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Crop loss to wildlife impedes local support for conservation efforts at Kibale National Park, Uganda. Systematic monitoring of crop loss to wildlife (mammals larger than 3 kg) and livestock was conducted in six villages around Kibale over a 2-year period. Five wildlife species accounted for 85% of crop damage events: baboons, bushpigs, redtail monkeys, chimpanzees, and elephants. Marked variation in frequency and extent of damage is reported within villages, between villages, and between wildlife species. Fields lying within 500 m of the forest boundary lost 4-7% of crops per season on average, but the distribution of damage was highly skewed such that maize and cassava fields were on occasion completely destroyed. Multivariate analysis was used to test predictors of damage, including human population density, guarding, hunting, sight distance, and distance from the forest. Tests were performed at two levels of analysis, field and village. Distance from the forest edge explained the greatest amount of variation in crop damage, although hunting also influenced the extent of crop damage. Elephants inflicted catastrophic damage to farms but their forays were rare and highly localized. Livestock caused considerable damage to crops but farmers seldom complained because they had institutionalized modes of restitution. Although most of the crop damage by wildlife is restricted to a narrow band of farmers living near the forest edge, risk perception among these farmers has been amplified by legal prohibitions on killing wild animals. Elevating local tolerance for wildlife will require diverse approaches, including channeling economic benefits to Kibale's neighbors and providing compensation in limited cases.

Corn seedlings respond to insect herbivore-inflicted injury by releasing relatively large amounts of several characteristic terpenoids and, as a result, become highly attractive to parasitic wasps that attack the herbivores. Chemical evidence showed that the induced emission of volatiles is not limited to the sites of damage but occurs throughout the plant. This evidence was obtained by comparing the release of volatiles from leaves of unharmed (control) seedlings with the release of volatiles from undamaged leaves of seedlings with two injured leaves treated with caterpillar regurgitant. Immediately after injury no differences were measured in the released volatiles, but several hours later the undamaged leaves of injured plants released the terpenoids linalool, (3E)-4,8-dimethyl-1,3,7-nonatriene, and (3E,7E)-4,8,12-trimethyl-1,3,7,11-tridecatetraene in significantly larger amounts than leaves of unharmed plants. Other volatiles that are released by herbivore-injured leaves were detected occasionally only in trace amounts from the undamaged leaves of a damaged seedling. The systemic release of volatiles by injured corn coincided with attractiveness to the parasitoid Cotesia marginiventris; undamaged leaves of injured plants became significantly more attractive than leaves from control seedlings. These findings show conclusively that when a plant is injured by an insect herbivore the whole plant emits chemical signals.

This review describes those mechanisms by which wind directly affects crop growth rates and hence yields. Wind-induced plant movement is capable of altering growth rates and leaf morphology, although this is unlikely to be a major cause of growth differences between sheltered and unsheltered crops grown outdoors. The wind's force can tear leaves or strip them from the plant. Dense plant canopies may suffer abrasion through intermittent or constant rubbing. Soil particles lifted into suspension by the wind have the potential to abrade and damage plant tissue. The wind's force can physically knock plants over, making crops difficult to harvest. Each of these mechanisms operates at a particular time of the growing season. Recovery, and hence final yield, depends on the growth stage and soil/plant moisture status when the damage occurred, the particular species and variety as well as the preceding and subsequent weather. The fact that damage effects are so dependent on the crop and the past weather makes modelling and any simple synthesis of direct wind effects difficult. The most common forms of damage likely in Australia's agricultural regions are from sandblasting and lodging. These damage events will be intermittent - their frequency depending on the local climate. Leaf tearing is likely in broad-leafed horticultural crops, and growth effects are also likely in any windy location. It is not possible to predict what the impact of this damage, and other direct effects, will be on final yields, Based on the results in the literature, protection from damage offered by windbreaks may have as large an effect on yields as incremental microclimate benefits.[PUBLICATION ABSTRACT]

The research reported in this paper concerns (1) Quebec potato farmers and the factors that compose their concern for environmental degradation and (2) the adoption of conservation practices using a two-stage decision-making process. The surveyed farmers are concerned mainly with the problem of pest infestation. Their awareness of environmental problems is raised by the level of educational attainment, membership in producers' organizations, and participation in government sponsored farm programs. The actual adoption of conservation practices by farmers is influenced by the extent to which they perceive environmental degradation to be a problem, their educational level, the expected crop loss to pests and weeds, the perceived health effects of farm chemicals application, and the availability of adequate information on the best management practices.

The hypothesis that generalist predators limit associated prey populations was tested using spiders, a group classically thought to be an insignificant component of the agroecosystem. Two habitat manipulations (addition of mulch and flowers) in separate and combined treatments were utilized to enhance spider numbers in a mixed vegetable system. Compared to control plots, significantly higher spider densities were observed in the plots to which mulch alone or both mulch and flowers had been added. Insect damage to the plants was significantly lower in the plots to which mulch had been added as well, which correlates with the lower numbers of pest insects in plots containing mulch. That spiders were the probable cause of the effect was demonstrated in plots containing both mulch and flowers but from which spiders had been systematically removed. Removing spiders from plots with mulch and flowers removed the effect of this treatment on pest numbers and plant damage. In addition, 84% of the predators observed foraging in the study areas during timed watches were spiders and 98% of the predation events observed were by spiders. In a separate experiment, spiders were added to a subset of individually bagged broccoli plants that had been infested previously with known numbers of herbivorous pests. Plant damage in bags lacking spiders averaged 93.3%, whereas damage averaged 31.8% in bags to which spiders had been added.

Monilinia fructigena (Aderh. & Ruhl.) Honey causes considerable yield losses in pome fruit culture. During a field study in the Netherlands in 1997 and 1998, the increase in disease incidence in time was assessed and final pre- and post-harvest losses were recorded in the susceptible apple cultivars James Grieve and Cox's Orange Pippin. Each individual tree was considered as a unique quadrat, and the spatial distribution of diseased fruits among fruit trees at every assessment date was characterised by a dispersion index, Lloyd's index of patchiness (LIP). Spatial autocorrelation was applied to detect potential clustering of trees with diseased fruits within rows. In cv. James Grieve, the rate of increase of disease incidence was constant up to harvest time, whereas in cv. Cox's Orange Pippin disease incidence increased markedly 3 weeks before harvest time, which coincided with the harvest of cv. James Grieve in neighbouring rows. Pre-harvest disease incidence was 4.2-4.3% in cv. James Grieve in both years, in cv. Cox's Orange Pippin this was 4.4% in 1997 and 2.7% in 1998. Post-harvest yield losses amounted on average 1.5-2.0% for both cultivars, no significant differences were found between the cultivars (t-test, P=0.05). Both in 1997 and 1998, clustering of diseased fruits among fruit trees was detected; LIP values were significantly higher than 1 (P=0.05 in 1997, P=0.01 in 1998). Clustering of trees with diseased fruits was detected in 1998, when significant (P=0.05) positive correlation coefficients occurred for 2nd, 3rd and 4th lag-order distances in cv. James Grieve, and a significant (P=0.05) positive first-order correlation in cv. Cox's Orange Pippin. Wounding agents, such as insects and birds, may play an important role in the underlying disease dynamics, and crop losses may be minimised by control of these agents.[PUBLICATION ABSTRACT]

Experiments were conducted to measure the photosynthetic response of three crop and four tree species to realistic concentrations of ozone and (for tree species only) simulated acidic rain. The ozone concentrations were representative of those found in clean ambient air, in mildly to moderately polluted air such as occurs in much of the United States during the summer, and in more heavily polluted air. However, the highest concentrations of ozone used were lower than those found regularly in the Los Angeles area. The mean pH of the simulated acid rain treatments ranged from more alkaline to much more acidic than the mean pH of precipitation in the United States. Exposure to any increase in ozone reduced net photosynthesis in all species tested. In contrast, acidic rain had no negative effect on photosynthesis in tree species, and no interaction between ozone and acidic rain was observed. Ozone-induced reductions in photosynthesis were related to declines in growth or yield. Species with higher stomatal conductances and thus higher potential for pollutant uptake exhibited greater negative responses to similar ozone treatments. Since exposure to ozone concentrations typical of levels of the pollutant observed in the eastern half of the United States reduced the rates of net photosynthesis of all species tested, reductions in net photosynthesis may be occurring over much of the eastern United States.

For nonexperimental data, asymmetric specifications of the role of damage control inputs impose restrictions of homotheticity or nonjointness on the underlying technology. A generalized symmetric form where damage control inputs affect factor diminution functions motivates use of symmetric specifications. Panel data and estimation methods are presented to produce robust estimates of damage control productivity that are free of heterogeneity bias. Estimates of the productivity of pesticides for French cereal farm production illustrate that fixed firm and time effects are important. Estimates indicate substantially smaller marginal productivity of pesticides than reported by past studies.

The plant spacing of early cabbage (Brassica oleracea L. var. capitata) was studied at the Experimental Field of the Biotechnical Faculty in Ljubljana, during the 2001 and 2002 growing season. The cultivars, which included ‘Vestri’, ‘Parel’, ‘Delphi’, ‘Destiny’ and ‘Hermes’, were each spaced at 20, 30 and 40 cm within rows and 30 cm between rows or populations equivalent to 166,000, 108,000 and 82,000 plants ha-1. The experimental variables measured were marketable yield (per head and per hectare), yield characteristics (head diameter and head volume), quality characteristics (core volume, head density, soluble solids and dry matter) and onion thrips damage ratings. There was no interaction effect of cultivar and planting spacing on the measured variables. Marketable yield per head, head diameter and volume, core volume and head density generally increased as the within-row plant spacing increased, whereas, dry matter was significantly decreased at lower plant spacing. Soluble solids were not affected by plant spacing. The yield potential of cabbage was higher at cv. ‘Vestri’ than at the other cultivars. The onion thrips damage rating was severe at the lowest plant spacing and contributed to the reduced yield. A higher damage rating was established in the cv. ‘Parel’ but this didn't have a statistically significant influence on the weight loss of yield. Poskus s sadilnimi razdaljami zgodnjega zelja (Brassica oleracea L. var. capitata) je bil opravljen na Laboratorijskem polju Biotehniške fakultete v letih 2001 in 2002. Medvrstna razdalja za pet kultivarjev zelja (‘Vestri’, ‘Parel’, ‘Delphi’, ‘Destiny’ in ‘Hermes’) je znašala 30 cm, medtem ko so bile razdalje v vrsti 20, 30 in 40 cm, kar, preraČunano na površino enega ha, pomeni 166.000, 108.000 oz. 82.000 rastlin. Ugotavljali smo tržni pridelek (na glavo in na ha), lastnosti pridelka (premer glave in prostornino glave), kvalitativne lastnosti (prostornino vretena, gostoto glave, suho snov in sušino) in ocenili poškodbe, ki jih je povzroČil tobakov resar. Med dejavnikoma kultivar in gostota sajenja ni prišlo do interakcije, ki bi vplivala na opazovane lastnosti. Tržni pridelek glav, premer in prostornina glav, prostornina vreten in gostota glav so na splošno narašČali z veČanjem razdalje v vrsti, medtem ko se je pri najmanjši gostoti sušina znaČilno zmanjšala. Sadilna razdalja ni vplivala na vsebnost suhe snovi. Cv. ‘Vestri’ se je v primerjavi z preostalimi kultivarji izkazal kot kultivar z možnostjo doseganja najvišjih pridelkov. Poškodbe, ki jih je povzroČil tobakov resar, so bile najveČe pri najmanjši sadilni razdalji in so bile razlog za zmanjšanje pridelka. NajveČ poškodb je pretrpel cv. ‘Parel’, a to ni statistiČno znaČilno vplivalo na izgubo pridelka.