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שלח באימייל הדפס
 
Name: Phyllis Weintraub, Ph.D. (Researcher)
Units: Gilat CenterEntomology
Research Interests / Job description  
Tel:  +972-8-9928678
Cell: 0506-220-170
Fax:08-992-6485
Email:    phyllisw@volcani.agri.gov.il
Office location:Gilat Research Center
Address:Gilat Research Center
D.N. Negev, 85280
Israel

Researcher

Research Interests / Job description
Biological and physical control of insect and mite pests, vectors of phytoplasmas
CV  

Broad Mite in the Arava, Israel

by Phyllis Weintraub

The broad mite, Polyphagotarsonemus latus (Banks) is known as a broadly and obligatorily phytophagous pest. Although it is primarily distributed in tropical and subtropical climes, in the hot and dry Arava in is found in greenhouses. The mite usually feeds on the lower leaf surface which causes leaf edges to become rigid and bronzed, and roll under, it causes distortion  and/or discolorment of flower rays, and discoloration (usually brown or bronze), blistering of fruits, and stunting of plants.

Female broad mite

Photo 1: Broad mites are nearly transparent. The only features readily visible are the digestive system (seen as white markings in the photo) and the legs.

Gerson (1992) recently reviewed its biology and control; P. latus is a relatively small, plant-parasitic mite which, through a combination of short generation time (4-5 days, 20-30 generations per year) and high fecundity (ca. 5 eggs per day), can quickly overexploit its environment, leading to plant death. The adult is straw colored with a white stripe down its back (see Photo 1) and is narrower abdomenally. The adult male is smaller (0.11 mm) and faster moving than the female. Further, the adult male has greatly enlarged hind legs for lifting and placing the pharate female (also called pupae or quiescent nymph) perpendicularly on his back.

Broad mite A very unusual discovery was made more than a decade ago that broad mites are carried on the legs of white flies (Photo 2). This phoresy in P. latus is unusual and is very important means of dispersal. Work has recently been completed on the attraction of broad mites to different whitefly species (Bemisia tabaci (Gennadius), Dialeurodes citri (Ashmead), Aleyrodes singularis Danzig and Trialeurodes lauri (Signoret)) as well as the thrips, Frankliniella occidentalis (Pergande), and the allate aphid, Myzus persicae (Sulzer) (Palevsky et al.,2001). Broad mites are attracted to all tested species of whiteflies, although levels of attraction vary with species. Attachment level to thrips and aphids was negligible.

Studies on the broad mite in the Arava were started in the autumn of 1999. Surveys were made during the summer months to try and discover where these mites lived and survived the hot dry summers during which time greenhouses are free of plants. Although more than 20 species of plants, many of which are known to be good hosts for the broad mite, in four locations were examined by hand lens and microscopically, no broad mites were found. Additionally, whiteflies were sought out but only immature stages were found.

Furthermore, at the beginning of each growing season, samples of plants arriving from organic nurseries were examined microscopically for presence of broad mites before being introduced into clean greenhouses. Unfortunately, it was found that some nurseries produced and sent infested plants. During the process of planting several greenhouses, virtually all plants became infested, thus creating an immediate need for treatment.

Trials to date have examined the efficacy of sulfur powder, sulfur sprays, vaporized sulfur and the introduction of the predatory mite, Neoseiulus cucumeris. Sulfur sprays are more efficacious than powdered sulfur and are easier to apply. Sulfur vapor, while effective, is detrimental to the greenhouse screening. While sulfur was additionally advantageous in controlling powdery mildew, it apparently adversely affects thrips predators as a significant increase in thrips populations and thrips-damaged fruit was observed. Neoseiulus cucumeris was very effective at controlling moderate levels of broad mites (Figs 1 and 2).

Figure 1

Fig. 1: Sachets of N. cucumeris were distributed in a pepper greenhouse.

Figure 2

Fig. 2: N. cucumeris were released on (Nc 1) every plant, (NC 2) every second plant, (Nc 4) every fourth plant, and (Control) on no plants.

Over the course of 3 years of trials, N. cucumeris was very effective at controlling broad mite populations. The first year of trials, sachets were distributed throughout a 100 m2 tunnel. Sachets initially contain a mix of about 500 N. cucumeris and a food source (the bran mite, Tyrophagus putrescentiae). These breeding units will last up to 6 weeks and can yield up to 8,000 predatory mites under optimum conditions. Due to regulations restricting the importation of sachetes, N. cucumeris (with T. putrescentiae) were released in loose bran for the subsequent 2 years. The loose bran can only support T. putrescentiae for about a week due to lack of humidity; therefore, N. cucumeris populations only double or triple on the bran mite. This did not adversely affect their ability to control broad mites; control was equal to sulfur treatments.


Literature Cited:

Gerson, U. 1992. Biology and control of the broad mite, Polyphagotarsonemus latus (Banks) (Acari: Tarsonemidae). Exp. & Appl. Acrol. 13:163-178.

Palevsky, E., Soroker, V., Weintraub, P., Mansour, F., Abu-Moach, F. and Gerson, U. 2001. How specific is the phoretic relationship between broad mite, Polyphagotarsonemus latus (Banks) (Acari: Tarsonemidae), and its insect vectors? Exp. & Appl. Acrol. 25: 217-224.

Weintraub, P.G., Kleitman, S., Mori, R., Shapira, N. and Palevsky, E. 2003. Control of Broad Mites (Polyphagotarsonemus latus (Banks)) on Organic Greenhouse Sweet Peppers (Capsicum annuum L.) with the Predatory mite, Neoseiulus cucumeris (Oudemans). Biol. Cont. 26:300-309.

 

Pest Control by Vacuum Removal

by Phyllis Weintraub

hat the state of agriculture today is highly dependent on chemicals to control pest species, and that many of these species exhibit resistance to pesticides, is axiomatic. New and innovative means of controlling pest populations are being explored, albeit slowly. We have designed and tested a new field-scale vacuum machine.

 

Arrows indicate direction of air flow. A - housings for impellers; B - cover of exit portal for insects an debris; C - frame to raise and lower suction inlet with respect to outlet air jets; D - junction point to raise and lower unit (D=male; F=female); E - suction inlet; F- outlet air jets.

This schematic shows the unique design: two blowers are directed perpendicularly to, and on either side of a bed of plants, to dislodge insects; a vacuum located above encompasses the entire area between the blowers to immediately remove the insects that are dislodged. Walklate (1994) showed, using a computer simulation, that an outlet jet of air blowing at 30m/sec affects a much greater area than a suction inlet of the same size and airflow. The vacuum unit can be raised or lowered to accommodate plant height. Furthermore, the unit can be completely raised above the plants by hydraulics at the end of a row for turning. Insects are exhausted through the impeller blades and thus even the smallest are completely destroyed

Since 1991, trials have been run on celery, tomato, potato and melon crops to evaluate the efficacy of the vacuum unit for use in insect pest management. Efficacy was evaluated by field observations, yellow sticky traps, hand vacuum sampling before and after treatment, and by taking leaf samples. All insects evaluated were effectively removed by the vacuum unit; typically, population reductions of 50 - 75% were achieved with agromyzid leafminers, whiteflies, leafhoppers, and aphids. In some trials, notably, whiteflies, reductions were achieved which lasted from week to week (Weintraub et al., 1996; Weintraub and Horowitz, 1999)

 

 

 

Densities of Whiteflies on Melon. Samples (1 meter-row) were taken with a hand-held vacuum unit immediately before and after the field was vacuumed, and from the non-treated control and insecticide-treated plots.

One concern is that there might be extensive physical damage to the plants as a direct result of the tractor and blowing/vacuuming actions on the plants, or to the yield (as in potato crops) as a result of soil compression. Visual observations and comparison of yield results have shown that the plants are not significantly damaged. Further, there is no observable increase in plant diseases (such as Phytophthora).

While we do not envision that this form of mechanical control will ever be the sole means of insect control in a field situation, we can foresee its benefits when used in insect pest management programs. Predator/parasitoid complexes usually can not overcome high pest populations. However, by reducing insect populations first by field vacuuming and then immediately releasing biological control agents, efficacy may be greatly improved. Field vacuuming is likewise fully compatible with chemical control measures, reducing pest populations either instead of a regular pesticide treatment or immediately before application.

Literature Cited:

  1. Walklate, P.J. 1994. Aerodynamic methods for controlling insects. Vine Weevil Workshop Conf. Proc., 6 June 1994, Rochester, Kent, U.K. pp. 1-6.
  2. Weintraub, P.G., Arazi, Y. and Horowitz, A.R. (1996) Management of insect pests in celery and potato crops by pneumatic removal. Crop Protection 15, 763-769.
  3. Weintraub P.G. and Horowitz, A.R. (1999) Management of the whitefly, Bemisia tabaci (Genn.), on melon by pneumatic removal. Ins. Sci. Applicat. 19:173-178.

Additional Information on Mechanical Control:
Weintraub, P.G. and A.R. Horowitz. (2000). Vacuuming Insect Pests: the Israeli Experience. In, La Lutte Physique en Phytoprotection. Eds. C. Vincent, B. Panneton and F. Fleurat-Lessard. pp. 315-324. Editions INRA, Paris. English edition to follow.

 

The Pea Leafminer, Liriomyza huidobrensis, in Israel

by Phyllis Weintraub

he pea leafminer, Liriomyza huidobrensis (Blanchard), was described originally as Agromyza huidobrensis from South America (Blanchard 1926). There, it was under natural biological control until it was secondarily subjected to massive amounts of insecticides in the 1970s directed at a lepidopterean pest in potatoes (Chavez and Raman 1987). As documented in Weintraub and Horowitz (1995), the pea leafminer was introduced to, and spread throughout, Europe as a chemically resistant pest, and subsequently was introduced to Israel. The first outbreak in Israel occurred in February 1992 in the Jordan Valley, when chrysanthemum growers suddenly encountered a leafminer that could not be controlled chemically. The leafminer was formally identified as L. huidobrensis and probably had entered Israel from Europe a year or two before the outbreak in the Jordan Valley.

Liriomyza huidobrensis is easily distinguished from the other major agromyzid pest in Israel, L. trifolii. In general, L. trifolii is smaller and distinctly yellowish in appearance; whereas the overall appearance of L. huidobrensis is dark. See the diagram (Fig.1) for specific differences.

Fig 1 Color Differences Between Liriomyza huidobrensis and L. trifolii.
A1, B1, C1 - L. trifolii.
A2-3, B2-3, C2 - L. huidobrensis.
A. Fly head showing background coloration.
B. Body side (mesopleuron)
C. Back (mesonotum and scutellum).

Both species cause similar damage which reduce photosynthesis and aesthetic appearances: females perforate leaf surfaces with their ovipositor to feed on plant juices.

eggs are laid on the underside of leaves where larvae then create "mines" or "tunnels" as they burrow in the leaves.

Liriomyza huidobrensis huidobrensis is a pest in open fields from autumn, but most notably in spring; it is not found in the summer. Liriomyza huidobrensis adults are resistant to conventional insecticides. At present, the only effective insecticides are translaminar insecticides, which penetrate the leaves to affect the leafminer larvae (abamectin, cyromazine, neem and spinosad). Although L. huidobrensis is highly polyphagous, the two most important field crops affected in Israel are potatoes and celery.

Potato Crops:
Initial studies were concerned with monitoring methods and diel activity (Weintraub and Horowitz, 1996). Optimum catches are when yellow sticky traps are placed at, or slightly above, plant height. Vacuum sampling is effective, and has the additional benefit of sampling parasitoids species. Leaf samples are the best means to monitor larvae and the effects of insecticides.

Leafminers are found in potatoes from autumn to spring, adult populations in commercial fields have peaked during the first to second week of April. Growers, responding to this peak of adult activity, first begin applying insecticides to control the leafminers and made make multiple applications until the end of the season in May or June. Trials were designed to reduce the number of insecticide applications by utilizing knowledge of the biology of the leafminer with the known mode of action of the available insecticides, thus treating the larval population that eventually will cause this peak of adult activity. The single application of these insecticides, 10-14 d before the anticipated adult peak, was intended to kill the larvae present in potato leaves. Both abamectin and cyromazine were highly effective in suppressing larval populations (Fig. 2) (Weintraub, 2001).

figure 2: Effect of insecticide sprayed on potatoes on 4/4

Fig. 2 Effect of insecticide sprayed on potatoes on 4/4.

A series of trials were performed: a) plots were treated with conventional insecticides to kill natural enemies of the leafminer, thus promoting its activity, b) plots were treated with translaminar insecticides to kill the leafminer larvae, and c) plots were left untreated. These trials were intended to determine economic threasholds. Although these trials were repeated for 3 years, no yield losses were ever observed. In fact, based on growers yield records for 3 years before and 5 years after the leafminer was observed in the Negev region, yields have slowly increased since the leafminer arrived (Fig. 3). Apparently the year before the leafminer arrived in the Negev, record yields were obtained; the arrival of the leafminer coincided with a return to normal yields, hence the appearance of a decline in yield.

yield of potato varieties

Fig. 3 Yield of potato varieties based on kibbutz record. For each potato variety, the data presented represent an average yield from 3 or more kibbutzim for any one year. Only data from kibbutzim that grew a potato variety during the years before and after 1992 were used.

Celery Crops:
Celery is grown extensively in the western Negev and northern regions of Israel. In the 1994-95 season, about 90 hectares of celery was planted in the Bekah Valley, and the leafminer caused losses of about 50% of this crop. This occurred because the growers were waiting too long before treating, and making up to 25 insecticide applications (abamectin, cyromazine, dichlorovos, methamidophos, methomyl, pyrazophos, thiocyclam hydrogene oxalate, and combinations thereof) by spray or through the drip irrigation systems. Some of these insecticides actually promoted leafminers by killing natural enemies. It was demonstrated that six scheduled translaminar insecticide applications from the beginning of the season would effectively control the leafminer (Weintraub and Horowitz, 1998) (Fig. 4.). Additional trials, to check the duration of a single insecticide application, have shown that a single spray application suppresses larval populations for at least two weeks; applications through the drip irrigation systems are ineffective (Weintraub, 2001).

Fig. 4 Effect of insecticide applied on 19/5 to celery.

The effect of the leafminer on celery is different from potatoes in that the mines are in the marketable portion of the produce, the leaves and stalks. To be exported, there must be no visual evidence of the leafminer; all affected leaves and stalks must be stripped off, thus significantly reducing yields. Hence, the importance of early insecticide treatment to avoid large leafminer populations.

Literature Cited:

  1. Blanchard, E. 1926. A dipterous leaf-miner on Cineraria, new to science. Rev. Soc.
    Entomol. Argent. 1:10-11.
  2. Chavez, G.L. and Raman, K.V. 1987. Evaluation of trapping and trap types to reduce damage to potatoes by the leafminer, Liriomyza huiidobrensis (Diptera,
    Agromyzidae) Insect Sci. Appl. 8:369-372.
  3. Weintraub, P.G. and Horowitz, A.R. 1995. The newest leafminer pest in Israel,
    Liriomyza huidobrensis. Phytoparasitica 23:177-184.
  4. Weintraub, P.G. and Horowitz, A.R. 1996. Spatial and diel activity of the pea
    leafminer (Diptera: Agromyzidae) in potatoes, Solanum tuberosum. Environ. Entomol. 25:722-726.
  5. Weintraub, P.G. and Horowitz, A.R. 1998. Effects of translaminar versus
    conventional insecticides on Liriomyza huidobrensis (Diptera: Agromyzidae)
    and Diglyphus isaea (Hymenoptera: Eulophidae) populations in celery. J.
    Econ. Entomol. 91:1180-1185.
  6. Weintraub, P.G. 1999. Effects of cyromazine and abamectin on the leafminer
    Liriomyza huidobrensis and its parasitoid Diglyphus isaea in celery.
    Ann. appl. Biol. 135: 547-554.
  7. Weintraub, P.G. 2001. Effects of cyromazine and abamectin on the pea leafminer
    Liriomyza huidobrensis (Diptera: Agromyzidae) and its parasitoid Diglyphus isaea (Hymenoptera: Eulophidae) in potatoes. Crop Protection. 20: 207-213.
  8. Weintraub, P.G. 2001. Changes in the dynamics of the leafminer, Liriomyza huidobrensis, in Israeli potato fields. Intern'l J. of Pest Manage. 47: 95-102.

 

Vectors of Phytoplasmas in Carrots

by Phyllis Weintraub

Many plant pathogens, including phytoplasmas, are vectored by Homopterans. Their hemimetabolous life cycle has nymphs and adults feeding on the same plants; their piercing-sucking mouthparts enable them to reach specific plant tissues (such as phloem, where phytoplasmas are located), but cause minimum damage to the plants they feed upon. These insects often have wide host ranges; by feeding on phytoplasma-infected wild plants and crop plants, they vector the disease agent to healthy plants.

 

 
Adventitious roots  

Photo 1: adventitious roots
(Click on image to enlarge)

 Photo 2: "witches broom" leaf growth (Click on image to enlarge)

 

A yellows disease, caused by phytoplasmas, was found in carrots in 1995 in the Beit She'an area, which quickly spread to the rest of Israel. This disease causes adventitious roots (photo 1), deformation of the carrot, and exhibits typical "witches broom" leaf growth (photos 2, 3); it imparts a bitter taste and can affect storage. Identification of the phytoplasmas by universal and nested PCR had been done; both Aster Yellows and Western X have been found. (Orenstein et al., 1999)

Hyperplastic leaves
Photo 3: Hyperplastic leaves in a young plant

While the vector(s) are not yet known, monitoring of carrot fields for the last three years has shed some light on possible vectors. The following species are known vectors (world-wide) and have been caught in traps in relatively large numbers: Circulifer sp. (of the haematoceps complex), Austroagallia sinuata, Bactracomorphus glaber.

Table 1: Trapped in relatively large numbers

Circulifer

 

Bactracomorphus glaber

Circulifer

 

Bactracomorphus glaber

 

Austroagallia sinuate

Austroagallia sinuate

 

Macrosteles quadripunctulatus, Neoaliturus fenestratus complex, Orosius albicinctus, and Psammotettix sp. have also been trapped, although in smaller numbers (photos by Swerski or Weintraub).

Table 2: Trapped in very low numbers

Macrosteles quadripunctulatus

 

Orosius albicinctus

Macrosteles quadripunctulatus

 

Orosius orientalis

Neoaliturus fenestratus complex

 

Hyalesthes obsoletus

Neoaliturus fenestratus complex

 

Hyalesthes obsoletus

 

Psammotettix sp

Psammotettix sp.

 

The appearance of the disease is inconsistent from year to year. The disease was found in the Beit She'an area in 1995. In 1996, Kibbutz Sa'ad, in the western Negev, was struck by the yellows disease, but other kibbutzim in the area (3 - 8 kilometers distant) were not. In 1997 Kibbutz Dorot, 8 kilometers from Kibbutz Sa'ad, was severely affected, and again, other kibbutzim in the area were not. In 1998 a moshav near Tel Aviv (Moshav Tzofit) was severely infested. During the past few years infestation rates have been around 5%. When it occurs, the disease is most severe in the spring (60-70% of the crop being affected). Carrots are not grown in July and August, and autumn crops are only slightly affected, if at all.

Reference:
Orenstein, S., Franck, A. Kuznetzova, L., Sela I., and Tanne, E. 1999. Association of a phytoplasma with a carrot disease in Israel. J. Plant Pathol. 81:193-199.

 

Vectors of phytoplasmas in hybrid Limonium

by Phyllis Weintraub

healthy limoniumPhytoplasmas (minute, wall-less prokaryotes, class Mollicutes) can be vectored by grafting, parasitic plants (like Cuscuta spp.) or by certain phloem-feeding insects. There are three groups of insects that are known to vector phytoplasma, leafhoppers (Cicadellidae), planthoppers (Cixiidae) and one species of psyllid (to date, in carrots only). Their hemimetabolous life cycle has nymphs and adults feeding on the same plants; their piercing-sucking mouthparts enable them to reach specific plant tissues (such as phloem, where phytoplasmas are located), but cause minimum damage to the plants they feed upon. These insects often have wide host ranges; by feeding on phytoplasma-infected wild plants and crop plants, they vector the disease agent to healthy plants.

Although many species of Limonium (Plumbaginaceae Juss.), herbaceous perennials, are native to the Mediterranean region, seedlings for commercial production are usually imported from Europe, North America or Asia. Two hybrids are grown in commercial production in the Arava valley (located between the Dead Sea and Red Sea); L. latifolium x L. caspium (cv ‘Beltlaard'), and L. latifolium x L. bellidifolium (cvs ‘Misty', ‘Supreme' and ‘Sunglow'). These plants are grown primarily for export to Europe as cut flowers for floral arrangements. Flowers are grown for 1-10 years in tunnels (7 x 100 m) covered with plastic; both ends are open and ventilation holes are cut about every 2 m.

Two limonium tunnels

Inside limonium tunnel

 

For the first 15 years of commercial production, the crops were not affected by yellows disease. In October 2000 diseased plants were first observed in the northern Arava. Only L. latifolium hybrids were observed to be infected. Symptoms included: small and/or deformed/discolored flowers; small, narrow basal leaves, often yellow in color; excessive leaf growth (witches broom or ‘asparagus fern'); and eventual plant death.

Small leaves

Small leaves

"Asparagus fern"

Plant death

Since there were no parasitic plants present where Limonium was grown, either the plants arrived as infected seedlings and/or they were infected by insects carrying the phytoplasma. Since research started after the infection was observed by growers, there was no way of knowing if some seedlings were infected to begin with. However, new symptomatic plants were observed south of the initial observations, suggesting that infected leafhoppers were wind-borne and spreading the pathogen.

Monitoring proceeded with two methods, yellow sticky traps to passively collect insects and by hand vacuuming to collect live insects. The one known planthopper vector in Israel, Hyalethes obsoletus, was not caught.

Monitoring with yellow sticky traps resulted in the capture of 4 known vector species; Orosius orientalis (=albicinctus (Distant) subfamily Euscelini) populations were about 10x larger than populations of Circulifer haematocepts (Lethierry) (subfamily Deltocephalinae), C. tenellus (Baker) (subfamily Deltocephalinae), or Exitianus capicola (Stal) (subfamily Deltocephalinae).

Live insects were used in direct transmission studies. Insects were caged on Limonium seedlings which were checked after a month for phytoplasma.

Species

# Test Plants

# Plants Positive

O. orientalis

20

19

Circulifer spp.

19

17

E. capicola

3

1

In indirect transmission studies, uninfected colony-reared O. orientalis were placed on infected plants, then transferred to healthy seedlings and observed for symptoms of infection.

Date

# Plants

# Infected

January

30

6

April

6

5

May

1

1

Although all species were able to vector phytoplasma to healthy plants, the population of O. orientalis was 10x larger than any other species and it was the predominant species caught in Limonium. Circulifer spp. were primarily caught on beets and red chard that was also grown in the area. Exitianus capicola was primarily caught in grassy areas. Research is continuing.


References:

Weintraub, P.G., Pivnia, S. and Gera, A. (2001) New phytoplasma disease in Limonium and potential leafhopper vectors. Annual Meeting of the Entomological Society of America, San Diego, CA, USA. http://esa.confex.com/esa/2001/techprogram/paper_1220.htm

Weintraub, P.G., Kleitman, S., Pivonia, S., Gera A. (2002) New Phytoplasma Disease in Limonium and Probable Leafhopper Vector, Orosius orientalis (=albicinctus) (Matsumura) (Hemiptera: Cicadellidae). 11th Meeting of the International Auchenorrhyncha Congress, Potsdam, Germany. P 52.

Gera, A., Rosner, A. and Weintraub, P.G. (2003) Molecular identification of a phytoplasma associated with a new disease of Limonium hybrids and the leafhopper vector(s). 8th International Congress for Plant Protection, Christchurch, New Zealand. P 282.

 

Vectors of Phytoplasmas in Vinyards

by Phyllis Weintraub

omopterans are important vectors of many plant pathogens, including phytoplasmas. (Phytoplasmas are minute, wall-less prokaryotes, class Mollicutes, primarily located in the phloem sieve elements, associated with a number of plant diseases, and vectored primarily by Cicadelloidea and Fulgoroidea). Their hemimetabolous life cycle has nymphs and adults feeding on the same plants; their piercing-sucking mouthparts enable them to reach specific plant tissues (phloem), but cause minimum damage to the plants they feed upon. These insects often have wide host ranges; by feeding on phytoplasma-infected wild plants and crop plants, they vector the disease agent to healthy plants.

Diseased leaves

Photo 1: Click on image to view details

In the 1980's a yellows disease was first observed on wine grapes in Israel, and had devastating effects. To date, over 30 hectares of Chardonnay grape vineyards have been uprooted due to this yellows disease. Chardonnay grapes are especially sensitive to this new disease, although red and other varieties of white grapes are also affected. The leaves of diseased plants are easily distinguished (photo 1).

Diseased grapes

Photo 2: Click on image to view details

 

 

 

Diseased white grape varieties develop clusters normally over the course of the season but shortly before harvest the skins thicken, and the grapes dry and senesce (photo 2). Diseased red (and some white) grape varieties drop the clusters early in the season before the growers expend time and labor on fertilization, irrigation and tending the vineyards. Manifestations of the disease are not uniform throughout the Golan; a survey made in 1999 and 2000 in the most prevalent cultivars (Merlot, Sauvignon blanc, Cabernet Sauvignon and Chardonnay) showed that the highest levels of infection were found in the south, followed by the center, and the lowest levels in the north. Stolbur was found to be the predominant phytoplasma (~70%), although aster yellow (~11%), western-X (~5%), and mixtures of two phytoplasmas (~13%, 90% of which involved stolbur and aster yellows).

Hyalesthes obsoletus

 

Neoaliturus fenestratus complex

Hyalesthes obsoletus

 

Neoaliturus fenestratus complex

Circulifer

 

Dryodurgades dlabolai

Circulifer

 

Dryodurgades dlabolai

 

Megopthalmus scabripennis

Megopthalmus scabripennis

While the vectors are not yet known, some species trapped in the vineyards are suspect because they are already known to vector phytoplasmas and/or PCR analysis has shown that phytoplasma DNA was present in their bodies. Based on 5 years of trapping with yellow sticky traps, a distinct pattern has emerged; there are relatively high populations of vectors in the spring, virtually none during the summer, and moderate numbers in the autumn. In the autumn, leaf and planthoppers are probably moving from harvested fields since they are caught even after most of the grape leaves have turned brown and started to fall; Hyalesthes obsoletus is trapped in large numbers at this time. Species trapped in relatively large numbers in the spring include: Neoaliturus fenestratus complex, Dryodurgades dlabolai and Megopthalmus scabripennis. Species caught in low numbers in the spring include: Anaceretagallia laevis, Austroagallia sinuate, Circulifer sp. (of the haematoceps complex), Macrosteles quadripunctulatus and Orosius albicinctus (photos by Swerski or Weintraub).

Macrosteles quadripunctulatus

 

Orosius albicinctus

Macrosteles quadripunctulatus

 

Orosius orientalis

Austroagallia sinuate

 

Anaceretagallia laevis

Austroagallia sinuate
(click image to see a larger
version in a separate window)

 

Anaceretagallia laevis
(click image to see a larger
version in a separate window)

References:

Orenstein, S., Zahavi, T. and Weintraub, P.G. 2001. Distribution of phytoplasma in grapevines in the Golan Heights, Israel, and development of a new universal primer. Vitis 40:219-223.

Klein, M., Weintraub, P.G., Davidovich, M., Kuznetsova, L., Zahavi, T., Ashanova, A., Orenstein, S. and Tanne, E. 2001. Monitoring phytoplasma-bearing leafhoppers/planthoppers in vineyards in the Golan Heights, Israel. J. Appl. Entomol 125:19-23.

Updated on: 01/05/16 14:17
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