July 19, 2004 Volume 13 No. 18 Update on Pest Management and Crop Development
* = 1st catch
Geneva: Spotted Tentiform Leafminer 2nd flight began 6/17. The first
Highland: Degree days accumulated since the biofix
for Codling Moth
Spotted Tentiform Leafminer
Spotted Tentiform Leafminer
White Apple Leafhopper
Oriental Fruit Moth. This pest's development is tracked using a 45F DD model from biofix, defined as the first sustained moth catch. We are currently into the second brood, which started about June 30 in WNY. Pesticides to control this brood should be applied starting at 175-200 DD after this date, and continued on a 10-14-day interval if trap numbers exceed 10 moths/trap/week. Our sample numbers as of today:
Codling Moth. We are currently between the first and second brood control windows for this pest. With 1260 DD (base 50F) from the 1st catch of the season as a first spray date for the second brood, we currently have:
Obliquebanded Leafroller. 810 DD (base 43F) from the 1st catch corresponds with 90% hatch, and 950 DD is predicted to represent the 100% hatch point. Sites on a Spintor program should be approaching their 2nd application against the first summer brood. Our sample numbers so far:
A few orchards we have seen are in trouble from European red mites so far, but also keep in mind the potential for two-spotted mite, which can reach alarming levels in a hurry. Inspect your leaves using the 5 mite/leaf form on p. 70 of the Recommends, and be aware that two-spot populations increase more quickly than ERM, so be conservative in your interpretations. Acramite tends to be the most effective material against TSSM and Pyramite works better against red mites than it does on TSSM, but the main advice is to get out there and look at your foliage.
This perennial pest overwinters as a partially grown grub in the soil below the frost line. In the spring the grub resumes feeding, primarily on the roots of grasses, and then pupates near the soil surface. Adults begin to emerge during the first week of July in upstate N.Y., and if you have looked at any roses lately, you know that they are right on schedule this year. The adults fly to any of 300 species of trees and shrubs to feed; upon emergence, they usually feed on the foliage and flowers of low-growing plants such as roses, grapes, and shrubs, and later on tree foliage. On tree leaves, beetles devour the tissue between the veins, leaving a lacelike skeleton. Severely injured leaves turn brown and often drop. Adults are most active during the warmest parts of the day and prefer to feed on plants that are fully exposed to the sun.
Although damage to peaches is most commonly noted in our area, the fruits of apple, cherry, peach and plum trees may also be attacked. Fruits that mature before the beetles are abundant, such as cherries, may escape injury. Ripening or diseased fruit is particularly attractive to the beetles. Pheromone traps are available and can be hung in the orchard in early July to detect the beetles' presence; these products are generally not effective at trapping out the beetles. Fruit and foliage may be protected from damage by spraying an insecticide such as Sevin, or Provado (now labeled in peaches) when the first beetles appear.
(Information adapted from: Johnson, W.T. & H.H. Lyon. 1988. Insects that feed on trees and shrubs. Cornell Univ. Press.; and Howitt, A.H. 1993. Common tree fruit pests. Mich. State. Univ. Ext. NCR 63.)
Catches have not been terribly high yet, but they are beginning to show up in our statewide research blocks and in abandoned sites where the first emerging adults are often monitored. If you aren't monitoring in specific orchards and haven't yet applied a protective spray against AM (and aren't using Spintor for OBLR), prudence would suggest a bit of attention to this insect. Hanging a few volatile-baited sphere traps on the edge of susceptible plantings can provide a world of insight on when (and whether) immigrating flies are posing a threat. Growers on a Spintor program should be somewhere between the first and second spray of this material for leafrollers, which will provide protection against moderate AM pressure.
Western Flower Thrips
This formerly rare pest has been known recently to cause damage to nectarines and peaches in the Hudson Valley. Originally limited to western North America, this is now a cosmopolitan species that is a key pest in the greenhouse production of flowers and vegetables. Apparently, drought conditions and high temperatures encourage damaging populations that can affect stone fruit crops, particularly nectarines and peaches -- not exactly a description of our summer thus far, but who knows whether hotter weather might be just around the corner? The following information is taken from the PA Tree Fruit Production Guide: "...just prior to and during harvest,...adults move from alternate weed or crop hosts to fruit. [They] feed on the fruit surface in protected sites, such as in the stem end, the suture, under leaves and branches, and between fruit. Feeding ...results in silver stipling or patches. Silvering injury is particularly obvious on highly colored varieties. Because Lannate has a short preharvest interval (4 days), it can be used to control thrips during harvest." Also, SpinTor can be used within 14 days of harvest. An application after the first harvest may prevent subsequent losses; however, an additional application may be needed if thrips pressure is severe.
NECTRIA TWIG BLIGHT
Nectria twig blight is caused by the fungus Nectria cinnabarina. Symptoms of this disease appear in orchards during June and are easily confused with the shoot blight phase of fire blight. With both diseases, scattered terminal shoots wilt and produce a typical shepherd's crook at the end of the affected shoot. Fire blight infection is a serious problem, whereas the Nectria twig blight rarely causes economic damage.
The best way to differentiate the two diseases is to check for two characteristics that are unique to Nectria twig blight. Nectria infections are usually initiated through apple fruit stems that were left in the tree during the previous year's harvest. As a result, one can usually find a dried up "pulled stem" near the base of twigs that are dying from Nectria twig blight (Fig. 1). In some cases, the pulled stem that allowed entry of the fungus may break off during winter or spring, so pulled stems are not always evident on infected twigs, but they are usually present. The second diagnostic for Nectria twig blight is the presence of orange pustules at the node to which the pulled stem is attached (Fig. 2). The orange pustules (sporodochia) usually become evident by mid-July, especially on Rome Beauty trees, and produce conidia that are disseminated in autumn. On cultivars other than Rome Beauty, orange pustules may not appear until later in the season, or sometimes they may not appear at all.
Unlike fire blight infections, Nectria infections rarely extend more than one or two inches back into the tree beyond the infected node. However, girdling at the node causes the distal ends of infected twigs to collapse. Later in the season, the orange sporodochia may also appear on the twig beyond the node, but usually the pustules are most evident right next to the pulled stem. Nectria twig canker is most common on terminal-bearing cultivars such as Rome Beauty, but it also occurs occasionally on other varieties such as Fuji and Empire.
Why is there so much Nectria twig blight this year? Infections are more common following years that have a combination of relatively wet harvest seasons followed by at least one rapid temperature drop in late fall or early winter. Rains are needed to disseminate spores to the pulled stems after harvest, and a bit of winter injury during fall or early winter seems to enhance the ability of the fungus to move from the pulled stems into the node to which the stem is attached. Both of these infection criteria were met last year.
Fungicide sprays are not effective for controlling Nectria twig blight. Dead twigs can be removed during summer pruning or during dormant pruning the following winter. Leaving infected twigs in the tree during summer and fall does not have any significant effect on spread of this disease because the disease is more limited by fall/winter weather conditions than by presence of inoculum. N. cinnabarina colonizes many species of trees and shrubs, so inoculum is available from many sources other than apple trees.
Nectria cinnabarina occasionally causes cankers in older wood, especially on Empire trees (Fig. 3). However, the twig blight phase does not necessarily lead to development of cankers in older wood. Cankers are likely to develop only in trees that have suffered from repeated winter damage or other stresses that have compromised the natural resistance in the older wood.
REMINDER: CORNELL CENTENNIAL FRUIT FIELD DAYS AT GENEVA
Cornell University will host the Centennial Fruit Field Days and Equipment Show at the New York State Agricultural Experiment Station in Geneva, NY on July 27 and 28 from 8:00 am-4:00 pm. Fruit growers, consultants, and industry personnel are invited to tour field plots and learn about the latest research and extension efforts being carried out by researchers on the Geneva and Ithaca campuses. The focus will be on all commodities key to New York's $300 million fruit industry: apples, grapes, raspberries, strawberries, peaches, pears, cherries, and nectarines.
The event will be held on the Station's Fruit and Vegetable Research Farm South, 1097 County Road No. 4, 1 mile west of Pre-Emption Rd. in Geneva, NY. Signs will be posted. Attendees will be able to select from tours of apples, stone fruits, small fruits, and grapes. Admission is free and lunch is provided, courtesy of industry sponsors. Pre-registration is encouraged.For sponsorship and exhibitor information, contact Alison DeMarree at 315-589-9698 or Emailto: AMD15@cornell.edu. More information will be posted as it becomes available. To pre-register, contact Nancy Long at 315-787-2288 or Emailto: NPL1@cornell.edu. More information about this event and a complete agenda for both days is available at: http://www.nysaes.cornell.edu/pubs/press/2004/040622FruitFieldDays.html