent feeding and duration on a leaf were both signiÞcantly affected by bait type. B. dorsalis fed the longest on Provesta 621, with signiÞcantly less feeding on the other baits, and with all baits resulting in more feeding than water. The longest feeding times for B. cucurbitae resulted with Mazoferm E802 and Provesta 621, and all baits except GF-120 NF resulted in eliciting a signiÞcantly longer feeding duration than water. In separate toxicology assays for each species, signiÞcantly higher mortality resulted from bait formulations containing spinosad compared with blank baits, but no differences existed between GF-120 and GF-120 NF formulations. The differences are discussed between the two Bactrocera species primarily in regard to bait preference, extent of response, and previous work on laboratory ßies.

Visual host finding and form recognition by the cabbage root fly, Delia radicum, were studied using four shapes of yellow sticky traps as plant models. Cross, disc, and Y traps caught similar numbers of flies. Cross traps caught more females than ‘vertical’ or ‘horizontal’ rectangular traps. Black borders did not increase rectangle trap catches. Discs (8 cm diam.) at ground level caught more females than discs at 40 cm above ground. Larger discs (11.2 and 13.8 cm diam.) caught more females per trap than 8 cm diam. discs, but not as many per unit area. Volatile mustard oils were added to sticky cross traps as single and multiple‐component baits. Traps with multiple‐component baits did not consistently catch more females than single baited traps. Yellow traps baited with isothiocyanates caught 4–7 times as many females as clear plastic allylisothiocyanate (ANCS)‐baited traps. Results indicated yellow discs or crosses at ground level baited with ANCS effectively monitored female D. radicum. Main factors affecting landing of female D. radicum are suggested to be color of substrate, height above ground, presence of host volatiles in vicinity, visual prominence, and area of ‘attractive’ color. The view that host finding in some insects is mediated by complex responses to multichannel stimuli was supported. RÉSUMÉ Importance des stimuli visuels et olfactifs dans la perception des hôtes par les adultes de la mouche du chou, Delia radicum L'étude de la perception visuelle et de la reconnaissance des formes par les D. radicum adultes a été réalisée en utilisant des pièges jaunes gluants de quatre formes différentes comme leurres de plantes. Des pièges en croix, en disque et en Y ont permis la capture des mêmes nombres de mouches. Plus de femelles ont été capturées avec des pièges en croix qu'avec des pièges rectangulaires verticaux ou horizontaux. Les captures n'ont pas augmenté avec des pièges bordés de noir. Des disques de 8 cm de diamètre disposés au niveau du sol ont permis la capture de plus de femelles que des disques à 40 cm au‐dessus du sol. La capture par piège a été supérieure avec des pièges de 11,2 et 13,8 cm de diamètre qu'avec ceux de 8 cm, mais moindre par unité de surface. Des essences volatiles de moutarde ont été ajoutées aux pièges en croix comme appâts simples ou composés. Les pièges avec appâtes composés n'ont pas été significativement plus efficaces que les pièges à appâts simples. Les pièges jaunes appâts avec de l'isothiocyanata ont entraîné la capture de 4 à 7 fois plus de mouches que des pièges en plastique transparent appâtés avec de l'allylisothiocyanate (ANCS). Les résultats ont montré que des disques ou des croix jaunes appâtés avec de l'ANCS au niveau du sol permettent d'organiser un avertissement agricole contre D. radicum. Les principaux facteurs intervenant dans l'atterrissage des femelles de D. radicum semblent être la couleur du substrat, l'élévation audessus du sol, le contraste visuel, la présence de substance de l'hôte dans le voisinage, et l'aire d'attractivité de la couleur...

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Flyspeck disease caused by the Ascomycete fungus Schizothyrium pomi is a major component of a summer disease complex that has become an increasing problem on apple in the northeastern United States. This study describes the development of thyriothecia of S. pomi on one of its major reservoir hosts, wild blackberry, and suggests that temperature drives thyriothecium maturation. An empirical model relating thyriothecium maturity to degree-days from apple leaf budbreak in Massachusetts had a high coefficient of determination, R2 = 0.90. Ninety percent of thyriothecia matured between 540 and 1,625 degree-days from the budbreak biofix. S. pomi produced one generation of asci per year on blackberry. This discrete maturation period occurred well before signs of disease developed on apple fruit and before production of conidia. Considering that fungicide applications for scab management in commercial apple orchards also will protect fruit from flyspeck during early fruit development, it is unlikely that ascospores produced on reservoir hosts directly infect fruit. Instead, they probably initiate infections in reservoir hosts adjacent to commercial orchards, which produce conidia that are the inoculum which infects apple fruit in commercial production.

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