Whiteflies in blueberries - should we be concerned?

I'm attending the North American Blueberry Research and Extension Workers Conference in Kalamazoo, MI today and tomorrow, so I thought it would be a good time for a blueberry post.

I have been noticing large numbers of an unusual looking whitefly in blueberries for the last 2 years and now have an ID for it. Tetraleurodes ursorum does not have a common name, although the Florida Department of Agricultural & Consumer Services suggests it be called the bearberry whitefly. These whiteflies usually appear after harvest and are present on new growth. They are unique in their dark blueish black coloring, which almost makes them appear parasitized. Although many of the nymphs and pupae I collected in 2010 were parasitized, the dark color is their natural appearance. Whiteflies have a complex life cycle. Eggs hatch to a mobile 1st instar, termed a crawler. They then mature through a few stationary nymph stages to what is generally called a pupa but is really just a final, non-feeding nymphal instar. Because whiteflies do not undergo complete metamorphosis, the term pupa is a misnomer.

Whitefly nymphs and pupae on the underside of blueberry foliage in 2008. Photos: HJB

These whiteflies can reach extremely high numbers in NC blueberries. I have seen the back of leaves entirely covered in nymphs and pupae and their associated honeydew. Because they appear to be a post harvest feeder, it is unclear if they are causing any damage to the plant. This late summer, I plan to treat some of my new planting for whiteflies (assuming they are present there) and to then compare flower clusters next spring. Hopefully this will starting giving us a sense of what, if any, importance this unusual insect has for NC blueberries.

Whitefly adults on young blueberry foliage. Photo: HJB

Mystery holes on tobacco stalks

Tobacco stalk with holes.  Photo: Norman Harrell.

Wilson County field crops agent, Norman Harrell, sent me an email with the above picture attached.  A grower brought in the tobacco stalk concerned about what could be causing the holes.  I see this type of damage every year around this time, and it is not of economic concern.  Although any chewing insect (ie. crickets, beetles, grasshoppers) could potentially cause this type of injury, it's most likely due to either tobacco budworms or tobacco/tomato hornworms.  While these caterpillars typically feed on leaf tissue, they may occasionally take a bite out of the stalk.  Stalk injury like this does not impact the plant, and does not suggest that further damage is likely (unless hornworms are found when scouting).  The threshold for hornworms in tobacco is 1 inch-long or larger hornworm per 10 plants with parasitized hornworms counting as 1/5 of a worm because they eat approximately 1/5 of that of a healthy caterpillar.

Bottom line, however, is that stalk damage of this type may be caused by several insects, but is nothing to worry about!

First strawberry preplant meeting - July 28th

The first strawberry preplant meeting of the season (is it that time already?!) will be next Thursday, July 28th at the Mountain Horticultural Research Station in Mills River, NC.  Area horticulture agent, Sue Colucci has organized this meeting, and interested growers can find more details here.  I will be sharing results from our 2010 twospotted spider mite trials, discussing new insecticide options and IPM strategies for sap beetles in strawberries, and sharing information on unusual caterpillar issues from this year's harvest season.
Hope to see the mountain strawberry growers there!


Update
Sue Colucci has just posted an announcement for the meeting on her blog, Western NC Vegetable and Small Fruits News.

Tobacco Tour 2010 completed - pictures to come!

The 2010 Tobacco Tour proceeded this week Tuesday and Wednesday and visited 10 locations encompassing 20 Crop Sciences, Plant Pathology, Bio & Ag Engineering, and Entomology extension and research projects.  Over 120 people attended the eastern tour on Tuesday, and 50 people participated in the western tour Wednesday.  I, and Monique Rivera, took lots of great pictures, which I will post soon!

Grape phylloxera update

Grape phylloxera adults and eggs in foliar galls at RayLen Vineyard. Photo: HJB

Last Thursday I visited RayLen Vineyard to see the grape phylloxera (Daktulosphaira vitifoliae) infestation I posted about previously.  In person, the extent of the damage was even more impressive.  The Vidal Blanc vines were nearly completely infested.  This suggests that several generations have cycled through during this summer.  Vidal is a French-American hybrid grape.  Hybrids (ie. Traminette, Seyval Blanc, Chambourcin) are increasing in popularity among eastern grape growers because they are often more tolerant of our weather conditions that European varietals (ie. Merlot, Chardonnay, Cabernet Sauvignon).  However, it appears that some of these hybrids are more susceptible to foliar phylloxera.  Because they are grown on phylloxera tolerant rootstock, it is unlikely that phylloxera are also damaging roots.

Infested Vidal vines. Photo: HJB

Leaves at the base of the canes had no live phylloxera present.  I started to find live phylloxera about half way up the canes, and the youngest leaves had females and eggs in the galls as well as few crawlers.  

Mature grape phylloxera female and eggs (indicated by red arrow) and crawler (blue arrow) on a young grape leaf.  Photo: HJB

Donn Johnson, University of Arkansas small fruit entomologist, has posted several other images of eggs, crawlers and adults here.  The leaves with active infestations were near the end of canes and likely to be removed during hedging (which was planned for the next few days after my visit to RayLen), and because of this, I was reluctant to recommend a pesticide application.  Instead, I suggested removing as many infested leaves as possible during hedging/leaf removal and destroying them.  They could then follow this up with a pesticide treatment if crawlers or open galls (see below) were still present.  

Open galls on young leaves.  The insects in these galls are susceptible to contact insecticides.  Photo: HJB

It seems likely that phylloxera will continue to be a problem in French-American hybird grapes, which I am still a fan of for their many other good qualities.  The strategy at RayLen and other infested vineyards should include early season scouting for first generation phylloxera--likely to be a few galls near the base of cane in spring.  Once crawlers of this first generation appear, foliar treatments should be applied (some of the materials available for phylloxera management are listed in this University of Arkansas fact sheet). Regular scouting for subsequent generations should be conducted throughout the summer followed by treatment as they appear.  Severe phylloxera infestations weaken vines and leave them more susceptible to winter injury.

Phylloxera infested cane.  Photo: HJB

Watching the west: SWD organic trial results

Mark Bolda, University of California Cooperative Extension Farm Advisor in Santa Cruz County, has posted the results of a recent efficacy trial comparing organic management tools for SWD. According to this post, Pyganic and Entrust appeared to provide control of SWD in raspberries. Both of these materials are OMRI listed (organically acceptable).

More information
Results of Trial Testing the Efficacy of Several Organically Registered Pesticides for Control of Spotted Wing Drosophila in Raspberry

Hornworms in motion (not a pest alert!)

Those of us who work on and grow the crops they eat may think of tobacco hornworms (Manduca sexta) as pests to be controlled, but they are also import lab rats for all sorts of biological research. In fact, my undergraduate research studied hormone binding and transport in M. sexta in response to environmental stresses, so I have dealt with my fair share of hornworms in and out of the lab.

A recent study used hornworms as a model of locomotion and found that their gut and body move separately! See here for a nice summary and cool video!

ScienceShot: Caterpillar's Guts Crawl Independently of Their Bodies