CITRUS MELANOSE AND ITS CONTROL 15 
pycnidia are young but not liberating spores, the visible portions 
are usually dark or almost black; if the pycnidia are very young, a 
small pimple in the bark is all that can be seen. 
If there is a point where the organism sporulates more abundantly 
than another, it is somewhat below the leaf scars on twigs, especially 
in patches of bark that have turned white. Spore production is more 
abundant in tissue that has recently died than in those parts that 
have been dead for a year or more. Old weathered pycnidia usually 
show no signs of escaping spores. Many of these pycnidia, together 
with the surrounding bark, either partially weather away or drop out 
in a relatively short time, leaving empty cavities in the bark. In 
general it is less difficult to find inactive pycnidia than sporulating 
ones. 
This fungus produces spores in immature citrus fruits artificially 
inoculated, but spore production has not been observed in mature 
citrus fruits under natural conditions. During the last several years 
careful examinations have been made of the remains of mature 
oranges and grapefruit under bearing trees and on cull piles in all 
stages of active decomposition, as well as of the mummied hulls, 
without finding indications of pycnidia of the causal organism. 
The melanose fungus in nature sporulates principally in dead twigs 
and fruit stems. Deadwood in citrus trees may be the result of a 
wide range of conditions. Among the principal ones are infestations 
of scale insects; shading effects in the interior of the tree; the slow, 
wasting trunk and root diseases which frequently result in the death 
of twigs, limbs, or even trees ; frosts or freezes, storms and droughts, 
and other conditions which tend to lower the vitality. 
Under Florida conditions, and perhaps in most subtropical regions, 
scale insects are usually responsible for the death of more twigs than 
are all other agencies combined. Whenever the infestation is heavy, 
even for a short time, large proportions of the bearing wood are 
killed, and these insects, even when present in almost unnoticeable 
numbers, are responsible for the death of many twigs and small 
branches. 
Aside from the agencies causing the accumulation of deadwood, the 
length of time the parts have been dead with respect to the time 
when melanose outbreaks occur is of considerable importance. Parts 
that have died within two or three months are much more likely to 
harbor the causal organism than parts that have been dead many 
months. Those parts killed as late as September or October seldom 
are a source of infection that year, and normally do not act as 
especially fertile sources of infection the following year, but those 
killed in winter or spring almost invariably are excellent breeding 
places for the melanose fungus. Normally very little wood is killed 
during the summer, but that which is killed then is a source of fall 
infection. 
Fruiting pycnidia may be found at any time of the year, but usu- 
ally they are not abundant in midwinter. Ordinarily as spring 
comes on innumerable pycnidia begin to develop, and around the 
middle or latter part of April they are found in abundance, many 
of them filled with spores, whereas others seem to be in the very 
first stages of development. Well after May rains set in, these ma- 
ture fruiting bodies are not so easily found unless wet, but inactive 
