Secondary Ambrosia Beetles in Apparently Healthy Trees: Adaptations, Potential Causes and Suggested Research

Some ambrosia beetles are primary attackers of healthy, living trees, but in recent years normally secondary species have been increasingly observed attacking living trees, either as exotics or in their native geographic ranges. We identified five factors that could underlie an increasing prevalence of attack by secondary ambrosia beetles on living trees: (1) early flight before the host tree has recovered the ability to resist attack in the spring, possibly associated with climate change; (2) nutritional independence from the host that may enable ambrosia beetles to feed on ambrosia fungi that live on dead tissue in a living tree; (3) potentially pathogenic fungi that could become more pathogenic with climate change or through hybridization with exotic strains; (4) cryptic behavior that facilitates international transport and the establishment of exotic species and genotypes; and (5) a complex chemical ecology that enables secondary ambrosia beetles to locate stressed living trees that may temporarily appear to be suitable hosts for secondary beetles. We propose four avenues of research that will lead to an increased understanding of attack of living trees by ambrosia beetles, and may facilitate the implementation of effective pest management strategies and tactics: (1) intensive surveys, particularly for exotic beetle species and associated fungal strains; (2) molecular genetics studies that would facilitate the identification of known and new strains and genotypes, particularly of ambrosia fungi; (3) studies of the pathogenicity of ambrosia fungi as well as other fungi that could predispose trees to attack; and (4) investigations of the chemical ecology of tree-attacking species that could lead to new pest management tools and tactics.     

Effects of variable temperatures on responses ofAphytis melinus andA. lingnanensis to host density

The effects of three variable temperature regimes (18–24, 24–29, and 29–35°C) on the responses of two species of the genusAphytis Howard (Hymenoptera: Aphelinidae), parasitic upon the California red scale, were studied, and a test to analyze parasite behavior was developed.Aphytis lingnanensis Compere was generally more efficient thanA. melinus DeBach; however, whereas a high temperature regime (29–35°C) had a negative effect on the responses ofA. lingnanensis, it improved those ofA. melinus. The two species distributed their eggs in clumps, but were able to respond to increasing host density by reducing the number of eggs laid per encounter. The combined effects of numerical, and functional responses of the two species on host population were considered, with special reference to the mechanism of competitive displacement.     

Comparison of the seasonal occurrence and behavior of seven pine bark beetles (Coleoptera: scolytidae) in Israel

The seasonal occurrence, behavior and gallery system of seven sympatric pine bark beetles were examined at two sites, using trap-logs and trap-trees ofPinus halepensis. Two groups of beetles were recognized:(a) Tomicus destruens, Hylurgus micklitzi andHylastes linearis, which are monogamous, univoltine, breed during the winter and early spring, and prefer the lower section of the tree;H. micklitzi andH. linearis tend to infest the main root system,(b) Orthotomicus erosus, Pityogenes calcaratus, Carphoborus minimus andCrypturgus mediterraneus, which are polygamous, multivoltine, and breed from spring to autumn.O. erosus usually infests the lower stem sections,P. calcaratus occupies the thin smooth bark aboveO. erosus, andC. minimus develops on the top stem.Cr. mediterraneus lives in the mines and egg tunnels of the other species and uses their gallery entrance holes. Occupation of different stem sections by the beetles, and beetle damage as related to tree age are discussed.     

Presence of less-preferred hosts of the aphid parasitoids <Emphasis Type="Italic">Aphidius ervi</Emphasis> and <Emphasis Type="Italic">Praon volucre</Emphasis> reduces parasitism efficiency

Parasitoids are characterized by a defined range of hosts, either more specialist or generalist. Under natural conditions, females may encounter different host species on the same plant or in the same location. In this case, their preference for one host could influence their choice. However, the presence of less suitable hosts may also affect their choice and, in some cases, may reduce their interest in a patch where both preferred and less preferred hosts are available. The aim of the present study was to test the consequences of the simultaneous presence of three cereal aphids (Sitobion avenae Fabricius, Metopolophium dirhodum Walker, and Rhopalosiphum padi Linnaeus) on the parasitism by two of their parasitoids, Aphidius ervi Haliday and Praon volucre Haliday. Firstly, in the no-choice experiment, A. ervi parasitized on S. avenae at a significantly higher rate as compared to M. dirhodum, whereas no parasitism on R. padi was observed. P. volucre parasitized the three species of cereal aphids with a significant preference for S. avenae. Interestingly, when two or three host species were offered simultaneously in the same quantity to pairs of parasitoids, the level of parasitism was less than that observed for one host species alone. This observation exhibits a distractive effect on non-host species, from the defense mechanism of a non-suitable host or from the perception of bad quality patches. These results raise the question of the practical application of inundative release of parasitoids for biocontrol when several hosts are available simultaneously.     

A comparative study of the effects of constant temperatures on development time and survival of two coccinellid beetles of the genusChilocorus

The effect of constant temperatures on duration and rate of development and on survival of two species of predatory beetles of the genusChilocorus (Coleoptera: Coccinellidae) (one endemic and one imported) was studied. The observed data were analyzed and compared applying three different methods. The methods based on the logistic curve provided a better fit to the observed data as compared with the widely used Blünck-Bodenheimer equation. The imported speciesC. kuwanae had a faster rate of development than the endemic speciesC. bipustulatus at the lower temperatures tested (18°, 22°C), but it could not complete its development at 32°C. Survival ofC. kuwanae was considerably lower than that of the endemic species. As both species are active during the summer, it was concluded that the sensitivity ofC. kuwanae to high temperatures provides at least a partial explanation to the fact that this species has not become established yet in Israel.     

Response of three soft scales (Homoptera: Coccidae) to parasitization byMetaphycus Smrskii

The response of three soft scales: the pyriform scale —Protopulvinaria pyriformis (Cockerell), the mango shield scale —Protopulvinaria mangiferae (Green), and the capparis soft scale —Coccus capparidis (Green), to paiasitization by the parasiteMetaphycus swirskii Annecke & Mynhardt (Hymenoptera:Encyrtidae), was studied. Although the parasite was able to complete its development in any of these three host species, different rates of mortality of parasite immatures were recorded in the various hosts. Parasite mortality inP. pyriformis was due to egg encapsulation only and was higher in the field than under laboratory conditions (53.1%vs. 27.7%, respectively). InP. mangiferae a total of 55.4% mortality was observed, while inC. capparidis it reached only 14.0%, rendering the latter the most suitable of the three soft scales tested, for successful development ofM. swirskii.     

The Entomophthorales of Israel and their arthropod hosts: Seasonal occurrence

The seasonal occurrence of entomophthoralean host-pathogen combinations and of conidialvs. resting spore production in Israel is presented and discussed. The data recorded during 1968–1979 concern the following species and their recorded hosts:Conidiobolus apiculatus, C. coronatus, C. osmodes, C. thromboides, andConidiobolus spp.;Entomophthora planchoniana;Neozygites fresenii; Erynia erinacea, E. neoaphidis, E. nouryi, E. occidentalis, E. phalloides, E. phytonomi andE. radicans.     

Seasonal abundance of sap beetles (Coleoptera: Nitidulidae) in date plantations in Israel

Seasonal abundance of nitidulid beetles infesting date plantations in Israel was studied through captures of adults in traps.Carpophilus mutilatus andC. hemipterus were found throughout autumn, winter and spring; in the summer their populations declined considerably.Urophorus humeralis predominated during the summer whileHaptoncus luteolus was most abundant during late summer and autumn. Damage to ripening fruit by sap beetles is apparently inflicted mainly byH. luteolus andU. humeralis.     

大草蛉幼虫对不同寄主植物上烟粉虱卵的捕食功能反应与搜寻效应

为了研究不同寄主上大草蛉Chrysopa pallens(Rambur)幼虫对烟粉虱Bemisia tabaci(Gennadius)卵的捕食功能反应与搜寻效应,在室内条件下评估了大草蛉捕食功能反应模型,并研究了大草蛉3龄幼虫对棉花、烟草和辣椒上烟粉虱卵的搜寻效应和控害潜能。结果显示,在3种寄主植物上大草蛉3龄幼虫捕食量均随猎物密度的增加而升高,在烟草、棉花、辣椒上的捕食量分别为7.6~28.4、5.4~23.2、6.0~18.8粒;3种寄主植物上的大草蛉捕食功能反应均拟合Holling II、III功能反应模型;在烟草上大草蛉的瞬间攻击率最大,为0.470,处理时间最短,为0.021;在3种寄主植物上大草蛉3龄幼虫搜寻效应均随猎物密度的增加而下降,当猎物密度相同时,在烟草上的搜寻效应高于棉花和辣椒。研究表明,不同寄主植物能够影响大草蛉3龄幼虫对烟粉虱卵的瞬间攻击率及其搜寻效应。     

Variability of some plant species from different origins and their suitability for virus work

Plants of four species obtained from various sources were raised and compared for their suitability as test plants for a number of viruses. The species comprisedChenopodium amaranticolor (local lesion host of red clover mottle virus),Nicotiana glutinosa (local lesion host of tobacco mosaic virus (TMV)),N. rustica (systemic host of TMV, cucumber mosaic virus and tomato spotted wilt virus) andN. tabacum ‘White Burley’ (systemic host of TMV). Some sources proved to be more attractive as test plants or experimental hosts because of, e.g., production of more local lesions per unit of leaf area (C. amaranticolor andN. glutinosa), distinctness of lesions (C. amaranticolor), development of more pronounced systemic symptoms (N. rustica andN. tabacum ‘White Burley’), better growth characteristics (particularlyC. amaranticolor andN. rustica), smoother leaves being easier to rub (N. glutinosa) or more and bigger leaf formation (particularlyN. rustica). The implications for the interpretation of host range studies and the quest for propagation and assays hosts are discussed.     

Penetration and reproduction of root-knot nematodes on cucurbit species

Cucurbits are often cultivated in rotation with Solanaceae in double-cropping systems. Most cucurbits have been described as susceptible to root-knot nematodes (RKN) but little is known on their relative levels of susceptibility. Because RKN species differ in rates of root invasion and reproductive traits, isolates of M. arenaria, M. incognita and M. javanica were compared on five cucurbit hosts in experiments run in a climate growth chamber. They included zucchini squash cv Amalthee, cucumber cv Dasher II, melon cv Pistolero, pumpkin cv Totanera and watermelon cv Sugar Baby. All cucurbits were susceptible to the three RKN isolates although M. javanica showed higher invasion rates, faster development and higher egg production than M. arenaria on the selected cucurbits. Apparent differences among cucurbits were primarily due to root invasion rates and formation of egg masses. Both Cucumis species (cucumber and melon) were better hosts for nematode invasion and reproduction than zucchini squash, followed by watermelon. Large invasion rates followed by small reproduction traits were linked to M. incognita on zucchini squash. Reduced invasion rates and egg mass formation along with delayed early development were shown on watermelon.     

Successful disinfestations of sap-beetle contaminations from organically grown dates using heat treatment: A case study

Palm dates suffer from high infestations of sap-beetle (Coleoptera: Nitidulidae) populations. Organically grown dates are particularly subject to high infestations for lack of alternative treatments both during pre- and postharvest, while export requirements of null infestations are in effect. Present methods of postharvest control include treatments using CO₂, which are expensive and require several hours. In this report we describe an effective, short-duration and inexpensive method of postharvest heat-treatment using a postharvest heating container (PHHC). Laboratory experiments determined the optimum temperature regime for maximum escape of beetles from the fruit to be 55°C for 2.5 h; this temperature was attained at a rate of 1.8°C/min. Subsequent successful disinfestation of beetles was obtained in the PHHC after a total exposure time of 2.5 h. Sampling dates before and after treatment and quality control tests on cartons ready for export showed that this method compared in efficiency with CO₂ treatments but was much more economical.     

美国松木上4种长角天牛的检疫鉴定

本文记述了深圳口岸2016年从进境美国松木中截获的4种长角天牛,对其形态特征及分布和寄主进行了详细描述并编制了相应的检索表,可为口岸木材检疫提供参考。     

Potential distribution ranges in Europe for Ips hauseri, Ips subelongatus and Scolytus morawitzi, a CLIMEX analysis

Introduced bark and ambrosia beetles have become a worldwide problem for the forest industry as well as for recreational parks and nature reserves by directly damaging wood material and killing trees or by vectoring lethal tree diseases. In this study we used the climatic modeling program CLIMEX to simulate potential distribution ranges for three different Asian bark beetles, Ips hauseri (Reitter), Ips subelongatus (Motschulsky) and Scolytus morawitzi (Semenov) on the basis of their current distribution. The program calculates an ecoclimatic index based on the life cycle requirements of a species and thus represents the probability of a viable population existing at a certain location. Simulations show that all of the studied species have a potential distribution according to climatic factors. Also, potential hosts for these species grow in much of Europe, making the potential establishment of these species possible. Simulation with the Intergovernmental Panel on Climate Change (IPCC) climate change scenario A1B resulted in changes of 200 to 900 km at the northern and southern edges of the distribution ranges for the studied species.     

First report of flower chafer beetle, Oxycetonia versicolor, on pigeonpea and mungbean from Punjab, India

The occurrence of flower chafer beetle, Oxycetonia versicolor (Fabricius) (Scarabaeidae: Coleoptera) damaging the flowers of important grain legumes such as pigeonpea (Cajanus cajan (L.) Millsp.) and mungbean (Vigna radiata (L.) Wilczek) is reported for the first time from Punjab, India. Heavy infestation of these flower beetles at flowering may cause considerable damage to these crops. A mild to moderate level of infestation of 15?C17 beetles per ten plants was recorded at the time of peak flowering period on both the grain legumes. Adult beetles devour the flowers and buds, thereby greatly reducing the number of pods that are set. Information on important taxonomic characters of the beetle is highlighted in this report. Careful monitoring and timely reporting on this chafer beetle is necessary to avoid any future outbreak.     

Host plants of Anoplophora glabripennis,a review

Anoplophora glabripennis (Asian longhorned beetle) attacks many different broadleaf tree species. Although there is no doubt that A. glabripennis can complete its life cycle on species belonging to various genera such as Acer, Populus, Salix and Ulmus, there is conflicting information about the host plant status of many other species. Plant species may have been listed because of maturation feeding or oviposition, without evidence that A. glabripennis can actually complete its life cycle on these species. In the present review, 34 plant taxa that have been listed as A. glabripennis‐hosts are placed in four different categories based on information available through literature search and by personal communication with experts. The categories are: (I) plant species on which A. glabripennis has been reported to complete its life cycle (from oviposition to emergence of new beetles) under field conditions, (II) plant species on which A. glabripennis has completed its life cycle in laboratory or semi‐field experiments (i.e. plants and beetles reared in cages), (III) plant species on which A. glabripennis has been reported to complete part of its life cycle, and (IV) others. The following genera were placed in category I: Acer, Aesculus, Betula, Cercidiphyllum, Fraxinus, Platanus, Populus, Salix and Ulmus. The species Albizia julibrissin, Corylus colurna, Elaeagnus angustifolia, Fagus sylvatica, Koelreuteria paniculata, Malus domestica, Pyrus bretschneideri and Sorbus aucuparia were also placed in category I, although records on exit holes were limited. These species may be rather poor or unattractive hosts on which A. glabripennis may only incidentally oviposit and/or complete its life cycle or the species may be rather uncommon in outbreak areas thus far and, therefore, not frequently attacked. Elaeagnus angustifolia has also been reported to be resistant. For some of the species listed the host plant status may need confirmation. The list of category I species may also become longer in the future because several of the plant species listed only recently appeared to be true hosts, i.e. supporting completion of the full life cycle of A. glabripennis.     

Lateral transfer of a phytopathogenic symbiont among native and exotic ambrosia beetles

Different ambrosia beetle species can coexist in tree trunks, where their immature stages feed upon symbiotic fungi. Although most ambrosia beetles are not primary pests and their fungal symbionts are not pathogenic to the host tree, exceptional situations exist. Notably, Xyleborus glabratus carries a phytopathogenic symbiont, Raffaelea lauricola, which causes laurel wilt, a lethal disease of some Lauraceae species. Both X. glabratus and R. lauricola are natives of Asia that recently invaded much of the coastal plain of the southeastern USA. This study examined ambrosia beetles that breed in susceptible trees in Florida (USA), including avocado (Persea americana), redbay (P. borbonia) and swampbay (P. palustris). Raffaelea lauricola was recovered from six of eight ambrosia beetle species that emerged from laurel wilt‐affected swampbay trees, in addition to X. glabratus. Controlled infestations with cohorts of the six species other than X. glabratus revealed that each could transmit the pathogen to healthy redbay trees and two could transmit the pathogen to healthy avocado trees; laurel wilt developed in five and one of the respective beetle × host interactions. These results indicate flexibility in the lateral transfer of a non‐native ambrosial fungus to other ambrosia beetles, and for the first time documents the transmission of a laterally transferred phytopathogenic symbiont by new ambrosia beetle species. Additional work is needed to determine whether, or to what extent, the new beetle × R. lauricola combinations play a role in spreading laurel wilt.     

Screening of wildcucumis species against downy mildew (Pseudoperonospora cubensis) isolates from cucumbers

Under controlled inoculation, a set of 56 accessions belonging to 19 wild species of the genusCucumis was studied for resistance to seven isolates of cucurbit downy mildew (Pseudoperonospora cubensis (Berk. et Curt.) Rostow.) from cucumber. No resistance toP. cubensis was detected in theseCucumis accessions. In three host accession/pathogen isolate combinations, limited sporulation was observed. Nine newCucumis species are described as hosts forP. cubensis: C. africanus, C. ficifolius, C. figarei, C. meeusii, C. metuliferus, C. myriocarpus, C. leptodermis, C. sagittatus andC. zeyheri. Results are discussed in relation to the origin and evolution ofCucumis species.     

A two-year study of parasitoid entomofauna associated with spruce bark beetles (Coleoptera: Curculionidae) in the altimontane belt of Slovenia (Pohorje)

Parasitoids are known to be an important factor in the population density regulation of bark beetles. In our study of the parasitoid complex of spruce bark beetles in 2011 and 2012, we collected bark samples from trees infested with I. typographus from spruce stands in the altimontane belt of Slovenia. The samples were taken at different altitudes: 450, 700 and 1230 m above sea level. A total of 9 bark beetle species and 12 parasitoid species was found. Ips typographus was most abundant, with 93% of all species of scolytids. The parasitoid species that were found belonged mainly to the Pteromalidae and Braconidae families. By far the most abundant and frequent species was Roptrocerus xylophagorum, which represented 84% of all parasitoids and was present in all study samples. Differences in species composition, parasitoid species diversity, species abundance and parasitism rate were confirmed between locations and also between both years of our study.