Posts Tagged: hosts
Invasive Shot Hole Borers Threatening Trees in Southern California
[From the December 2016 issue of the UC IPM Green Bulletin] The Polyphagous shot hole borer (PSHB)...
Dry Shade Gardening
Tree canopies have a lot to do with how much light and moisture enter your garden. If your trees have broad, spreading canopies, they will cast more shade than upright trees, unless these upright trees are planted close together. If these trees are deciduous, the shade they cast will be seasonal and what you can plant beneath them may depend on when they leaf out and how dense their canopies become.
More critical to reducing shade is increasing moisture levels beneath trees. Tree roots extract every drop of moisture from the ground and leave nothing for other plants. A recommended approach to increasing moisture content in the soil is to build a well-draining raised bed and fill it with humus-rich, water retentive soil. Do not place your raised bed against or close to a tree trunk as this would interfere with oxygen availability to tree roots. Install an automatic irrigation system using soaker hoses or drip irrigation rather than a sprinkler system. The use of mulch materials such as bark, wood chips, straw, shredded leaves, even rocks, will help prevent water in the soil from evaporating too quickly.
To keep soil disturbances to a minimum, start with small understory plants. Begin planting at least 12 inches away from the trunk and plant in an outwardly direction. Spacing plants too closely reduces air circulation and encourages fungal diseases like powdery mildew. Avoid nicking tree roots, as you prepare the planting holes. Water the plantings thoroughly. Annually, apply 2 to 3 inches of topdressing such as compost, shredded leaves or well-rotted manure. This organic material replicates nature without damaging tree roots and provides many benefits.
Reproductive Hosts of Polyphagous Shot Hole Borer
Polyphagous Shot Hole Borer can go to over 100 and counting hosts, but the Fusarium that the ambrosia beetle carries can not reproduce on all tree species. It is this fungus that ultimately kills the tree. There are now though thirty-seven hosts on which the beetle will attack and the Fusarium will grow. Here is the current list, 14 of which are California natives:
Known Suitable Reproductive Host Trees:
*Native species to California
PSHB damage
Current status of the invasive Bagrada bug in California: geographic distribution and affected host plants
Bagrada bug [Bagrada hilaris (Burmeister)] is an invasive hemipteran insect (Family: Pentatomidae) that was first reported in Los Angeles County, California in 2008. It has now spread to several counties in California and is moving northwards.
Distribution: Citizen scientists have been instrumental in reporting the occurrence of Bagrada in various counties and are helping map its current distribution. As of September 2014, Bagrada bug is known to be present in Imperial, San Diego, Orange, Riverside, Los Angeles, San Bernardino, Kern, Kings, Inyso, Fresno, Merced, Ventura, Santa Barbara, Monterey, San Benito, Santa Cruz, San Mateo, Santa Clara, Alameda and Yolo Counties and is likely to be present in some other.
Distribution of Bagrada bug in various California counties as of September, 2014.
Bagrada bug is also spreading eastwards from California and is currently reported in Nevada, Arizona, Utah, New Mexico, and Texas.
Host plants affected: While Bagrada bugs are known to feed on a variety of host plants in addition to their preferred cruciferous hosts, serious damage to barley, carrot, corn, pepper, potato, tomato, and sunflower was recently reported by growers or gardeners. In a previous study where multiple food sources were offered, Bagrada bugs did not feed on tomatoes. They were also found on strawberries and reported to be present on other hosts, but damage has not been confirmed. Bagrada bugs might have been present on these plants as they move around in search of suitable food sources.
Damage to carrots from Bagrada bug feeding. (Photo by Rick Machado, Menifee)
Stippling and eventual necrosis of damaged tissue in chiko burdock. (Photo by Don DeLano, Pomona)
Backyard corn damaged by Bagrada bugs. (Photo by Larry Adcock, Arroyo Grande)
Adult Bagrada bugs on damaged pepper leaves. (Photo by Rick Machado, Menifee)
Seriously damaged seed potato plants (above) and tubers (below). (Photo by Rick Machado, Menifee)
Bagrada bug damage to sepals on sunflower. (Photo by Larry Adcock, Arroyo Grande)
Bagrada bug feeding damage to tomatoes. (Photos by Rick Machado, Menifee, above and Jennifer Evangelista, San Luis Obispo, below)
Bagrada bugs on strawberry foliage. Not seen to cause any feeding damage. (Photo by Jennifer Evangelista, San Luis Obispo)
Management: Regular monitoring, mechanical exclusion or removal, destruction of weed hosts, and chemical, botanical, and microbial pesticides continue to be available management options. There have been several queries in the past two months from home owners, community garden operators, and organic growers about serious Bagrada bug infestations. Avoiding cruciferous and other hosts at risk should be a serious consideration for community and home gardens where using some of the currently available management options is difficult.
What to do: If you see Bagrada bug in an area or on a host that is not previously reported, please contact Surendra Dara at skdara@ucanr.edu or 805-781-5940. This information will be useful to track the distribution of this pest.
Additional information:
Biology, damage, and control video: www.youtube.com/watch?v=gSj3AZoJIRM
Biology, damage, and control: //ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=4047
Potential organic solutions: //ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=11031
Host preference: //ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=9611
General information: //ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=8438
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