Weevil Damage Research Articles

Pine weevil (Hylobius abietis) damage to cuttings and seedlings of Norway spruce

Abstract Damage caused by pine weevil ( Hylobius abietus L.) to planted seedlings and cuttings of Norway spruce ( Picea abies (L.) Karst.) was studied at five clearcut sites in south-eastern Sweden. The main objective was to compare the two types of stock in terms of attack frequency and mortality due to pine weevil feeding. Cuttings and seedlings with the same initial stem-base diameter (4 mm) were compared. Two sites were harvested and scarified shortly before planting, two were harvested shortly before planting, but were not scarified, and one was harvested 2 years before and scarified the autumn before planting. The total mortality 5 years after planting was highest, greater than 90%, at the new, non-scarified sites, and lowest, 23%, at the old, scarified site. More than 90% of the mortality was caused by pine weevil feeding. Attack frequency and pine weevil induced mortality were significantly higher among seedlings than among cuttings. Mortality due to pine weevil damage was 4–43% higher in seedlings than in cuttings after the fifth year. Of the cuttings and seedlings that were attacked in the first year, a significantly higher frequency of the seedlings were girdled. The higher resistance of cuttings to pine weevil damage may partly explain the more rapid growth of cuttings reported in other studies. However, the causes of their higher resistance need to be further investigated. The thicker bark and needles on the stem base of the cuttings could be important in this respect.

Steam treatment as a vegetation management method on a grass-dominated clearcut

A field experiment was established to investigate whether a new site preparation technique by steam treatment could be used to control Deschampsia flexuosa vegetation. The experiment was conducted at a south Swedish clearcut dominated by Deschampsia. Growth and survival of planted Norway spruce seedlings in steam-treated plots were compared to seedlings planted in traditional soil scarified plots and in intact vegetation. A second experiment was conducted to study the duration of the heat in the soil during and after a steam treatment and its impact on vegetation reduction. Steam treatment efficiently killed the vegetation and duration for 60 s or more reduced the vegetation to less than 25% of that in untreated plots for 2 years. Steam treatment also reduced the vegetation to a greater extent than soil scarification. After the third growing season the total seedling height was greatest for spruce seedlings grown in steam-treated plots and soil scarified plots. The number of spruce seedlings attacked by pine weevil was about the same in steam-treated plots as in intact plots, however, seedling survival was significantly lowest in intact plots. Pine weevil damage on seedlings grown in steam-treated plots may have affected seedling growth negatively.

Effect of Overseeding Forages into Alfalfa on Alfalfa Weevil, Forage Yield and Quality

Many alfalfa (Medicago sativa L.) fields are sprayed each year with insecticides to control Egyptian alfalfa weevil (Hypera brunneipennis) and the alfalfa weevil (Hypera postica). Overseeding various species of legumes and grasses into established alfalfa has been proposed as a method to mitigate weevil damage without insecticides. Established fields of alfalfa were overseeded with legumes and grasses in randomized complete block designs in three years of study in a Mediterranean climate in the Sacramento Valley of California, USA. Several overseeding practices maintained or increased yields compared with the insecticide‐sprayed treatment. Overseeding increased or maintained forage yield, eliminating the need for insecticides. However, overseeding did not prevent weevil damage to alfalfa. Overseeding is best used to extend the life of alfalfa stands in the final year of production, since overseeding can thin alfalfa stands. Market acceptance for mixed‐species hay and harvest management of overseeded forages are the most important limitations to overseeding practices.

White/Red Pine Stand Response<br />to Partial Cutting and Site Preparation

Eastern white pine (Pinus strobus L.) often grows in association with red pine (Pinus resinosa Ait.) in fire-adapted stands (Ahlgren, 1976). Both pines may be well suited to partial cutting because of their high value and white pine’s mid-tolerance to shade and susceptibility to white pine weevil (Pissodes strobi Peck) damage when grown in 222open areas. Although these pines are major commercial species in eastern North America, relatively little is known about their physiology (Wetzel and Burgess, 1994) or their ability to regenerate and develop in managed stands (Hibbs and Bentley, 1987). Natural regeneration of pine after harvesting is often unacceptably low (Wray, 1985) and debate continues about how these stands can best be regenerated (Carleton et al., 1996). Well-defined management strategies are needed to encourage pine regeneration to help ensure the sustainability of this valuable resource (Stiell et al., 1994).

Biology and integrated pest management for the banana weevil Cosmopolites sordidus (Germar) ( Coleoptera : Curculionidae )

The banana weevil Cosmopolites sordidus (Germar) is the most important insect pest of bananas and plantains (Musa spp.). The larvae bore in the corm, reducing nutrient uptake and weakening the stability of the plant. Attack in newly planted banana stands can lead to crop failure. In established fields, weevil damage can result in reduced bunch weights, mat die-out and shortened stand life. Damage and yield losses tend to increase with time. This paper reviews the research on the taxonomy, distribution, biology, pest status, sampling methods, and integrated pest management (IPM) of banana weevil. Salient features of the weevil's biology include nocturnal activity, long life span, limited mobility, low fecundity, and slow population growth. The adults are free living and most often associated with banana mats and cut residues. They are attracted to their hosts by volatiles, especially following damage to the plant corm. Males produce an aggregation pheromone that is attractive to both sexes. Eggs are laid in the corm or lower pseudostem. The immature stages are all passed within the host plant, mostly in the corm. The weevil's biology creates sampling problems and makes its control difficult. Most commonly, weevils are monitored by trapping adults, mark and recapture methods and damage assessment to harvested or dead plants. Weevil pest status and control options reflect the type of banana being grown and the production system. Plantains and highland bananas are more susceptible to the weevil than dessert or brewing bananas. Banana production systems range from kitchen gardens and small, low-input stands to large-scale export plantations. IPM options for banana weevils include habitat management (cultural controls), biological control, host plant resistance, botanicals, and (in some cases) chemical control. Cultural controls have been widely recommended but data demonstrating their efficacy are limited. The most important are clean planting material in new stands, crop sanitation (especially destruction of residues), agronomic methods to improve plant vigour and tolerance to weevil attack and, possibly, trapping. Tissue culture plantlets, where available, assure the farmer with weevil-free material. Suckers may be cleaned by paring, hot water treatment and/or the applications of entomopathogens, neem, or pesticides. None of these methods assure elimination of weevils. Adult weevils may also invade from nearby plantations. As a result, the benefits of clean planting material may be limited to a few crop cycles. Field surveys suggest that reduced weevil populations may be associated with high levels of crop sanitation, yet definitive studies on residue management and weevil pest status are wanting. Trapping of adult weevils with pseudostem or corm traps can reduce weevil populations, but material and labour requirements may be beyond the resources of many farmers. The use of enhanced trapping with pheromones and kairomones is currently under study. A combination of clean planting material, sanitation, and trapping is likely to provide at least partial control of banana weevil.

Influence of Stem Diameter on the Survival and Growth of Containerized Norway Spruce Seedlings Attacked by Pine Weevils (Hylobius spp.)

Pine weevils (Hylobius spp.) feeding on stem bark of young conifer seedlings pose a serious threat to forest regeneration-planting programmes in Nordic countries. This study was designed to determine the threshold diameter for planted, untreated containerized seedlings, above which pine weevils cause little or no damage. The effects of sublethal weevil damage on seedling growth were also assessed. In total, 5320 containerized spruce seedlings were planted on scarified and unscarified plots on three sites in southern Sweden. Seedlings in six size classes, which differed with regard to age (1.5-3.5 yrs) and cultivation density (28-446 seedlings m 2) were grown using the Combicell system. None of the seedlings was treated with insecticides, except for those in the smallest class, where both untreated and treated seedlings were used. Inspections were made periodically during the first 3 yrs and after both 5 and 7 yrs. A statistically significant relationship was found between seedling losses due to pine weevil attack and seedling stem-base diameter at the time of planting out, on both scarified and unscarified plots. For seedlings with a stem-base diameter of around 10 mm, mortality due to pine weevil attack on scarified plots was low enough to be considered negligible. This threshold diameter was several millimetres greater for seedlings planted on unscarified plots. An analysis of the relationship between the extent of weevil damage and seedling growth rate showed that among surviving seedlings, those that grew fast tended to show low levels of damage. On unscarified plots, the mortality rate amongst seedlings treated once with a permethrin insecticide was only one-third that of untreated seedlings. On scarified plots, the corresponding difference was somewhat smaller. Repeated insecticide treatment resulted in a pronounced reduction in seedling mortality on the unscarified plots, whereas the effect was weaker on scarified plots.

Pine weevil (Hylobius abietis) antifeedants from lodgepole pine (Pinus contorta).

Pine weevils (Hylobius abietis) fed less on bark of lodgepole pine (Pinus contorta) than on bark of Scots pine (P. sylvestris). Two pine weevil antifeedants, ethyl trans-cinnamate and ethyl 2,3-dibromo-3-phenyl-propanoate, were isolated from bark of lodgepole pine. These two compounds significantly reduced pine weevil feeding in a laboratory bioassay. In field assays, the second compound significantly decreased pine weevil damage on planted seedlings. Ethyl 2,3-dibromo-3-phenylpropanoate has not previously been reported as a natural product.

Extra Food Supply Decreases Damage by the Pine Weevil Hylobius abietis

It has been suggested that reduced damage by the pine weevil ( Hylobius abietis ) under shelter trees might result from more food being available under shelter trees than on clear-cuttings. The shelter trees provide an extra supply of bark on branches and roots. Moreover, shelter trees favour some species in the ground vegetation (e.g. bilberry, Vaccinium myrtillus ) that could be used as food by the weevil. Two similarly designed field experiments, studied whether the amount of pine weevil feeding on planted conifer seedlings was affected by the availability of other food sources. In the first experiment, fresh pine branches were placed weekly on the ground for 6 weeks on a fresh clear-cutting in southern Sweden. This significantly reduced the amount of feeding on seedlings in treated 20 2 20 m plots. In the second experiment, damage tended to increase after mechanical removal of field vegetation (mainly bilberry), but the effect was not statistically significant. In conclusion, extra food in the form of coniferous bark could relieve seedlings from pine weevil damage; however, any effect of this kind due to the presence of field-layer vegetation remains to be demonstrated. Finally, there may be long-term population effects because of the extra food that the shelter trees provide for the reproductive weevils.

Changes in volatile terpene and diterpene resin acid composition of resistant and susceptible white spruce leaders exposed to simulated white pine weevil damage.

Induced (traumatic) resin in white spruce (Picea glauca (Moench) Voss) leaders resistant or susceptible to the white pine weevil (Pissodes strobi Peck) was analyzed for volatile terpenes and diterpene resin acids after simulated white pine weevil damage. Leaders from 331 trees were wounded just below the apical bud with a 1-mm diameter drill, coinciding with the natural time of weevil oviposition in the spring. Leaders were removed in the fall, and the bark and xylem from the upper and lower regions of the leader extracted and analyzed by gas chromatography. Unwounded trees had low amounts of resin in xylem compared with bark. In response to wounding, volatile terpenes and diterpene resin acids increased in the upper xylem (area of wounding), with resistant trees showing a greater increase than susceptible trees. Wounding caused monoterpenes in particular to decrease in the lower region of the leader (away from the drilled area) in greater amounts in susceptible trees than in resistant trees. In response to wounding, the proportion of monoterpene to resin acid increased in the upper and lower xylem of resistant trees, and slightly increased in the upper xylem of susceptible trees. Monoterpene-enriched resin is more fluid than constitutive resin, and probably flows more readily into oviposition cavities and larval mines, where it may kill immature weevils. Loss of resin components in the lower xylem suggested catabolism and transport of these materials to the site of wounding; however, energetic and regulatory data are necessary to confirm this hypothesis. This study provides a basis for measuring the ability of a tree to undergo traumatic resinosis that could be used to screen for resistance to white pine weevil.

The evolution of plant response to herbivory: simultaneously considering resistance and tolerance in Brassica rapa

Although the evolution of plant response to herbivory can involve either resistance (a decrease in susceptibility to herbivore damage) or tolerance (a decrease in the per unit effect of herbivory on plant fitness), until recently few studies have explicitly incorporated both of these characters. Moreover, theory suggests these characters do not evolve independently, and also that the pattern of natural selection acting on resistance and tolerance depends on their costs and benefits. In a genotypic selection analysis on an experimental population of Brassica rapa (Brassicaceae) I found a complex set of correlational selection gradients acting on resistance and tolerance of damage by flea beetles (Phyllotreta cruciferae: Chrysomelidae) and weevils (Ceutorhynchus assimilis: Curculionidae), as well as directional and stabilizing selection on resistance to attack by weevils. Evolution of response to flea beetle attack is constrained by a strong allocation cost of tolerance, and this allocation cost may be caused by a complex correlation among weevil resistance, weevil tolerance, flea beetle resistance, and flea beetle tolerance. Thus, one important conclusion of this study is that ecological costs may involve complex correlations among multiple characters, and for this reason these costs may not be detectable by simple pairwise correlations between characters. The evolution of response to weevil attack is probably constrained by a series of correlations between weevil resistance, weevil tolerance, and fitness in the absence of weevil damage, and possibly by a cost of tolerance of weevil damage. However, the nature of these constraints is complicated by apparent overcompensation for weevil damage. Because damage by both flea beetles and weevils had non-linear effects on plant fitness, standard measures of tolerance were not appropriate. Thus, a second important contribution of this study is the use of the area under the curve defined by the regression of fitness on damage and damage-squared as a measure of tolerance.

Oviposition Patterns of the Strawberry Bud Weevil (Coleoptera: Curculionidae) at Two Spatial Scales and Implications for Management

The strawberry bud weevil, Anthonomus signatus Say, is an important pest of strawberries in eastern North America. Typically, growers treat entire fields with insecticides on an annual basis when the number of clipped buds exceeds a threshold. The 3 objectives of this study were as follows: (1) to determine the distribution of weevil injury within strawberry fields, (2) to determine if managing only field borders would be effective, and (3) to determine if weevils preferentially oviposit in particular orders of flowers on an inflorescence. During a 3-yr monitoring period (1992–1994), A. signatus oviposition activity increased unidirectionally at a rate of ≈8 m or 10 rows (1.25 m centers) per year. In 7 grower fields in New York, only the 12-m perimeter of strawberry fields treated with insecticide reduced injury to a level similar to interior portions of the field. In the interior of these fields, insecticide treatments did not influence the level of weevil damage. Even when weevils damaged floral buds, only a small proportion (7%) were primary flowers that produce the largest fruit. On average, oviposition occurred disproportionally in secondary flower buds. These observations indicate that A. signatus can be managed effectively by treating the outside perimeter of fields rather than entire fields, planting cultivars that compensate the most for clipper injury on the perimeter, and suggest that thresholds could be raised because damage to large, primary buds is limited.

Economic Evaluation of Boll Weevil (Coleoptera: Curculionidae) Management Options for Early-Planted, Irrigated Cotton in the Texas Rolling Plains

A full-season, threshold-based insecticide control program, primarily for boll weevils, Anthonomus grandis grandis Boheman, was compared with no insecticide control in irrigated cotton in the northern Texas Rolling Plains from 1993 to 1995. These 2 insecticide-use options were compared in 3 cotton varieties (Paymaster HS-26, TAMCOT HQ95, All-Tex Quickie) and 2 row spacings (76 cm and 102 cm). Cotton was planted in late April–early May each year, which is an earlier planting time than the preferred period of late May–early June. Net returns per hectare were calculated for each treatment and used to determine the most cost-effective chemical and row spacing management option for each cultivar. Of the 29 insecticide applications for thrips, boll weevils, bollworms, Helicoverpa zea (Boddie), and cotton aphids, Aphis gossypii Glover, during the 3-yr study, 23 were for management of boll weevils. Boll weevil damage was lowest in HS-26 in the 76-cm spacing and in Quickie in the 102-cm spacing; these cultivars produced fewer squares and bolls in these 2-row spacings, respectively, than did the other 2 cultivars. Average yield and net income were higher in the 76-cm row spacing than in the 102-cm spacing, and yield and income were higher in HS-26 and HQ95 than in Quickie in both row spacings. Average yields were higher in treated plots, but average net income was higher in untreated cotton. In the 76-cm row spacing, highest net return was obtained from untreated Quickie ($161.10/ha), whereas in the 102-cm row spacing, highest net returns were obtained in treated HS-26 ($174.47/ha) and untreated HQ95 ($167.25/ha). In treated and untreated cotton, the break-even yields were 697 and 514 kg lint per hectare, respectively. In treated plots, yields for HS-26 in both 76- and 102-cm row spacings and for HQ95 in the 76-cm row spacing exceeded the break-even yield. Yields in all untreated plots, except Quickie in the 102-cm row spacing, exceeded the break-even yield. Based on comparisons of net returns between treated and untreated plots of each cultivar, only HS-26 in the 102-cm row spacing responded adequately to a full-season insect control program. In all other comparisons, net returns were numerically higher in untreated plots. Insecticidal control should be tailored to the cultivar and row spacing used.

Variation in damage by terminal shoot insects among jack pine families

The susceptibility of jack pine, Pinus banksiana Lamb., to damage by the white pine weevil, Pissodes strobi (Peck) and the eastern pine shoot borer, Eucosma gloriola Heinrich, was examined over a three-year period (1994–1996) in a 400-family genetic test near New Liskeard, Ontario. Of the 7180 trees examined, white pine weevil damaged 1041 and eastern pine shoot borer damaged 1913 trees, yielding damage frequencies of 14.5% and 26.6%, respectively. Thirty families of jack pine never sustained weevil damage during the study period, while only one family escaped damage by the shoot borer. The expected, and observed, damage rates were significantly different for the weevil, but not for the shoot borer. There was no discernible spatial pattern in the incidence of shoot damage by either insect species, based on the geographic location of the parent trees. The data suggest that there is a basis for pursuing further studies to evaluate genetic resistance in tree improvement programs.

Evaluation of the impact of sweetpotato weevil (Cylas formicarius) and of the effectiveness of Cylas sex pheromone traps at the farm level in Indonesia

We evaluated the impact of sweetpotato weevil ( Cylas formicarius (Fabricius); Coleoptera: Apionidae) and of other direct pests and diseases (rats, Ceratocystis fimbriata, white grubs, rootrots and root cracks), and the effectiveness of C. formicarius sex pheromone traps at the farm level in four villages in East and Central Java, Indonesia during 1994 - 1996. Marketable yields of sweetpotato and damage from weevils and from other pests and diseases were higher during the dry season, when damage from weevils reached 8.2% and the impact of other pests and diseases was 16.3%, reducing marketable yield from 3.32 to 2.50 kg/m2. During the wet season damage from sweetpotato weevil and from other pests and diseases dropped to 2.1 and 12.7% respectively. Varietal differences in damage from weevil and from other pests and diseases were not significant. In field trials with sex pheromone, lure loadings of 10, 50 and 100 mug placed at trap densities of 9, 25 and 100 traps/ha the average yield was 2.41 kg/m2 with sweetpotato weevil and other direct pests and diseases accounting for losses of 2.7% and 4.7% respectively. However, there were significant location-specific differences in weekly trap catch averages and in seasonal trap catch patterns. Trap catches ranged from averages of 475 and 584 weevils/week in the villages of Bendunganjati and Turi to 254 and 46 weevils/week in Ngargoyoso and Kradenan. The highest trap catches occurred at the highest sex pheromone loadings in all four locations. The effect of trap density on average weekly trap catch depended on location, with no significant effect of trap density on trap catch when the data from all locations were pooled. There was no statistically significant impact of sex pheromone traps on losses from sweetpotato weevil, although fields with blank lures had consistently higher levels of sweetpotato weevil damage. The highest trap catches occurred in Turi, which also had the highest levels of weevil damage. The use of sex pheromone traps led to damage reduction, even when weevil pressure and damage levels were low, as in the village of Kradenan. This suggests that there is potential for traps to play a role in reducing weevil damage in situations of higher weevil pressure.

Effect of Reforestation Methods on Pine Weevil (Hylobius abietis) Damage and Seedling Survival

Örlander, G.1 and Nilsson, U. (Swedish University of Agricultural Sciences, The Southern Swedish Forest Research Centre, Asa Forest Research Station, S-360 30 Lammhult, Sweden and Swedish University of Agricultural Sciences, The Southern Swedish Forest Research Centre, Box 49, S-230 53 Alnarp, Sweden). Effect of reforestation methods on pine weevil (Hylobius abietis) damage and seedling survival. Received Feb. 16, 1998. Accepted Sept. 15, 1998. Scand. J. For. Res. 00: 000-000, 199X. Damage to Norway spruce (Picea abies (L.) Karst.) seedlings by the large pine weevil, Hylobius abietis (L.) (Coleoptera: Curculionidae), was monitored in relation to clear - cutting age and silvicultural treatments in southern Sweden. New clear - cuttings were established on four sites during five consecutive years, and seedlings were planted on them from 1989 through 1993. In total, 31 774 seedlings were planted on 20 clear - cuttings. The measures evaluated were seedling insecticide treatment, application of herbicide to ground vegetation, scarification (mound) and planting late in the season. In addition, the effects of slash removal and seedling type were studied. The pine weevil was, by far, the dominant damaging agent. Planting without insecticide or soil treatment on fresh, one- or two - year - old clear - cuttings resulted in a mean level of weevil - caused mortality exceeding 60%. The results indicate that the risk of serious damage by pine weevils remains high until the clear - cuttings reach four or five years of age. Killing the vegetation with herbicide had no effect on pine weevil damage. Slash removal decreased damage on older clear - cuttings, but the effect was small. Scarification (mounding) strongly reduced damage. On fresh clear - cuttings the mean mortality caused by pine weevils in mounded plots was 13%, whereas it was 77% in the controls. The mounding effect varied between sites and clear - cuttings of different ages. Late planting (10 June instead of 1 May) reduced damage on two- and three - year - old clear - cuttings. Three - year - old, bare - rooted seedlings were not damaged as seriously as two - year - old, containerized ones, but the effect was probably due to the larger size of the bare - rooted seedlings. Non - lethal injury resulted in reduced seedling growth. Damage by pine weevils varied between years and within growing seasons. However, on fresh, one- and two - year - old clear - cuttings, damage was severe enough to cause high mortality during all studied years.

Variation in Elatobium abietinum Attack on Picea glauca and its Relation to Pissodes strobi Resistance

White spruce (Picea glauca (Moench) Voss) is host to several pests, including the white pine weevil (Pissodes strobi (Peck)) and the green spruce aphid (Elatobium abietinum (Walker)). The larvae of the white pine weevil damage spruce leaders by consuming the cortex while the green spruce aphid is a defoliator. White spruce emblings (seedlings produced by culturing tissues from seed embryos) from 18 families previously ranked for resistance to the white pine weevil were defoliated to varying degrees by the green spruce aphid in a natural outbreak that developed within a holding shadehouse. A strong relationship was shown between damage caused by the aphids and weevil resistance. Emblings ranked as highly weevil - resistant sustained significantly less aphid defoliation.

ANTS, STEM-BORERS, AND FUNGAL PATHOGENS: EXPERIMENTAL TESTS OF A FITNESS ADVANTAGE INPIPERANT-PLANTS

This study tests experimentally the hypothesis that Pheidole bicornis ants increase the fitness of Piper ant-plants (Piperaceae) in Costa Rican forests. In two experiments with naturally occurring Piper ant-plants, ∼50 individuals were randomly selected and maintained either as controls (with ants) or as ant-exclusion plants (without ants) for 2 yr. Leaf replacement rates and seed production, as measures of relative plant vigor and reproductive potential, were significantly greater in control plants with intact ant colonies than in plants from which ant colonies were experimentally excluded by periodical treatment with dilute insecticide. A series of experiments was designed to assess the relative contribution of antiherbivore defense, nutrient procurement, and antipathogen defense as potential mutualistic functions of the ants. To assess the fitness effects of antiherbivore defense, leaf replacement rates and seed production were measured on plants to which artificial folivory was applied over a 2-yr period (33% of each leaf blade removed), and stem-boring weevil damage was monitored on plants with and without ants. Nutrient procurement by ants was estimated quantitatively, and net leaf production was monitored experimentally on control plants (with ants), on plants without ants, and on nutrient-enriched plants with ants (microquantities of fertilizer added to lower stem). Epiphyll loads, phylloplane spore densities, and disease incidence were compared on experimental plants with and without ant colonies. The results indicate that folivory, the classical parameter measured in ant-plant studies, was not related to differences in fitness in Piper ant-plants; instead, ant disruption of stem-borers and ant foraging on inflorescences to reduce fungal invasion were identified as probable mechanisms by which ants conferred an average fitness advantage of at least 60 and 10%, respectively, in the 2nd yr of the comparison. Although neither antifolivore defense nor nutrient provisioning by ants appeared to benefit Piper plants, they may contribute synergistically or may operate on temporal or spatial scales not included in the study. For example, nutrient provisioning may allow Piper ant-plant species to occupy and compete favorably in poor-soil habitats not evaluated in these experiments.

Histological response of resistant and susceptible white spruce to simulated white pine weevil damage.

The traumatic wound response of families of white spruce, Picea glauca (Moench) Voss, resistant or susceptible to the white pine weevil, Pissodes strobi (Peck), were compared after simulated weevil damage. Leaders from 331 trees were wounded just below the apical bud in the spring, coinciding with the natural time of weevil oviposition. A portable 1-mm diameter drill was used to drill 24 holes per leader. Leaders were removed in the fall and examined for evidence of traumatic resin canal formation. Drilled trees had a traumatic wound response 8 times greater than that of undrilled trees; however, undrilled trees also formed some resin canals in response to unknown causes. In the drilled trees, the traumatic wound response extended into the lower part of the leader, where it could possibly affect older larvae. Trees from resistant families responded with greater intensity than trees from susceptible families, by producing multiple rings of traumatic resin canals. Trees from resistant families also responded more rapidly than trees from susceptible families based on number of cells to the first ring of traumatic resin canals. Trees from some resistant families exhibited no traumatic resin canal formation, showing considerable within-family variation and suggesting that other resistance mechanisms might be important. In the year after drilling, there was a reduction in tree diameter growth and trees suffered a reduction in constitutive resin canals in the bark, which suggests some energetic cost of traumatic resin production. There was no indication that the extent of constitutive defenses, as measured by density of cortical resin canals before wounding, was related to the ability to produce traumatic resin canals. Screening trees based on their capacity to produce traumatic resin canals may be useful in selecting genotypes resistant to white pine weevil.

Control of Boll Weevil on Cotton with Selected Insecticides, 1997

Abstract A test was conducted at the Macon Ridge location of the Northeast Research Station to evaluate the efficacy of selected insecticides against boll weevil on cotton planted 22 Apr. Plots consisted of 4 rows (40-inch centers) X 50 ft. Treatments were arranged in a RCB design and replicated 4 times. Insecticides were applied on 28 and 30 Jun, 3, 8, and 11 Jul. Applications were made with a high-clearance sprayer calibrated to deliver 6 gpa through TX-8 hollow cone nozzles (2/row) at 47 psi. Treatments were evaluated by examining 50 cotton flower buds (squares) per plot 2-4 DAT for evidence of boll weevil damage. No additional foliar insecticides were applied to the plots during the test. The plots received 0.10, 2.08, and 0.08 inch rainfall on 28 Jun, 7 Jul, and 8 Jul, respectively. Data were analyzed with ANOVA, and means were separated according to DMRT.

Control of Armyworms and Pepper Weevil on Bell Pepper, Spring 1997

Abstract Transplant were set 10 Mar, 12 inches apart on 8-inch-high and 32-inch-wide beds of EauGallie fine sand covered with white polyethylene mulch. Each plot consisted of a single row of 14 plants with rows on 5-ft centers. Treatments were replicated 4 times in a RCB design and were applied with a 2.5-gal, hand-held CO2-powered sprayer on 2, 7, 14, 21, 29 Apr, 5, 19, 27 May, 2, 11, 18, 25 Jun, 2 and 9 Jul. The sprayer was outfitted with a single nozzle with a D-5 disk and #45 core and delivered 100 gpa at 60 psi. Fruit were harvested on 21 May and 9 Jun. The number and weight of undamaged fruit and the number of fruit damaged by armyworm larvae were determined. Fruit also were examined for the presence of oviposition scars on the outsides of the fruit and for the presence of larval feeding damage caused by the pepper weevil inside the fruit. On 14 Jul, all fruit were harvested and examined for the presence of oviposition scars and internal pepper weevil damage.