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The influence of total resin flow in loblolly pine, Pinus taeda L., on initial colonization by the southern pine beetle, Dendroctonus frontalis Zimmermann (Coleoptera: Scolytidae), was investigated. Resin flow of trees was manipulated mechanically so that it followed the same pattern of decrease and near cessation as seen in trees successfully attacked by southern pine beetle. There were also intermediate treatments where resin flow was allowed to recover after near cessation. Beetles were introduced by means of mesh cages attached to the mid-bole of trees and left until the end of the longest wounding treatment. In trees where resin flow was reduced, significant increases in number of attacks, total gallery length, and length of gallery free of resin occurred.

The influence of total resin flow in loblolly pine, Pinus taeda L., on initial inoculation of the blue stain fungus Ophiostoma minus (Hedgc.) Syd. & P. Syd., a fungal associate of southern pine beetle (Dendroctonus frontalis Zimmermann (Coleoptera:Scolytidae)), was investigated. Resin flow of trees was mechanically manipulated so that it followed the same pattern of decrease and near cessation as seen in trees successfully attacked by southern pine beetle. There were also intermediate treatments where resin flow was allowed to recover. The fungus was inoculated into holes drilled to the xylem surface and allowed to grow for a specified time period. The lesion that formed as a result of the induced reaction was then measured and compared with lesions formed in trees for which resin flow was not manipulated. The experiment was conducted three times in 1993 and 1994 and twice in 1995. It was hypothesized that with decreased resin flow, O. minus would be less inhibited and that growth would be greater before being stopped by the induced reaction. It was found that longer lesions occurred in trees where wounding was prolonged and resin flow was decreased below that of control trees. Mixed results were obtained for trees in intermediate wounding treatments.Key words: oleoresin, blue stain fungus, defenses, bark beetles, induced reaction, Dendroctonus.

The beet armyworm, Spodoptera exigua (Hubner), is a sporadic but devastating secondary pest of cotton. Scouting cotton for egg masses is commonly recommended for identifying potential outbreaks and for proper timing of insecticide applications. However, there is disagreement regarding where to look on the plant for beet armyworm eggs. We investigated and quantified placement of egg masses by laboratory colony females within cotton and pigweed (a preferred wild host plant) canopies of different heights. In cotton, almost all egg masses were deposited on the undersides of leaves, and ≈80% of the egg masses were consistently located in the upper 50% of the cotton canopy, and horizontally within the inner 50% of the canopy around the central axis. Although this trend was consistent among all categories of plant height tested, variation about the means decreased with increasing height. A smaller sample of wild females indicated similar vertical placement, but horizontal placement extending further distally in the canopy. Our results indicate that scouting for egg masses on the underside of leaves in the upper half of the canopy will recover ≈80% of the egg masses present on the plants. In pigweed, egg masses were commonly laid within the inner 50% of the canopy, but along the upper 80% of the vertical axis. As in cotton, variation about the means was less in taller plants. The number of eggs per egg mass was 29% less in cotton than in pigweed. This positional information will aid in further efforts to investigate, predict, and manage beet armyworm populations in cotton and noncotton hosts.

Longevity, duration of the oviposition period, realized fecundity, potential fecundity, and egg fertility of the beet armyworm, Spodoptera exigua (Hubner), were examined in the laboratory under three different adult diet regimes. All parameters were significantly reduced for the water-only diet compared with 10% honey or sucrose diets, except fertility, which could not be measured after 5 d because of high mortality of water-fed females. Oviposition was highest the night after mating and decreased in a logarithmic manner thereafter. In the carbohydrate-fed moths, 92% of lifetime realized fecundity occurred by the fourth night of oviposition. Although our data indicate that carbohydrates in the adult diet can increase realized and potential fecundity, most of the lifetime complement of oocytes (91%) is present at the time of eclosion from the pupa. Pupal weight was significantly correlated with lifetime potential fecundity, explaining 37–66% of the variation among moths depending on adult diet, and this effect was substantial. Taken together, our results suggest that the bulk of variation in realized fecundity is generated in the larval stage, provided suitable oviposition substrate is available for the adults. This information will be important in understanding population dynamics of beet armyworm and to improving our ability to predict population outbreaks from sampling data.

Basic information on oviposition behavior of Neodiprion fulvicepsis presented. We present evidence which suggests that adults possess circadian rhythms for emergence and female oviposition activity. A behavioral catalog was developed and it was found that females, while inactive, spend 54% of their time oriented basally on needles and, while active, 18% of their time walking up and down needles. A description of the oviposition sequence and time spent in each step is presented. It was determined that females spend a significantly longer time cutting the first egg pocket than successive egg pockets. We also present evidence of an oviposition deterrent factor.

1 The effect of ponderosa pine (Pinus ponderosa Doug]. ex Laws) water stress, measured by xylem water potential, on oviposition preference and egg development of Neodiprion fulviceps was determined by two laboratory experiments in 1987 and 1988. 2 In the first experiment, adult females were allowed to choose between foliage from water-stressed, watered, and untreated control trees. 3 Significant differences were found between treatments in xylem water potential in 1987 but not in 1988. 4 Females chose water-stressed trees and a positive correlation was found between female preference and xylem water potential in 1987 but not in 1988. 5 In the second experiment, females were placed in globe cages with a single branch from each treatment and allowed to oviposit. 6 Significant differences were found among treatments in egg survival in 1987 but not in 1988. 7 These results indicate that sawflies can distinguish between stressed and non-stressed trees and that this behaviour is adaptive in that egg survival was greatest on the preferred treatment.

Resin flow was measured at four heights along the bole of loblolly pine, Pinus taeda L., using two, four, and eight wounds per height in May, June, July, and August of 1990. Consistent differences in resin flow between heights were observed with the eight per height treatment. The greatest amount of flow was found to be from the midbole and below. The differences in flow for the two and four samples per height treatments followed the same pattern as the eight per height treatment; however, no statistical differences were detected. Total flow for the entire tree was found to increase from May to August. Key words: oleoresin secretory system, Pinus taeda, southern pine beetle, insect – host interaction, induced response.