Scaffolds 99 index

EGG HUNT REVIEW

(Peter Jentsch pjj5@cornell.edu, Entomology, Highland)

We observed our first eggs of pear psylla in Highland on 29 March, roughly a week before my kids were out hunting Easter eggs. Favorable overwintering conditions are contributing to high spring populations. Traditional dormant oil applications made shortly after the onset of psylla oviposition have been successful at reducing early season egg-laying activity, despite their low efficacy on the overwintering adults. Oil applications can provide pear growers additional time prior to insecticide applications, helping to keep nymph numbers down going into pear bloom.

Many growers have taken advantage of the dry soil conditions that are making early oil applications feasible this year. Our recent counts of Bartlett pears at the Highland Station show a five- to six-fold increase in oviposition comparing 3% dormant oil applied twigs with unsprayed twigs (17 eggs/100 buds vs. 110 eggs/100 buds on 4/5).

The importance of reducing spring oviposition by using dormant oil may not appear as critical this year, given the diversity and effectiveness of newly registered pear psylla materials. Recently registered on Pears, Agri-Mek has become the Hudson Valley industry standard for psylla control, replacing Mitac, and the synthetic pyrethroids, Asana, Ambush and Pounce. Provado and Pyramite, both registered on pears, have had good results against nymphs in field trials. Recent tests using split applications of Agri-Mek (10 oz/Acre at 10-14 days post-petal fall and again 14 days later) have shown greater persistence in controlling nymph populations into the growing season.

One logical approach to early season egg suppression is to delay nymph development. By postponing oviposition using oil, nymph development is often delayed, leaving a larger portion of nymphs in the earlier susceptible stages of development to be exposed to insecticide treatments. Another approach to early season egg suppression is resistance management. By lowering the egg and subsequently the nymph population using oil, fewer individuals are exposed to pesticide residue, lowering the tolerant population and reducing the reproductive resistance potential. Another strategy is to lower the nymph population, allowing the use of 'IPM'-related materials such as M-Pede (formerly Safer Soap) or hydrophobic clay, which may not control high psylla populations, but which are more capable of managing populations under low to moderate pest pressure. The additional benefit of the use of oil is the miticidal effect on pear rust mite and European red mite.

For those growers looking to use a 'soft' approach in pear management this season, early management of psylla using oil may help in controlling a runaway population later this season.

HOME ON THE DISTILLATION RANGE

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

Most growers don't hesitate to express their lack of enthusiasm for applying oil sprays, particularly during the early season, and for reasons that make quite a bit of sense: it takes too much water, and therefore too much time, which means a greater chance of running into poor spraying weather, and of cutting up the not-yet-firm orchard floor. Nevertheless, the accomplishment of getting a thorough prebloom oil spray applied is often related with a note of achievement that is at least proportionate in scale, and also for good reasons: the high degree of coverage possible, which results in the high level of efficacy against its target pests, the sound resistance management practice it represents, and even the relative compatibility with other management tactics like biological control. That being said, the devil is in the details, and details are what we have to be concerned with just now.

Pear Psylla

Psylla adults beat many of us out into the orchards with last week's summer preview, and egg-laying could be noted here and there by those who hadn't yet managed a preventive oil spray (nearly everyone).

Early oil applications can be very useful against pear psylla all through the Swollen Bud stage; although it's capable of killing adults and nymphs that are contacted directly, oil is used chiefly because the residue causes a reduction in egg-laying for an extended period after treatment. The strategy behind the use of oil is to delay the timing of any needed insecticide spray until as late as possible before (or after) bloom; see the following article on Pear Psylla for more details. Oil rates depend on when you start: If your buds are at the Dormant stage, one spray of 3% oil, or two of 2% through Green Cluster are recommended; if you start at Swollen Bud, one spray at 2% or two at 1% up to White Bud should be adequate for this purpose, especially if applied as soon as the psylla become active (50 F or above). This will also give some red mite control at the same time.

European Red Mite

Despite the newly acquired prebloom miticides that are now available for apples, a delayed-dormant spray of petroleum oil from Green Tip through Tight Cluster can be a preferred approach for early season mite control, both to conserve the efficacy and help lessen the likelihood of resistance to our contact miticides. Technically, we have been advising that it is possible to get good control of overwintered eggs using 2 gal/100 at the Green Tip through Half-Inch Green stage, or 1 gal/100 at Tight Cluster; this advice assumes ideal spraying conditions and thorough coverage. As we all know, oil applications don't always live up to our expectations, not only because of weather and coverage problems, but also because proper timing is difficult, especially if you have a number of blocks to cover. That is, we have seen mites start to hatch when the trees are at solid Tight Cluster, so naturally the oil loses its ability to smother mites that are able to avoid (or ford) the droplets. For practicality's sake, there are a couple of guidelines to follow.

First, to ensure that mites are in the egg stage, start on your blocks as soon as the weather and ground conditions permit, even if this means using a higher rate. Also, tend toward the high end of the dosage range, especially if there's been no frost during the 48-hour period before your intended spray, and no danger of one for 24-48 hours afterwards. A distinction that might be worth making is to use 1.5 gal/100 if the buds linger somewhere between Half-Inch Green and full Tight Cluster during your chosen spray period.

Good coverage of the trees is naturally critical to take advantage of oil's potential efficiency; this in turn requires adequate spray volume delivered at an appropriate speed. Experience and research have shown that a 1X concentration (300 gal/A) is clearly preferable; however, if all other conditions are optimal (weather, speed, calibration), then 3X, or 100 gal/A, is the highest concentration that should be expected to give acceptable control at any given time. Growers like to concentrate more than this to save time and the hauling of extra water, but the problems this can cause usually aren't worth the tradeoff.

And, just a quick aside here to flog a dead horse, I'll bet a majority of apple growers used Apollo or Savey on at least some of their blocks last season, and probably with good results. Before automatically going right back to the same jug (or bag), give a few seconds' thought to the two faces of miticide resistance. Right now, you're probably seeing it as something that exists in the hazy future, if at all. More than likely, you wouldn't want to be in the shoes of many of your counterparts in other countries, who have met resistance firsthand in the recent past, after using one of these products consecutively for 2-3 years and now have to scratch them both off the list of usable tools. Don't follow Apollo with Apollo or Savey; don't follow Savey with Savey or Apollo. Try oil now, and Agri-Mek at Petal Fall, or even eliminate the Agri-Mek in low-pressure blocks and use Pyramite later if it becomes necessary.

& Co.

We used to think that San Jose Scale might actually be on the decline in N.Y., but a small flurry of reports last season attested that they aren't gone yet. In this case, a 2% oil treatment at Half-Inch Green will control the nymphs, and this is a preferred treatment if no other problem insects need to be controlled.

San Jose scale crawler

Combining the oil with an insecticide has not been shown to be more effective than using the oil or insecticide alone. If you choose not to use oil against the scale nymphs, or if you have Rosy Apple Aphid or other early season insects to be controlled, an insecticide would be more appropriate. For both of these pests, Lorsban 4EC or Supracide (2EC or 25WP) have proven very effective during the Green Tip to Tight Cluster stage. Check the opening buds for infestations of Rosy Apple Aphid.

Colony of rosy apple aphid nymphs

Treatment would be advisable upon finding one colony per 100 clusters.

PSYLLA CRAZY AFTER ALL THESE YEARS

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

Originally introduced accidentally from England into Connecticut about 1832, the pear psylla has 3-4 generations a year, depending on the length of the growing season for the area. The overwintering adults pass the winter in litter on the ground or in cracks in the tree bark. On warm spring days, prior to the trees breaking dormancy, these adults can be found on the trunks, twigs, and branches.

Pear psylla adult

The first eggs in the spring are laid prior to bud burst, on the terminals and spurs. As the foliage appears and for succeeding generations, the eggs are laid on the new leaves.

Pear psylla eggs

First egg hatch occurs about the time the foliage appears. The pear psylla is a "flush feeder", meaning that the nymphs feed and develop primarily on the newer, more tender growth. By midway through the growing season, the majority of leaves are hardened off and psylla development then may be limited primarily to the water sprouts.

Once the nymph begins to feed, a honeydew drop forms over the insect; the psylla develops within this drop for the first few instars.

Pfear psylla nymph enclosed by its honeydew droplet

Honeydew injury occurs when excess honeydew drips onto and congregates on lower leaves and fruit. Under bright sunlight and dry conditions, the honeydew can kill the leaf tissue and produce a symptom called "psylla scorch". The honeydew is a good medium for sooty mold growth. When it occurs on the fruit, it russets the skin and makes the fruit unsaleable.

Pear russetting caused by sooty mold growing on psylla honeydew

Excessive feeding and the injection of toxic saliva by large populations of psylla can cause a tree to wilt and lose its leaves prematurely. This reduces tree vigor, which can take the tree several years to recover.

Ladybird beetles, lacewings, syrphids, snakeflies, and predatory bugs have been recorded feeding on the psylla. There are also two wasp parasitoids of pear psylla in the U.S. However, to obtain commercially acceptable fruit in New York, pear psylla must be controlled with insecticides.

Registered insecticides for summer use on pears are historically unreliable in controlling pear psylla because of the development of resistance in psylla populations to materials that were once effective. In addition, N.Y. growing conditions necessitate management practices for fruit size attainment (vigorous fertilization and significant canopy pruning) that are favorable for the rapid buildup of psylla populations. Contributing to this situation of incomplete control is the widespread use of materials for other pests that are highly destructive to natural control agents, such as pyrethroids and carbamates. These factors virtually assure a yearly infestation of an insect that would otherwise be a relatively insignificant orchard resident, and at best, a grower can hope to keep psylla populations barely under control. Large numbers of adults left in the orchard at the end of the summer overwinter and initiate the next spring population, while natural control agents don't have the chance to recover before the next encounter with destructive pesticides.

Current management recommendations call for prebloom oil applications, and insecticide sprays to manage nymphal populations that build beyond 1-2 per leaf, starting anytime after Petal Fall and throughout the summer. Agri-Mek used shortly after Petal Fall has given good control if applied correctly (well-timed, adequate coverage, combined with an oil adjuvant), and Dick Straub's trials in the Hudson Valley have shown the utility of split applications of Pryamite or Provado, also starting soon after Petal Fall.