Overfeeding. . . Begonias require ju- 
dicious feeding in order to produce large 
well formed specimens, but overfeeding 
causes perhaps more damage and short- 
ens their lives more than any other fac- 
tor. The quick acting fertilizers such as 
fish-meal and fish-emulsions are of or- 
ganic nature and can hardly do damage 
unless used in excessive quantities. The 
first sign of overfeeding is a rich bluish- 
green color of the leaves which curl un- 
der. The plants will produce distorted 
flowers smaller in size, but gradually as 
the nitrogen in the soil dimishes, they 
will come out of it and perform nor- 
mally. If chemical nitrogen is used in 
such form as nitrate of soda, sulphate of 
ammonia or nitrate of potash, the plants 
simply burn up if overfed. The growth 
will be stunted with small flowers or 
none, and upon maturing the tubers, 
you will find them completely petrified. 
The ideal feeding is to keep the plants 
always slightly hungry by giving them 
light doses of liquid fish-meal or any 
other commercial fertilizer recommended 
for tuberous begonias and religiously fol- 
lowing the directions prescribed on the 
containers. If foliage is a blue-green with- 
hold feeding as they are receiving too 
much nitrogen. Start feeding again when 
the foliage is a soft green color. Very pale 
green foliage is a sign of a deficiency of 
nitrogen and requires increased feeding. 
Rotting of plants... The tissue of 
begonia plants is quite sensitive to any 
decaying material which they contact. 
If young plants are set out in a soil 
heavily enriched with manure and the 
decaying parts of the manure come in 
contact with the stem, the plant will 
often rot off at the base. This happens 
more in warmer regions especially with 
high humidity and seldom appears un- 
der cool conditions prevailing along the 
Pacific Coast. A little clean soil or sharp 
sand placed around the stem when plant- 
ing seedlings will prevent the rotting 
off to a great extent. When flowering, 
the plants should be kept clean of all the 
debris of the old flowers and flower 
stems. Flowers should be removed leav- 
ing all of the flower stem or if cut, as 
much of the stem as possible, as the open 
wound immediately starts molding. If 
a stem is left long enough, it will mature 
and fall off from the main stem before 
the mold can reach its entire length. If 
cut too short, the mold will infect the 
main stem and if not checked, will decay 
the whole plant eventually. Old petals 
falling in the crotch of the leaves may 
start mold in an area which could be 
scraped clean with a knife, dried with a 
cloth, and dusted over with zerlate so it 
can heal. If the main stem is badly 
molded, it can be cut off below the in- 
fected part or even completely off if 
necessary. The plant should be kept 
slightly drier as it will send new shoots 
out as a rule trying to recover its health. 
In this way tubers can be saved and al- 
though weakened, they may perform well 
again the following year. If stem rot is 
not checked, it will go all the way down 
into the tuber and destroy it completely. 
Diseases and insects . . . Begonias 
are comparatively free of ills or at least 
they were until a few years ago. The only 
serious infection in the past was cycla- 
men mites which was rare rather and 
confined usually to greenhouses where 
many other plants were grown. The first 
sign of it is rusty brown streaks on the 
foliage and stems, the buds turning 
brown in the very young stage and fall- 
ing off. An effective control can be had 
by spraying with various insecticides rec- 
ommended for red spider and mites. 
Bacterial leaf-spot appeared several 
years ago and attacks the plants chiefly 
in the greenhouses where there is high 
humidity and not enough aeration. It is 
most damaging to the young seedlings in 
their germination stage, and we have 
been controlling it with a weak solution 
of Greenol, spraying every five days until 
the plants reach the size for outdoor 
planting. It seldom attacks plants when 
they are larger and hardly ever if they 
are grown outdoors. 
Mildew, appearing for the first time in 
1951 in isolated areas and spreading 
everywhere since, is perhaps the most 
serious enemy of tuberous begonias so 
far. Preventive Dusting with COPO 
TOX DUST No. 10 gave so far the best 
result, controlling the mildew well. How- 
ever, where infection became _ heavily 
established spraying with Koppersol was 
quite effective. Well grown plants will 
resist disease to a great extent. Keeping 
the foliage dry—especially at night also 
prevents the spread of any fungus dis- 
ease. 
Strawberry-weavil is wide spread par- 
ticularly in the north, and the damage 
to the begonias is caused by the larvae 
of the brachyrhinus beetle during sum- 
mer months. The beetles emerge from 
their dormant stage in early May and 
June laying their egges all summer long. 
The eggs, which are deposited around 
the stem of the plant, hatch rapidly, 
living in their first and second stage on 
decaying material such as leafmold and 
manure. It is in their third, fourth, and 
fifth stage as the larvae gets larger that 
it burrows into the tuber, tunneling back 
and forth until the bulb is completely 
destroyed. The only effective control is 
feeding with a mixture of three per cent 
calcium arsenate in bran or apple bait 
spread among the plants during May and 
June when the beetles feed and before 
the egg laying period begins. 
