Arthropod presence and potential significance in North Carolina grown hops
Hannah Burrack
Department of Entomology
North Carolina State University
Integrated pest management �The basics
Minimize
Monitor
Manage
Integrated pest management �The basics
Minimize
Monitor
Manage
Sample, Monitor, and correctly indentify potential pests and natural enemies
Create the least hospitable environment for pests
When insects reach an economic threshold (based on sampling)
Integrated pest management �Key terms
Economic injury level (EIL)
�
Economic threshold (ET)
Sample
Integrated pest management �Key terms
Economic injury level (EIL): The amount of damage or injury which results in an economic loss greater than cost of management. In other words, the amount of damage resulting in monetary loss.�
Economic threshold (ET): The damage of damage, injury, or pest population level at which action should be taken to avoid reaching the EIL.
Sample: Observations of pest populations in a planting, usually random. Monitoring is sampling regularly over time.
Integrated pest management �Key terms
Economic injury level (EIL): The amount of damage or injury which results in an economic loss greater than cost of management. In other words, the amount of damage resulting in monetary loss.�
EIL = C/VIDK
C = cost of management/production unit
V = value of/unit production
I = injury/pest
D = damage/injury
K = proportional reduction/marginal control
Integrated pest management �How do insects damage plants?
Integrated pest management �How do insects damage plants?
Integrated pest management �How do insects damage plants?
Arthropods in North Carolina hops �The usual suspects – known pests of hops
Spider mites (Tetranychus spp.)
Twospotted spider mites are the most common pest in the western US. We have at least one other species feeding on hops in the southeast. Spider mites can damage foliage and cones.
There is no research based threshold for spider mites in hops, but western growers treat when1-2 mites are found per leaf in a random sample.
Severe, moderate, mild, and no spider mite injury on cones (L to R). Photo: bugwood.org
Mites are attracted to and reproduce more on stressed plants.
Mites are managed with miticides and biological control.
Arthropods in North Carolina hops �The usual suspects – known pests of hops
P. humuli alate
Photo: bugwood.org
Photo: bugwood.org
Hop aphid (Phorodon humuli)
Specialists on hops and injure plants through their feeding and the production of honeydew on which sooty mold can grow. Aphids can also feed internally on cones, and contaminate harvested product.
Arthropods in North Carolina hops �The unusual suspects – potential pests of hops
Hop stalk borer
(Papaipema circumlucens)
Hop stalk borer larvae have been found feeding at the base of bines. HSB feeding is characterized by galling in addition to tunneling. Larvae in the bines may be very difficult to manage.
Arthropods in North Carolina hops �The unusual suspects – potential pests of hops
Eastern comma caterpillar
(Polygonia comma)
Eastern comma caterpillars were found in early 2010 on hops in western NC. It is unclear if these generalist insects are a significant pest.
Polygonia comma adult
Arthropods in North Carolina hops �The unusual suspects – potential pests of hops
Leaf hoppers and thrips
Graphocephala versuta have been present in high numbers as both nymphs and adults. They are also recorded from cannabis, a close relative to hops. It is unclear what damage leafhoppers may cause in hops.
Nymph
Adult
Cast skin
Thrips (Frankliniella spp.) can be present in high numbers in hops plantings, but damage attributable to them has not been observed.
Arthropods in North Carolina hops �What have we observed at the NCSU hop yard?
During the 2011 growing season…
We collected 10 leaf samples from each plot (at the NCSU Lake Wheeler Road Field Laboratory) weekly and counted the number of spider mites, predatory mites (good guys), aphids, and leafhopper nymphs.
We placed a yellow sticky trap in each plot, which was changed weekly. We counted the number adult leafhoppers, thrips, aphids, and beneficial insects (in this case, ladybugs) on each trap.
We rating defoliation on the middle plants of each plot.
(We didn’t see any meaningful >5% defoliation on any plant at any time)
Arthropods in North Carolina hops �What have we observed at the NCSU hop yard?�Trap captures
Arthropods in North Carolina hops �What have we observed at the NCSU hop yard?�Mites over time by variety
Arthropods in North Carolina hops �What have we observed at the NCSU hop yard?�Leafhopper nymphs over time by variety
Arthropods in North Carolina hops �What have we observed at the NCSU hop yard?�Aphids over time by variety
Arthropods in North Carolina hops �What do our observations tell us about possible hops pests and their management?
Mites are attracted to stressed plants, and plants with the highest numbers also were the least vigorous and lowest yielding.
Leafhopper nymphs and aphids were present in the highest numbers on the varieties which had the highest yield.
Plant health may be more important in the short term than insect pests.
Amanda Harding collected and compiled all insect data.
This project was supported through the Golden LEAF Foundation.
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