Control of Leaf-footed Bug Leptoglossus zonatus and Shield-backed Bug Pachycoris klugii with Entomopathogenic Fungi

The pathogenicity of three isolates of Beauveria bassiana (Bals.) Vuil. and one isolate of Metarhizium anisopliae (Metsch.) Sorok. (Deuteromycotina: Hyphomycetes) was assessed in the laboratory against adults of the leaf-footed bug Leptoglossus zonatus (Dallas) (Heteroptera: Coreidae) and the shield-backed bug Pachycoris klugii Burmeister (Heteroptera: Scutelleridae), the two most frequent pest species in physic nut ( Jatropha curcas L., Euphorbiaceae) plantations in Nicaragua. In a dipping bioassay, the median lethal concentration (LC) of the most efficient strain, M. anisopliae NB, was determined as 4.34 106 50 conidia/ml for adult P. klugii . In a field trial, a scheduled high-volume spray regime using B. bassiana increased fruit yield by 28%, and was more effective than malathion or an aqueous extract of ground neem seeds. The effectiveness of M. anisopliae was further tested in field cages covering entire trees and containing a predetermined number of insects. Mineral oilbased ultra-low volume controlled droplet applications of M. anisopliae at a rate of 1 1010 conidia/tree were made using hand-held Micron ULVA + sprayers. The corrected mortalities ranged from 65% in P. klugii to 94% in L. zonatus.     

Watermelon growth,fruit yield and plant survival as affected by squash bug (Hemiptera: Coreidae) feeding

Adult squash bugs, Anasa tristis (De Geer) (Heteroptera: Coreidae), were confined on watermelon plants at differing phenological stages and at densities of zero to four per plant in one trial and zero to 32 per plant in three additional trials. Squash bugs were allowed to feed on the plants until plants died or fruit matured. Plant foliage, roots, and fruit were harvested and weighed to determine effects on growth and productivity. Growth and fruit production was regressed on number of squash bugs and results indicated that an increasing density of squash bugs feeding on vining and flowering stage plants resulted in significant reductions in plant growth and fruit yield. When plants were infested at the fruit set stage of growth, there was either less effect or no effect on plant growth and fruit production. Plant mortality increased as the density of squash bugs increased regardless of the stage of growth when plants were infested with squash bugs.     

The invasive Leptoglossus seed bug,a threat for commercial seed crops,but for conifer diversity?

Among the recent introductions of alien insects in Europe, the polyphagous western conifer seed bug, Leptoglossus occidentalis Heidemann (Heteroptera; Coreidae) can seriously be regarded as a major threat for all the European conifer forests. In the current study combining laboratory and field experimentations, we characterized first bug damage by developing specific damage categories on seeds of different conifer species by the use of X-ray. Secondly, we investigated the impact of the invasive bug on key conifer species used for afforestation in Western and Central Europe. For this purpose, we performed germination tests on predated seeds which revealed that even light damage (consumption of <1/3 of the whole seed content) strongly reduced the germination capability of the seed. We also compared the impact of feeding on the proportion of filled seeds. Second year cones of Pinus sylvestris and Pinus nigra have been enclosed and offered to different life stages (nymphs and adults) and the results showed a significant reduction of filled seeds whatever the life stage. In field, we annually surveyed the bug seed damage for six different conifer species planted in southwestern French seed orchards. Taking into account the economic value of improved seeds in seed orchards, economic impact of bug damage was important although never exceeded 25 %. Two natural or semi-natural alpine pine stands were also surveyed and appeared to be highly affected by the bug (up to 70 % of damaged seeds). Therefore, bug damage could also be considered as a serious threat for seed production in natural stands.     

Impact of Leptoglossus occidentalis (Hemiptera: Coreidae) on Douglas-fir seed production

We investigated the effect of feeding by the western conifer-seed bug, Leptoglossus occidentalis Heidemann, on seed production in developing cones of coastal Douglas-fir, Pseudostuga menziesii (Mirb.) Franco, with respect to seed bug life stage and sex (nymphs, adult females, and adult males) and timing of feeding (early, mid-, and late season cone development). Feeding by females on caged cones for a 2-wk period during late season cone development reduced the proportion of full seeds in cones by approximately 70% compared with caged control cones. There was no significant difference among nymphs, adult females, and adult males with respect to the proportion of empty or partially fed-upon seeds produced during the same feeding period. Feeding by nymphs for 2 wk early in the season resulted in a threefold increase in the number of unextractable seeds fused to cones compared with the control. Weight measurements of harvested seeds indicated that radiography is an accurate tool to distinguish among Douglas-fir seeds that have sustained light, moderate, or severe damage. Determining the full impact of L. occidentalis on conifer seed production will require the development of a reliable method to distinguish between naturally aborted seeds and seeds emptied through feeding by seed bugs.     

Ecology and economic impact of two plant bugs (Hemiptera: Miridae) in commercial vineyards

The current study investigated the seasonal phenology, spatial distribution, feeding damage and economic impact of two plant bugs, Lygocoris inconspicuous Knight and Taedia scrupeus Say, in commercial vineyards. For both plant bugs, densities of nymphs were higher on vines located near the edge of woodlots rather than in the interior of vineyards, which may be attributed to the presence of wild vines and other alternate host-plants in wooded areas. Nymphs of both species fed on apical leaves and developing fruit clusters of vine shoots, initiating development after swelling of buds in the spring and reaching the adult stage when vines were in bloom. Confining high densities of L. inconspicuous (10 nymphs) on individual shoots early in the season resulted in significant reduction of the number of fruit clusters per shoot, even when feeding was restricted to short (7 d) duration; the average weight of fruit clusters, in contrast, was not affected to a large extent by feeding activity of nymphs. An experiment evaluating the impact of low density of L. inconspicuous (0-0.3 nymphs per shoot) indicated a marginally significant negative relationship between density of nymphs and average weight of fruit clusters. Control measures may be economically justified when population density exceeds a combined threshold of one nymph of either L. inconspicuous or T. scrupeus per 10 shoots of vines.     

盲蝽类害虫种群密度与危害的调查方法

盲蝽是棉花、果树等作物上的一类重要害虫。盲蝽的卵产在植物组织中,若虫活动性和隐蔽性强,成虫善于飞行扩散。针对盲蝽各个虫态的习性,发展了田间种群发生与危害调查技术,为其种群监测提供了科学支撑。     

True bug (Heteroptera) impact on cocoa fruit mortality and productivity

The real impact of true bug damage on cocoa pods has never been assessed precisely. We conducted a 2-yr study on 1,080 cocoa trees on 36 farms in Cameroon to assess the contribution of true bugs to fruit mortality and production loss. The cocoa fruiting cycle, fruit mortality, and damage caused by true bugs as well as other pests and diseases were monitored on a weekly basis. True bug damage also was described on 2,500 ripe pods per year. Pod weight, bean number, and bean weight were measured and compared for different degrees and types of damage on the ripe pods. Our results showed that true bugs were the main external cause of young fruit abortion. They reduced the abundance of young fruit by up to 10%. In contrast, although one-third of the ripe pods sampled had true bug lesions, only 4% were moderately to heavily damaged. The mean weight of ripe pods was reduced by 12% when there was medium to heavy damage. While the mean weight of wet beans was reduced significantly (by 3-10%), the number of beans per pod was not changed by damage. Despite the reduction in mean weight, the overall weight of beans for the pods sampled was reduced by <2%. Therefore, our study confirmed the common assumption that the economic impact of true bug damage on mature pods is negligible on cocoa farms in Cameroon. However, true bugs have a significant impact on young fruit mortality.     

Effect of mango weevil (Coleoptera: Curculionidae) damage on mango seed viability in Hawaii

The mango weevil, Cryptorhynchus (= Sternochetus) mangiferae (F.), is a federally quarantined pest that prevents shipment of mangos from Hawaii into the continental United States. Although this monophagous weevil allegedly causes reduced seed germination, damage to the fruit pulp, and premature fruit drop in mangos, there are few studies examining these potential sources of crop loss. We conducted studies to assess the effect of mango weevil infestation on seed viability while making observations on the frequency of pulp feeding. Naturally infested seeds from mature fruit were planted in pots and scored for successful germination. Germination rates for infested seeds were equal to those of uninfested control seeds in a polyembryonic cultivar ('Common'), whereas germination was significantly reduced for infested seeds of a monoembryonic cultivar ('Haden') compared with uninfested control seeds but germination of infested seeds was still > 70%. To assess seed tolerance of damage, seeds were artificially damaged by cutting away 25, 50, or 75% of the cotyledon before planting and scored for germination. None of the damage treatments was significantly different from the undamaged controls, indicating that mango seeds can withstand substantial damage and still germinate successfully. Over the 2-yr period we conducted experiments, only four of 3,602 mango fruits (0.11%) showed evidence of direct feeding damage to the pulp. Results suggest that C. mangiferae is a less serious pest of mangos than previously thought.     

Damage potential of an introduced biological control agent Agonosoma trilineatum (F.) on bellyache bush (Jatropha gossypiifolia L.)

The seed-feeding jewel bug, Agonosoma trilineatum (F.), is an introduced biological control agent for bellyache bush, Jatropha gossypiifolia L. To quantify the damage potential of this agent, shadehouse experiments were conducted with individual bellyache bush plants exposed to a range of jewel bug densities (0, 6 or 24 jewel bugs/plant). The level of abortion of both immature and mature seed capsules and impacts on seed weight and seed viability were recorded in an initial short-term study. The ability of the jewel bug to survive and cause sustained damage was then investigated by measuring seed production, the survival of adults and nymph density across three 6-month cycles. The level of seed capsule abortion caused by the jewel bug was significantly affected by the maturity status of capsules and the density of insects present. Immature capsules were most susceptible and capsule abortion increased with jewel bug density. Similarly, on average, the insects reduced the viability of bellyache bush seeds by 79% and 89% at low and high densities, respectively. However, sustaining jewel bug populations for prolonged periods proved difficult. Adult survival at the end of three 6-month cycles averaged 11% and associated reductions in viable seed production ranged between 55% and 77%. These results suggest that the jewel bug has the potential to reduce the number of viable seeds entering the soil seed bank provided populations can be established and maintained at sufficiently high densities.     

Maternal regulation of fecundity: non-random ovule abortion inCassia fasciculata Michx.

Summary We examined the extent of ovule abortion and the within-fruit pattern of abortion inCassia fasciculata, an annual legume, and tested the hypothesis that abortion can result from competition for limited maternal resources among developing fruits and seeds. In a natural population at Mayview, IL, 53.4% of ovules in mature fruits matured as seeds; 43.4% showed some development but aborted, and 3.1% showed no development over virgin ovules. In a greenhouse experiment in which treatments were applied after most fruits were initiated, nutrient addition and partial root removel had no effect on abortion, but drought reduced the proportion of ovules maturing to 75% of the control mean. A fruit thinning experiment was conducted in which the number of fruits initiated on certain plants was limited. Control plants had more ovule abortion than fruit-thinned plants, suggesting that abortion resulted from competition for limited maternal resources. A position effect was observed in both field and greenhouse populations; ovules toward the fruit base (pedicellar end) had higher frequencies of abortion than those at the distal end. Thus, ovule abortion, like fruit abortion in this species, is non-random. Indivisuals regulate fecundity at both the whole fruit and individual seed levels.Scientific contribution no. 1357 from the New Hampshire Agricultural Experiment Station     

Fruits of apple and sweet persimmon are not essential food sources for Riptortus pedestris (Hemiptera: Alydidae) which causes fruit-spotting

Riptortus pedestris (Fabricius) (Hemiptera: Alydidae) has recently become an important fruit-spotting bug of apple and sweet persimmon trees in Korea. Although fruits of cultivated species are unsuitable food for some fruit-spotting bugs, the dietary importance of fruits of apple and sweet persimmon for R. pedestris is unknown. We evaluated harvested fruits of apple and sweet persimmon with or without soybean seeds as a food source for R. pedestris by investigating nymphal development time, immature mortality, preovipositional period, fecundity, and adult size in the laboratory. No first instars of R. pedestris that were fed only apple or sweet persimmon fruits became third instar nymphs. When supplemented with soybean seeds, both fruits supported nymphal development and reproduction of R. pedestris. However, fruits combined with soybean seeds were not a better diet than soybean seeds only. Therefore, apples and sweet persimmons are not essential food sources for the development and the reproduction of R. pedestris. These results suggest that R. pedestris may not reproduce on fruit trees, thus explaining the absence of eggs and nymphs of this bug on fruit trees in orchards. Management of nearby vegetation of fruit orchards would be important for reducing damage by adult R. pedestris.     

FLOWER,FRUIT AND SEED ABORTION IN TROPICAL FOREST TREES: IMPLICATIONS FOR THE EVOLUTION OF PATERNAL AND MATERNAL REPRODUCTIVE PATTERNS

Flower, fruit and immature seed abortion was studied in seven self-incompatible species of trees in a tropical lowland semideciduous forest. The species showed considerable variability in fruit and seed set and the rate at which flowers and fruits were aborted. The amount of flower and fruit abortion also varied over time within species. Small samples of open-pollinated flowers in three species showed adequate amounts of pollen on the stigma, but it could not be determined whether the pollen was compatible or incompatible. In a species with multiseeded fruits, the aborted fruits contained significantly fewer seeds than those retained on the plant. Position of fruit within the inflorescence and of seed within the ovary also had a marked effect on abortion: fruits and seeds at certain positions had a higher probability of abortion than those at other positions. Experiments to test the effect of pollen source on abortion were inconclusive. The factors underlying abortions were evaluated in the context of three mutually non-exclusive hypotheses. It is concluded that selection for increased pollen dispersal and uncertainty in paternity of the zygotes are major factors underlying abortions.     

How granivorous Coreus marginatus (Heteroptera: Coreidae) recognises its food

Phytophagous insects select their host plant using multiple sensory modalities including vision, olfaction, gustation and mechanoreception. In the laboratory, we investigated the role of vision, olfaction and gustatory sense in the perception of cues released by seeds of different plant species in granivorous Coreus marginatus (Heteroptera: Coreidae). Juvenile insects were put in a choice arena and offered with different seeds on which they feed naturally (Polygonum, Rumex) and seeds which are not their natural food (Stellaria). Individual bugs were manipulated in one of three ways: 1. blackened compound eyes, 2. coated sensillae on antennae, 3. coated tip of labial pouch. Control individuals were not manipulated. The behaviour of each bug was observed for 12 h. Control bugs fed for a significantly longer time than manipulated ones. Individuals with any senses impaired fed on Stellaria, whereas, the control individuals ignored it. The results suggested that seed selection requires information from all three sensory organs: compound eyes, antennae and sensillae on labial pouch. Further research is required to unravel the importance of each sense for the seed selection.     

Effect of ovule position within the pod on the probability of seed production in Bauhinia ungulata (Fabaceae)

BACKGROUND AND AIMS: It has been claimed that ovules linearly ordered within a fruit differ in their probabilities of reaching maturity. This was investigated by studying the effect the position of an ovule within the pod has on seed abortion and seed production in Bauhinia ungulata. METHODS: Fruits collected during the dry seasons of 1999, 2000 and 2001 were opened, and the number, position and status of each ovule within the fruit were recorded. A GLM model was used to assess the effects of population, tree identity and ovule position within the pod on ovule fertilization, seed abortion, seed damage and seed maturation in two populations of B. ungulata. KEY RESULTS: Nearly 30% of the ovules were not fertilized in 1999; this percentage dropped to 5% the following two years. Seed abortion (50%) and seed damage (15%) were the same every year during the study period. Only 15% of the initial ovules developed into mature seeds in 1999; this value increased to 35% in 2000 and 2001. However, seed survivorship was dependent on the position of the ovule within the pod; non-fertilized and early aborted ovules were found more often near the basal end of the ovary. The frequency of seed damage was not affected by position. Mature seeds were found mainly in the stylar half of fruits, where ovules are likely to be fertilized by fast pollen tubes. CONCLUSIONS: The pattern of seed production in B. ungulata is non-random but is dependent upon the position of the ovule within the pod. The results suggest that the seeds produced within a fruit might differ in their vigour.     

Selective seed abortion affects the performance of the offspring in Bauhinia ungulata

BACKGROUND AND AIMS: Under the microgametophytic competition hypothesis, a non-random pattern of seed abortion is expected, in which only the most vigorous seeds reach maturity. In a previous study, it was found that Bauhinia ungulata (Fabaceae) exhibits a pattern of seed abortion dependent on the position of the ovule within the ovary; ovules located in the stylar half of the fruit, close to the point of entry of pollen tubes to the ovary, have a low probability of seed abortion, whereas ovules in the basal half of the fruit are aborted with a high probability. METHODS: A series of experimental fruits was generated, in which ovules from either the stylar (treatments 1 and 2) or the basal (treatments 3 and 4) half of fruits were destroyed, to evaluate whether these patterns of selective seed abortion have an effect on the vigour of the offspring in B. ungulata. KEY RESULTS: Only 53 % of the seed from control fruits germinated. Seed set in fruits from treatments 1 and 2 showed a significantly lower (33-43 %) percentage of germination; the germination of seeds from fruits in treatments 3 and 4 (49-51 %) did not differ from control seeds. In addition, it was found that the differences in vigour of the offspring are not random with respect to the position of the ovule in the pod. CONCLUSIONS: The overall performance of the seeds correlated with their likelihood of maturation. Seeds located at the basal half of the treatment fruits showed lower values of vigour than seeds located on the stylar half. The differences were more marked for early measures of fitness.     

Burrower bugs (Heteroptera: Cydnidae) in peanut: seasonal species abundance, tillage effects, grade reduction effects, insecticide efficacy, and management

Pitfall traps placed in South Carolina peanut, Arachis hypogaea (L.), fields collected three species of burrower bugs (Cydnidae): Cyrtomenus ciliatus (Palisot de Beauvois), Sehirus cinctus cinctus (Palisot de Beauvois), and Pangaeus bilineatus (Say). Cyrtomenus ciliatus was rarely collected. Sehirus cinctus produced a nymphal cohort in peanut during May and June, probably because of abundant henbit seeds, Lamium amplexicaule L., in strip-till production systems. No S. cinctus were present during peanut pod formation. Pangaeus bilineatus was the most abundant species collected and the only species associated with peanut kernel feeding injury. Overwintering P. bilineatus adults were present in a conservation tillage peanut field before planting and two to three subsequent generations were observed. Few nymphs were collected until the R6 (full seed) growth stage. Tillage and choice of cover crop affected P. bilineatus populations. Peanuts strip-tilled into corn or wheat residue had greater P. bilineatus populations and kernel-feeding than conventional tillage or strip-tillage into rye residue. Fall tillage before planting a wheat cover crop also reduced burrower bug feeding on peanut. At-pegging (early July) granular chlorpyrifos treatments were most consistent in suppressing kernel feeding. Kernels fed on by P. bilineatus were on average 10% lighter than unfed on kernels. Pangaeus bilineatus feeding reduced peanut grade by reducing individual kernel weight, and increasing the percentage damaged kernels. Each 10% increase in kernels fed on by P. bilineatus was associated with a 1.7% decrease in total sound mature kernels, and kernel feeding levels above 30% increase the risk of damaged kernel grade penalties.     

The Effects of Seed Number and Prior Fruit Dominance on the Pattern of Fruit Production in Cucurbits pepo (Zucchini Squash)

Many plants, especially of species with indeterminate reproduction,show first-fruit dominance, in which the presence of developingfruit reduces future fruit maturation by increasing the abortionof later (younger) fruit and by inhibiting subsequent flowerproduction. We examined the effects of seed number on first-fruitdominance by experimentally manipulating the number of pollengrains that were deposited onto stigmas of zucchini squash andthen monitoring flower production, fruit growth, and fruit maturation.Our findings show (1) that fruits containing more seeds growfaster and achieve greater size; (2) that the presence of 6–15-d-oldfruit significantly decreases the probability of female flowerproduction while significantly increasing the probability offruit abortion; (3) that the number of seeds in the prior developingfruit has a significant effect on the probability of flowerproduction and fruit abortion, and (4) that when seed numbervaries among the fruits on a vine the fruit with the fewestseeds are the most likely to abort. It is concluded that thestrength of dominance by a developing fruit depends on the numberof seeds it contains and that this also influences the resultof fruit to fruit competition. Fruit abortion, fruit growth, Cucurbita pepo, size of pollen load, seed number, zucchini, squash     

Suitability of physic nut (Jatropha curcas L.) as single host plant for the leaf-footed bug Leptoglossus zonatus Dallas (Het., Coreidae)

The leaf-footed bug Leptoglossus zonatus (Dallas) (Het., Coreidae) was reared in Nicaragua on a diet consisting of unripe physic nut ( Jatropha curcas L., Euphorbiaceae) fruit only. The suitability of this host plant is described by the mortalities in the developmental stages from egg to adult, which are presented in a life table, and the durations of the different stages. Pre-oviposition time, number of ovipositions and total number of eggs per female are given. Biometric measurements of all instars were made. Protein, oil and water content of fresh physic nut fruit were measured throughout a whole year. The results show that physic nut is a highly suitable host plant, which can maintain populations of this insect pest throughout the whole year as fruit are constantly present with only little fluctuation in their nutritional quality.     

Lantana camara and the fruit- and seed-damaging fly,Ophiomyia lantanae (Agromyzidae): Seed predator,recruitment promoter or dispersal disrupter?

The seed damaging fly, Ophiomyia lantanae is a widespread agent that infests the fruits and seeds of Lantana camara. Its effectiveness in reducing seed dispersal or seedling recruitment has not been comprehensively tested. We determined the effects of O. lantanae damage on fruit removal rates of L. camara in a field study. We also investigated recruitment responses (seed germination in growth cabinets and seedling emergence in pot trials) of two common L. camara biotypes, pink and pink-edged red (PER) to O. lantanae damage. We found that fewer damaged fruits were removed than undamaged fruits, suggesting that frugivores select against damaged fruit. In all recruitment experiments, the responses to damage were biotype dependent. In germination experiments, these differential responses were primarily due to significantly reduced germination of damaged PER seeds. Seedling emergence from pots of the PER biotype was also lower in damaged seeds (27.5%) than undamaged seeds (56.1%). In contrast, emergence increased with seed damage in the pink biotype, from 28.2 to 41.1%. O. lantanae damage significantly reduced seed mass only in the smaller seeded PER biotype. In the larger seeded pink biotype, it may have promoted seedling emergence by interfering with dormancy mechanisms. We also examined in situ seed banks at L. camara populations prior to peak seed production. Mean viable seed densities ranged from 78.6 to 402.8 seeds m⁻². Of these, non-dormant seeds comprised 24.6 to 98.2 seeds m⁻², suggesting that recruitment is unlikely to be seed limited. We conclude that while O. lantanae influences recruitment and dispersal processes, the magnitude of the responses measured are unlikely to greatly influence plant densities in south-east Queensland infestations.     

种子植物的选择性败育及其进化生态意义

种子植物的选择性败育是指植株在花粉源、传粉次序、果实在植株上的位置和发育果实中的种子数目等因素或者这些因素综合作用的基础上对发育中的幼果或种子选择性败育的现象。植株可以选择性地败育位于果序顶部或基部的果实以及位于果实基部、中部或柱头端的种子。此现象在被子植物中比较普遍,特别是在豆科、十字花科和紫草科中最为常见。导致植物选择性败育的主要原因主要有资源限制和遗传因子两个方面。植物通过选择性败育部分自交或基因型较差的果实或种子,不仅可以提高母本和后代的适合度,而且还可以提高果实或种子的扩散效率。因此,对选择性败育的研究在深入了解植物的结实结籽格局、探讨其进化式样与机制等方面具有重要意义。该文系统总结了国际上有关植物选择性败育的研究工作,重点介绍了选择性败育发生的式样、导致选择性败育的因素、选择性败育的进化生态意义,以及目前研究选择性败育现象的主要方法,并对该领域今后研究前景进行了展望。