Macadamia Nuts in Hawaii: History and Production - ctahr ...
Macadamia Nuts in Hawaii: History and Production - ctahr ...
Macadamia Nuts in Hawaii: History and Production - ctahr ...
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Figure 72. <strong>Macadamia</strong> racemes show<strong>in</strong>g effects of Botrytis c<strong>in</strong>erea<br />
<strong>in</strong>festation (right) compared with normal racemes (left).<br />
Figure 73. <strong>Macadamia</strong> racemes show<strong>in</strong>g Phytophthora capsici <strong>in</strong>festation.<br />
(Normal racemes are shown <strong>in</strong> Fig. 72.)<br />
56<br />
formed (Fig. 73). The <strong>in</strong>festation first appears<br />
as m<strong>in</strong>ute necrotic spots on the racemes, but<br />
it very rapidly develops to encompass the<br />
total structure. Flowers <strong>and</strong> fruits do not develop<br />
normally.<br />
3. The Kretzschmaria clavus (34, 35, 37) root<br />
<strong>and</strong> trunk rot symptom is especially noticeable<br />
when the trees are about 15 to 25 years<br />
old (Fig. 74). Its ecology has not been completely<br />
established <strong>and</strong> further studies are<br />
needed, but at this time, young trees planted<br />
<strong>in</strong> the same spot where a tree has previously<br />
succumbed seem to grow normally, probably<br />
<strong>in</strong>dicat<strong>in</strong>g that this organism develops very<br />
slowly. The Kretzschmaria root rot is aga<strong>in</strong><br />
more prevalent <strong>in</strong> the wet areas of Hilo <strong>and</strong><br />
Pahoa. More work on this fungus has been<br />
funded by the Governor's Agricultural Coord<strong>in</strong>at<strong>in</strong>g<br />
Committee through the <strong>Hawaii</strong><br />
<strong>Macadamia</strong> Producers Association.<br />
Phytophthora c<strong>in</strong>namomi has been associated<br />
with trunk canker <strong>in</strong> macadamia. However, this<br />
<strong>in</strong>festation is rarely found <strong>and</strong> apparently does not<br />
affect production (23, 36, 87). It probably exists<br />
only as a harmless member of the microbial community<br />
(36).<br />
Figure 75 shows a nut-set picture of a tree <strong>in</strong> the<br />
leeward area of Kona, where the high mounta<strong>in</strong><br />
br<strong>in</strong>gs about a temperature reversal for most of<br />
Kona, result<strong>in</strong>g <strong>in</strong> a dry w<strong>in</strong>ter when the flowers<br />
are develop<strong>in</strong>g. This temperature situation <strong>in</strong><br />
Kona is very unlike the wet condition <strong>in</strong> Hilo <strong>and</strong><br />
the w<strong>in</strong>dward sides of the Isl<strong>and</strong>s, where the<br />
flower<strong>in</strong>g season is wet <strong>and</strong> cold. Under this dry<br />
condition <strong>in</strong> Kona, Botrytis c<strong>in</strong>erea <strong>and</strong> Phytophthora<br />
capsici develop slowly; nut set is conseq<br />
uently very good.<br />
With the advantage of h<strong>in</strong>dsight after 30 years<br />
of active macadamia production, the evidence<br />
now on disease manifestation <strong>and</strong> control <strong>in</strong>dicates<br />
that a better alternative on l<strong>and</strong> is the use of<br />
areas that are cool <strong>and</strong> dry <strong>in</strong> the w<strong>in</strong>ter months.<br />
This will reduce the bad effect of flower blights. If<br />
economic considerations can be resolved, macadamia<br />
planted <strong>in</strong> dry areas where irrigation water<br />
is available <strong>and</strong> is applied will lend itself further<br />
to better control of its serious diseases, <strong>in</strong>clud<strong>in</strong>g<br />
Kretzschmaria root rot. Such a reth<strong>in</strong>k<strong>in</strong>g is a<br />
better alternative <strong>and</strong> worth consider<strong>in</strong>g as a first<br />
step <strong>in</strong> macadamia disease control <strong>and</strong> macadamia<br />
production.<br />
Rats. Without a thorough rat eradication pro-