By Bob Purvis
Alaska members of the Alaska Pioneer Fruit Growers may sometimes feel that, compared to Washington State, they have few advantages and many disadvantages in growing tree fruits. As one who has grown fruit trees in Anchorage, then in Pullman (near the Washington-Idaho border, elevation 2350’), and now in Selah (five miles north of Yakima, elevation 1200’), I’d like to compare the three locations.
With respect to soils, Pullman was probably the most favorable location. The pH of the soils in our yard there was close to neutral; the soils wore fertile, with no mineral elements in short supply and few rocks. The soils were rather heavy, with a high clay content but the apple, pear, cherry, apricot and plum trees I planted there grew quite well. There was sufficient rainfall (22” per year) such that only in July, August and sometimes September was supplemental irrigation needed. In Anchorage, the soils are acidic, cold, and often poorly drained.
The soils in our part of Selah were nearly ideal for fruit growing in 1900, but the heavy use of lead arsenate as a broad- spectrum pesticide before 1950, plus the use of this site as an apple orchard until 1972, have caused some problems in establishing fruit trees, especially for the stone fruits, Arsenic tends to inhibit root growth, it appears, especially at the levels tested here (84 ppm in the top foot of soil). The soils here are alkaline (pH 7.5 to 8.0), and the water is high in calcium carbonate (free lime), a problem rarely seen in Alaska or Pullman. Furthermore, the annual rainfall here is only 8”. The consequence of having alkaline soils and calcium carbonate in the irrigation water is that under certain conditions, lime-induced iron chlorosis appears in the leaves near the shoot tip. The interveinal areas of the leaf turn yellow, then white, while the veins remain green. If allowed to continue, the leaves thus affected will die, and ultimately the tree also. I learned during 1993 that of the rootstocks on which my apple trees were grafted the Siberian crabapple (Malus baccata) was most susceptible to lime-induced iron chlorosis, although it could be corrected within several days time with a watering of Miracid liquid fertilizer. Malus ranetka was also somewhat susceptible, Antonovka seedlings much less so, and the clonal Mailing rootstocks and “Mark” rootstock have not suffered from it at all Evaporation of irrigation water on the leaves of the trees results in deposits of calcium carbonate, which can bum the leaves and reduce their ability to photosynthesis.
Boron and sometimes zinc are oftentimes present in marginal or deficient amounts here, but this was not the case in Pullman and is probably not in Alaska’s largely virgin soils.
The pest problems are much different in Washington than in Alaska. Here, there is a well- established population of insect pests. Codling moth, the worst enemy, is a real scourge of apples in Selah, requiring sprays of
Guthion (a restricted-use pesticide) or diazinon at least two and usually three times during the growing season. Leaf miner is also a problem, sometimes a very serious one in commercial orchards, and the powerful pesticides such a Vydate used to control it wipe out the predators of not only leaf miner, but of other pests as well. Pear slugs, which also feed on the leaves, were a problem both in Pullman and here, and sometimes aphids can be troublesome. Leaf rollers are a problem, too, especially in late springs. Lastly, during 1992, I had some problems with San Jose scale on my “Seneca” prune plum. Pew of these pests are ever a problem in Alaska.
Vertebrate pests in Alaska were primarily moose, rabbits, and voles. While moose are not a problem here, gophers are-both in Pullman and in Selah (and, for that matter, most of the Yakima Valley). Mice can be a problem in winter, and birds are a major problem for growers of cherries, and even apricots and peaches in our neighborhood.
With large numbers of fruit trees nearby, there are lots of hosts for disease organisms, but the dry climate tends to create a less favorable environment for most diseases. The main disease I have seen on my apple trees here, in Selah, is powdery mildew, especially on cultivars such as “Jonagold”. I have not seen apple scab nor perennial canker, nor fireblight on my pear trees, thus far, although 1992 was one of the worst years the Yakima Valley has seen in a while for fireblight outbreaks. On stone fruits, the main disease I have seen is coryneum blight on my apricots. Its main symptom is small purplish spots on the fruits (I have not seen this) and later, small red spots on the leaves. If the leaves are seriously affected, Coryneum can also make apricot trees defoliate earlier in the fall, and can cause girdling cankers and even death on peach trees if it gets well established.
The growing season is much longer here than in Anchorage (about 170-180 days vs. 123), and temperatures can get quite hot (we recorded four days in the summer of .1992 with 100-105°F, although this is unusual). Furthermore, we occasionally have weather warm enough in winter to de-harden the flower buds of peaches and apricots; and if it is followed quickly by subzero cold, that can wipe out the following season’s crop. April frosts are a hazard to growers of stone fruits both here and in Pullman, but we had a bumper crop of both peaches and apricots here at our house this year and in 1992. The low relative humidity and the elevation results in 35-40° temperature swings from day to night most clear days from March through September. In July, the warmest month of the year, the average high is 88°F, with an average low of 53°F, vs. 65°F and 50°F, respectively, for Anchorage. Pullman’s July temperatures run a few degrees cooler than Yakima’s. The average temperature for January, the coldest month in Yakima, is 36°F for the high and 18°F for the low. During my time in Pullman (1989-1992), I recorded temperatures as low as -19°F at our home, and during our first winter (1992-1993) in Selah, a low of -6°F with about 16” of snow on the ground.
Central and eastern Washington have a great advantage over Alaska in terms of good weather for fruit growing after the frost season is past and in length of- growing season and amount of clear sky. We can grow a far greater diversity of fruits here than Alaska can ever hope to, but in terms of insect pests and diseases, and soil fertility and water management Alaskans can be thankful they have simpler problems to solve than we do here for the tree fruits they can grow. Am I glad to be growing fruit here rather than in Alaska? Yes-the opportunities are much greater, and while the problems are more complex, they can be solved with time and perseverance.