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NUMBER 1220 February 9, 2010


CORN

EPA Cancels Fipronil Use in Corn
By Ric Bessin

The EPA last week announced the cancellation of all uses of fipronil as an in-furrow insecticide for corn. This impacts all formulations including Regent 4SC, Regent 80 WG, and Regent 1.5G. In Kentucky, this insecticide has been used to manage a number of soil insects in corn.
Persons other than the registrant (Bayer) may continue to sell or distribute existing stocks of fipronil products with previously approved labeling until such stocks are exhausted. Growers may use existing stocks of fipronil products until existing stocks are exhausted. Any use of existing stocks must be in a manner consistent with the previously approved labeling for that product.

Federal Register Volume 75, Number 22, Pages 5584-5585, February 3, 2010.

FRUIT CROPS

Managing Strawberry Pests
Bessin
   
  Figure 1. Spittelbug nymphs.   Figure 2. A tarnished plant bug
       

Strawberries can be a high revenue crop for growers in Kentucky, but need to manage several strawberry pests including meadow spittlebug, tarnished plant bug, and sap beetles. While each of these can affect yields in different ways, they may also drive away business at u-pick farms. Management of these pests needs to begin early, before the damage starts to appear.

The meadow spittlebug is an annoying pest on strawberries that can stunt plants and reduce berry size, but more importantly, particularly u-pick growers, is the annoyance that spittle masses cause pickers. While harmless, people are annoyed by the spittle. Spittlebugs are recognized by the white masses spittle on leaf petioles and stems. The tiny green nymphs produce the spittle covering to protect themselves from predators and desiccation. Nymphs feed for five to eight weeks during mid spring before entering the adult stage. It is this nymphal stage that needs to be managed. Adults are seen on foliage usually go unnoticed because they produce no spittle. High spittlebug numbers are often associated with weedy fields, so proper weed control along with other practices encouraging healthy plants are important.

 
Figure 3. The picnic beetle is one of several sap beetle species.  
   

Prebloom sprays are rarely needed for spittlebugs, but u-pick growers should keep levels below one spittle mass per square foot through prebloom to appease customers. Begin estimating spittlebug at 10% bloom by inspecting five to ten 1-square-foot areas per acre at two week intervals. Spread plants and inspect the crowns as well as leaves and stems. Control is considered at one spittlebug per square foot. If sprays are needed, care should be taken to avoid damaging insect pollinators during bloom.

Tarnished plant bug is a common sap-feeding insect attacking a wide range of economically important plants. It can cause considerable damage by damaging young berries before receptacles expand. These damaged areas do not develop along with the rest of the berry, resulting in misshapen "catfaced" fruit. Tarnished plant bug has a greenish-brown body marked with yellowish and black dashes with a characteristic small yellow-tipped triangle behind the head. The nymphs are smaller, slender, and pale green insects. Adults become active in April and begin egg laying in weeds.

Most damage takes place just after petal fall. Early June bearing varieties can escape most tarnished plant bug injury because pest populations are small and consist of less damaging early instars. Late maturing cultivars are more susceptible to damage. Plantings near alfalfa fields, woods, or weedy areas may be more prone to damage. Alternative hosts, especially weeds and seed-producing plants should be eliminated around the planting early in the season. Regular mowing or weeding may help, but should be avoided just before or during the blossom period. From pre blossom until harvest, shake blossoms or fruit clusters from ten to fifteen plants per acre over light colored pan. Treatment is suggested when levels reach an average of 0.5 nymphs per cluster.

Sap beetles are attracted to odors of fermenting plant sap and can be serious pests of strawberries. Damage may appear as small holes in the bottom of the berry, or as large sections devoured from the side. Beetles may spread rot-causing disease organisms from berry to berry. Sap beetle species range from black to brown, but flattened and broadly oval with short wing covers.

The best management practice for sap beetles is sanitation. Keep fields as clean of ripe fruit as possible through timely removal of damaged, diseased, and overripe fruits. Problems often first occur after a rainy period during harvest, when there may be a buildup of overripe fruit. Sprays for sap beetles are available but difficult to use because they are applied to a crop that is ready for harvest. Therefore, selecting an insecticide with a short harvest interval is essential. Sprays should be applied only if absolutely necessary. Label directions should be read and followed carefully.

Apples Vary in Resistance to Cedar Rust Diseases
By John Hartman

       
   
  Figure 4. Cedar apple rust telial horns during a wet period in springtime (P. Bachi photo).   Figure 5. Cedar quince rust with telia forming on cedar twig in April.
       
   
  Figure 6. Cedar apple rust lesions on upper and lower surface of apple leaves (Clemson U. photo).   Figure 7. Aecia (tubular structures) in cedar apple rust lesions on apple fruit surface (C. Kaiser photo).
       

In Kentucky apple orchards where early spring fungicide applications were missed or not used in 2009, cedar apple rust and cedar quince rust caused significant loss. Cedar apple rust and cedar quince rust are caused by the fungi Gymnosporangium juniperi-virginianae and G. clavipes. This time of year, these two fungi overwinter in galls or twig swellings on infected eastern red cedar (Juniperus virginiana) trees. In spring, the galls or swellings produce bright orange gelatinous material called telia (Figures 4 & 5) which produce spores that infect nearby apple leaves or blooms.

On apple leaves, cedar apple rust causes bright yellow-orange spots (Figure 6) with the underside of the spots appearing as yellow-brown lesions having small dark tubular structures (aecia). The aecia break apart to release red-brown spores. Similar aecia form on the surface of infected fruit (Figure 7). Cedar quince rust does not infect leaves, but causes significant fruit damage. Often times a large green lesion appears on the calyx end of the infected fruit causing puckering and distortion of the fruit (Figure 8). The brown spongy lesion is not superficial, but extends to the core (Figure 9), making infected fruit unsalable.

A recent article in the journal Plant Health Progress (Biggs, et al., October 2009, “Relative Susceptibility of Selected Apple Cultivars to Cedar Apple Rust and Quince Rust”) provides data on the reactions of dozens of apple cultivars to these two rust diseases. As part of a northeast regional research project going on for over a decade, apples were evaluated simultaneously over the years in New York, Connecticut, West Virginia, Virginia, and North Carolina. University of Kentucky Extension personnel can access the details of this and other plant-related research from the Plant Management Network through U.K.’s on-line subscription sponsored by the U.K. Plant Pathology Department.

A recent article in the journal Plant Health Progress (Biggs, et al., October 2009, “Relative Susceptibility of Selected Apple Cultivars to Cedar Apple Rust and Quince Rust”) provides data on the reactions of dozens of apple cultivars to these two rust diseases. As part of a northeast regional research project going on for over a decade, apples were evaluated simultaneously over the years in New York, Connecticut, West Virginia, Virginia, and North Carolina. University of Kentucky Extension personnel can access the details of this and other plant-related research from the Plant Management Network through U.K.’s on-line subscription sponsored by the U.K. Plant Pathology Department.

   
 
Figure 8. Quince rust-infected apple fruit with distorted puckering at the calyx end.
   
 
  Figure 9. Brown spongy discoloration inside cedar quince rust-infected apple (APS photo).
   
 
  Figure 10. Apple flower in spring.

Results of the cedar apple rust evaluations found in this report can be summarized as follows:

  • Apple cultivars with generally highest resistance to leaf infection by cedar apple rust included Enterprise, Gala Supreme, Golden Supreme, NY 65707-19, NY 75414-1, NY 79507-49, NY 79507-72, Sundance, and Zestar.
  • The most susceptible apple cultivars included Braeburn, Cameo, Chinook, Creston, Crimson Crisp, Gold Rush, Princess, Scarlet O’Hara, and Shizuka.
  • Other susceptible cultivars included Ambrosia, Arlet, BC 8S-26-50, CQR10T17, Cripps Pink, Delblush, Fortune, Fuji Red Sport, Ginger Gold, Golden Delicious, Hampshire, Honeycrisp, NJ 90, NJ 109, Orin, Pinova, Pioneer Mac, Pristine, Rogers McIntosh, Runkel, Sansa, Senshu, September Wonder, Suncrisp, Sunrise, and Yataka
  • On the fruit, incidence of cedar apple rust did not vary among cultivars; thus incidence of cedar apple rust on leaves was not correlated with incidence on fruit.
  • It is possible that there are different races of the cedar apple rust fungus at different locations so that results could vary from one location to another.
    Cedar quince rust evaluations can be summarized as follows:
  • Disease incidence on very susceptible cultivars in some locations in some years reached 50% or more.
  • Highly susceptible cultivars at one location or another included Cameo, Crimson Crisp, Fortune, Golden Supreme, NJ 109, Shizuka, and Suncrisp.
  • The cultivars Runkel and Sundance were ranked lowest for quince rust.
  • Resistance to cedar apple rust and cedar quince rust are not related.
  • Results from one location to another and year to year were quite variable possibly because the phenological window for quince rust infection is fairly narrow. Maximum susceptibility occurs during bloom (Figure 10) so that later- or earlier- blooming cultivars could escape infections during rain events that occurred while others are in bloom.

Where cedar rusts are a threat, Kentucky growers attempting to grow apples as certified organic will want to select scab-resistant cultivars that are also resistant to cedar rusts. Cultivars resistant to apple scab such as Enterprise, NY 65707-19, NY 75414- 1, NY 79507-49, NY 79507-72, and Sundance were among those most resistant to cedar apple rust. Sundance was also the least susceptible to quince rust. By contrast, scab-resistant CQR10T17, Crimson Crisp, GoldRush, Princess, Pristine, and Scarlet O’Hara, were highly susceptible to cedar apple rust and would require early season fungicide applications for rust management in spite of their resistance to scab.

Information and recommendations in Kentucky Pest News are have been written for audiences in Kentucky. Readers outside of Kentucky should be aware that situations and regulations in Kentucky may differ from those in their particular location, and should consult their local Cooperative Extension Service for guidance.

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