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(Art Agnello ama4@nysaes.cornell.edu, Entomology, Geneva)

Obliquebanded Leafroller

We have yet to catch the first obliquebanded leafroller adult in western N.Y., but it won't be too much longer before the first moths start showing up, considering this spring's warm trend. Depending on the location, larvae can be found now in many stages of development, from the very tiny to the pupal stage in some of the more advanced sites. This would therefore be an advisable time to hang a wing-type pheromone trap in problem apple blocks, to fix the date of first emergence in your specific area. Recall that we recommend sampling at 600 DD (base 43°F) after the first adult catch, to determine the need and timing for treatment. It pays to keep an eye on the daily highs and lows for your area if you are doing your own trapping, as it's likely that our "normal" first sampling date of July 5 will turn out to be too late again this year.

WING TRAP

Larvae of the first OBLR summer brood cause two kinds of damage -- foliar feeding injury and rolling of the leaves, and more importantly, injury caused by feeding on the surface of the developing fruits. This fruit damage is usually more serious than the spring feeding by overwintered larvae, because more of the fruit injured late in the season remains on the tree at harvest. Despite the rather extreme measures some growers wage in the spring against the early generation larvae, you should remember that even an excellent control program against the overwintered brood does not eliminate the possibility of a problem summer population.

Late season fruit feeding injury caused by second brood obliquebanded leafroller larvae

To maximize the effectiveness of any sprays against the first summer generation OBLR infestation, you should sample leaf and fruit clusters at the proper time. The value of knowing the precise date of first adult flight on your own farm cannot be emphasized too strongly, and maintaining a few pheromone traps is not terribly difficult or time consuming. Check traps two or three times a week until the first adult is caught. Wait for 600 degree-days (43°F base) after this date to begin sampling for 2nd- or 3rd-instar larvae. Degree-day (DD) values can be obtained for some locations from NEWA (Northeast Weather Association) or from Cooperative Extension service letters. Alternatively, you can estimate them each day by using the following formula:

Degree Days for 1 Day = 1/2 x [Daily Maximum Temp. + Daily Minimum Temp.] — 43.

Guidelines for sampling can be found on pp. 48 and 53 of the Recommends. Sample from random trees that are representative of the entire block, examining 10 expanding leaf terminals per tree. It is not necessary to pick the terminals. Record the number of samples infested with live larvae; do not count actual numbers of larvae in an infested terminal, and do not count damaged terminals that have no OBLR in them, or those containing only dead OBLR. To minimize bias, choose half of your samples from inside the tree canopy, including some watersprouts, and the other half from near the outside of the canopy. If the tree is more than 10 ft tall, try to include some clusters from the mid- to upper canopy area. Use the 3% infestation threshold for fresh fruit, and 10% for processing fruit. A "Stop Sampling and Treat" decision means that a spray to control OBLR is recommended at this time. A "Stop Sampling, Don't Treat" decision indicates that you should return in 3—5 days, after 100 more degree-days have accumulated, and repeat the sample. Recommended materials include SpinTor, a B.t. product (such as Dipel, Biobit, Javelin, Agree, etc.), Lorsban, Lannate, or possibly Asana, depending on the population pressure, field history, and resistance/tolerance particulars of your orchards.

Because of the difficulty of adequately controlling problem OBLR in N.Y., the preferred spray strategy in blocks with a history of heavy populations is to forgo the sampling and make 2—3 applications based on DD accumulation (base 43°F) after the first sustained moth catch. The recommended application timings are 300 DD (usually about 7—10 days after first catch), with additional sprays at 10—14-day intervals thereafter.

Summer Oil for European Red Mite

In situations where European red mite pressure or the crop's sensitivity to them haven't necessarily justified an early season treatment with Agri-Mek, Apollo or Savey, this is the time of year when a summer oil program might be considered as an alternative preventive approach. Field research trials conducted in commercial and experimental apple orchards in western N.Y. have shown the effectiveness of using a highly refined oil in a seasonal program to control mites throughout the summer. Some examples of these products are Sunspray Ultra Fine Spray Oil (Sun Refining & Marketing, Philadelphia), Stylet-Oil (JMS Flower Farms, Vero Beach, FL), and Omni Supreme (an ExxonMobil product formulated using Orchex 796 and distributed in our area by Helena); others are labeled and may be available, although we haven't tested all brands.

Our approach is to make three applications, on a preventive schedule, immediately after the bloom period, before mite populations have a chance to build. The first application can be any time from petal fall to 1—2 weeks later, followed by two additional sprays at 10—14-day intervals. The oil is not concentrated in the tank, but rather mixed on the basis of a rate per 100 gallons of finish spray solution; for instance, at the 1-gal. rate, a spray tank holding 500 gallons receives 5 gallons of oil. The sprays are applied at a volume sufficient to obtain adequate coverage of the canopies; in most cases, we recommend 100 gal. per acre. Dosages that we have tested are 6.5 oz., 1 qt., and 1, 2, and 3 gal./100 gal. of finish spray solution. Results of our tests can be summarized as follows: the 2 and 3 gal. rates effectively controlled mite populations for the entire season in all but the most extreme cases; the 1 gal. rate maintained control of moderate populations but was not effective against severe mite pressure (a fourth spray was necessary later in the summer); and the lower rates provided only minimal control (light population pressure), permitting unacceptable mite numbers by mid-July in orchards with moderate or severe populations.

Overall, the results of this work demonstrated that summer oil applications can be used to effectively control European red mite populations in many orchard situations. So far, mites have not demonstrated an ability to develop a resistance to oil, and oil is less toxic to at least some beneficial species than are traditional toxicants. Although it is possible to kill some predator mites by directly spraying them, overall mortality is not very high. Some potential drawbacks to keep in mind if using this management strategy:

• potential compatibility problems with some fungicides needed to control summer diseases, particularly captan.

• small necrotic leaf lesions in some situations such as drought stress or on certain varieties, especially when high-rate (2% or more) applications take place under poor drying conditions.

• a tendency for increased "scarf skin" in some varieties such as Red Rome and Jonathan.

Cherry Fruit Flies

No adults have been reported caught on sticky board traps yet, but because of the zero tolerance in cherries for insect damage or presence, it's prudent to begin sprays in your cherries now (for this pest as well as for curculio). Guthion, Imidan (tart cherries only), Sevin, Diazinon or the pyrethroids are all effective treatments. Sevin and Imidan will also control black cherry aphid.

Cherry fruit fly maggot feeding inside of fruit

Lesser Peachtree Borer

Remember to get your trunk and scaffold sprays on peaches and cherries during the first week of June if borers are a problem in your blocks. This pest increases the severity of Cytospora canker infections in peaches and is often found within the canker; by feeding in the callous tissues, it interferes with the tree's natural defenses against the disease. Infestations can be determined by the presence of the insect's frass, which resembles sawdust, in the gum exuded from the wound. In peaches, you can use Lorsban 4E, Thiodan, Asana, Ambush, or Pounce for this application. In cherries, use Lorsban 50WP (tarts only) or 4E, Thiodan 50WP, Asana, Pounce or Ambush as a trunk spray ONLY; do not spray the fruit.

Leaf Weevil

This is about the time of year that a bright metallic green snout beetle about 1/5" in length appears in apple orchards and strawberry fields, sometimes in considerable numbers. This weevil is most likely Polydrusus impressifrons, also called simply the leaf weevil. It is of European origin and was first reported in New York in 1906. The larvae live in soil, where they feed on roots of various plants. The adult weevils feed on the foliage of many host plants, including birch, poplar, and willow, but also apple, pear, and strawberry. Leaf feeding is usually not extensive enough to justify special sprays. In commercial orchards, the normal cover spray program will take care of this problem. If the weevil appears in great numbers in a nursery, control using an OP may be necessary.

(Peter Jentsch pjj5@cornell.edu & Dick Straub rws9@cornell.edu, Entomology, Highland)

Leafhoppers, owing to the mild Hudson Valley winter, have fared well and are presently in the later stages of their first generation. Nymphs of white apple leafhopper (WALH), Typhlocyba pomaria McAtee, and potato leafhopper, Empoasca fabae (Harris), two of the three predominant species that feed on apple, have been found in the Hudson Valley. As with many of the other insects, they follow suit with the early spring apple phenology we are experiencing.

The WALH overwintered in the egg stage within the young twigs of apple. They have since hatched and are feeding on cluster and mature leaves of apple, causing the typical white stippling associated with leafhopper feeding injury.

White mottling damage of apple leaves caused by white apple leafhopper feeding

They are in their 4th to 5th instar in Hudson Valley orchards and are more numerous in orchards in which efficacious insecticides have not been applied or in those in which Sevin was not used at thinning.

A third leafhopper species that has an alternate host ecology is the rose leafhopper (RLH), Edwardsiana rosae (Linnaeus). It migrates from neighboring hosts, primarily wild (multiflora) rose, to apple in the late spring to lay eggs. It then completes one to two generations on apple before returning to rose to overwinter during autumn. By scouting in July and August, the differences between species can be noted once the nymphs have reached third instar, when their wing pads can be observed. Dark spots at the bases of setal hairs can be seen on the thorax of the RLH, whereas the WALH lacks spots.

Newly hatched White appple leafhopper nymph

Fifth (last) instar rose leafhopper nymph

Recent findings have shown the rose leafhopper begins its migration to apple at the time florabunda rose is in the bloom stage (approx. 700 DD +/- 50, base 48°F). In the Hudson Valley this will occur this week (on May 30, adults were found on apple).

The application of persistent efficacious insecticides against the adult migratory population has been shown to reduce egg laying and thus the second and third generation of RLH. Organo-phosphorous insecticides (azinphos-methyl/Guthion, phosmet/Imidan) have little effect on any of the leafhoppers. If RLH is a mid- to late season pest in particular blocks, then an application prior to RLH migration may prove cost-effective. Provado and Sevin are effective on adults of both WALH and RLH, reducing succeeding generations. Both of these materials, when used at the recommended rates, will control adults over the migration period of approximately two weeks. They are relatively safe to the predatory mite complex and also pollinators if the XLR formulation of Sevin is used.

The Michigan model for predicting this insect's development gives fairly accurate predictions of codling moth activity in N.Y. As many as two insecticide applications may be made for each of the two generations per year, depending on the severity of pressure. Degree days are accumulated from the date of first sustained moth catch, and the first spray is applied at 250 DD (base 50°F), which corresponds with predicted 3% egg hatch. A second spray may be applied 10—14 days later. If pressure is not too severe, one spray will suffice, applied instead at 360 DD after the biofix date (which we're calling May 19 in Geneva, May 16 in Appleton and May 8 in Highland). To control the second generation, the timing is 1260 DD after this same biofix date. Degree days (base 50°F) accumulated so far in Geneva = 59, Appleton = 82 and in Highland = 236.

end of this issue

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