Effects Of Leaf Surface Characteristics And Spray Droplets On Effectiveness Of Selected Glyphosate Formulations

Laboratory and glasshouse studies were conducted to examine the effect of leaf surfaces and spray droplets on the effectiveness of glyphosate on some selected plants. The broad leaves plants selected were Diodia ocimifolia, Borreria latifolia, Clidemia hirta, Cleome rutidosperma, Mikania micrantha and Asystasia gangetica, while the narrow leaves consisted of Eleusine indica, Imperata cylindrica, Cyperus kylingia, Axonopus compressus, Pennisetum polistachyon and Paspalum conjugatum. The deposition of pesticide depends on the morphology of leaf surface, thus the leaf surface roughness and epicuticular wax were evaluated. The plants were categorized accordingly to the different type of roughness based on the estimation of three roughness parameters Ra (arithmetic average height parameter), Rq (root-mean-square roughness parameter corresponding to Ra), and Rz (average of high peaks and low valleys over the evaluation length). The leaf was examined by using scanning electron microscopy for the surface roughness while the epicuticular wax content of the leaf was extracted by using chloroform. The amount of wax extracted from the plants varied between species. For broad leaves plant, M. micrantha (44.22μgcm-2) contained the highest quantity of wax. Clidemia hirta (24.03μgcm-2) and A. gangetica (23.03μgcm-2) were grouped in the plant with medium quantity of wax while C. rutidosperma (16.52μgcm-2), B. latifolia (14.19μgcm-2) and D. ocimifolia (10.75μgcm-2) were grouped in plant with low quantity of cuticular wax weight. For narrow leaves plant, E. indica (44.23μgcm-2) and I. cylindrica (49.88μgcm-2) have the highest quantity of wax. Pennisetum polystachion (32.16μgcm-2) and C. kylingia (22.85μgcm-2) were categorized under the plant with medium quantity of wax whereas P. conjugatum (19.59μgcm-2) and A. compressus (16.78μgcm-2) were categorized with low quantity of wax. The wax on the abaxial and adaxial leaf surface of the broad leaves plants was found to be significantly different. In contrast, the amount of wax on the abaxial and adaxial leaf surface of the narrow leaves plants was more or less similar. For the leaf surface roughness of the broad leaves species, B. latifolia were categorized as the roughest followed by C. hirta, D. ocimifolia, A. gangetica, and C. rutidosperma. Mikania micrantha had the smoothest leaf surface among the broad leaves species. On the other hand, the narrow leaves of P. polistachyon were identified as the roughest followed by I. cylindrica and P. conjugatum while E. indica, A. compressus and C. kylingia were categorized in the smoothest surface

Asymptomatic pathogen infection alters interactions at higher trophic levels

Plants and insects have intimate and complex relationships. However, other species, such as plant pathogens, may change the way plants and their herbivores interact. Plant diseases can change the host plant quality, alter physical and physiological traits and defensive capability. These changes can have a consequential effect on insects associated with the infected plant, thus altering interactions between species. However, the effects of these interactions can quantitatively vary amongst individuals and may influenced by many factors including the severity of plant disease (e.g. if the infection is symptomatic or asymptomatic). To date, little is known on the effect of asymptomatic pathogen infection on insects at higher trophic levels. My research aims to examine how patterns of interactions between plants, microbes and insects change when plant pathogen infection is asymptomatic. I examined the effect of asymptomatic plant pathogen infection on the life history and behaviour of herbivorous insects, and its consequent effects on an insect community at higher trophic levels. In the laboratory, I found that asymptomatic pathogen infection altered plant traits and changed the life history and behaviour of an herbivorous insect and its parasitoid. In the field, the effect of asymptomatic pathogen infection differed between plant varieties and species of insect involved. Asymptomatic pathogen infection greatly affects the assemblage and population dynamics of aphids on one variety of lettuce (Tom Thumb), but no significant effects were found on Little Gem. However, both lettuce varieties were less attractive to natural enemies when asymptomatically infected. The asymptomatic pathogen infection also modulated the interaction of plants and insects on neighbouring plant. More aphids were found on the uninfected plant neighbouring an asymptomatic infected plant, and thus influencing the number of natural enemies observed. These findings show the importance of asymptomatic pathogen infection to the ecological interactions at higher trophic levels in the laboratory and field. Pathogen infection, even if asymptomatic, can influence interactions between organisms. This is of considerable interest to both pure and applied ecologists, and can affect the success of biological control programme in agriculture systems

Does This Look Infected? Hidden Host Plant Infection by the Pathogen Botrytis cinerea Alters Interactions between Plants, Aphids and Their Natural Enemies in the Field

Few studies have considered whether hidden (asymptomatic) plant pathogen infection alters ecological interactions at the higher trophic levels, even though such infection still affects plant physiology. We explored this question in two field experiments, where two varieties of lettuce (Little Gem, Tom Thumb) infected with Botrytis cinerea were either (1) naturally colonised by aphids or (2) placed in the field with an established aphid colony. We then recorded plant traits and the numbers and species of aphids, their predators, parasitoids and hyperparasitoids. Infection significantly affected plant quality. In the first experiment, symptomatically infected plants had the fewest aphids and natural enemies of aphids. The diversity and abundance of aphids did not differ between asymptomatically infected and uninfected Little Gem plants, but infection affected the aphid assemblage for Tom Thumb plants. Aphids on asymptomatically infected plants were less attractive to predators and parasitoids than those on uninfected plants, while hyperparasitoids were not affected. In the second experiment, when we excluded natural enemies, aphid numbers were lower on asymptomatically and symptomatically infected plants, but when aphid natural enemies were present, this difference was removed, most likely because aphids on uninfected plants attracted more insect natural enemies. This suggests that hidden pathogen infection may have important consequences for multitrophic interactions

Assessment of Insect Abundance and Diversity in Paddy Fields Cultivated with Beneficial Plants, Turnera trioniflora

Beneficial plants such as Turnera can be a good shelter and provide a food source for insects. The presence of insects, especially natural enemies in paddy fields is very important because the insects help in natural pest population control. However, detailed studies on the composition of insects in paddy fields cultivated with Turnera plants are still lacking. Therefore, a study was conducted in Besut, Terengganu to determine the population abundance and diversity of insects in paddy fields cultivated with the beneficial plant, Turnera trioniflora. Two paddy fields were selected as sampling plots which cultivated with T. trioniflora plants (Plot A) and without T. trioniflora plants (Plot B). For each plot, three Malaise traps, five yellow pan traps, and five pitfall traps were used to collect insect samples on a weekly basis during the paddy planting season (February-May 2021). Samples collected were brought to the laboratory for identifying processes up to order level. Results showed that a total of 3818 individuals of insects consisting of 10 orders (i.e. Diptera, Hymenoptera, Lepidoptera, Coleoptera, Hemiptera, Orthoptera, Thysanoptera, Odonata, Mantodea, and Blattodea) were successfully collected from both plots with a significance different (p < 0.05). Among them, the Diptera dominated the number of individuals collected at 52.12% (n=1990) and followed by Hymenoptera at 16.87% (n= 644) and Lepidoptera at 12.40% (n=474). Whilst the Blattodea order was the least abundant with 0.07% (n=3). Plot A and Plot B recorded a total of 1995 and 1823 individuals, respectively and no significant difference (p > 0.05) of insect abundance was recorded between both plots. However, the diversity of insects in Plot A was slightly higher (H’=1.57) than in Plot B (H’=1.23). In conclusion, the insect’s abundance and diversity in a paddy plot cultivated with T. trioniflora plants was relatively higher than in a paddy plot cultivated without T. trioniflora plants. This study has provided a set of basic data on the abundance and diversity of insects in paddy fields which is very helpful for further studies on the relationship between T. trioniflora beneficial plants and insects

Ovipositional Behaviour Preference of Oriental Fruit Fly, Bactrocera dorsalis Hendel (Diptera: Tephritidae) on Different Host Fruits

The oriental fruit fly Bactrocera dorsalis Hendel (Diptera: Tephritidae), is a polyphagous insect pest that gives severe damage to orchard fruits when the female adults lay their eggs into the fruits. However, the damage can be reduced by manipulating the behavior of this female insect. Thus, this study aimed to determine the ovipositional  preference behavior  of B. dorsalis on different host fruits. The experiment set up was laboratory-based ‘no-choice’ and ‘choice’ of oviposition behavior by the insect. The parameter recorded were the number of fruit visit, duration of fruit visit, number of attempted to oviposit, number of ovipositing and duration of oviposition completed. Guava (Psidium guajava L), mango (Mangifera indica L.) and papaya (Carica papaya L.) were used as host fruits. In the no-choice experiments, the host fruits significantly influenced the number of fruit visit and duration of the visit of B. dorsalis female. The most fruit visited by B. dorsalis female was mango compared to other host fruits whilst papaya shows the longest duration of the host fruit visit by B. dorsalis. Although the characteristics of host fruits differs, the number and duration of oviposition by B. dorsalis shows no significant difference among the host fruits and no activity of oviposition was recorded on guava fruit. When given a choice of different host fruits, the duration of fruit visit and number of attempt to oviposit by B. dorsalis significantly differed among host fruits. However, the host fruits does not influenced the number of fruit visit, number of oviposit and duration of oviposition completed. Interestingly, only guava shows the egg oviposition activity by B. dorsalis females whilst no oviposition behaviour was observed on mango and papaya. Results obtained in this study will benefit the study of insect pest behaviour which then can be use in biological control program in order to reduce the agriculture damage

Leaf Surface Characteristics of Selected Malaysian Weed Species of Oil Palm

Laboratory and glasshouse studies were conducted to examine the leaf surface characteristics of selected weed species of oil palm. The broadleaf weeds selected were Asystasia gangetica, Borreria latifolia, Cleome rutidosperma, Clidemia hirta, Diodia ocimifolia and Mikania micrantha, while for the narrow leafs, Axonopus compressus, Cyperus kylingia, Eleusine indica, Paspalum conjugatum and Pennisetum polistachyon were investigated. The weeds were categorized into different types of roughness based on the macroscopic roughness, microscopic roughness and the estimation of three roughness parameters: Ra (arithmetic average height parameter), Rq (root-mean-square roughness parameter, corresponding to Ra), and Rz (average of high peaks and low valleys over the evaluation length). The leaf was examined using scanning electron microscopy (SEM) for the surface roughness, while the epicuticular wax content of the leaf was extracted using chloroform. The amount of wax extracted from the weeds varied between species. For broadleaf plants, Mikania micrantha (44.22 µg/cm2) was identified as the plant that contained the highest quantity of wax. Clidemia hirta (24.03 µg/cm2) and Asystasia gangetica (23.03 µg/cm2) were grouped in the plants with a medium quantity of wax while Cleome rutidosperma (16.52 µg/cm2), Borreria latifolia (14.19 µg/cm2) and Diodia ocimifolia (10.75 µg/cm2) were grouped in the plants with a low quantity of cuticular wax weight. For narrow leaf plants, Eleusine indica (44.23 µg/cm2) and Imperata cylindrica (49.88 µg/cm2) were recognized as the plants that contained a high quantity of wax. Pennisetum polystachion (32.16 µg/cm2) and Cyperus kylingia (22.85 µg/cm2) were categorized under the plants with a medium quantity of wax, whereas Paspalum conjugatum (19.59 µg/cm2) and Axonopus compressus (16.78 µg/cm2) were classified under the plant with a low quantity of wax. The wax on the abaxial surface data of the broadleaf weeds was found to be significantly different when compared to the adaxial surface data. In contrast, the amount of wax on the abaxial and adaxial leaf surface of the narrow leaf weeds was more or less similar. For the leaf surface roughness of the broadleaf species, Borreria latifolia was categorized as the roughest, followed by Clidemia hirta, Diodia ocimifolia, Asystasia gangetica and Cleome rutidosperma. Mikania micrantha had the smoothest leaf surface among the broadleaf species. On the other hand, the narrow leaf of Pennisetum polistachyon was identified as the roughest, followed by Imperata cylindrica and Paspalum conjugatum, while Eleusine indica, Axonopus compressus and Cyperus kylingia were categorized as having the smoothest leaf surface

Population Abundance of Insect Trapped on Different Colours of Sticky Trap in Pumpkin (Cucurbita moschata) Field

A study was conducted to attract insects using different colours of sticky trap in pumpkin (Cucurbita moschata) field. Sticky trap was chosen as it is one of a method to estimate the insect population density in field as it requires a low cost and less skilled labour. Four different colours of sticky traps (i.e. red, white, blue and yellow) were used to determine the insect population abundance at the pumpkin field. All the traps were installed at the height of 100 cm at a random of 1 ha of pumpkin plot with five replicates for each colour and the insect samples were collected weekly for three months (October-December 2019). Overall, a total of 13,052 insects were collected throughout 11 weeks of sampling. The results showed that the percentage of insect population abundance recorded the highest was on week eight (15.01%) whilst the least abundance of insects trapped was on week one (2.28%). The most attractive colour to attract insects was significantly the yellow colour (44.34%) followed by blue (20.12%) and white (19.15%) whilst the lowest insect trapped was on red colour (16.40%). A total of nine insect orders recorded were; Diptera, Hemiptera, Coleoptera, Hymenoptera, Lepidoptera, Orthoptera, Blattodea, Isoptera and others. Diptera was the most abundant of insect’s order trapped in the yellow trap with 3427 individuals and followed by Hemiptera order (1022 individuals). Whilst the Isoptera order was the least number of insects caught on a red colour trap with only one individual. In conclusion, our findings showed that the yellow sticky trap colour is the most attractive to attract insects of C. moschata compared to other colours. Therefore, this study could provide essential knowledge that may be useful for the future ecological survey of insects of C. moschata

Survey on Pest and Disease of Corn (Zea Mays Linn) grown at BRIS Soil Area

A field survey was conducted to identified insect pest, beneficial insect and plant disease that associated with corn (Zea mays Linn) at BRIS soil area. Hybrid sweet corn variety Sugar King 516 was used as a sentinel plant in this study. All insect pest and beneficial insect observed at the experimental plot was collected and identified in the laboratory. Corn plant that shows the symptom of disease infection was collected for the isolation of pathogen and identification. The data on plant growth such as plant height, corn ear height, dry straw weight, ear weight, ear length, grain dry weight and shell weight was recorded. Data obtained shows the performance and adaptability of hybrid sweet corn variety Sweet King 516 in this experiment was comparable to the local hybrid sweet corn grown at other BRIS soil area at Terengganu. There is no strange pattern on the plant growth, thus prove that the insect infestation or disease infection does not disturb the plant development. Thirteen species of insect pest were identified. There are grasshopper (family Acrididae), katydid (family Tettigoniidae), sweet potato bug (Physomerus grossipes- family Coreidae), derbid plant hopper (Proutista moesta- family Derbidae), cotton stainer (Dysdercus sp- family Pyrrhocoridae), largid bug (Physopelta sp- family Largidae), corn leaf hopper (Peregrinus maidis- family Delphacidae), corn rootworms (Diabrotica virgifera- family Chrysomelidae), green chafer beetle (Anomala albopilosa- family Scarabaeidae) and tussock moth (Orgyia sp- family Erebidae). Three species of predatory insect were identified; Asian lady beetles (Harmonia axyridis- family Coccinellidae), transverse lady beetle (Coccinella transversalis- family Coccinellidae) and assassin bug (family Reduviidae). Two species of fungal pathogen that attacks corn in this experiment were identified as Fusarium sp. and Puccinia sp. Data obtained in this study provides info on pests and diseases associateed with corn, thus could be beneficial for the farmers to be prepared with the best pest and management strategies for their corn plantation at BRIS soil area. Keywords: Sweet corn, insect pest, plant disease, BRIS soi

Penentuan oviposisi kumbang Callosobruchus maculatus (Coleoptera: Bruchidae) ke atas pelbagai jenis kekacang

Callosobruchus maculatus (Bruchidae: Coleoptera) merupakan serangga perosak produk bijirin simpanan yang menyerang pelbagai jenis kekacang di ladang dan stor penyimpanan. Spesies betina C. maculatus dilaporkan mempunyai sifat kecenderungan untuk bertelur bergantung kepada jenis bijiran kekacang. Oleh itu, kajian ini telah direka bentuk untuk menilai pengaruh kandungan protein dan karbohidrat di dalam pelbagai jenis kekacang ke atas keputusan untuk mengoviposit telur oleh C. maculatus dan kejayaan telur tersebut untuk menetas. Kajian ini direka bentuk secara rawak dengan lima jenis rawatan dan sejumlah lima replikasi. Rawatan merangkumi Kacang Tanah (Arachis hypogea L.), Kacang Merah (Phaseolus vulgaris L.), Kacang Hijau (Vigna radiata L.), Kacang Soya (Glycine max L.) dan Kacang Lembu (Vigna unguiculata L.). Kajian dijalankan melalui dua kaedah berbeza iaitu (a) kaedah pilihan, di mana semua jenis kekacang dicampur, maka serangga boleh memilih untuk bertelur pada mana-mana jenis kekacang dan (b) kaedah tanpa pilihan, di mana serangga hanya diberikan satu jenis kekacang sahaja untuk bertelur. Jumlah kandungan karbohidrat dan protein di dalam kekacang pula dianalisis menggunakan kaedah titrasi dan Kjeldahl. Dapatan kajian menunjukkan bahawa apabila diberi pilihan, C. maculatus memilih untuk bertelur pada Kacang Lembu (97.2±17.2) diikuti oleh Kacang Hijau (84.8±16.4), Kacang Merah (57.0±12.7), Kacang Soya (49.4±10.4) dan Kacang Tanah (5.4±2.6). Corak bertelur adalah hampir sama apabila C. maculatus tidak diberikan pilihan iaitu jumlah telur terbanyak ditemui pada Kacang Hijau (48.8±12.4) dan Kacang Lembu (45.4±12.1), tetapi dengan jumlah telur yang lebih sedikit berbanding kaedah pilihan. Kandungan karbohidrat di dalam kacang hijau (51.07%) dan kandungan protein dalam Kacang Lembu (34.84%) diramalkan mempengaruhi keputusan untuk bertelur oleh C. maculatus. Walau bagaimanapun, aktiviti bertelur oleh C. maculatus didapati tidak mempengaruhi kejayaan telurnya untuk menetas memandangkan hanya telur yang diletakkan pada kacang lembu dan kacang hijau yang telah menetas. Kajian lanjut perlu dijalankan untuk mengenal pasti faktor-faktor lain yang mungkin mempengaruhi tabiat bertelur C. maculatus bagi memastikan kaedah kawalan yang berkesan dapat dilaksanakan dalam mengekang serangga perosak ini dari terus membiak