Whether a garden is souse in sun or deep in shade , at least one of the more than 1,000 begonia species ( Begonia spp . ) and 1000 of begonia cultivars can lift it from terrene to magical . As semitropic and tropical plants , most begoniassurvive winters outdoors in U.S. Department of Agriculture plant hardiness zones 10 through 11 . Elsewhere , they can be lifted before the first frost and stored indoors for the winter . Frost is n’t their only enemy ; the humidness begonias love expose them to powdery mildew . Treat an infection culturally or organically before resorting to chemical fungicide .
The Fungi
Two powdery mold fungi ( Erysiphe cichoracearumandOidium begoniae ) taint begonias . breaking wind or water carry their spore to begonia leaves , but they want the correct condition to shoot .
The chances of infection increasewhen water vapor — or humidity — in the air condenses as temperature drop and wash the begonia ' leaf . Without any moisture , spores landing on the leaves do n’t germinate . On slenderly damp leaves , they germinate in only one hour . Standing water on the leave drown the spores . The terror of infection is highest on begonias grow in nuance at temperature waver between 60 and 80 point Fahrenheit .
Cultural Treatments
water system begonias in midmorning by scatter them from above . Sprinkling murder spores already on the leaf , and submerge the I land before the leaves dry out . To lower the humidity around potted begonias , space their sight at least 1 foot apart for dependable atmosphere circulation . Prune mildewed folio at the first sign of infection and dispose of them in seal off plastic bags . Remove them with clear , sharp stem cutters rinsed in rub alcohol between cut and after use .
The Milk-and-Water Treatment
A solution of 1 part skim or raw milk to 9 parts watersprayed on overrun plants reduces powdery mildew symptom up to 90 percent , reports the National Gardening Association . The collar is that the milk - and - water solution wo n’t work on tone - garden begonias . It needs sunlight to spark its mildew - killing properties , according to researcher Peter Crisp of Australia ’s Adelaide University . Spray begonias in sun until the resolution coat all their surfaces . Repeat hebdomadally until mold - favoring conditions subside .
Neem Oil Treatment
Correctly treating begonias with constitutive , quick - to - use neem oil color spraycontrols powdery mildew without hurting honeybee or other beneficial insect .
sentence the treatment for the the other morning or after sullen , when bees are n’t pollinating . In tranquil , juiceless weather with a temperature below 90 degrees Fahrenheit , water the plants well . Dress in protective article of clothing , including a long - sleeved shirt , long pants , waterproofed gloves , a respiratory masquerade party and prophylactic goggles .
- cake the begonias until they dribble , being certain to tally the backs of the leaves . * * Repeat weekly as long as you see symptom , and then every other calendar week as long as the weather rest wry and temperature remain between 60 and 80 degree F.
