THE AVOCADO INDUSTRY IN ISRAEL – AN OVERVIEW

Shaul Homsky

Formerly Chief Specialist for Subtropical Fruit-crops and Head of Fruit-growing Division, the Extension Service, Ministry of Agriculture and Rural Development, Israel

(Previously published in english in: Alon Hanotea Vol. 49, No. 10, October 1995. Revised and updated by the autor in July 2000).

ENVIRONMENTAL GROWING CONDITIONS IN ISRAEL

Climate:

Israel is located along the southern part of the eastern coast of the Mediterranean Sea, between latitudes 30^o and 33^o north. The climate in the avocado-growing regions is subtropical: Warm rainless summers and cool rainy winters. The rainy season is mainly from November through March. Annual precipitation varies from an average of 200 mm in the south, to 700 mm in the northern coast.

A major part of the avocado-growing area in the country is along the coastal plain, but an additional notable growing area is located in the interior hot valleys. Table No.1 summarizes the mean, maximum and minimum temperatures for each month in two locations: Bet Dagan, in the coastal plain, and Deganya Alef, in the hot Sea of Galilee Valley.

Temperatures below 0^oC are not common in the avocado-growing areas. In Israel avocado orchards were planted taking into consideration topographical influences, in accordance with a nationwide topo-climatological survey implemented by the Meteorological Service: sites with frost hazard were avoided, particularly after the mid-seventies. Nevertheless, once in 8 – 10 years, temperatures have dropped in some avocado-growing areas to -2^o - 4^o C, and have fallen down, in some low pockets, to -7^o C . Severe damage to fruit and trees occurred under such extreme conditions.

A more serious threat to avocado crops in Israel is the adverse weather conditions, which occur occasionally in April and May, a season of flowering and fruit-set. Hot spells, called Hamsines, with temperatures of 40⁰ C, and in rare cases - even 46⁰ C (accompanied by very low relative humidity), have caused severe crop failures, particularly when they lasted several days and when they occurred just after the end of blooming. Extreme events occurred on a nationwide scale in 1970, 1980 and 1988.

Soils

Three-quarters of the total avocado areas in the country are planted on various types of Grumusols, heavy-textured soils containing 8-20% lime (CaCO₃), with pH 7.8 – 8.2 and with fair internal drainage. In the coastal plain, some orchards are planted on loamy sand with no lime (pH 7-7.3) or, in the South West, with 5-10% lime. In the Sea of Galilee Valley, some orchards have been planted on very calcareous soils, (40 % CaCO₃), with trees grafted on specific adaptable rootstocks (see “Rootstocks”).

Irrigation Water

All avocado orchards, like most other tree crops in Israel, are regularly irrigated throughout the dry hot season. Most of the water in Israel is supplied by a government owned company and allocated by the State Water Authority, according to quotas linked to land tenure. Water is either pumped from underground reservoirs, containing 50-400 ppm Cl, or supplied from the National Water Carrier, starting at the Sea of Galilee, which contains 190-250 ppm Cl. (EC: 0.8 – 1.2 dS/m). The price of water is determined, practically, by the government (presently – around 20 cents per l m³).

Table No. 1: Mean daily maximum and minimum temperatures per month (ºC) in Bet Dagan and Deganya Alef.

Month	Bet Dagan		Deganya Alef
	Minimum	Maximum	Minimum	Maximum
January	6.6	17.9	8.4	17.6
February	6.8	19.2	8.8	19.6
March	8.6	21.5	10.4	22.5
April	11.6	24.6	13.0	26.8
May	13.6	26.7	16.3	31.7
June	17.7	29.3	16.3	34.9
July	19.3	30.6	19.0	36.0
August	19.6	30.9	22.0	36.1
September	18.1	28.0	20.6	34.6
October	14.8	26.9	17.5	30.5
November	11.2	24.2	13.7	25.0
December	8.2	19.4	9.9	19.1

Note: Bet Dagan represents the coastal plain; Deganya Alef represents the hot valley of the Sea of Galilee (Altitude 200 m below sea-level).

Regional distribution of orchards

The area of avocado in the country is estimated at 5,000 - 5,5000 Ha in 2000. It stays more or less stable due to the fact, that the deducted area of up-rooted or neglected orchards is replaced by new plantings. About 70% are grown along the coastal plain, mostly in its northern and central parts; about 20% are spread out in the interior valleys: Huleh (in the north), Sea of Galilee Basin and the Valley of Jezre’el. The remaining 10 %, are spread in more southern parts of the country. Orchards with high production can be found in all the above regions. However, the coastal plain north of Acre, known as the Western Galilee, has been renown for years for its higher-than-average yields, resulting probably from factors such as a favorable climate, suitable soils and relatively low salinity of irrigation water. In addition, the percentage of ‘Hass’, one of the most productive cultivars in the country for a long period, was higher in this region than in others.

However, those higher regional yields have dropped in the last decade, partly due to the gradual increasing salinity of the local irrigation water, a phenomenon, which might have induced a decrease in the average yields of ‘Hass’ more than in other cultivars (Table 2).

75% of the total avocado area in the country is cultivated by kibbutzim (cooperative agricultural settlements) 30-100 ha each. The rest is cultivated mainly in small family orchards of 1-3 ha.

Table 2 represents an area of about 1,500 ha of orchards belonging to collective settlements (Kibbutzim). The data was provided by the courtesy of the 'Miluot', a regional packing house. It does not represent national averages.

Table 2: Yields by avocado cultivars in various periods, in the "Western Galilee" (t/ha, rounded off)

Cultivar	Average of 17 seasons 1970/1-1986/7	Average of 10 seasons 1989/90 -1998/9
Ettinger	14.0	12.0
Fuerte	9.0	11.0
Hass	15.0	10.0
Nabal	15.0	14.5

Development of the industry – a brief history

The first grafted avocado trees were introduced to Israel in 1924 at the Mikveh-Israel Agricultural School. Research was initiated in the early thirties: Introduction of cultivars, and observation plots. Small avocado nurseries were established in the mid-forties. Planting on a commercial scale started in the 1950s, and by 1960 the total avocado area reached 300 ha. The success in the initial export of avocado on a commercial scale encouraged further planting and in 1970 the area grew to 2,100 ha, of which 1,000 ha were already bearing fruit, producing 7,200 tons of which 4,400 were exported.

In the course of the next thirteen years, the avocado growing area expanded rapidly, reaching its peak of more than 11,000 ha, of which 55% were at bearing age. In 1983, production was almost 60,000 tons of which 80% were exported.

The above rapid growth was induced by a combination of several factors, mainly:

a) High profitability in the sixties and the seventies due to adequate yields (average of 10 t/ha) and very high export prices of US$ 2,000-2,800 per ton (adjusted to present $ value), F.O.B. Israel. Those prices were obtained in Europe owing to very intensive and expensive promotion activities.

b) Financial supports by the government (20% allowance plus 50% loan on establishing costs), and by other national funds, for planting of export fruit crops.

c) Relatively low labor requirements compared with other fruit crops. This trait has been particularly important to kibbutzim, which tried to avoid the use of hired labor at that time.

The sixties and the seventies were noted for the intensive research and extension activities in avocado, carried out by the Ministry of Agriculture, (the Agricultural Research Organization, and the Extension Service), with the active participation of grower's organizations and individual growers.

However, in the early eighties - the situation changed for the worse. The following factors were responsible for this change:

1) Since 1982/83, growers experienced several successive seasons of poor return per ton, partly due to unfavorable exchange rates, particularly in the 1984/85 season. (Table 3).

2) The season of 1986/7, with an unprecedented bumper crop of 127,000 tons, was Followed by a succession of several years with low yields: This resulted from a coincidence of extreme alternate off-season in 1987/8, followed by the disastrous 1988/9 season (85% crop failure due to a rare heat-wave), and this was followed by the severe frost of February 1989. Disappointing production also took place in the seasons of 1992/3 and 1993/4, in which weather factors could have played a partial role.

3) The widespread planting in the late seventies and early eighties was sometimes hasty and expanded to marginal climatic and soil sub-regions. In addition, the use of poor saplings, sometimes with rootstocks that were unsuitable to local soil types and salinity of irrigation water, was not uncommon at that time.

4) The gradual increase in salinity of irrigation water in considerable areas has probably caused a decrease in yields, particularly in orchards planted originally on Mexican rootstocks (which are susceptible to salinity).

5) A series of drought years brought about a reduction in quotas of water for agriculture in the early nineties, including avocado groves. Many growers cut their irrigation by 20-25% for 2-3 years until 1994, when the quotas were resumed. Unfortunately, dry winters returned in 1998/99 and 1999/00, and shortage in water became again an acute national problem.

Table 3 demonstrates the downfalls in the Israeli avocado production in the late eighties and part of the early nineties. The period of erratic and low crops have shaken the dominant position of Israel as the main stable supplier of avocado to the European markets. Meanwhile, the growing demand for avocado in those markets has attracted offers by other countries.

All the above problems induced massive neglect and uprooting of avocado orchards, and brought new planting almost to a standstill during a long period. The planted area has decreased to 5,000 - 5,500 ha, out of which new top-grafted trees, as well as some new plantings, constitute 10%. Experienced and more successful growers resume planting.

Cultivars

In 1970, with a total avocado area of 2,100 ha, the percentage of the main cultivars was: ‘Fuerte’ - 43 %, ‘Ettinger’ - 20 %, ‘Hass’ - 17 % and ‘Nabal’ - 10 %. This proportion was based on the accumulated experience and on the preference of the export markets at that time. The recommendations on cultivars were set by the Subtropical Fruit Governing Board and by the Extension Service. The Board has guided the research and development of the avocado industry in the country from 1960 until 1989. It included representatives from research, extension services, growers and the exporting body.

The above composition of cultivars has changed considerably during the years, and in 1999 it was estimated as follows: ‘Hass’ - 27 %, ‘Ettinger’- 27 %, ‘Fuerte’ - 17 % and ‘Nabal’ - 3 %. The rest: ‘Reed’- 9 %, ‘Pinkerton’- 8 %, ‘Ardith’- 6 %, and various – 3 %. Following are some remarks on the main commercial avocado cultivars, all, except for ‘Ettinger’, introduced to Israel from California.

‘Ettinger’: A local selection of a chance seedling. Parentage is unknown, but it contains certain traits of the Mexican race such as tolerance to low temperatures (4 hours of -6^o C in a mature tree) and thin skin. Harvest season is early but short: mainly October through November. Bright green skinned, with good commercial size. High internal quality. Yields are good to medium.

’Fuerte’: Apparently several clones were introduced to Israel, some of them not productive. The practice of girdling, applied in some orchards, (mainly in the seventies), did not solve the problem of erratic and medium to low yields of this cultivar. Therefore, it lost its dominance in the orchards and was uprooted or top-worked to more productive cultivars in many orchards. This trend has recently slowed down in view of encouraging results of Paclobutrazol applications in stabilizing its yields. The main harvest season is November through February.

‘Hass’: The most productive commercial cultivar until 1987/8; however average yields have decreased up to 1995 (Table 2). This cultivar suffers from average small fruit size, a phenomenon which is aggravated in older plantations, under increased soil compacting, and under increased salinity of water: All of the above are common events in the industry. Harvest season is November through April – May. (Sometimes later)

‘Reed’: Introduced only in 1969. Precocious and productive tree. Fruits are slightly oversized. The main harvest season for export is April-May, but many growers delay harvest to the summer (June-August) for the local market.

‘Pinkerton’: Planted mainly in the hot interior valleys, but recently started to expand to the costal plain. Very productive. Picked in December and January.

‘Ardith’ ("00-28"): Resulted from the breeding program of Dr. Berg at UC Riverside. Successful mainly in the coastal plain. Very vigorous tree, relatively productive. Dark green skin. Picked in March-April.

‘Nabal’: The tree is very sensitive to winter storms causing limb breakage and fruit fall, to frost and to Pyriform Scale (see "Pests and Diseases"). It is productive, but a strongly alternate bearer. Average fruit-size is bigger than desired. Harvest season is mainly March and April.

Here and there, in the older orchards, there are still some ‘Wurtz’, ‘Benik’ and ‘Horshim’ (a local chance seedling). Recent new plantings (or top-working) include ‘Reed’, ‘Pinkerton’, ‘Ettinger’, ‘Hass’ and ‘Ardith’. No other cultivar resulting from the local breeding program, or from introduction, has yet reached a stage of being recommended for full commercial planting. New types are being tested mainly on an experimental scale and some of the promising ones are planted on a semi-commercial scale.

Rootstocks

In the sixties, the mother-trees for rootstock seeds were hundreds of different seedling trees, mainly of the Mexican race. In addition, seeds were obtained from cultivars: Mexican, like ‘Topa-Topa’, ‘Northrop’ and ‘Mexicola’; Guatemalan (‘Nabal’), and later - West Indians or their hybrids, like ‘Lula’, ‘Winslowson’, ‘Waldin’, ‘Fuchs’ etc.

At that period, a large-scale field research on avocado rootstocks was initiated. In this unprecedented work, led by Dr. A. Ben-Ya'akov, many new orchards were planted with a prearranged planting design of various rootstocks, without interfering with the original plan of cultivars in each orchard. A large group of avocado growers actively participated in this program. They collected yield data for every tree in their commercial orchard, which was a common practice in many orchards in the country until the mid eighties, and was aimed at thinning out the less productive trees. The above "nationwide experiment" included hundreds of different rootstock types, and it gradually grew to include 300 different plots with more than 140,000 trees. This planting program continued into the eighties and also included experiments with clonal rootstocks. Notable differences in the effects of the various seedling rootstocks (and later of clonal rootstocks) were found, with regards to fruitfulness, tolerance to high salinity, to high lime content and even to soil aeration. Gradually and consistently, inferior rootstocks were screened out of the list of recommended mother-trees.

Recent demands are still mainly for nursery trees grafted on selections of seeded rootstocks, primarily ‘Deganya 117’ and some ‘Ashdot 17’ and ‘Tsrifin 99’, all local West Indian types. In addition, rootstocks grown from seeds of certain West Indian cultivars are also in demand, like ‘Waldin’ and ‘Fairchild’.

Since the mid-eighties, clonal (vegetative) rootstocks selected locally by Dr. Ben-Ya'acov were added to the list, such as ‘VC 65’ and ‘VC 66’, tolerating alkalinity and salinity, or ‘VC 55’, ‘VC207’, ‘VC256’, tolerating salinity and Phytophthora root rot (Phytophthora cinnamomi). The local demand for those rootstocks is still very limited, due to higher cost of the saplings and to scanty experience. However, they are already tested also in other countries

CULTURAL PRACTICES

Irrigation:

All the avocado orchards in Israel are grown under irrigation. Around 60% - 70% of the avocado area in Israel is irrigated by mini-sprinklers of various outputs and types. The rest is irrigated by drip irrigation: 2 lines of drippers (and sometimes 3 lines) per row of trees, and 40 - 50 cm between drippers on the line. So far, no obvious differences between the two methods have been observed with regard to the effect on orchard performance. Mini-sprinklers are considered advantageous as means for partial alleviation of frost or hot-spell damages. Drip-irrigation, renowned as water-saving and also as adaptable to possible future use of recycled water, is gaining more popularity in recent years.

Calculation of daily water consumption is based, in many orchards, on regional or local data on evaporation (from “Class A” pan), plus orderly readings of tensiometers. The recent common practice of irrigation is based only to a small extent on results from irrigation-experiments. The typical present practice of irrigation during the peak season, July through September, for mature orchards, is as follows:

Intervals of 1 - 2 days between irrigations with mini-sprinklers; (daily with drip); calculated water-dose by a crop-coefficient of 0.70 – 0.75 (70 – 75% of the evaporation). This means a daily use, during the peak season, of 5 - 5.5 mm in the coastal plain (around 8,000 m³/ha per season) and 7 – 7.5 mm in the interior hot valleys (around 11,000 m³/ha per season).

Fertilization:

The results of several experiments in avocado fertilization carried out in Israel have not been sufficient, so far, to serve as a general guide for recommendations. Present practices in most of the orchards are based partly on the results of leaf analysis and partly on local experience and observations on tree vigor and on crop load. Consulting with the Extension staff or with a regional researcher is a prevalent custom.

The present practice is "Fertigation" – application of fertilizers through the irrigation system. N is applied along the whole irrigation season, and in many orchards - pre-bloom application of N (1/4 of the annual dose) is practiced. A common annual dose per ha of bearing orchards is 200-300 kg N, 50 – 70 kg P₂O₅ (applied in the fall) and 200 - 400 kg K₂0. Manuring, with composts, is common in some orchards, mainly in "Bio-organic" plantations (covering 250 ha).

Iron-induced chlorosis is widespread in many areas, either due to high lime content in the soil together with past use of susceptible rootstocks, or due to poor soil aeration. Fertilization with Iron Chelates is a common practice for correction.

Zinc deficiency is occasionally observed but rarely treated. At this point, very little attention has been given to Boron deficiency because common visual symptoms have almost not been observed. The issue seems to deserve more attention in view of the relatively low level of Boron in many leaf analysis results.

Management of Tree Crowding (pruning, thinning, etc.)

The common planting density of avocado in Israel, 270-410 trees/ha (according to cultivar and growing conditions) was planned in the past for future thinning-out of trees. This practice was recommended at that time particularly for ‘Fuerte’ and ‘Nabal’; the solution suggested for problems of crowding and shade in ‘Hass’ was pruning. However, growers were often late with accomplishing the thinning, and pruning was light or limited to occasional topping. Consequently - the trees grew very tall, and rejuvenation of the orchard became unavoidable.

The above situation has gradually changed, and since the end of the eighties – more attention was paid in due time to management of tree crowding: Annual hedging and topping (mechanical or manual) has become a dominant practice. Recent planting distances (7 m between the rows and 3 – 4 m between the trees) and the present composition of the cultivars planted – alleviate the above practice even more.

An additional procedure is being followed recently in some orchards, particularly with ‘Hass’: “Gradual Rejuvenation”, i.e. heading-back of one main scaffold branch every year.

Weed Management

The common practice in young orchards is spraying with pre-emergence herbicides near the trees (on 1-1.5 m strip) twice a year, and occasional mowing (or sometimes chemical control) between the tree rows. In mature orchards, the necessity of weed control decreases due to shading, together with the natural mulching with accumulated leaves. Pruned thin branches are generally shredded and serve as additional mulch. In weeded parts (more exposed to light, etc.), pre-emergence or contact herbicides are applied.

Pollenizers and Pollinator

Local research, supported by Izozym`s technique, has shown that ‘Ettinger’ is a potent pollenizer for ‘Hass’, ‘Pinkerton’, ‘Ardith’ and even for ‘Fuerte’(in spite of belonging to its “B” group). Application of these findings has already taken place in all new plantings, as well as in many bearing orchards where ‘Hass’ was planted in solid blocks (by top-working 10 % -15 % of the trees to ‘Ettinger’). ‘Ettinger’ itself enjoys pollination by ‘Ardith’. ’Reed’ is believed to be pollinated by ‘Nabal’, and vice versa.

Honey bees are the main pollinator of avocado in Israel and most growers rent beehives for this purpose, putting about 2-3 hives per hectare.

Pests and Diseases

Avocado in Israel is not greatly troubled by pests, probably due to several factors:

a) Careful conservation of natural biological balance, owing to intensive research and extension work, and strict practices of biological control.

b) The fact of avocado being a relatively new crop in a country remote from its centers of origin.

c) Strict quarantine measures taken during the introduction of avocado propagation material, and the ban on the import of avocado fruits.

d) Events of extreme high and low temperatures that may have hindered the development of some avocado pests prevalent in the tropics.

The main avocado pests in Israel are:

Boarmia selenaria: A looper that feeds on fruitlets and fruits, which may cause considerable reduction in yield and damage to fruits if not monitored and controlled biologically in time (by 1-2 sprays with Bacillus thuringiensis).

The Pyriform scale (Protopulvinaria pyriformis) particularly attacks ‘Nabal’ but has been observed on other cultivars. Control measures are generally spot-sprays with mineral oil, combined with spreading of wasps of the genus Metaphycus or of Cryptolemus montrouzieri.

The Greenhouse Thrips (Heliothrips haemorrhoidalis) may sporadically attack various cultivars, particularly ‘Ardith’. Triphobius semiluteus is used as a natural enemy.

The Orchid Thrips (Chaetanaphothrips orchidii) is relatively new, and still studied.

Diseases:

The climate in Israel is unfavorable to the development of diseases of fruit or canopy of avocado, and they have never been observed in the orchards.

Avocado Root-rot (Phytophthora cinnamomi) was first identified in Israel in 1982. So far its scattered spread has been very limited (less than 30 – 40 hectares), mainly in moist spots of very heavy soils or other sites with poor drainage. Encouraging preliminary results has been gained with some local clonal resistant or tolerant rootstocks.

Inflorescence Dieback has caused serious damage in some years, mainly in 'Hass', by reduction of yields of infected trees. The factors responsible for this phenomenon are still unknown.

Growers’ organization, harvesting and packing

Most growers belong to the “Israeli Avocado Association” and market their product through Agrexco Company Ltd., which runs 80% of the export and 60% - 70% of the local avocado market (The rest – by the companies “Mehadrin” and “Tnuport”).

Nine regional packing houses serve the industry, seven of which are linked with Agrexco: Two principal ones (20-30% of the total, each), four medium sized (8-10% each) and three small packing houses (3-4% each).

National export standards for fruit maturity and external quality, which are more severe than the EEC standards, are set by a statutory committee and inspected by the Inspection Service for Agricultural Produce for Export, Ministry of Agriculture.

At the beginning of the season, which is generally during the last week of September, the harvest starts in each region according to criteria of percentage of dry matter (representing oil content) for each cultivar. Harvest timing is determined after a repeated systematic sampling survey. Later, the harvest continues according to a pre-planned weekly program and allocation of quotas to growers or to packing houses by the relevant company. This is based on combined considerations of market demands, size of stocks, availability of produce from each location, etc. Selective harvesting by size is common. Hundreds of hydraulic ladders ("Cherry Pickers"), produced in Israel, are used for picking in tall trees, up to 6.5m. Exportable avocados are packed in 4kg cartons and shipped by sea to their intended markets.

In recent years, the average export percentage of the whole registered crop has been between 50% and 70%, whereas almost all the rest is sold fresh in the local markets. (Per Capita consumption of around 5 Kg.) Rejects and fruit for industry rarely exceed 1-2% of the crop.

Production, export and prices

The main countries of destination for exported avocado have been France (50 – 60 %), Germany (15 %), and Great Britain (10 %). Table No. 3 presents data on yearly national avocado registered production, exports and average F.O.B. seasonal average prices, for the last twenty seasons, each running from September through May(in some years – through June).

Unregistered local marketing of avocado has grown in the last decade, perhaps due to the increasing local demand. Due to this account, it is estimated that 5 % to 10 % should be added to each of the production figures of the last seven years (Table 3).

Table 3: Israeli Avocado - Production and Export (in 1,000 tons, rounded off)

Season	Production	Export	F.O.B. Price/T, $US
1979/80	32	26	1,630
1980/81	8^a	7	2,200
1981/82	40	33	1,400
1982/83	59	49	960
1983/84	52	43	970
1984/85	75	60	760^b
1985/86	65	52	1,030
1986/87	127	88	930
1987/88	33	26	1,480
1988/89	17^a	12	1,840
1989/90	46	35	1,350
1990/91	53	38	1,410
1991/92	74	50	1,160
1992/93	38	27	1,200
1993/94	43	29	1,250
1994/95	51	36	1,230
1995/96	74	49	960
1996/97	72	43	950
1997/98	62	35	930
1998/99	40	24	1,100 (eco)
1999/00	73	45	920 (euro)

a = Rare extreme heat-wave in May destroyed most of the crop.

b = Unfavorable exchange-rate for the dollar.

Present main production problems

1 ) Average National Yield/ha

The Average national Yield/ha for the last six years ( 12.5 t/ha) can be considered good when compared to the same averages for California or Spain. Nevertheless, this yield can not be considered as sufficient for the Israeli producer - under the present and the foreseen costs of production (particularly – cost of irrigation-water) and in view of the avocado trade tendencies.

However, it has been found that considerable differences in yields exist between orchards with the same cultivars in the same region. A 20 years’ average yield (with pronounced fluctuations between years) of well-cared orchards in the coastal plain, has been 10 tons/ha. But outstanding orchards produced the following average yields during the same period: ‘Fuerte’ - 12t/ha, ‘Ettinger’ and ‘Nabal’ - 18 t/ha, ‘Hass’ - 20 t/ha.

The above can be explained only by large differences in the level of orchard care and management, and it reveals the unused potential of production in the existing avocado area. Hence the need for intensifying extension activities and for further rising of the professional and managerial levels of growers.

Additional factors involved in insufficient yields/ha in many orchards seems to be the following: Flowering and fruit-set of the main commercial cultivars take place from March through May, a season of very unstable weather with temperatures too high and/or too low for optimal pollination and fruit-set. Major damage to the avocado crop on a national level has been caused by extreme and prolonged heat waves shortly after fruit-set (Table 3).

Another factor. There is often a marked reduction in bee activity (pollination) in avocado orchards during the main flowering season of the major cultivars, which coincide with the flowering of very strong competitors for bees, like the vast areas of citrus and of wild vegetation.

2) Scarcity of water:

Increasing prices and the scarcity of irrigation water may create, in the near future, a major constraint to the whole avocado industry. This issue can be identified, perhaps, as the most crucial production problem in the long run.

3) Increasing salinity

The salinity of irrigation ground water in major avocado producing regions is gradually increasing and could be responsible, at least partially, for the decrease in yields in those areas, particularly where orchards were planted on Mexican rootstock. Replacing with new plantings based on more tolerant rootstocks is gradually practiced recently.

4) The size of ‘Hass’ fruits:

Local ecological factors downgrade the fruit-size of this leading cultivar, which becomes smaller than demanded by the trade. (See “Cultivars”). The efforts to breed or introduce a bigger ‘Hass’ have not yet resulted in any desirable replacing cultivar.

Research and Extension

The Israeli avocado industry has been characterized since its inception by close contacts and rapid flow of information between the Extension Service, the Agricultural Research Organization (the Volcani Center), the Faculty of Agriculture in Rehovot - and the growers. The first two bodies are a part of the Ministry of Agriculture.

The Ministry contributes around US$ 200,000 annually to research in avocado, in addition to covering costs of infrastructure and salaries of permanent researchers. The Israeli Avocado Association (and formerly the Avocado Growers' Corporation) invest around US$ 200,000 annually plus an additional contribution of US$ 50,000 by regional organizations of growers.

Presently, (July 2000) the main research topics in avocado are:

1) Search for better cultivars.(screening selections from local previous breeding project, and from introduction).

2) Improving production by plant growth regulators.

3) Efficacious irrigation.

4) Post-harvest physiology, pathology and technology.

5) Biological pest control.

The Extension staff comprised of a team of 9 regional Extension Agents, specializing in subtropical fruit crops and guided by a nationwide professional coordinator (all affiliate to the Extension Service, Ministry of Agriculture and Rural Development, Division of Fruit-growing). In addition to their extension activities, they are involved in field experiments and contribute to enriching the inventory of knowledge in avocado production. They are assisted by other extension officers who cover agricultural domains such as plant protection, "field service" (i.e.: irrigation and fertilization of crops), agricultural machinery, agricultural economics, etc., located in the same region or operating on a national level.