Complete Defoliation Research Articles

<i>In vitro</i> Characterisation of Endophytic Fungi Strains from Lantana camara Leaves Displaying Antifungal Activity Against Phytophthora colocasiae

Colocasiae esculenta is an important tropical tuber crop susceptible to attack by many diseases. The most devastative among these is Taro leaf blight cause by the pathogen Phytophthora colocasiae. The pathogen can cause rapid complete defoliation and crop destruction and under some circumstances, the disease can attack harvested corms and cause heavy losses during storage. Endophytes constitute an important source of bioactive secondary metabolites and enzymes. Based on their phytochemical properties, they can be used as a source of antifungal agent for the treatment of some infectious diseases. In order to evaluate the impact of endophytes on plant defence, in vitro evaluation of the growth effect of endophytic fungi against P. colocasiae was conducted in dual culture, after isolating and screening endophytic fungi from L. camara leaves for their production of some extracellular enzymes (amylases, lipases, laccases, protease and cellulose) and some secondary metabolites (tannins, saponins, phenols, cardiac glycoside) using standard procedures. In-vitro culture techniques with Potato Dextrose Agar (PDA) as culture medium were used to isolate endophytes from L. camara leaf tissues. Isolate identification was done using macroscopic and microscopic characteristics. These isolates were then tested in vitro to evaluate their morphological growth effect against P. colocasiae via the dual culture. Five endophytic fungi were isolated from Lantana camara leaves and coded L1, L2, L3, L4 and L5. The L2, L3 and L5 strains were filamentous and showed coenocytic hyphae which bore some structures’ called conidiosphores identified as Cladosporium sp. L1 strain was filamentous fungi having clamp connections hyphae (bridge-like growth) above hyphal septa and brown sclerotia. L4 strain showed very tiny interwoven and tightly parked mycelia. As enzyme activities, all the strains were found to produce amylase and not protease. L1, L3 and L4 were able to synthesis laccase while L5 produced cellulose and lipase. For the secondary metabolites, all the strains were able to produced tannins and cardiac glycoside but they did not synthesis saponins. L1, L2 and L4 strains were able to produced phenol. In dual culture, the growth of the pathogen decreased the growth rate of the endophytes. L2 strain grew normally by forming an arc around P. colocasiae growth while L3 and L5 strains induced the pathogen to grow on the opposite side of P. colocasiae. Concerning L1 and L4 strains, there were no effect. Based on the antifungal activities against P colocasiae, these strains L2 and L3 could be used for biological control of taro life blight.

Can lessons learned 30 years ago contribute to reducing the impact of the fall army worm Spodoptera frugiperda in Africa and India?

The rapid spread of the fall army worm ( Spodoptera frugiperda) across sub-Saharan Africa, and now South Asia, has created surprise and distress to the smallholder farmers of both regions who face hunger and economic stress because of this pest. There has been high-quality support from the international agricultural information sector, but there has also been advice that may not be applicable to the farming systems of smallholder farmers. That comment arises from lessons learned from involvement with a similar pest outbreak of a related pest species in India starting in the mid-80s. Post-rainy season groundnut (peanut) Arachis hypogaea is a high-value crop in the coastal region of Andhra Pradesh. Changes in the management of tobacco crops to the North of the groundnut belt resulted in invasions of Spodoptera litura. The groundnut farmers responded by applying a wide range of insecticides that did nothing to protect their crops from further defoliation. Scientists from the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT) initiated research that enriched the knowledge of this crop–pest relationship. For instance, they showed that groundnut plants could withstand close to complete defoliation with little loss in yield. Farmers also learned that the cessation of their insecticide regime allowed natural enemies of the caterpillars to take over the management of the pests. They were showed how to enhance the populations of the coccinellids and the birds that were the key predators. ‘Citizen Scientists’ led this process. Non- and quasi-governmental organizations took over the extension process. They were provided with ongoing personal and technical support, for instance, the provision of definitive facts about the high levels of insecticide resistance, encouraging cultural control techniques, and of exploiting natural enemies, including entomopathogens. The involvement of the ICRISAT team later extended into the groundnut fields of South East Asia.

Effects of defoliation on whole‐plant maize characteristics as forage and energy crop

AbstractHail affects yield and quality of maize crops, and consequences also depend on the growth stage at which the injury occurred. Whole‐plant maize (WPM) silage is often used within the same farm for cattle feeding and biogas production. The present study aimed to verify the effects of hail damage, simulated by artificial defoliation, on yield and chemical and nutritional features, as well as on biochemical methane potential (BMP) of maize forage. In a randomized block design with three replicates, four defoliation levels (0%, 33%, 66% and 100% of leaf area removal respectively) have been applied at either the V12 (12th leaf), R1 (silking) or R3 (milk) stages for two consecutive years. WPM yield, chemical and nutritional features, and BMP were measured. Dry‐matter (DM) yield per hectare was progressively reduced (p < 0.001) with increasing levels of defoliation and with application at V12 in comparison with R1 or R3 (1.26 vs. 1.39 and 1.46 kg ha−1 for V12 vs. R1 and R3; p < 0.003). Nutritive value and BMP per unit of product were less altered than dry‐matter yield per hectare by defoliation. Anticipating defoliation reduced net energy for lactation (5.26 vs. 5.46 MJ kg−1 DM for V12 and R3 respectively; p = 0.02). Total defoliation resulted in an accumulation of nitrates (NO3) compared to the other treatments (3.98 vs. 1.53 g NO3 kg−1 DM; p < 0.001). BMP was mainly reduced by early and complete defoliation. Equations were developed to estimate the effects of defoliation on yield, composition, and nutritive and energetic values of WPM.

Histopathologic characterization of the process of Marssonina brunnea infection in poplar leaves

Marssonina brunnea (Ellis & Everh.) Magnus, the causative pathogen of Marssonina leaf spot of poplars (MLSP), can lead to complete defoliation and tree death. Although MLSP has been studied for over 30 years, its precise process of infection is currently unclear. In this study, we present the process of M. brunnea infection in detail using several types of microscopy. When the conidia came into contact with the poplar leaves, they developed germ tubes to attach to the leaf surface. During the first 2 days post inoculation (dpi), infection vesicles (IV) and primary hyphae (PH) formed within host cells. The plasma membranes of the host cells penetrated by IV remained unbroken and intact organelles were visible, indicating that the IV did not kill the host cell. At 3 dpi, secondary hyphae (SH) began to appear within and outside the host cells. The ultrastructural evidence indicated that the SH could kill the host cells rapidly, producing black spots on the surfaces of the leaves. These results collectively suggested that M. brunnea is a typical hemibiotrophic fungus. In addition, M. brunnea could develop intercellular infective hyphae (IH) for expansion. Our findings also confirmed that the germ tubes, IV, and SH are crucial structures for the disease interactions and showed that the two formae speciales of M. brunnea share the same infection histopathological features. This provides important insight for further research into M. brunnea.

Evolutionary changes in growth, regrowth and carbohydrate storage in an invasive plant

We hypothesized that due to the absence of specialist herbivores in introduced ranges, invasive plants have evolved decreased allocation to carbohydrate storage for regrowth ability and as a consequence allocate more to growth. In this study, we compared plant growth, carbohydrate storage and regrowth ability of invasive and native Jacobaea vulgaris in response to complete shoot defoliation. We used invasive J. vulgaris genotypes from three geographically and climactically distinct regions and compared these with native genotypes from Europe. We found that invasive genotypes initially grew larger while native genotypes regrew larger after defoliation. Before defoliation, the carbohydrate storage in roots of invasive genotypes was 38% lower than native genotypes. Biomass after regrowth increased with root carbohydrate storage while it decreased with structural root mass, showing that it is crucial to study root storage and structural components separately in order to investigate plant regrowth. All studied traits of invasive populations from the three geographically and climatologically distinct regions changed in the same expected direction suggesting that the shifts in herbivore guild were causal to the observed change in growth and regrowth ability rather than environmental factors.

A lepidopteran (Imbrasia belina) might influence tree-grass balance of Colophospermum mopane savanna

Traditional explanations of tree-grass coexistence in African savannas are based on competition between these growth forms or demographic bottlenecks of trees maintained by fire or mammalian browsers. Perturbation of their “balance” may result in an alternate system state of woody encroachment. Invertebrate herbivory has never been offered as an explanation. We developed a consumer-resource model which illustrated that annual irruptions of a lepidopteran (Imbrasia belina), known as mopane worm, can determine the tree-grass balance of semi-arid Colophospermum mopane savanna in southern Africa. Model performance was sensitive to the abundance, hence mortality, of mopane worms, owing to their complete defoliation of tree leaf biomass resulting in altered competitive relations between trees and grasses. Invertebrate herbivores have been recognized in other systems as agents for effecting a state change of host tree populations; this modeling study offers a first indication of such a role for the well-researched tree-grass relations of African savannas.

Effects of forest tent caterpillar defoliation on carbon and water fluxes in a boreal aspen stand

Insect outbreaks can significantly influence carbon (C) and water balances of forests. Forest tent caterpillars (FTC) (Malacosoma disstria Hübner) are one of the most prominent insects found in aspen forests in Canada and have the potential to considerably influence regional C and water fluxes. In the summer of 2016, an FTC infestation occurred in a ca. 100 -year-old trembling aspen (Populus tremuloides) stand in the southern boreal forest where the longterm research site known as Old Aspen (OA) is located. The infestation led to nearly complete defoliation of the canopy during the leafing out period when photosynthesis, and thus C uptake, is progressing towards maximum levels. We used 21 years of eddy-covariance (EC) and climate measurements covering pre-infestation and infestation periods to estimate the impact of the FTC infestation on net ecosystem production (NEP), gross ecosystem production (GEP) and evapotranspiration (E). Defoliation in 2016 reduced annual NEP to −130 g C m−2 y−1 and GEP to 798 g C m−2 y−1, respectively, which were much less than their 20-year means (NEP = 118 ± 53 g C m−2 y−1, GEP = 1057 ± 74 g C m−2 y−1), and resulted in the most negative annual NEP value of the 21 years of measurements at the OA site. NEP for 2016 was even lower than values observed during three drought years (2001–2003). However, FTC infestation caused little effect on annual E. FTC infestation reduced the near-surface remotely-measured greenness index, green chromatic coordinate (GCC), to ∼0.32 on June 10 in comparison to ∼0.40 in other years. The defoliation, observable from space as reductions in normalized difference vegetation index (NDVI) values, also showed a negligible effect on E but a large effect on the C fluxes.

First Report of Alternaria arborescens Species Complex Causing Leaf Blotch and Associated Premature Leaf Drop of ‘Golden Delicious’ Apple Trees in the Netherlands

Apple (Malus domestica) is an important fruit crop in the Netherlands, with a total production area of 7,600 ha in 2016, and 1,600 ha of fruit tree nurseries. For decades, fruit growers and nurseries have reported a leaf blotch, characterized by irregular light brown spots, bordered by a dark brown to purple margin, and premature leaf drop, mainly on ‘Golden Delicious’. The disease causes severe, sometimes almost complete defoliation. Leaf blotch typically appears in early July and is most severe in the latter part of the growing season. In a survey in August 2014, affected ‘Golden Delicious’ leaves were collected from different orchards and taken to the laboratory. Next, 20 leaves per location were rinsed with sterile water, sprayed with 70% ethanol until droplet runoff and rinsed again with sterile water, and tissue sections were excised from lesions using a sterile scalpel and placed onto potato dextrose agar (PDA). The PDA plates were incubated at 20°C in the dark, and single spore isolates were transferred to fresh PDA plates. These isolates produced fast-growing colonies of irregular shape, tan brown to black and felty. Sporulation patterns showed long conidiophores with extensive terminal branching. Conidia were ovoid with a tapering apical beak and a size range of 10 to 30 × 5 to 10 μm, with 1 to 5 septa. The isolated fungi were morphologically identical to small spored Alternaria spp. (Simmons 2007). However, small spored Alternaria spp. cannot be identified based on morphological characteristics (Woudenberg et al. 2015). The identity of 12 representative isolates from two different orchards in their 4th growing season, located in the central part of the Netherlands, was determined by multilocus gene sequencing. To this end, genomic DNA was extracted using the UltraClean Microbial DNA isolation kit (MoBio Laboratories, Carlsbad, CA). Sequences of the ITS region, the endoPG gene, and the anonymous region OPA10-2 locus were amplified and sequenced as described in Woudenberg et al. (2013, 2015) and deposited under GenBank accession numbers MG744449–MG744460 (ITS), MG744473–MG744484 (endoPG), and MG744461–MG744472 (OPA10-2). MegaBLAST analysis revealed that our ITS, endoPG, and OPA10-2 sequences matched with >99 to 100% identity to Alternaria arborescens species complex (SC) isolates in GenBank (AF347033 and KP124400 [ITS], AY295028 and KP124104 [endoPG], and KP124712 and KP124714 [OPA10-2]). Subsequently, Koch’s postulates for three A. arborescens SC isolates were performed in the laboratory on ‘Golden Delicious’ leaves. Surface sterilized leaves were inoculated on the abaxial side with 10 μl of a suspension of 10⁵ conidiospores ml–¹ water, prepared from a 14-day-old PDA culture, after wounding with a needle, with four inoculations per leaf. Inoculated leaves were sealed in a plastic box and incubated in darkness at 20°C. The experiment was carried out in five replicates. Symptoms appeared within 7 days on 100% of the leaves, while mock-inoculated controls with water remained symptomless. Fungal colonies isolated from the lesions cultured on PDA morphologically resembled the original isolate from the infected leaves. The identity of the reisolations was confirmed as A. arborescens SC by sequencing. To our knowledge, this is the first report of A. arborescens SC causing leaf blotch and subsequent premature leaf drop of apple cultivars in the Netherlands. Multiple Alternaria species groups are associated with leaf blotch diseases of apple in Australia and Italy (Harteveld et al. 2012; Rotondo et al. 2012). A. arborescens-like isolates are most prevalent in Australia and are mostly associated with leaf blotch symptoms (Harteveld et al. 2012).

Effects of simulated seedling defoliation on growth and yield of cotton in southern New South Wales

Early-season leaf loss due to damage by thrips (Thysanoptera: Thripidae) is considered an important issue by Australian cotton growers. To understand the potential impact of early-season leaf loss in the southern region of New South Wales, we investigated the effects of artificial defoliation on cotton growth, maturity timing and lint yield over four seasons (2013–14 to 2016–17) in commercial cotton crops in the Riverina district. Four defoliation scenarios were investigated: (i) complete defoliation, 100% removal of all true leaves from all plants; (ii) partial defoliation by plant, 100% removal of all true leaves from 75% of plants; (iii) partial defoliation by leaf, removal of 75% of leaf area from all individual true leaves on all plants; and (iv) no defoliation. Defoliation was done by hand at the onset of the 2-, 4-, and 6-node growth stages. Defoliated plants were initially shorter than undefoliated (control) plants, but by ~100-days post seedling emergence, height differences were no longer statistically significant in two of the four seasons. Defoliation did not affect the total number of bolls shortly before harvest. However, complete defoliation delayed crop maturity by up to 18 days and partial defoliation by plant delayed crop maturity by up to 8 days. Because of the delays, fully defoliated plants often had fewer open bolls shortly before harvest and yielded significantly less than undefoliated plants in three of the four seasons. A laboratory experiment with caged cotton seedlings showed that weekly introductions of up to10 thrips per seedling (predominantly onion thrips (Thrips tabaci), the most abundant species on cotton in the region) caused significant clubbing in true leaves, but the total leaf area was not significantly reduced at the 6-node stage. Implications of the results for southern cotton integrated pest management are discussed.

Relative contributions of hydraulic dysfunction and carbohydrate depletion during tree mortality caused by drought.

Drought-induced tree mortality has been observed worldwide. Nevertheless, the physiological mechanisms underlying this phenomenon are still being debated. Potted Robinia pseudoacacia and Platycladus orientalis saplings were subjected to drought and their hydraulic failure and carbon starvation responses were studied. They underwent simulated fast drought (FD) and slow drought (SD) until death. The dynamics of their growth, photosynthesis, water relations and carbohydrate concentration were measured. The results showed that during drought, growth and photosynthesis of all saplings were significantly reduced in both species. The predawn water potential in both species was ~ -8 MPa at mortality. The percentage loss of conductivity (PLC) was at a maximum at mortality under both FD and SD. For R. pseudoacacia and P. orientalis, they were >95 and ~45 %, respectively. At complete defoliation, the PLC of R. pseudoacacia was ~90 % but the trees continued to survive for around 46 days. The non-structural carbohydrate (NSC) concentrations in the stems and roots of both FD and SD R. pseudoacacia declined to a very low level near death. In contrast, the NSC concentrations in the needles, stems and roots of P. orientalis at mortality under FD did not significantly differ from those of the control, whereas the NSC concentrations in SD P. orientalis stems and roots at death were significantly lower than those of the control. These results suggest that the duration of the drought affected NSC at mortality in P. orientalis. In addition, the differences in NSC between FD and SD P. orientalis did not alter mortality thresholds associated with hydraulic failure. The drought-induced death of R. pseudoacacia occurred at 95 % PLC for both FD and SD, indicating that hydraulic failure played an important role in mortality. Nevertheless, the consistent decline in NSC in R. pseudoacacia saplings following drought-induced defoliation may have also contributed to its mortality.

First Report of Alternaria Black Spot Caused by Alternaria alternata on Blue Honeysuckle in Poland

Blue honeysuckle (Lonicera caerulea L. var. kamtschatica Sevast.) is becoming increasingly popular in Poland. Each year, the growing area of this plant increases significantly because it produces one of the earliest crops, and its berries contain a high concentration of antioxidants (i.e., vitamins A and C, potassium, calcium, phenolic compounds, and anthocyanins). Symptoms of Alternaria leaf spot were observed on blue honeysuckle plants growing in allotment gardens in Kanie (52°08′08″N, 20°47′14″E, Mazovia Province) and Kopalino (54°47′34″N, 17°50′02″E, Pomerania Province) in 2015 to 2016. The initial infections were noted on leaves at the end of June. Under favorable conditions, complete defoliation was observed at the beginning of August. Symptoms on leaves consisted of oval to irregularly shaped spots, 1 to 4 mm in diameter. They were initially black and later turned brown with a dark brown to black border. Over time, the center of the spots developed a gray shade. The spots were surrounded by a yellowish halo. The lesions gradually enlarged and sometimes coalesced. In 2015 and 2016, infected leaves were collected and sections (3 × 4 mm) were excised from the margin of diseased leaf tissue, disinfested with 1% sodium hypochlorite for 2 min, transferred to potato dextrose agar (PDA), and incubated at 25 ± 2°C. Twenty single-spored isolates were obtained from the developed colonies of the fungus. On potato carrot agar (PCA), cultures were olive brown with sparse, white-gray aerial mycelium. The conidiospores were obpyriform to obclavate, light brown to dark brown, with 1 to 6 transepta and 0 to 2 longisepta. After 9 days on PCA, 100 conidia were measured to be 12 to 46 × 7 to 17 µm. Morphological characteristics were similar to those described for Alternaria alternata (Fr.) Keissl (Simmons 2007). For the pathogenicity test, four isolates were grown on salt nutrient agar (SNA) for 10 days. Inoculations were performed on 2-year-old plants of blue honeysuckle cultivars Wojtek and Duet growing in pots. Plant leaves (three plants per isolate) were rinsed with sterile water. Next, they were inoculated with a spore suspension (∼10⁶ spores/ml) of each isolate using a pipette. Control plants were treated with sterile water. All plants were incubated in a moist chamber (Sanyo) at 27°C during the day and 20°C during the night, 90% relative humidity, and 16-h photoperiod. After 10 days, first leaf spots developed on the inoculated plants. The control plants remained symptomless. The pathogen was successfully reisolated from the spots and confirmed to be identical with the original fungal isolate, fulfilling Koch’s postulate. To confirm the morphological identification, genomic DNA was extracted from four single-spore isolates (JK8, JK2.3, JK 4.2, and Alt4). The internal transcribed spacer (ITS1, 5.8S, and ITS2) region of rDNA and the translation elongation factor (TEF1-α) gene were amplified with primers ITS1 and ITS4 (White et. al 1990) and EF1-728F (Carbone and Kohn 1999) and EF2 (O’Donnell et al. 1998), respectively. One representative sequence for the ITS and one for the TEF1-α gene were deposited in GenBank (accession nos. MF564200 and MF564197), respectively. BLAST analysis showed 99% identity with A. alternata sequences published in GenBank at the ITS (AF347031) and TEF1-α (KC584634) regions. Based on the morphology and molecular studies, the causal agent of Alternaria black spot on the blue honeysuckle was identified as A. alternata. To our knowledge, this is the first report of this pathogen on blue honeysuckle worldwide.

Detection and Management of Mango Dieback Disease in the United Arab Emirates.

Mango is affected by different decline disorders causing significant losses to mango growers. In the United Arab Emirates (UAE), the pathogen was isolated from all tissues sampled from diseased trees affected by Lasiodiplodia theobromae. Symptoms at early stages of the disease included general wilting appearance of mango trees, and dieback of twigs. In advanced stages, the disease symptoms were also characterized by the curling and drying of leaves, leading to complete defoliation of the tree and discolouration of vascular regions of the stems and branches. To substantially reduce the devastating impact of dieback disease on mango, the fungus was first identified based on its morphological and cultural characteristics. Target regions of 5.8S rRNA (ITS) and elongation factor 1-α (EF1-α) genes of the pathogen were amplified and sequenced. We also found that the systemic chemical fungicides, Score®, Cidely® Top, and Penthiopyrad®, significantly inhibited the mycelial growth of L. theobromae both in vitro and in the greenhouse. Cidely® Top proved to be a highly effective fungicide against L. theobromae dieback disease also under field conditions. Altogether, the morphology of the fruiting structures, molecular identification and pathogenicity tests confirm that the causal agent of the mango dieback disease in the UAE is L. theobromae.

Sal Defoliation in Kanha Tiger Reserve - Search for Causative Agents

Surveys conducted during the epidemic defoliation in Sal forests of Kanha Tiger Reserve, Mandla Forest Division, Madhya Pradesh, revealed the occurrence of four insect defoliators belonging to the order Lepidoptera, viz. Caviria sericea Moore (Lymantriidae), Hyposidra talaca Walker (Geometridae) Trabala vishnou Lefroy (Lasiocampidae) and Trypanophora semihyalina Kollar (Zygaenidae). The defoliation period was observed to be rainy season of the year (July-October). Defoliation intensity was noticed to be varied greatly. Complete defoliation of Sal trees was recorded and some ranges were observed to be severely affected. Among the insect species recorded, C. sericea is the first record of occurrence of Sal defoliator.

Sensitivity analysis of RapidEye spectral bands and derived vegetation indices for insect defoliation detection in pure Scots pine stands

This study investigated the statistical relationship between defoliation in pine forests infested by nun moths (Lymantria monacha) and the spectral bands of the RapidEye sensor, including the derived normalized difference vegetation index (NDVI) and the normalized difference red-edge index (NDRE). The strength of the relationship between the spectral variables and the ground reference samples of percent remaining foliage (PRF) was assessed over three test years by the Spearman’s ρ correlation coefficient, revealing the following ranking order (from high to low ρ): NDRE, NDVI, red, NIR, green, blue, and red-edge. A special focus was directed at the vegetation indices. In both discriminant analyses and decision tree classification, the NDRE yielded higher classification accuracy in the defoliation classes containing none to moderate levels of defoliation, whereas the NDVI yielded higher classification accuracy in the defoliation classes representing severe or complete defoliation. We concluded that the NDRE and the NDVI respond very similarly to changes in the amount of foliage, but exhibit particular strengths at different defoliation levels. Combining the NDRE and the NDVI in one discriminant function, the average gain of overall accuracy amounted to 7.8 percentage points compared to the NDRE only, and 7.4 percentage points compared to the NDVI only. Using both vegetation indices in a machine-learning-based decision tree classifier, the overall accuracy further improved and reached 81% for the test year 2012, 71% for 2013, and 79% for the test year 2014.

Decrease in growth increment of Populus euphratica upon defoliation by Lepidopteran larvae in a Central-Asian floodplain forest

Populus euphratica is a constitutive tree species of the mostly monospecific forests along Central-Asian rivers. In the hyper-arid climate along the Tarim River, Xinjiang, NW China, these trees are phreatophytes with continuous access to the groundwater. Those poplar stands are often moderately to completely defoliated by Lepidopteran larvae in spring. In a P. euphratica stand at the middle reaches of the Tarim River, which grew close to the river and to the water table, we tested whether severe defoliation significantly reduces the trees' radial stem increment and their production of above-ground wood biomass even at ample water supply by the river.Tree-ring analyses and allometric regressions revealed a drastic decrease in radial stem increment and annual above-ground wood production upon complete defoliation even in a period of ample water supply, which otherwise would have allowed maximum productivity. The loss of above-ground production by herbivory amounted to approximately 44% relative to the high production rate of the year before complete defoliation. During the recent decade, however, only the amount of river discharge – but not the estimated intensity of defoliation – was (marginally) significantly correlated with the stem increment. We conclude that in P. euphratica forests growing close to the river and to the groundwater, tree growth is mainly related to the amount of river discharge, but can be significantly reduced in years with complete defoliation. Therefore, defoliation events should be considered in assessing the productivity of these riparian forests.

The expression of a candidate cucumber fruit sugar starvation marker gene CsSEF1 is enhanced in malformed fruit induced by salinity.

The cucumber (Cucumis sativus L.) gene Cucumis sativus Somatic Embryogenesis Zinc Finger 1 (CsSEF1) was suggested to be a good marker gene for sugar starvation in fruit. The expression of this gene in fruits is dramatically upregulated in plants that have suffered either complete defoliation or prolonged darkness. CsSEF1 was initially discovered as a gene that was upregulated during somatic embryogenesis. We examined the difference in fruit parts and the effect of pollination on the upregulation of CsSEF1 induced by defoliation treatment. The results indicated that the upregulation of CsSEF1 in fruit by defoliation is not dependent on the presence of developing embryos. The expression of CsSEF1 was upregulated in malformed fruit induced by salinity in which the development of placenta was arrested. Partial cutting of the distal part of the fruit showed that if placenta tissue remained there was no upregulation of CsSEF1, whereas when placenta tissue did not remain there was a marked upregulation of CsSEF1. These results could be consistently interpreted as showing that placenta tissue induced the transport of photoassimilates to the fruit and that without developing placenta tissue, pericarp tissue suffers from severe sugar starvation. This interpretation, in turn, enforces the view that CsSEF1 is a good marker gene of fruit sugar starvation.

KUTU PUTIH SINGKONG, PHENACOCCUS MANIHOTI MATILE-FERRERO (HEMIPTERA: PSEUDOCOCCIDAE): PERSEBARAN GEOGRAFI DI PULAU JAWA DAN RINTISAN PENGENDALIAN HAYATI

Cassava mealybug, Phenacoccus manihoti Matile-Ferrero (Hemiptera: Pseudococcidae): Geographic distribution in Java and initiation of biological control. Cassava mealybug, Phenacoccus manihoti Matile-Ferrero (Hemiptera: Psedococcidae), is a recently introduced pest in Indonesia. Parasitoid Anagyrus lopezi (De Santis) (Hymenoptera: Encyrtidae) was imported to control the pest. Studies were conducted to determine geographic distribution of P. manihoti throughout Java, and to evaluate the potential of the parasitoid as a biological control agent. Geographic distribution of the pest was determined through field survey, whereas evaluation of the parasitoid was studied through cage experiment and field release. Our survey revealed that the cassava mealybug has spread throughout Java. Heavy infestations caused shortened and distorted stems, complete defoliation, and stunted growth. In cages containing only mealybugs, all cassava plants (100%) died after two months. Whereas in cages containing both mealybugs and three pairs of parasitoid, rate of parasitization was 25% and plant mortality 20%. Parasitoids released in the field were able to survive, reproduce, and establish under Bogor climatic condition. These might indicate that parasitoid A. lopezi is a potential natural enemy to be used in biological control program of the cassava mealybug.

Population surge of zigzag elm sawfly (Aproceros leucopoda (Takeuchi, 1939): Hymenoptera: Argidae) in the Northern Cis-Azov Region

Zigzag elm sawfly Aproceros leucopoda (Takeuchi, 1939) is a dangerous invasive pest of elm trees, which quickly spreads in Europe. The initial range of A. leucopoda covers Japan, the east of China, the Korean Peninsula, and the Russian Far East. Within the territory of Ukraine, the species was found for the first time in 2006 in Lugansk oblast. The first population surge of zigzag elm sawfly was registered in artificial plantations of Siberian elm (Ulmus pumila) in Donetsk and Zaporizhzhya oblasts in the summer of 2014. It led to complete defoliation of plantations over a large area. The wide distribution, quantity, and scale of damage testify that the species has become naturalized completely in the region. The appearance of new dangerous pest demands the development and adoption of measures to control pest populations.

Diversity and specificity of sap-feeding herbivores and their parasitoids on Australian fig trees

The ecology, diversity, and parasitoid complex of plant–sap feeding insects of the family Homotomidae (Hemiptera: Psylloidea) specialised on fig trees (Ficus) have so far received little research attention. They are ecologically important, however, as occasional outbreaks of the homotomid Mycopsylla fici may cause complete defoliation of its host plant, the Moreton Bay fig (Ficus macrophylla). Mycopsylla proxima, the only other species reported from Australia, feeds on F. rubiginosa without any recorded outbreaks. We searched for homotomids and their parasitoids on eight Ficus species on the east coast of Australia, Lord Howe Island (LHI), and in Auckland, New Zealand, and detected them on three Ficus species. Using mitochondrial and nuclear DNA sequences, we delimited three Mycopsylla species, including a putative new species on F. watkinsiana. We also characterised six (including one previously described) parasitoid species of the genus Psyllaephagus (Hymenoptera: Encyrtidae) based on congruent morphological characters and molecular data. Each of the homotomid species was highly host specific to a single fig species, whereas parasitoid species varied in host specificity: three host specific to M. fici and three host generalists. Geographic distribution varied among parasitoid species; e.g. one host-specific species was found on both the mainland and LHI, but a second species only on LHI. Our study revealed previously unrecognised diversity in fig homotomids and especially in their parasitoids. The herbivores and parasitoids showed contrasting patterns of host specificity. Interestingly, M. fici, the only outbreak species, had the highest diversity of associated parasitoid species and was the only species with host-specific parasitoids.

Effects of defoliation and site quality on growth and defenses of Pinus pinaster and P. radiata

The susceptibility to pests and pathogens is frequently of only minor consideration by foresters when selecting tree species to plant, but growth reductions from pests and pathogens are commonly large relative to productivity differences among tree species. Because the selection of tree species and sites when establishing plantation forests has potential effects on subsequent damage by pests, there is need for consideration of joint effects of tree species, site quality, and risk of pests. We tested here how site quality influences the response of two pines species that differ in their evolutionary history with a primary pest in the system. Our specific research objectives were to (1) measure the growth response of two pine species (the native Pinus pinaster and the introduced P. radiata) to defoliation by the pine processionary moth, across a gradient of nutrient availability and (2) compare the constitutive and delayed defoliation induced chemical defenses of these two pine species on sites of low and high quality. We analyzed variation in foliar nitrogen, terpenes, tannins, total phenols and four defensive proteins. The impact on tree growth from experimentally applied defoliation by PPM was surprisingly low. Even with complete defoliation, large sample sizes, and baseline measurements that accounted for much of the variation among trees, we observed only modest effects on diameter growth and no effects on height growth; volume growth was initially reduced by only 6–8% initially, with full recovery within 3 years of defoliation. Pinus radiata, the faster growing species, had higher concentrations than P. pinaster of foliar N while P. pinaster had up to 12 times higher concentrations of terpenes, these results match with predictions of the resource availability hypothesis (RAH). Pinus radiata foliage was relatively rich in tannins and total phenolics. The pine species also differed in defensive proteins. Pinuspinaster had higher concentrations of peroxidase (POD), polyphenol oxidase (PPO) and chitinase (CHI), while P. radiata had higher concentrations of trypsin inhibitor (TI). Finally there was no evidence for delayed inducible defenses in either pine species following PPM defoliation; both species seem to use other defensive strategies to counter predictable attacks by the herbivore. In our study region, defoliation by PPM may not be a primary consideration in the selection of pine species for production forests, but this conclusion need not hold in regions where pines grow more slowly or are exposed to multiple years of defoliation by PPM.