There are several unlike but fairly unwashed problems on Rieger begonia . The three military issue we see most often on begonia submitted toMichigan State University Plant & Pest Diagnosticsare impatiens necrotic spot virus , bacterial blight ( Xanthomonas axonopodis pv . begonia ) and unsubtle touch . Each of these is triggered by a pest or pathogen with specific management strategy . It is important to be familiar with the symptom of each ; early detection and action can prevent further losses .
Figure 1 . symptom of impatiens necrotic spot virus on Rieger begonia foliage . observe the rings and partial rings of various sizes on this one leafage . Photo by MSU Plant & Pest Diagnostics .
Impatiens necrotic blot computer virus ( INSV)Symptoms of INSV depart widely count on the host . In begonias , the symptom typically include ringspots on the leafage . ring may commence as a lily-livered area but over time this tissue dies , leaving a necrotic outline . These rings may be incomplete circles but still have define margins .
This virus has a wide emcee compass and is vectored by thripid . Quick action is needed to prevent further spread throughout the production area . symptomatic test outfit are available for use in the greenhouse and these provide flying resultant role . sample can also be sent toMichigan State University Plant & Pest Diagnosticsfor examination .
Bacterial blight ( Xanthomonas axonopodis pv . begonia)Symptoms of this disease typically begin at the leafage margin . Wedge - shaped greensick areas are an initial symptom , but this discoloration is subtle and easily overlooked ( Figure 2A ) . Symptoms often are n’t noticed until sphacelus begins at the leaf margin . Over time , disease procession and elderly leaf toward the bottom of the plant may completely break down while young leaves have more characteristic symptoms ( Figure 2B ) . This pathogen is specific to begonia and , fortunately , will not circulate to other cosmetic crops . bear on to theMSU Extensionarticle series , “ substantive concept for carry off Xanthomonas in begonia — Part 1 , ” release in 2018 for more entropy on the biology and management of this pathogen .
Figure 2 . ( A ) Early symptom of bacterial blight let in yellowed areas , bordered by nervure . Necrotic tissue is start to produce at the leaf margin . ( B ) Advanced symptoms include dead leaves toward the bottom of the plant as well as large lesion . Photo by MSU Plant & Pest Diagnostics .
Broad mitesBegonias infested with across-the-board mites have foliage with a coppery discoloration visible on the undersurface of the leaf ( Figure 3A and B ) , blossom can also be damaged . New growth may be distorted in both texture and shape ( Figure 3B ) . Overall , plants that are damaged by the toxic saliva become unthifty . Broad mites are almost microscopic and may be difficult to see even with a hired hand lens . More information about broad mites can be receive at “ panoptic mites in decorative crops — Part 1 : Challenges and treatment ” from MSU Extension .
Figure 3 . ( A and B ) Russeting and bronze of the depressed leaf surface and petiole and ( C ) thickened , harden new growth make by all-embracing mites . Photo by MSU Plant & Pest Diagnostics .
Source : Michigan State University ( Jan Byrne and Howard Russell )
