Heavy Defoliation Research Articles

In vitro Efficacy of Different Fungicides against Leaf Blight of Sunflower

Sunflower is one of the major oilseed crops cultivated in India. Alternaria leaf blight is one of the fungal diseases of Sunflower caused due the pathogen Alternaria helianthi, which is one of the significant limitations in the cost-effective cultivation of Sunflower in India. It is estimated that 20 to 80% losses in yield and heavy defoliation have been observed due to A. helianthi causal agent of leaf blight of Sunflower. Present investigation on evaluation on efficacy of different fungicides against leaf blight of Sunflower under in vitro condition by using Completely Randomized Design was conducted at Department of Plant Pathology, Dr. Sharadchandra Pawar College of Agriculture, Baramati during. Under this study seven fungicides viz., Chlorothalonil 75% WP, Hexaconazole 5% EC, Carbendazim+Mancozeb 75% WP, Carbendazim 50% WP, Tebuconazole 25.9% EC, Propiconazole 25% EC and Azoxystrobin 23% SC were evaluated against the pathogen Alternaria helianthi causing leaf blight in Sunflower at their recommended concentration and observation on mean radial mycelial growth and percent mycelial growth inhibition of pathogen was calculated. Results revealed that among various fungicides the three fungicides viz., Hexaconazole 5% EC, Tebuconazole 25.9% EC and Propiconazole 25% EC were found most effective with minimum mean mycelial growth and having maximum and similar (94.44%) percent growth inhibition of pathogen and rest of the fungicides tested were comparatively less effective against the pathogen A. helainthi associated with leaf blight of Sunflower.

Estimation of Disease Intensity against Cercospora Leaf Spot of Okra (Abelmoschus esculentus L.) Moench through Bio-control Agents with Chemical Fungicides under Prayagraj Condition of India

Okra (Abelmoschus esculentus L.) also known as bhendi is one of the most common vegetable preferred in every household of India. Cercospora leaf spot incited by Cercospora abelmoschi. is one of the emerging disease in Uttar Pradesh Region. An experiment was conducted in Central Research Farm ,SHUATS , Prayagraj in Kharif season of 2022 to evaluate the efficacy of bioagents and chemicals viz., T0 – Untreated control,T1 Mancozeb (1%) + Trichoderma(4%) , T2 - Mancozeb (1%) + Pseudomonas(4%) , T3 Mancozeb (1%) + Bacillus subtilis(4%), T4 - Mancozeb (1%) + Trichoderma (2%) + Pseudomonas(2%) ,T5 - Mancozeb (1%) + Pseudomonas(2%) + Bacillus subtilis(2%), T6 Mancozeb (1%) + Bacillus subtilis(2%) + Trichoderma(2%), T7 - Mancozeb (1%) against Cercospora leaf spot of okra. C. abelmoschi initiates with sooty black, angular spots and cause heavy defoliation Studies revealed that minimum disease intensity was observed in T4 - Mancozeb (1%) + Trichoderma (2%) + Pseudomonas (2%) and is hereby considered as the best treatment out of all the treatments.

Traits-mediated responses of caterpillar communities to spongy moth outbreaks and subsequent tebufenozide treatments.

Outbreaks of the spongy moth Lymantria dispar can have devastating impacts on forest resources and ecosystems. Lepidoptera-specific insecticides, such as Bacillus thuringiensis var. kurstaki (BTK) and tebufenozide, are often deployed to prevent heavy defoliation of the forest canopy. While it has been suggested that using BTK poses less risk to non-target Lepidoptera than leaving an outbreak untreated, in situ testing of this assumption has been impeded by methodological challenges. The trade-offs between insecticide use and outbreaks have yet to be addressed for tebufenozide, which is believed to have stronger side effects than BTK. We investigated the short-term trade-offs between tebufenozide treatments and no-action strategies for the non-target herbivore community in forest canopies. Over three years, Lepidoptera and Symphyta larvae were sampled by canopy fogging in 48 oak stands in southeast Germany during and after a spongy moth outbreak. Half of the sites were treated with tebufenozide and changes in canopy cover were monitored. We contrasted the impacts of tebufenozide and defoliator outbreaks on the abundance, diversity, and functional structure of chewing herbivore communities. Tebufenozide treatments strongly reduced Lepidoptera up to six weeks after spraying. Populations gradually converged back to control levels after two years. Shelter-building species dominated caterpillar assemblages in treated plots in the post-spray weeks while flight-dimorphic species were slow to recover and remained underrepresented in treated stands two years post-treatment. Spongy moth outbreaks had minor effects on leaf chewer communities. Summer Lepidoptera decreased only when severe defoliation occurred, whereas Symphyta declined one year after defoliation. Polyphagous species with only partial host plant overlap with the spongy moth were absent from heavily defoliated sites, suggesting greater sensitivity of generalists to defoliation-induced plant responses. These results demonstrate that both tebufenozide treatments and spongy moth outbreaks alter canopy herbivore communities. Tebufenozide had a stronger and longer lasting impact, but it was restricted to Lepidoptera, whereas the outbreak affected both Lepidoptera and Symphyta. These results are tied to the fact that only half of the outbreak sites experienced severe defoliation. This highlights the limited accuracy of current defoliation forecast methods, which are used as the basis for the decision to spray insecticides.

New insights into the relationships between livestock grazing behaviors and soil organic carbon stock in an alpine grassland

Grazing affects soil carbon (C) storage in grassland ecosystems through livestock trampling, defoliation, and excretion of urine and dung. However, independent effects of those grazing behaviors on soil organic C (SOC) remains unclear, particularly in alpine grassland ecosystems. To address this knowledge gap, a one-year field experiment was conducted on the eastern edge of the Qinghai-Tibetan Plateau to study the effect of grazing behaviors, including light vs. heavy trampling, light vs. heavy defoliation, and excretion of urine and dung, of yak (Bos grunniens) on SOC stock. Our results showed that trampling, particularly light trampling, significantly increased SOC stock in the 0–10 cm soil layer. The increase of soil bulk density and SOC concentration were the main reasons for the increase of surface SOC stock under trampling. Heavy defoliation significantly increased SOC stock in the 20–30 cm depth in comparison to light defoliation (4.4 vs. 2.9 kg C m-2), but neither affected SOC stock in the 0–30 cm soil profile. In contrast, excretion significantly lowered SOC stock by 9.3 kg C m-2 (0–30 cm), linked to the decreased soil bulk density and SOC concentration, and the decreased microbial biomass C, which might have lowered the microbial contribution to SOC storage. Our study of independent grazing effects showed that short-term livestock excretion caused the loss of SOC stock while intensive trampling or defoliation did not. Our findings have implications for managing livestock grazing behavior to maintain SOC stock in alpine grassland ecosystems.

The increasing threat to European forests from the invasive foliar pine pathogen, Lecanosticta acicola

European forests are threatened by increasing numbers of invasive pests and pathogens. Over the past century, Lecanosticta acicola, a foliar pathogen predominantly of Pinus spp., has expanded its range globally, and is increasing in impact. Lecanosticta acicola causes brown spot needle blight, resulting in premature defoliation, reduced growth, and mortality in some hosts. Originating from southern regions of North American, it devastated forests in the USA’s southern states in the early twentieth century, and in 1942 was discovered in Spain.Derived from Euphresco project ‘Brownspotrisk,’ this study aimed to establish the current distribution of Lecanosticta species, and assess the risks of L. acicola to European forests. Pathogen reports from the literature, and new/ unpublished survey data were combined into an open-access geo-database (http://www.portalofforestpathology.com), and used to visualise the pathogen’s range, infer its climatic tolerance, and update its host range. Lecanosticta species have now been recorded in 44 countries, mostly in the northern hemisphere. The type species, L. acicola, has increased its range in recent years, and is present in 24 out of the 26 European countries where data were available. Other species of Lecanosticta are largely restricted to Mexico and Central America, and recently Colombia.The geo-database records demonstrate that L. acicola tolerates a wide range of climates across the northern hemisphere, and indicate its potential to colonise Pinus spp. forests across large swathes of the Europe. Preliminary analyses suggest L. acicola could affect 62% of global Pinus species area by the end of this century, under climate change predictions.Although its host range appears slightly narrower than the similar Dothistroma species, Lecanosticta species were recorded on 70 host taxa, mostly Pinus spp., but including, Cedrus and Picea spp. Twenty-three, including species of critical ecological, environmental and economic significance in Europe, are highly susceptible to L. acicola, suffering heavy defoliation and sometimes mortality. Variation in apparent susceptibility between reports could reflect variation between regions in the hosts’ genetic make-up, but could also reflect the significant variation in L. acicola populations and lineages found across Europe. This study served to highlight significant gaps in our understanding of the pathogen’s behaviour.Lecanosticta acicola has recently been downgraded from an A1 quarantine pest to a regulated non quarantine pathogen, and is now widely distributed across Europe. With a need to consider disease management, this study also explored global BSNB strategies, and used Case Studies to summarise the tactics employed to date in Europe.

Influence of weather parameters on progress of Alternariaster leaf blight of sunflower

One of the major disease in sunflower i.e., blight caused by Alternariaster helianthi can infect all growth stages and causes severe losses. It is seed borne pathogen and causes heavy defoliation under congenial climate and yield losses estimated from 20 to 80%. A field study was conducted on impact of weather parameters on Alternariaster leaf spot of sunflower during kharif, for four years i.e., 2013-14, 2014-15, 2015-16, 2016-17 at RARS, Nandyal with four different dates of sowing, using two cultivars KBSH-44 and morden and the disease was recorded at weekly interval. Influence of weather parameters on PDI corresponding to the same week or previous week were observed and the conditions like moderate temperatures, relative humidity (RH-I>80% and more RH-II), more rainfall and crop age have more influence on disease development. Correlation coefficient values for combined data of four years indicated that PDI was negatively correlated with Tmax, Tmin, rainfall and wind velocity on both cultivars and positive with RH-I and plant age. Regression equations in all the individual experimental years and in total indicated that Tmin, Tmax, RH-I, rainfall and age significantly influence the disease progress. Apart from these factors, dew point, spore load, sunshine hours and micro climate may also affect disease development. Hence, disease progression mainly depends on weather conditions. More AUDPC values observed in later date of sowings than early date of sowings.

First Report of Leaf Black Spot Caused by Alternaria alternata on Rosemary (Rosmarinus officinalis L.) in China.

Rosemary (Rosmarinus officinalis L.) is an aromatic, evergreen, medicinally important shrub and widely used for cooking, tea, cosmetics as well as medicinal materials. It is grown in many countries including China that had more than 9300 hm2 of commercial cultivation area in 2021. In March 2020, a leaf spot disease sporadic occurred in field rosemarry plants in Nanyang City (32º51´ N, 111º36´ E), Henan Province, China. The disease outbreaked in September with a disease incidence of 57-83%. Symptoms initially appeared as small brown leaf spots that gradually expanded into dark blackbrown irregular lesions. Most of the spots started from the leaf tip or leaf margin, and gradually spread to the leaf base, resulting in heavy defoliation especially on rainy days. Diseased leaf segments (1×3 mm) were surface-sterilized by dipping in 1% sodium hypochlorite for 1 min, rinsed three times with sterile distilled water, and plated on potato dextrose agar, then incubated at 28°C in the dark for 5 days. Twelve fungal isolates with the same morphological characteristics were obtained from nine affected leaves. The fungal colonies were initially white and turned gray brown with flocculent aerial mycelia and a whorled back. Conidia were frequently born in a long chain, with a short beak, brown or light-brown, 13.2 to 48. 7 (average 26.1) × 4.0 to 13.1 (average 8.0) μm in size (n=148) with 0 to 8 transverse and 0 to 3 longitudinal/oblique septa. Phenotypic features of the isolates agreed with those of Alternaria alternata (Simmons et al. 2007). Two isolates Aa1 and Aa2 were randomly selected for molecular and pathogenicity tests. DNA was extracted from mycelia. Partial sequences of internal transcribed spacer (ITS) and translation elongation factor 1-alpha (TEF1-α) were amplified using the primer pairs ITS1/ITS4 and EFI-728F/EFI-986R (Wei et al. 2022), respectively. The GenBank accession nos. were OK036714 and OK036715 for ITS, and ON951980 and ON951981 for TEF1-α of Aa1 and Aa2, respectively, with a maximal identity of greater than 99% to multiple A. alternata strains. In the neighbour joining phylogenetic tree of the amplified ITS and TEF1-α sequences both Aa1 and Aa2 clustered with A. alternata strains, clearly separating them from other Alternaria spp. For pathogenicity test, conidial suspensions (1×106 spores /mL) of Aa1 and Aa2 were separately sprayed on healthy one-year-old rosemary plants (n=3) with their leaves slightly wounded with a sterilized needle. Control plants (n=3) were sprayed with sterile water. Both inoculated and control plants were incubated at 90% RH, 28 °C. After 14 days, all the inoculated leaves showed black brown lesions similar to those on naturally affected field plants, whereas controls remained symptomless. Fungal cultures with the same phenotypic features as the inocula were constantly re-isolated from the infected leaves. A. alternata was reported as pathogen causing foliar necrosis on rosemary in Italy (Perello et al.1995) and leaf spot (or leaf blight) on multiple plant species such as Actaea dahurica (Hai et al. 2022), and Ligustrum japonicum (Wei et al. 2022) in China. This is the first report of A. alternata causing leaf black spot on rosemary in China.

Bio-efficacy of new fungicide, Tebuconazole- 430SC against coffee leaf rust disease, Hemileia vastatrix Berk and Broome

Coffee is an important plantation crop cultivated worldwide and used as stimulating drink. Coffee leaf rust (CLR) disease is one of the devastating disease affecting foliage of Coffee, limiting Coffee production worldwide. It is caused by an obligate parasite Hemileia vastatrix, which reduce photosynthetic area in turn results in heavy defoliation and die-back of branches. In India CLR management is accomplished with one contact fungicide spray (Bordeaux mixture @ 0.5%) and effective systemic fungicide spray during pre and post monsoon periods respectively. However, to find an alternative to the recommended fungicide the studies were conducted to know the efficacy of new fungicide Tebuconazole 430 SC against CLR. The results revealed that, in the laboratory conditions, complete inhibition of the uredospore germination was observed in Tebuconazole 430 SC @ 0.5 ml/L and 0.75 ml/L and Hexaconazole 5 EC @ 2 ml/L. However, in lower concentration Tebuconazole 430 SC @0.25 ml/L there was 98.97 per cent inhibition and in Copper Oxychloride 50 WP @ 5.5 g/L 87.49 per cent inhibition was observed over control. Field trials indicated that, at all the locations, Tebuconazole 430SC @ 0.75ml/L was found very effective which recorded maximum disease reduction followed by Tebuconazole 430SC @ 0.5ml/L which was found on-par with the currently recommended fungicide Hexaconazole 5 EC @ 2 ml/L and minimum disease reduction was observed in Copper oxychloride 50 WP @ 5.5g/L.

Response of Soil Moisture to Infrequent Heavy Defoliation of Chemically Thinned Juniper Woodland

In semiarid regions of the western United States, there is heightened interest in tree removal to increase water availability for other uses such as forage growth and groundwater recharge. This study was conducted in central New Mexico to determine the effects of heavy infrequent defoliation of chemically thinned juniper woodland (Juniperus monosperma) on soil moisture. Each of three cattle-grazing exclosures (CD, FG, and KI) was instrumented: 1) beneath trees with a set of three soil moisture probes (0−25, 25−50, and 50−75 cm depth) and one soil temperature probe under live trees (control) and dead trees (herbicide-treated); and 2) between trees with one soil moisture and one soil temperature probe in control and herbicide-treated intercanopy plots. Each plot had three clipped and three unclipped subplots. Mean daily maximum surface soil temperature was highest (17.19°C) in intercanopy, intermediate (16.13°C) under herbicide-treated, and lowest (14.90°C) under control trees. Topsoil moisture (0−25 cm depth) was different among treatment combinations from late July to early September 2006. Thus, the control unclipped combination had the highest topsoil moisture while the herbicide-treated unclipped combination had the lowest topsoil moisture. Comparing other depths, control unclipped plots had higher soil moisture in the middle layer (25−50 cm) and bottom layer (50−75 cm) than at the top from late August to early November 2006. Results imply that clipping on chemically thinned juniper woodlands does not increase soil moisture at any depth, yet macropore flow and water absorption on deep soil layers, underneath live trees, might help to store soil moisture for longer periods in water-limited environments.

Defoliation impacts on morpho-physiological attributes and yield of tomato

The experiment was conducted under sub-tropical condition during two successive seasons (November-March) of 2017-18 and 2018-19 to investigate the effect of defoliations on morpho- physiological attributes and yield of tomato. The experiment comprised of five levels of defoliation viz., 0 (control), 3, 6, 9 and 12 leaves defoliation from the base out of 17 leaves at the beginning of flowering stage and two widely cultivated varieties viz., TM-110 and TM-135. The plant characters such as leaf area, plant height, number of leaves plant-1, straw weight plant-1, absolute growth rate, number of fruits plant-1, individual fruit weight and fruit yield were not affected up to 6 leaves defoliation irrespective of seasons and genotypes. Interestingly, photosynthesis, nitrate reductase and reproductive efficiency increased with increasing defoliation levels. Morpho-physiological parameters and yield attributes were better in 3 and 6 leaves defoliated plants over the control with being the highest in 6 leaves defoliated plant, which resulting the highest fruit yield. Heavy defoliation not only reduced source sizes but also decreased total sink (fruits) causing lower fruit yields. The lowest morpho-physiological attributes and fruit yield was recorded in 12 leaves defoliated plants. These results indicate that tomato plants can tolerate one-third leaf loss during reproductive stage and the knowledge of which might be essential for maintaining better quality tompato production. SAARC J. Agric., 20(1): 87-96 (2022)

Pest categorisation of Malacosoma disstria.

The European Commission requested the EFSA Panel on Plant Health to conduct a pest categorisation of Malacosoma disstria Hübner (Lepidoptera: Lasiocampidae), commonly known as the forest tent caterpillar, for the territory of the EU. M. disstria is a North American polyphagous leaf‐eating pest primarily feeding on deciduous trees belonging to the genera Acer, Malus, Populus, Prunus, Quercus and Tilia. It is a univoltine species. Eggs are laid on twigs and branches. Larvae emerge in the spring to feed on buds and fresh leaves. Host plants can be completely defoliated although they often refoliate and recover within a few weeks. Nevertheless, three consecutive years of heavy defoliation or repeated periods of defoliation combined with drought can cause extensive tree mortality. As such, M. disstria is regarded as one of the most serious hardwood forestry insect pests in North America. Population upsurges leading to outbreaks are cyclical, generally nine to 13 years apart and can last 2–3 years. Outbreaks have been reported in eastern North America since the late 18th century. Outbreaks in western Canada have spanned up to 200,000 km2. Plants for planting, cut branches and isolated bark provide pathways for entry. Host availability and climate suitability suggest that large parts of the EU would be suitable for establishment. The pest could spread naturally by flight within the EU. Eggs on plants for planting could also facilitate spread. The introduction of M. disstria into the EU could lead to serious outbreaks causing significant damage to forest, orchard and amenity trees and shrubs. Phytosanitary measures are available to inhibit the entry and spread of this species. M. disstria satisfies the criteria that are within the remit of EFSA to assess for it to be regarded as a potential Union quarantine pest.

Fungi Causing Leaf Spot Diseases of Soyabean: Their Epidemiology and Integrated Management Strategies

Majority of the leaf spot diseases on soybean crop is caused by different pathogenic fungi. Under favourable conditions and severe infection, it may result in heavy defoliation. It decreases the production efficiency of the crop by reducing the surface area available on leaves for photosynthesis. With less photosynthetic activity, the yield may be reduced significantly. Thus, making it a production constraint by reducing the economic viability of the infected soybean crop. Cercospora leaf spot, Target leaf spot, Alternaria leaf spot, Brown Spot, Phyllosticta leaf spot are the major leaf spots caused due to fungus in the soybean crop worldwide. In this review, we are discussing about economic importance, symptomatology, causal organism, disease cycle, epidemiology and integrated management of leaf spots caused due to fungal infection in the soybean crop.

Growth Rate, Dry Matter Accumulation, and Partitioning in Soybean (Glycine max L.) in Response to Defoliation under High-Rainfall Conditions.

The frequency of heavy rains is increasing with climate change in regions that already have high annual rainfall (i.e., Sichuan, China). Crop response under such high-rainfall conditions is to increase dry matter investment in vegetative parts rather than reproductive parts. In the case of soybean, leaf redundancy prevails, which reduces the light transmittance and seed yield. However, moderate defoliation of soybean canopy could reduce leaf redundancy and improve soybean yield, especially under high-rainfall conditions. Therefore, the effects of three defoliation treatments (T1, 15%; T2, 30%; and T3, 45% defoliation from the top of the soybean canopy; defoliation treatments were applied at the pod initiation stage of soybean) on the growth and yield parameters of soybean were evaluated through field experiments in the summer of 2017, 2018, and 2019. All results were compared with nondefoliated soybean plants (CK) under high-rainfall conditions. Compared with CK, treatment T1 significantly (p < 0. 05) improved the light transmittance and photosynthetic rate of soybean. Consequently, the leaf greenness was enhanced by 22%, which delayed the leaf senescence by 13% at physiological maturity. Besides, compared to CK, soybean plants achieved the highest values of crop growth rate in T1, which increased the total dry matter accumulation (by 6%) and its translocation to vegetative parts (by 4%) and reproductive parts (by 8%) at physiological maturity. This improved soybean growth and dry matter partitioning to reproductive parts in T1 enhanced the pod number (by 23%, from 823.8 m−2 in CK to 1012.7 m−2 in T1) and seed number (by 11%, from 1181.4 m−2 in CK to 1311.7 m−2 in T1), whereas the heavy defoliation treatments considerably decreased all measured growth and yield parameters. On average, treatment T1 increased soybean seed yield by 9% (from 2120.2 kg ha−1 in CK to 2318.2 kg ha−1 in T1), while T2 and T3 decreased soybean seed yield by 19% and 33%, respectively, compared to CK. Overall, these findings indicate that the optimum defoliation, i.e., T1 (15% defoliation), can decrease leaf redundancy and increase seed yield by reducing the adverse effects of mutual shading and increasing the dry matter translocation to reproductive parts than vegetative parts in soybean, especially under high-rainfall conditions. Future studies are needed to understand the internal signaling and the molecular mechanism controlling and regulating dry matter production and partitioning in soybean, especially from the pod initiation stage to the physiological maturity stage.

Climate change and defoliation interact to affect root length across northern temperate grasslands

Abstract Grassland plants, especially their root systems, are dynamic and can buffer changes resulting from exposure to multiple stressors; however, the interactive stressor effects on root dynamics and associated above‐ground growth are poorly understood. Here, we examine the effects of changed precipitation and air temperature, and defoliation intensity on root length dynamics and above‐ground biomass using the third year data from a multifactor experiment conducted across three northern temperate grasslands. We found that root length was more sensitive to the changes in environmental and management conditions than root mass, demonstrating the importance of root length as an indicator of rapid root system changes. Across all sites, warming, altered precipitation and defoliation intensity interacted to affect root length while above‐ground biomass was only affected by defoliation intensity, indicating that the root system was more responsive than above‐ground biomass when climatic conditions change. Overall, drought reduced root length, particularly under low defoliation intensity, as well as in combination with warming and heavy defoliation, highlighting the risk of additive effects of such environmental stresses. Across unclipped plots, above‐ground biomass was positively associated with total root length, the latter of which further interacted with precipitation, to affect above‐ground biomass. Compared to defoliated communities, non‐defoliated plant communities exhibited a greater ability to maintain above‐ground biomass under drought conditions via increases in root system efficiency (the amount of above‐ground biomass produced per unit of root length invested). Our results highlight the rapid change of root length in the face of interactive stressors. We postulate that the degree of stability in above‐ground biomass is driven by the altered root system dynamics or species turnover. Future studies are warranted that more directly assess how root length responses under climate change impact other important plant traits in grasslands. A free Plain Language Summary can be found within the Supporting Information of this article.

Seedlings of the Invasive Strawberry Guava Psidium cattleianum Were More Sensitive to Defoliation Than the Closely Related Malagasy Native Eugenia goviala in a Simulated Herbivory Experiment

The success of non-native plants in their recipient environments is often attributed to their relatively lower herbivorous attack (i.e., leaf damage). However, whether non-native plants are inherently more tolerant to leaf damage than native ones remains unclear. We conducted a field experiment to test the effects of clipping (25%, 50%, and 75% leaf area loss) on growth (stem height and production of new leaves) of the natural regenerations of invasive strawberry guava Psidium cattleianum (Myrtaceae) and its closely related native, Eugenia goviala (VU, Myrtaceae,), in a degraded forest in Andasibe, Madagascar. Each clipped individual was paired with a neighboring control (0% defoliation). Survival rates after 105 days were high (&gt;93%) for both species and were not related to clipping levels. Eugenia goviala increased stem growth by 98% at 25% clipping but exhibited no response at higher clipping levels. Clipping tended to reduce stem growth in P. cattleianum but effects were only significant at 75% defoliation (46% reduction in stem growth). Defoliation did not affect the production of new leaves but we detected a tendency for P. cattleianum to produce fewer leaves at higher clipping levels. These results indicate a higher sensitivity to defoliation in the invasive strawberry guava compared to its close native relative E. goviala, which does not support the hypothesis that non-native plant species are more tolerant to leaf damage than native ones. Heavy defoliation can represent a substitute for mechanical control of the strawberry guava. Future studies should focus on identifying suitable native herbivores as part of an integrated control program for this invasive species.

The impact of leaf-eating caterpillars (Heortia vitessoides) infestation on agar trees in Carita forest research station, Province of Banten

The gregarious caterpillars of Heortia vitessoides Moore is a major defoliator of agar trees. The pest seriously threatens the existing agar tree plantation that has been widely cultivated in the community. Pest attacks began to occur in Indonesia since 2005, resulting in the damage and death of agar tree plants in various regions.To determine the impact of pest attack, a study was conducted through periodic monitoring at agar plantation in Carita Forest Research Station (CFRS), Banten Province, from April 2012 to March 2015. Monitoring was conducted in three plots of agar plantations. Each plot consists of six permanent subplots and in each subplot 15 samples of agar tree were randomly choosen. Data were collected and analyzed on monthly basis according to the intensity of defoliation and the mortality of agar trees. Defoliation intensity was determined by the percentage number of trees suffering defoliation in four damage categories, i.e.: light (10-25%), moderate (25-50%), heavy (50-75%), and severe (75-100%). Tree mortality was calculated as the annual percentage of dead trees. The study showed that the defoliation occurred throughout the year in varying degrees of damage. The monthly percentage of defoliated trees is about 30-70% annualy. The high percentage of tree defoliation mainly occurs during dry and early rainy season (June-December). Higher percentage of heavy and severe defoliations were found mostly at seedling. Repeated heavy defoliation causes stunted growth and tree mortality. Early monitoring and control of pests are very important to be done regularly to prevent the damage wider and heavier.

Difference in capacity of clonal integration between terrestrial and aquatic Alternanthera philoxeroides in response to defoliation: implications for biological control

Clonal integration can contribute to the invasiveness of amphibious plant, Alternanthera philoxeroides, but whether this differs between life-forms and whether such difference is underlying their biological control efficacy have scarcely been addressed. We aimed to determine whether clonal integration differs between life-forms and whether terrestrial form with lower biological control efficacy shows greater capacity of clonal integration in response to defoliation. In a greenhouse experiment, we subjected terrestrial and aquatic A. philoxeroides to four levels of experimental defoliation, i.e., 0 (control), 20% (mild), 50% (moderate), and 80% (heavy) leaf clipping, with the stolon connections being either severed or intact. The results showed that clonal integration greatly improved the growth and clonal propagation of both life-forms, especially under heavier defoliation. The shoot/root ratios of both life-forms were significantly increased by clonal integration under heavy defoliation. Moreover, higher level of resource sharing and greater division of labor promoted the terrestrial form to perform better than the aquatic form. These results supported our hypotheses that terrestrial A. philoxeroides can benefit from clonal integration more than aquatic form under herbivory, which may be an alternative mechanism accounted for the low efficacy of biological control of A. philoxeroides in the terrestrial habitats.

Clonal integration increases tolerance of a phalanx clonal plant to defoliation

Defoliation by herbivores commonly imposes negative effects on plants, and physiological integration (resource sharing) can enhance the ability of guerilla clonal plants to tolerate stresses. Here we examined whether physiological integration can increase the ability of phalanx clonal plants to withstand defoliation. On a high mountain grassland in southwestern China, we subjected the phalanx clonal plant Iris delavayi within 10cm×10cm plots to three levels of defoliation intensity, i.e., control (no defoliation), moderate (50% shoot removal to simulate moderate herbivory) and heavy defoliation (100% shoot removal to simulate heavy herbivory), and kept rhizomes at the plot edges connected (allowing physiological integration) or disconnected (preventing integration) with intact ramets outside the plots. Defoliation significantly reduced leaf biomass, root biomass and ramet number of I. delavayi. Clonal integration did not affect the growth of I. delavayi under control, but significantly increased total biomass, rhizome and root biomass under heavy defoliation, and leaf biomass and ramet number under moderate defoliation. We conclude that clonal integration associated with resource reallocation plays an important role in maintaining the productivity of the alpine and subalpine grassland ecosystems in SW China where clonal plants are a dominant component of the grasslands and are commonly extensively managed with moderate grazing intensity. Our results also help to better understand the adaption and tolerance of phalanx clonal plants subjected to long-term grazing in the high mountain environment.

Timing and frequency are the critical factors affecting the impact of defoliation on long term growth of plantation eucalypts

Insect defoliation of plantation Eucalyptus sp. is a ubiquitous problem, not only in their native Australia but also in many other countries where Australian defoliators have invaded the introduced eucalypt plantations. Although eucalypts are very resilient to defoliation, their growth suffers and reduces the economic benefits of the resource. An artificial defoliation trial investigated the critical factors relating to patterns of insect defoliation that affect the long-term growth of the plantation eucalypt, E. nitens, in Tasmania, Australia. Current season’s adult-phase foliage was removed manually from two- to three-year-old trees to test four factors: severity (50% or 100% of current adult foliage, equivalent to 11% or 25% of total foliage); disbudding following defoliation (with or without disbudding), timing of defoliation (early or late in the summer) and frequency (for one or two consecutive years). Growth parameters of the trees were measured annually for four years after the initial defoliation, and again thirteen years later, before harvest. The most significant factors affecting the growth of the trees were timing and frequency of defoliation; severity of defoliation and disbudding did not have significant effects over the long term. Trees that received either light or heavy defoliation late in the season for two consecutive years were at least 17% smaller in diameter and MAI in diameter was reduced by at least 21% compared to untreated trees over one rotation. This means they would need to be grown for three to four more years to reach the same stand volume as undefoliated trees at harvest. This would have serious cost implications for plantation managers. To prevent these economic losses, an integrated pest management system should focus on protecting eucalypts from defoliation of 50% or more of current season’s adult foliage late in the summer, and in particular, preventing defoliation from occurring in concurrent years. In addition, the continual decline in growth rates of defoliated trees relative to undefoliated trees beyond the initial four years of measurement also suggests that defoliation impacts predicted by models based on short term studies may need to be treated conservatively.

Resistência a ácaros de clones de seringueira nas condições do noroeste paulista

Resumo Calacarus heveae Feres (Eriophyidae) e Tenuipalpus heveae Baker (Tenuipalpidae) podem causar intenso desfolhamento em plantas de seringueira. Na perspectiva do Manejo Integrado de Pragas, o uso de clones com resistência é uma importante estratégia de controle. O objetivo deste trabalho foi avaliar a resistência de clones de seringueira ao ataque desses ácaros em experimento conduzido em Votuporanga (SP). Foram avaliados os clones IAC 301, IAC 330, IAN 4493, OS 22, PB 233, PB 254, PC 96, PC 119, PC 140, PC 141, PM 10 e RRIM 600, totalizando 12 tratamentos e 3 repetições, em delineamento experimental em blocos casualizados. As avaliações populacionais de C. heveae e T. heveae foram realizadas pela contagem em laboratório dos ácaros e exúvias presentes em 6 folíolos por parcela. Os níveis de desfolhamento foram avaliados com uma escala de notas variando de 0 (ausência de desfolhamento) a 5 (desfolhamento total). Os clones IAC 301, PB 254 e PC 119 apresentam resistência por não preferência e/ou antibiose ao ácaro C. heveae.