Field evaluation of synthetic sex pheromone traps for the cocoa mirid Sahlbergella singularis (Hemiptera: Miridae)

BACKGROUND: Field trapping experiments were conducted to evaluate the attractiveness of five different pheromone blends as well as the impact of trap design on attractiveness towards cocoa mirids, Sahlbergella singularis Hagl. and Distantiella theobroma (Dist.), in Cameroon. RESULTS: A total of 361 adults of S. singularis (359 males and two females) were caught. The highest numbers of mirids were found in traps with pheromone blends that combined a monoester and a diester, compared with traps with the diester or the monoester individually and control traps with no pheromone. Rectangular traps caught significantly more mirids compared with delta traps. The mean number of 5.1 mirids trap^?1 year^?1 caught in rectangular traps was significantly higher compared with the 1.8 mirids trap^?1 year^?1 for the delta traps. CONCLUSION: The data revealed that rectangular traps containing pheromone blends combining both the monoester and the diester have a good potential to lure and trap adult males of S. singularis on cocoa farms. The pheromone blends used were specific for S. singularis, and the use of pheromone traps appears to be a promising strategy for incorporation into integrated pest management strategies for the monitoring or even the control of S. singularis in cocoa plantations. Copyright © 2011 Society of Chemical Industry     

Field susceptibility of the cocoa mirid,Sahlbergella singularis haglund (heteroptera) to some new insecticides

Two groups of insecticides were screened against the cacao mirid, S. singularis in small-scale field trials from September 1969 to January 1972. In first group 0.05% promecarb, 0.04% phosphamidon and 0.02% monocrotophos were equally effective and superior to 0.05% mecarbam in the three days after spraying but 0.05% promecarb was most toxic to bugs by the seventh day. In the 0.15 to 0.2% range, all four insecticides showed similar toxicity within 3 days of spraying but only 0.15% mecarbam and 0.2% promecarb maintained control to the seventh day. For mecarbam, phosphamidon and monocrotophos, control at 0.15% was better than at 0.05, 0.04 and 0.02% respectively 7 days after spray whilst 0.2% was superior to 0.05% promecarb 2 days after spray and not afterwards. At either 0.21 or 0.33 lb/acre insecticides in the second group (pirimiphos methyl, HOE 2960, CA 6900 and dicrotophos) gave identical level of control of mirids and control at the latter dosage rate was not better than at the former. There was no significant difference between 3 and 4 oz a.i./10 gal water/200 trees in toxicity to mirids and the insecticides gave equally good control of the bugs at both dosage levels till 35th day after spray. On the basis of efficacy and safety of use, promecarb CA 6900 and pirimiphos methyl were deemed suitable for further (large scale) trials.     

Foliar resistance of cacao (Theobroma cacao) to Phytophthora palmivora as an indicator of pod resistance in the field: interaction of cacao genotype, leaf age and duration of incubation

The effects were studied of four leaf development stages (LDS) and three durations of incubation (DI) on the accuracy of leaf-disc tests on eight cacao (cocoa) clones (C) for predicting field resistance to phytophthora pod rot caused by Phytophthora palmivora . The clones were known to possess different general combining abilities (GCA) for pod resistance in the field, evaluated monthly at harvest over a 9-year period. Disease severity (DS) was affected strongly by C, DI and LDS, with increasing levels of significance. Two- and three-way interaction effects were smaller than the clone effect, but still significant. Clone effects were most significant for LDS3 (i.e. leaves 50–60 days old) and for DI5 and DI7 (observations made 5 and 7 days after inoculation, respectively). Coefficients of rank correlation between DS and field results were significant for seven of the 12 treatments, with highest values obtained again for treatments LDS3/DI5 ( r = 0·87) and LSD3/DI7 ( r = 0·93). Pooling of data for different LDS and DI treatments did not further improve the correlation with field results. However, these correlations were improved (from an average of 0·74 to 0·88) when the GCA values for field resistance were based on weekly observations, carried out in one year, including losses of pods and cherelles. It was concluded that, when carried out in a standardized manner and under optimal conditions, the leaf-disc test may explain 75–90% of the genetic variation for field resistance of cacao genotypes to P. palmivora .     

Biodiversity and biogeography of the cacao (Theobroma cacao) pathogen Moniliophthora roreri in tropical America

Moniliophthora roreri , the cause of moniliasis or frosty pod rot, occurs on the neotropical rainforest genera Theobroma and Herrania . While this basidiomycete has had devastating effects on the cacao tree ( T. cacao ) in tropical America, where it is confined, little is known of its biogeography and intraspecific genetic variability. Here, AFLP and ISSR profiles of 94 isolates of M. roreri from across its geographic range in Central/South America were analyzed. The study provided limited evidence to support the hypothesis that M. roreri is capable of sexual reproduction. The highest levels of genetic diversity occurred in Colombia and not in Ecuador as originally believed. The fungus was broadly divided into five genetic groups. Two of these have a wide geographic range: Bolívar group (north of Santander in Colombia, eastern Venezuela, peripheral Ecuador, Peru), and Co-West group (western Colombia, central Ecuador, Central America). The other groups are all apparently endemic to Colombia (Co-East and Co-Central groups) or north-western Ecuador ( Gileri group). We speculate that central/north-eastern Colombia may represent the centre of origin for M. roreri . Sequence data from the internal transcribed spacer region of the nuclear rDNA repeat were congruent with the AFLP/ISSR results, dividing M. roreri into two broad groups: the Orientalis group, comprising most isolates from the Co-East, Co-Central and Bolívar groups, and the Occidentalis group, comprising isolates from the Co-West and Gileri groups. The spread of M. roreri into new areas and countries mediated by human activity is discussed.     

Field evaluation of the impact of Sahlbergella singularis Haglund infestations on the productivity of different Theobroma cacao L. genotypes in the Southern Cameroon

Journal of Plant Diseases and Protection - Mirids (Sahbergella singularis and/or Distantiella theobroma) are the major pests of cacao farms in Africa. Cocoa production losses due to these species...     

A novel use of Nesidiocoris tenuis (Reuter) (Hemiptera: Miridae) as inoculative agent of baculoviruses

Background

Alphabaculoviruses are Lepidoptera-specific virulent pathogens that infect numerous pests, including the Spodoptera complex. Due to their low environmental persistence, the traditional use of Alphabaculoviruses as bioinsecticides consist in high-rate spray applications with repeated treatments. Several abiotic and biotic factors can foster its dispersion, promoting their persistence in the agroecosystem. Amongst biotic factors, predatory arthropods can disperse the viruses by excretion after preying on infected individuals. Therefore, this study focused on promoting predator's ingestion of nucleopolyhedrovirus (NPV)-treated diets, and the later exposition of the insect host to leaf surfaces contaminated with predator excreta. The virus–host–predator system studied was Spodoptera littoralis nucleopolyhedrovirus (SpliNPV), Spodoptera littoralis (Boisduval) and Nesidiocoris tenuis (Reuter). The infective potential of N. tenuis feces and the retention time of SpliNPV were assessed under laboratory conditions after feeding on treated diets (sucrose solution and Ephestia kuehniella eggs).

Results

Mortality of S. littoralis larvae was lower via N. tenuis excretion than in positive control (spray application) in the first infection cycle, together with a delay in host death. In the second infection cycle, both SpliNPV-treated diets triggered 100% mortality. Both diets allowed the transmission of SpliNPV, with a faster excretion via sucrose solution compared to E. kuehniella eggs. SpliNPV remained in N. tenuis digestive tract and was viable after excretion at least for 9 days for both diets.

Conclusions

This study demonstrated the potential of the predator N. tenuis as inoculative agent of baculoviruses, representing a new alternative that, along with inundative applications, might contribute to improve pest management strategies. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.     

An optimized screening method for identifying levels of resistance to Crinipellis perniciosa in cocoa (Theobroma cacao)

The effects of host age, leaf number, host type (clone or seedling), pathogen spore concentration and incubation time on inoculation with Crinipellis perniciosa (witches' broom disease of cocoa) were studied in greenhouse experiments using susceptible cocoa genotypes. Three methods of inoculation (agar-drop, water-drop and spray) were also tested. An optimized inoculation method was selected and tested for its repeatability as well as its ability to discriminate between various levels of resistance to C. perniciosa in cocoa. The optimized method (350 000 viable basidiospores per mL, 60 h incubation, agar-drop technique) produced 100% infection repeatedly, on both clonal and seedling plants of a susceptible genotype. Seedling age (2–12 months) and leaf number did not significantly affect the percentage of plants with symptoms or broom characteristics. This method discriminated effectively between the various levels of resistance in 14 cocoa genotypes and is recommended as an inoculation method to identify levels of resistance in germplasm collections. Symptom severity was shown to be a better measure of resistance than infection success.     

Foliar resistance of cacao (Theobroma cacao) to Phytophthora palmivora as an indicator of pod resistance in the field: the effect of light intensity and time of day of leaf collection

Resistance of cacao leaves to Phytophthora palmivora was studied with regard to the time of leaf collection (morning, afternoon) and the degree of exposure of the leaves to light in the field (low, medium and high). The efficiency of leaf disc inoculations in predicting field resistance of nine clones was compared with that of detached and attached pod inoculations. Significant effects were observed, with leaves exposed to high light intensity and collected early in the afternoon showing highest susceptibility. The effect of time of leaf collection was reduced when leaves were stored overnight and leaf discs prepared and inoculated the following day, as compared to inoculations on the day of collection. Interactions between the main factors were significant, though less substantial than the clone effects. The most significant correlations with pod resistance ( r  = 0·70 to 0·97) were obtained for leaves collected early in the morning and exposed to intermediate shade conditions in the canopy. For other treatments, the correlations with pod resistance were still positive ( r  = 0·23 to 0·83) but often not significant. Pod inoculations in the laboratory were better correlated with field resistance ( r  = 0·92) than pod inoculations in the field ( r  = 0·72). Detached pod inoculations were also better correlated with leaf disc inoculations than those of attached pods. The results confirm the validity of laboratory inoculations of leaves and pods to assess field resistance to Phytophthora . Standardization of the leaf disc test is essential to obtain reliable results.     

Impact of mirid (Creontiades spp.) (Hemiptera: Miridae) pest management on Helicoverpa spp. (Lepidoptera: Noctuidae) outbreaks: the case for conserving natural enemies

Creontiades spp. (Hemiptera: Miridae) are sucking pests that attack buds, flowers and young pods in mungbeans, Vigna radiata (L.), causing these structures subsequently to abort. If left uncontrolled, mirids can cause 25-50% yield loss. Traditional industry practice has involved prophylactic applications of dimethoate to control mirids at budding and again a week later. The present trial was initiated to highlight the dangers of such a practice, in particular the risk of a subsequent Helicoverpa spp. lepidopteran pest outbreak. A single application of dimethoate halved the population of important natural enemies of Helicoverpa spp., and caused an above-threshold outbreak of Helicoverpa spp. within 11 days. This shows that even a moderate (e.g. 50%) reduction in natural enemies may be sufficient to increase Helicoverpa spp. populations in mungbeans. As a result, prophylactic sprays should not be used for the control of mirids in mungbeans, and dimethoate should be applied only when mirids are above the economic threshold. Indoxacarb was also tested to establish its effect on Helicoverpa spp., mirids and natural enemies. Indoxacarb showed potential for Helicoverpa spp. control and suppression of mirids and had little impact on natural enemies.     

Baseline toxicity of several pesticides to Hyaliodes vitripennis (Say) (Hemiptera: Miridae)

Hyaliodes vitripennis (Say) is a univoltine indigenous predacious mirid. It has been reported in several orchards where IPM programmes are used. It is a generalist, and feeds on phytophagous mites in addition to other arthropods. In Quebec, a foliar application of imidacloprid, deltamethrin or lambda‐cyhalothrin is used at least once per season to manage arthropod pests such as leafhoppers and leaf‐eating caterpillars. Meanwhile, several applications of metiram, flusilazole, myclobutanil and mancozeb are made to control apple scab [Venturia inaequalis (Cooke) Winter]. In laboratory trials, comparison of lethal concentrations of the three insecticides against H vitripennis nymphs and adults showed no significant difference. However, when lethal concentrations were compared between two growth stages for each insecticide, a significant difference was noted between adults and nymphs treated with lambda‐cyhalothrin, adults being more susceptible than nymphs. No such difference could be detected for imidacloprid or deltamethrin. When LC₅₀ values were compared with the manufacturer's label rates, deltamethrin and imidacloprid were toxic to the nymphs and adults, and lambda‐cyhalothrin was slightly toxic to the nymphs and moderately toxic to the adults. Among the fungicides evaluated in the laboratory, myclobutanil showed moderate toxicity to adults at the manufacturer's label rate. The remaining fungicides had no toxic effects to adults or nymphs, even at four times the manufacturer's label rate. © 2001 Society of Chemical Industry     

Effect of method of inoculation, inoculum density and seedling age at inoculation on the expression of resistance of cocoa (Theobroma cacao L.) to Verticillium dahliae Kleb.

Soil drench and stem puncture inoculation were compared as methods for selecting cocoa cultivars with resistance to Verticillium dahliae. Disease progress was more rapid and induced symptoms were more severe following stem puncture and, under glasshouse conditions, differences between cultivars were detected 15 days after inoculation. Moreover, using stem puncture, inoculum densities of 10⁴ conidia/ml were sufficient to differentiate resistant and susceptible cultivars, whereas with the soil drench method, inoculum densities of 10⁷ conidia/ml were necessary. Although a substantially higher proportion of plants were affected by stem puncture inoculation, the resistance of cultivar Pound-7 remained effective at high inoculum densities of 10⁸ conidia/ml. With either method, older seedlings were more susceptible to V. dahliae than younger ones. However, with stem puncture, 15-day-old seedlings were sufficiently susceptible for a valid disease assessment. In contrast, with soil inoculation, 60-day-old plants were required. In a nursery trial with 15-day-old seedlings, seven cocoa genotypes previously selected as resistant, moderately resistant or susceptible to Verticillium dahliae , on the basis of root inoculation, were ranked in the same order when stem punctured. Stem puncture inoculation of young seedlings is cost-effective in terms of time and space, and is therefore recommended for screening of cocoa for wilt resistance, especially in large-scale breeding programmes.     

黑肩绿盲蝽的线粒体基因组结构

为研究黑肩绿盲蝽Cyrtorhinus lividipennis的谱系地理和遗传结构, 本文测定并分析了其线粒体基因组全序列。结果表明:黑肩绿盲蝽线粒体基因组全长16 835 bp (GenBank登录号:OK149286), 包括13个蛋白质编码基因(PCGs), 22个tRNA基因, 2个rRNA基因和1个非编码区, 呈闭合双链环状DNA分子结构。线粒体基因组中A+T含量高达76.8%, G+C含量为23.2%, 呈现明显的AT偏向性; 13个蛋白质编码基因均以通用密码子ATN作为起始密码子; 蛋白质编码基因中呈现出明显的氨基酸偏好性, 异亮氨酸含量占比最高, 为10.78%; 22个tRNA基因中有21个tRNA形成典型的三叶草式二级结构; 系统发育树显示, 盲蝽科的11个种聚为两大分支, 黑肩绿盲蝽以99％的自展支持率位于其中的一个分支内。本研究结果将为黑肩绿盲蝽作为天敌昆虫来防治水稻害虫提供帮助。     

The dimpling bug,Campylomma austrina Malipatil (Hemiptera: Miridae): the damage and its relationship with ants in mango orchards in the Northern Territory of Australia

The dimpling bug, Campylomma austrina Malipatil, has been recognised since 2002 as a serious mango pest in the Northern Territory, Australia. To fully understand the damage the bug causes and its relationship with ants, field experiments were conducted in five mango orchards in the Darwin area from 2001 to 2003 along with laboratory rearing trials. The latter revealed that the dimpling bug sucked sap mainly from the ovary of the flowers. As the ovary ripened, each puncture resulted in a black pimple on the skin of the marble-sized fruit (<5 mm in diameter). All of the most heavily damaged marble-sized fruits (>10 pimples/fruitlet) dropped from the trees. A field survey and field experiments showed that marble-sized fruit damage levels on trees bearing abundant weaver ants, Oecophylla smaragdina Fabricius, were similar to those protected by chemical insecticides, however both suffered less damage than trees bearing fewer or no weaver ants or black ants, Iridomyrmex sp. We propose that the weaver ant is an efficient bio-control agent of the dimpling bug, and to limit the bug damage, high levels of weaver ant populations are required in mango orchards.     

Factors influencing the production of basidiocarps and the deposition and germination of basidiospores of Crinipellis perniciosa, the causal fungus of witches' broom on cocoa (Theobroma cacao)

The production of basidiocarps by Crinipellis perniciosa on detached, dead witches'brooms from cocoa was assessed in relation to temperature, light, cocoa clone, age of broom and type of tissue, in cabinets with a daily cycle of 8 h wet and 16 h dry. More basidiocarps formed and matured at 20–25°C than at 25–30°C. In the latter regime the pilei were smaller and white, instead of the usual crimson colour, and the stipes were longer. No basidiocarps formed at 30–35°C. At 20–25°C. more basidiocarps formed and matured with light at 100 μE m^-2 s^-1 during the wet period than at 10 μE m^-2 s ^-1. Only one basidiocarp and five primordia developed on 20 brooms kept in the dark. Brooms from 10 cocoa clones at Pichilingue. Ecuador, differed in basidiocarp productivity. most basidiocarps forming on brooms from Seavina and least on ICS clones. The numbers of basidiocarps produced on brooms aged 1.2.3 or 4 months when detached from cocoa trees were similar but time to initiation of the first primordium differed considerably. More basidiocarps formed at nodes than internodes.
The discharge of basidiospores was optimal at 20–25°C and 80% RH: germination was optimal in water agar films. Neither process was dependent on light.     

Weeds as hosts for new crop pests: the case of Protortonia navesi (Hemiptera: Monophlebidae) on cassava in Brazil

Weeds may serve as reservoirs for new and invasive insect pests. The cassava root scale ( Protortonia navesi ) is a recent pest in the Brazilian 'Cerrado' that causes qualitative and quantitative damage by sucking plant sap. Recently, field surveys revealed that many common weeds in this region act as host for P. navesi in cassava fields. In a discrete survey, 15 weed species were identified that were hosting P. navesi . Among these, 13 species occurred during the cropping season and five were observed 4 months after cassava harvest. Eight months after harvest, only cassava volunteer plants were found to be hosting P. navesi . This survey provided a real example of the problem created when weeds host new crop pests. The management of weeds (including crop volunteers) needs to be considered as part of generalised pest management and pest invasion prevention schemes. Effective weed management can be a means of limiting the survival of new pests and the re-infestation of susceptible crop species in subsequent years. Simple studies like this point to a practical need to create greater collaborations between pest management researchers working within discrete pest categories.