Sex Pheromone of the Introduced Pine Sawfly, Diprion similis, Revisited to Define a Useful Monitoring Lure: Deviating Chiral Composition and Behavioural Responses Compared to Earlier Reports

Extracts of Diprion similis females contained about 15 ng of the sex pheromone precursor 3,7-dimethylpentadecan-2-ol per female. After derivatisation with (S)-2-acetoxypropanoyl chloride, we found that the major stereoisomer in the extract was (2S,3R,7R)-3,7-dimethylpentadecan-2-ol. Small amounts of other stereoisomers of 3,7-dimethylpentadecan-2-ol were also identified in the extract, namely 1% of (2R,3S,7S), 0.3% (2R,3R,7R) and 0.4% of (2R,3R,7S). An unknown fifth substance showed a very similar spectrum to 3,7-dimethylpentadecan-2-ol, both in SIM and full scan mode. None of the earlier suggested behavioural synergistic isomers ((2S,3S,7S), (2S,3S,7R) and (2S,3R,7S)) were detected in the extracts. In field tests in Ontario, Canada, the earlier identified main pheromone component, viz. the propanoate of (2S,3R,7R)-3,7-dimethylpentadecan-2-ol, was tested alone and in combination with other stereoisomers, earlier reported to be synergistic. No synergistic effects were detected and the threo four-isomer blend was as attractive as the pure main compound. Thus, one of the few examples of a diprionid sawfly using more than one substance in its sex pheromone could not be confirmed. The results also suggest that monitoring programs can use the more easily synthesized threo-blend without losing efficiency. Furthermore, the study suggests that other diprionid pheromones may benefit from a reinvestigation, to clarify possible synergistic effects of stereoisomers.

Efficacy of Piper nigrum (Piperaceae) extract for control of insect defoliators of forest and ornamental trees

The acute toxicities of an extract obtained from a plant within the Piperaceae family and related synthetic analogues were tested against four common Canadian forest pest insects. The acute toxicity of the extract from black pepper, Piper nigrum L., was assessed after 1, 24, and 72 h by the percent larval mortality. The 24 h LC50 estimates for the P. nigrum extract were (in order of decreasing sensitivity) 0.012% for the introduced pine sawfly, Diprion similis (Hartig) (Hymenoptera: Diprionidae), 0.053% for the forest tent caterpillar, Malacosoma disstria Hubner (Lepidoptera: Lasiocampidae), 0.282% for the gypsy moth, Lymantria dispar (L.) (Lepidoptera: Lymantriidae), and 0.998% for the spruce budworm, Choristoneura fumiferana (Clemens) (Lepidoptera: Torticidae). There was no significant increase in mortality after 72 h. Seventy percent of L. dispar larvae dropped off or moved from branches within 1 h of application of 0.2% P. nigrum extract, indicating that these compounds have a repellent effect. Pipercide and nor-pipercide were more toxic to L. dispar and M. disstria larvae than piperolein A and a P. sarmentosum Roxb. amide 72 h after either oral or topical administration of these compounds. Toxic effects of piperamides were more pronounced by oral ingestion. Ninety percent mortality of L. dispar larvae occurred following an oral dose of 5 µg pipercide in diet, whereas mortality was only 40% following topical treatment at 5 µg pipercide/insect. Whole Piper extracts might be useful for the control of sawflies and tent caterpillars in small-scale applications, based on the demonstrated efficacy and reduced risk potential.

Diapause Induction in a Kentucky Population of Diprion similis (Hymenoptera: Diprionidae)

Critical photoperiod, sensitive stage for diapause induction, and requirements for termination of diapause were studied in a colony of the introduced pine sawfly, Diprion similis (Hartig), established from a feral Kentucky population. We investigated induction of diapause in the laboratory under photoperiods of 10:14, 11:13, 12:12, 13:11, 14:10, 15:9, and 16:8 (L:D) in the first trial, and added a photoperiod of 9:15 (L:D) in the second trial. Individuals exposed to light periods ≤12:12 (L:D) entered diapause; individuals in a photoperiod > 13:11 (L:D) bypassed diapause. The sensitive stage was determined using reciprocal switches of diapause-inducing (9:15) and non-diapause inducing (16:8) L:D regimes. Our studies indicated that late instars of the introduced pine sawfly are significantly sensitive to photoperiod. Termination of diapause in D. similis did not require a cold or chilling period. All individuals from critical photoperiod trials were kept at 22°C to determine the duration of diapause. Diapausing individuals emerged from the cocoon after 82 to 105 d, compared to 6 to 23 d for individuals not entering diapause.

Utilization of dry matter and elements by larvae of the sawflies Neodiprion sertifer (Geoff.) and Diprion similis (Hartig) feeding on Scots pine needles

Consumption and proportions of dry matter and various elements utilized by late-instar larvae of Diprion similis (Hartig) and Neodiprion sertifer (Geoff.) feeding on previous years' needles of Scots pine (Pinus sylvestris L.) were determined gravimetrically and by means of cellulose as an indigestible marker substance. The only discrepancy between the two methods was for phosphorus intake by N. sertifer females. Female larvae of D. similis utilized larger proportions of dry matter, nitrogen, and potassium and less phosphorous than female larvae of N. sertifer; both species utilized similar proportions of calcium and magnesium. Combined male–female groups of N. sertifer larvae utilized larger proportions of dry matter, potassium, and magnesium compared with female larvae. The proportions utilized were ranked as follows: nitrogen (50–59%), phosphorous (22–39%), magnesium (15–29%), calcium (9–15%), and potassium (6–17%). Nonpositive sodium budgets precluded calculation of utilization of this element. The proportions of dry matter utilized by these sawflies are similar to those for 10 species of foliage-consuming Hymenoptera and fall toward the lower end of the range of values for phytophagous insects. Nitrogen utilization figures for these sawflies fall within the range of values reported for insects that consume tree foliage.

Morphology and ultrastructure of an intertergal pheromone gland in the abdomen of the pine sawfly Neodiprion sertifer (Insecta, Hymenoptera): a potential source of sex pheromones

An abdominal intertergal gland of the sawfly Neodiprion sertifer was found in both sexes of the sawfly N. sertifer, which is in contrast with Diprion similis, in which the gland is known only from the female. The gland lies laterally on each side of tergite II in the fat body between the tergite wall and trachea and opens into the fold of the arthrodial membrane between tergites II and III. The emission of secretion from the gland is controlled by a muscle opening the gland duct. Expansion of the lateral trachea probably forces the secretion out of the gland's lumen.The intertergal gland is a typical insect epidermal pheromone gland formed by three cell types: glandular, ductule, and hypodermal cells. The glandular cells have microvilli-lined cavities surrounded by numerous mitochondria. From these cavities arise ductules, surrounded by ductule cells, merging into other ductules that open into the lumen of the gland. The hypodermal cells underlie the cuticular walls of the lumen. This scheme is now well-known from many insect species as typical of epidermal pheromone glands with a draining duct. Finally, the possible function of the intertergal gland's secretion is discussed.

EFFECT OF A PHENYL-BENZOYL UREA [l-(4-CHLOROPHENYL)-3-(2,6-DIFLUOROBENZOYL)-UREA] ON DIPRION SIMILIS (HYMENOPTERA: DIPRIONIDAE)

Ingestion of a phenyl-benzoyl urea [1-(4-chlorophenyl)-3-(2,6-difluorobenzoyl)-urea] by Diprion similis (Hartig) interferes with molting. At the highest concentration (1% solution) tested, it prevents ecdysis but does not prevent apolysis. The Cuticle of pharate larvae is thinner than normal but the formation of melanin in the cuticle is not inhibited. At a concentration of.01%, ecdysis is usually completed but many survivors fail to feed following the molt. This failure is associated with the accumulation of a fibrous material in the midgut. Prior to the molt, food consumption as measured by faecal output is not impaired.

PARASITOIDS OF THE INTRODUCED PINE SAWFLY, DIPRION SIMILIS (HYMENOPTERA: DIPRIONIDAE), IN MINNESOTA

Parasitoids of the overwintering generation of the introduced pine sawfly were surveyed in Minnesota. The parasitization rate was greatest in cocoons collected from foliage in fall 1971, but there was nearly complete mortality of sawflies and parasitoids in cocoons above the snowline by April 1972. Monodontomerus dentipes (Dalm.) most commonly emerged from cocoons collected from trees and shrubs in fall 1971. Exenterus amictorius (Panz.) was the most common parasitoid of cocoons collected from duff in both 1971 and 1972.