Thrips and Pansy Spot in Apple

Thrips and Pansy Spot on Apple

At a recent orchard meeting, we discussed a symptom of thrips infestation on apple called pansy spot.  This injury looks like the petals of a blossom, light in color against the color of the apple skin (Fig. 1).  Thrips injury referred to as pitting was recognized in the 1950s (Swift and Madsen 1956); if the injury was no too severe, fruit outgrew the injury before harvest.  A paper a few years later reported a discoloration of apple skin referred to as pansy spot (Madsen and Jack 1966).  Pansy spot was determined to be caused by a reaction to the egg punctures made by thrips (the main culprit was western flower thrips (WFT), Frankliniella occidentalis).  Certain varieties were more sensitive than others, notably McIntosh and Spartan (the variety of concern at our orchard meeting was Pink Lady).  These thrips move from host to host as each comes into bloom – their host range is broad.  Thrips are present during bloom, when they lay eggs in flower parts. The resulting generation matures, and the resulting adults perform additional oviposition into the developing apples.  The apple tissue surrounding this cohort of punctures develop the pansy spot discoloration.  Other apple varieties experienced the thrips oviposition, but did not develop pansy spot.  Madsen and Jack (1966) determined that the best time to apply control measures was petal fall, when nymphs are present but have not produced the offending adults.  Later work on WFT in apple has shown that the highest egg injury is not necessarily associated with the highest thrips numbers (Terry 1991).  Often eggs are laid in sepals or other tissues where the injury does not become apparent.  Eggs are often laid on more mature clusters, and on king blooms rather than lateral buds.

A similar timing to Madsen and Jack (1966), but possibly a little earlier, was determined more recently in British Columbia (Cockfield et al. 2007), who found the greatest impact by a spray resulted from application from full bloom to about 5 mm fruit diameter.  Few eggs were laid in ovary tissue during bloom – eggs in this tissue (most likely to cause pansy spotting) increased starting about 8-13 days following full bloom.  Obviously bloom sprays can’t be used in order to protect pollinators; therefore the optimal spray timing would be from petal fall until 5 mm fruit diameter.

Sampling

Thrips can often be detected by examining the interior of floors, or rapping blooms on a sheet of paper to dislodge the tiny insects.  However, additional sampling methods have been developed.  Different color sticky panel traps were compared in British Columbia (Bradley and Mayer 1994).  Blue and white traps caught 4- and 3- times more thrips than yellow traps.  Several chemical attractants were added, but these did not provide enough added attraction to be worthwhile.  Beating trays still compared favorably for versatility and speed of data collection.

In Australia, sticky traps were found to be better than beating samples, and blue traps were also considered the best (Broughton and Harrison 2012).  Chemical attractants helped with some thrips species (including WFT) but not others.

Environmental effects and biological control

There is variable natural mortality of thrips.  There is a non-feeding pupal stage that occurs beneath the soil surface.  If there is significant rainfall at this time, many of these pupae drown, resulting in lower adult populations.

Various types of ground cover were compared in British Columbia apple orchards: Bare soil, grass and weedy ground covers were compared for their impact on WFT populations. Weedy ground cover increased WFT in trees during the first week of bloom, but this did not cause an increase in fruit injury. The F1 generation of WFT (the generation causing pansy spot) in cluster samples were lower in trees where green lacewing larvae were introduced at bloom. Still, these population differences were not associated with differences in fruit injury (Cossentine et al. 1999).  Nicholls et al. (2000) also found thrips populations were reduced by flowering ground covers, apparently by fostering natural enemies.  Anthocorids such as Orius are effective predators of thrips.

Chemical management of thrips

Thrips are prone to develop resistance to insecticides; it is therefore important to rotate among mode of action classes.  However, options are limited.  In our control recommendations (VCE 2018), the following materials are listed for thrips on stone fruits (we have not included thrips in the apple section until now; the peach materials are also available in apple): Assail (G), Delegate (E), Entrust (E), Lannate (G).  Another material, with an additional mode of action is Surround (kaolin).  This may be an effective tool against WFT; Larentzaki et al. (2008), reported that kaolin increased mortality, decreased oviposition, and decreased hatch of eggs in onion thrips, Thrips tabaci.

At our orchard meeting, we discussed the potential impact of the plant growth regulator Apogee (prohexadione-calcium).  While there is little information on the efficacy of this use, there has been some promising research on effect of Apogee on other insects.  Paulson et al. (2005) examined the role against pear psylla (PP), spirea aphid (SA) and obliquebanded leafroller (OBLR).  PP populations were reduced in pear, as well as SA and OBLR in apple.  Not only was there direct mortality, but there was a synergistic effect against PP and SA when imidacloprid was added.  Tsagkarakis et al. (2012) reported that Apogee reduced egg production and survival of Asiatic citrus psyllid.  There should be research to further investigate the role of Apogee since not all studies have been consistent – for example, no effect was reported for potato psyllid (Prager et al. 2013).

References

Bradley, S. J., and D. F. Mayer. 1994. Evaluation of monitoring methods for western flower thrips, Frankliniella occidentalis (Thysanoptera: Thripidae), during the blossom period of 'Granny Smith' apples. J. Entomol. Soc. Brit. Colum. 91.

Broughton, S., and J. Harrison. 2012. Evaluation of monitoring methods for thrips and the effect of trap colour and semiochemicals on sticky trap capture of thrips (Thysanoptera) and beneficial insects (Syrphidae, Hemerobiidae) in deciduous fruit trees in Western Australia. Crop Protect. 42: 156-163.

Cockfield, D., E. H. Beers, D. R. Horton, and E. Miliczky. 2007. Timing of oviposition by western flower thrips (Thysanoptera: Thripidae) in apple fruit. J. Entomol. Soc. Brit. Colum. 104: 45-53.

Cossentine, J. E., E. J. Hogue, and L. B. M. Jensen. 1999. The influence of orchard ground cover and introduced green lacewings on spring populations of western flower thrips in apple orchards. J. Entomol. Soc. Brit. Colum. 96.

Larentzaki, E., A. M. Shelton, and J. Plate. 2008. Effect of kaolin particle film on Thrips tabaci (Thysanoptera: Thripidae), oviposition, feeding and development on onions: A lab and field case study. Crop Protect. 27: 727-734.

Madsen, H. F., and I. D. Jack. 1966 The relation of thrips to pansy spot on apples. Can. Entomol. 98: 903-908.

Nicholls, C. I., M. P. Parrella, and M. A. Altieri. 2000. Reducing the abundance of leafhoppers and thrips in a northern California organic vineyard through maintenance of full season floral diversity with summer cover crops. Agric. Forest Entomol. 2: 107 - 113.

Paulson, G. S., L. A. Hull, and D. J. Biddinger. 2005. Effect of a plant growth regulator prohexadione-calcium on insect pests of apple and pear. J. Econ. Entomol. 98: 423-431.

Prager, S. M., O. M. Lewis, K. Vaughn, and N. Nansen. 2013. Oviposition and feeding by Bactericera cockerelli (Homoptera: Psyllidae) in response to a solar protectant applied to potato plants. Crop Protect. 45: 57-62.

Swift, J. E., and H. F. Madsen. 1956. Thrips damage to apple. J. Econ. Entomol. 49: 398-399.

Terry, L. I. 1991. Frankliniella occidentalis (Thysanoptera: Thripidae) oviposition in apple buds: Role of bloom state, blossom phenology, and population density. Environ. Entomol. 20: 1568-1576.

Tsagkarakis, A. E., M. E. Rogers, and T. M. Spann. 2012. Applications of plant growth regulators to container-grown citrus trees affect the biology and behavior of the Asian citrus psyllid. J. Am. Soc. Hortic. Sci. 137: 3-10.

VCE.  2018.  2018 Spray Bulletin for Commercial Tree Fruit Growers. Va. Coop. Ext. Serv. Publ. 456-419.  

Insects today: grape tumid gall and eightspotted forester

Hello everyone,

Today I came upon an adult eight-spotted forester, shown here:

Larvae will feed on grape foliage, but are seldom in high enough numbers to warrant treatment.  But the larvae are conspicuous (and rather pretty!) and may get your attention.  See the following link for more information:

http://www.virginiafruit.ento.vt.edu/8spot.html

Today I received a question on the use of Movento for grape tumid gall.  GTG is a cecidomyiid, a tiny fly resembling a mosquito in the adult stage (but non-biting!).  Ovipositing females insert eggs into a range of grape tissues, which give rise to reddish galls on petioles, shoots, rachis, etc.  Normally numbers are low, but some varieties are sensitive, and control may be be needed.  There is no specific monitoring method for GTG adults - if needed (on sensitive varieties with a history of infestation), apply when first galls appear.  More information can be found in the linked page:

http://www.virginiafruit.ento.vt.edu/grapegalls.html

 More later,
Doug

First hatch of spotted lanternfly eggs

Hello everyone,

This week (Wednesday, May 9) we had the first egg hatch of spotted lanternfly in Winchester (the only site with confirmed presence of SLF).  On Tuesday we examined eggs on trees in the infested area, with no sign of hatch.  When the same trees were examined on Wednesday early in the day, young first instars (still pale in color) were seen clustered on an egg mass (photographed by Eric Day of the Dept. of Entomology).  Later in the day, Mark Sutphin (VCE - Frederick County) photographed darkened nymphs with white spotson the same trees - so we are recording May 9 and the first egg hatch.

If you find nymphs like this (black with white spots), please report it using our reporting web site (https://ask.extension.org/groups/1981/ask).  We need to know of any infestations outside of the known area in the north part of Winchester.

More later!

Doug

color were seen clustered on an egg mass (photographed by Eric Day of the Dept. of Entomology).  Later in the day, Mark Sutphin Winchester) photographed darkened nymphs on the same trees - so we are recording May 9 and the first egg hatch.

Bud swell in grapes: Grape flea beetle and climbing cutworms

Hello, everyone,
At yesterday's vineyard IPM workshop n Madison County, vines were at bud swell.  This is a key time for a couple of pests.

Grape flea beetle adults feed on primary buds at this time.  This is mainly a problem in parts of blocks near wooded edges - but in such rows I have seen 40% of the primary buds destroyed.  This is a metallic blue-green beetle that is almost 5 mm long. Adults overwinter in debris in and near the vineyard. They become active early in the spring and lay eggs in cracks in the bark, at bases of buds, between bud scales, and on leaves. Eggs are light yellow and are laid in masses; they hatch in a few days and larvae feed on grape leaves for 3-4 weeks. Larvae are brown with black spots, and reach a length of 10 mm. Larval feeding damage consists of characteristic chain-like feeding marks on leaves, although occasionally this injury may appear more extensive. However, the damage by adult grape flea beetles is more important. The beetles eat holes into the sides of buds and gouge out the contents as the buds swell. Such injury occurs most prominently on thick-leaved grapes which have large buds, such as the American cultivars `Concord' and `Niagara'. It should be noted that climbing cutworms can cause similar damage. However, damage by the latter pest complex is usually more ragged in appearance. Adults also feed on the unfolding leaves.  For more information, visit http://www.virginiafruit.ento.vt.edu/GFB.html.

Climbing cutworms also attack primary buds, but injury can be more generally distributed throughout the block. 
The biology of the various climbing cutworms varies considerably but the peak flight periods and generations for some of the common species are listed above. The most common species have one or two generations per year and overwinter as half-grown larvae on the soil in leaf litter and orchard debris. A few other species overwinter as eggs or even as adults. The species which overwinter as larvae begin to become active as the weather warms, generally in mid-April. This group of moths derives its name from the larval habit of climbing trees to feed on buds and young foliage during the night, and then crawling back down to the ground to seek shelter under leaf litter, killed grass, or debris on the vineyard floor during the day. The larvae often curl up tightly when disturbed. Hundreds of larvae may feed on a single tree. The larvae mature by May and enter the soil to construct pupal chambers. In two-generation species, second generation feeding is minor. 
Most injury from climbing cutworms occurs in the spring when they feed on primary buds or young shoots. In severe cases, all buds may be killed, so that growth is delayed considerably compared to uninjured cordons.  While growth will likely resume later from secondary or tertiary buds, yield from such shoots is reduced, and harvest maturity is erratic, especially when considering bunches produced on other, uninjured vines.  For more information, visit http://www.virginiafruit.ento.vt.edu/cutwormsgrape.html.

More later,
Doug

Vineyard Pest Management Workshop.

There will be a vineyard IPM workshop held on April 17 at Early Mountain Vineyard, 6109 Wolftown-Hood Rd, Madison, VA 22727.  Specialists will discuss weed science, plant pathology and entomology, including updates on invasive pests.

Agenda:

11:00 am Welcome and vineyard management reminders- Tremain Hatch

11:30 Weeds and vineyard floor management – Jeff Derr

12:30 Lunch bring a bagged lunch

1:00 Worker Protection standards update – Micah Raub VDACS

1:45 Insect management for the vineyard – Doug Pfeiffer

2:30 Pathogen management in the Vineyard – Mizuho Nita

3:15 Grape IPM tool and scheduling exercise –Mizuho Nita

4:00 clean up and adjourn

Pear psylla management

Hello, everyone,

At this week's orchard meeting in Albemarle County, there was quite a bit of discussion on pear psylla.  With recent increases in pear acreage in the state, there is more interest in pear psylla, a key pest of pear throughout North America (originally introduced from Europe, along with pear - there are no native American pear species).  I am inserting below the pear psylla material from the Virginia Fruit web site - watch for updates as we adjust our management recommendations.  A key point to note now is the appearance of the eggs. Eggs are laid in spring by the overwintered adults, especially in the crevices at the base of fruit spurs.  These are light in color at first, later turning a light orange color.

Pear Psylla, Cacopsylla pyricola (Foerster)

I. Introduction: Pear psylla (PP) is the most important insect pest of pear in all pear-growing regions (Asian pear species are less susceptible). It is responsible in large part (along with fire blight) for the decline of cultivation of pear in the eastern states. It is the only one of several European pear psyllids to have been introduced into North America. It was first introduced into Connecticut around 1832, and reached Virginia (Charlottesville) by 1894. II. Hosts: PP develops only on pear.


III. Description: Summer form: The length of adults to the tip of folded wings is about 8/100 - 11/100 inch (2.0-2.75 mm). The color is light orange to red brown, with darker markings (four stripes along the back). The legs and antennae are mostly light brown to orange. Wings are clear with a conspicuous black spot on the hind edge (at the midline when at rest). Winter form: The length of adults to the tip of folded wings is 13/100 - 16/100 inch (3.3-4 mm). The body color is now very dark red-brown to black (Plate 87). The wing veins are very dark and conspicuous, and the wing spot is now more pronounced. In both forms, the head is a little over half as long as wide. The antennae are 1 1/2 times as long as width of head.
Eggs are pale cream to yellow-orange. They are elliptical in shape, with a tiny peg inserted into plant tissue. Nymphs are pale yellow when young, but have brown sclerotized plates when older. They resemble flat aphids in shape.




IV. Biology: Adults overwinter in or near pear orchards. Few adults are mated before overwintering. In early spring adults return to the trees, mate and begin ovipositing in crevices on fruit spurs and on young leaves as they unfold. There are three generations during the spring and summer. In the fall, when daylength falls below 13.5 hours, an overwintering form is produced which is darker than the summer adult. There is some degree of reduced fecundity in crosses between these forms.
Females lay an average of more than 300 eggs during their life. Most oviposition by summer adults occurs near leaf midveins; egg survival is also highest near midveins. As nymphs develop, they become engulfed in a droplet of accumulating honeydew. Such droplets may contain the shed skins of the preceding instars.
Recent research at USDA indicates that a transgenic pear line (developed for resistance to fire blight) may be less suitable as a host for pear psylla.


V. Injury: Although it is classed here as an indirect pest because it feeds on leaves, the main source of economic injury is to the fruit. Honeydew supports growth of sooty mold and causes a black russet on fruit; necrotic areas on foliage may also develop. PP serves as the vector for the mycoplasma-like organism causing pear decline when European scions are grown on Asian rootstocks. The latter problem is avoided by choice of rootstock/scion combination. Sooty mold and leaf injury may reduce photosynthesis and return bloom.




VI. Monitoring: PP may be monitored in several ways. In the spring, examine growth scars on spurs and twigs for the appearance of the first eggs. This method is used to time the delayed dormant application. Adults may be monitored by a beating tray method or with yellow sticky traps. A beating tray size of 18x18 inches (45x45 cm) was used in Connecticut; the tray is held beneath a limb and the limb is jarred three times in succession, sampling four limbs on each of 10 trees per block. Adults are counted on the surface of the tray.
Action should be taken when the first eggs laid in the spring appear. Research in Washington State has found that a peak density of 0.3 nymphs/leaf causes detectable fruit injury on both `Anjou' and `Bartlett'. Populations causing 9 and 18 nymph-days per leaf caused injury on the two varieties, respectively, with no significant effect of period during the season. Averages of 1.0-1.2 adults per beating tray or 4.4-6.9 adults per sticky trap were recommended as action thresholds by Connecticut researchers.


VII. Control: Dormant oil may be applied when eggs begin to appear in spring (see photo above). Various insectides are registered for post bloom control. Horticultural spray oil may be applied.  This is more highly refined than dormant oil and should not be confused.  Also, a lower rate is used, 1 qt/100 gal, rather than the 2 gal / 100 gal recommended in dormant sprays.  Horticultural spray oil is recommended to be included with avermectin sprays.

Katydid eggs found during winter pruning

Hello, everyone,

Over the last few weeks, I have received images of eggs laid on grapevines, in an overlapping scale-like fashion (usually in two rows).  These are likely seen as pruning progresses.  These are katydid eggs (photo attached).  Many katydids feed on plant tissue, while some are predatory.  Even for phytophagous species, numbers are rarely high enough to cause an economic concern.  Katydids are leaf mimics and less often seen than heard.  Their chorusing is a pleasant addition to a summer night! https://www.youtube.com/watch?v=TjM9tZE_bDg

More later!
Doug