Scaffolds 01 index

(Art Agnello ama4@nysaes.cornell.edu and Harvey Reissig whr1@nysaes.cornell.edu, Entomology, Geneva, and Dick Straub rws9@cornell.edu, Entomology, Highland)

Once again, the N.Y. weather has figured out yet another variation on the theme of getting to a given destination without traversing any known territory. We thought for sure that this spring would at last be one of those mythical "normal" ones that warmed slowly into a pleasant, if hesitant, calm period of bloom, perhaps to be followed by just a bit too much rain to suit everyone's preferences. However, the pre-summer heat wave that had all the weathermen clucking and the schoolkids sporting shorts and sandals, also generated an all too familiar turbo pink-to-fullblast bloom sequence that left even the honeybees breathless from exertion. Despite the predicted cool-front slowdown this week, many eastern N.Y. apple orchards have already entered the petal fall period, and the rest of us won't be far behind. As you're no doubt aware, petal fall is the pivotal time for establishing a foundation for the control of many of the most important arthropod pests. Here once again are some important points to keep in mind for the petal fall insecticide sprays:

1) To minimize the hazard to honey bees, apply pesticides only after ALL petals have fallen in the block and when no bees are actively foraging on blooming weeds (evening is better than early morning).

2) Do not use Lannate on early McIntosh, Wealthy, or Dutchess because of possible injury to fruit and foliage.

3) Although our research trials haven't consistently borne this out, postbloom use of pyrethroid insecticides has been known to encourage the buildup of certain pests such as mites and woolly apple aphid. Try to limit use of these materials to one application per season to delay resistance development and extend their useful field life.

4) When choosing an insecticide for this application, keep in mind its range of activity, both adverse and beneficial. For example,

- if Sevin is applied for thinning, it will also help to control plum curculio and white apple leafhopper (even at the 1 lb rate); however, it does have detrimental effects on Amblyseius fallacis predator mites.

- Carzol acts not only against European red mite, but will also control white apple leafhopper; however, it is not kind to predatory mites. Recall that petal fall is now the latest that this material can be used because of a recent label change.

- Agri-Mek is recommended at petal fall for maximum efficacy against mites; this is also the timing at which it will have its greatest effect against white apple leafhopper nymphs and sapfeeding spotted tentiform leafminers. It is not likely to be too useful against rosy apple aphid.

5) Be aware of the destructive effects of any spray materials on beneficial mites and insects (refer to Tables 5 and 12 on pp. 45 and 52 in the 2001 Recommends.)

6) Do not use Vydate or Sevin during the first 30 days after bloom without taking into account their thinning effects.

Mites

Many growers may have been unable to do as good as job as they would have liked with their early season mite programs again this year. Conditions were fairly lousy for oil spraying in western N.Y., and the pink period didn't last nearly long enough for some of the other prebloom acaricide products. Although early reports indicate lower than normal levels of mites this year, even in historically problematic orchards, some European red mite management strategies will need to take into account the always unpredicatable (and always critical) early prebloom mite development conditions. Mite hatch has already been noted in western N.Y., and the relatively natural inclination to rely on a good rescue material such as Pyramite carries the implicit requirement of vigilant monitoring for threshold numbers and timely action when a treatment is needed. The predictions call for this summer to be drier and warmer than normal, which means that high numbers and significant leaf damage can develop very rapidly when the mites do show up.

Our message, as ever, is that it is always wise to keep an eye on the foliage throughout June and July to detect unreasonable mite buildup, because it doesn't take much to boost numbers into the problem category. Until June 30, we recommend a threshold of 2.5 motile stages (anything except eggs) per leaf. Explicit yet simple instructions on assessing mite densities can be found on the mite sampling charts in the Recommends (starting on p. 60).

Among rescue-type products, Pyramite applied in a timely manner should generally do the best job, and is most likely to give you control for the remainder of the season, but don't stop examining the foliage altogether. It's advisable not to use this product more than once per season, even though 2 applications are allowable. This is not only out of consideration for potential resistance development, but also because Pyramite has some toxicity to predator mites, and hitting them twice won't do much to allow their establishment.

Kelthane can be used if you have no reason to suspect resistance in your populations, or if none has been applied in a given block for at least 5 years. Vendex is still available, and has been shown in some of Dick Straub's trials to be one of the more effective treatments for twospotted spider mites. Keep in mind that TSSM populations can increase faster than red mites.

Plum Curculio

Plum curculio (PC) adults move into orchards from overwintering sites in hedgerows or the edges of woods and are present in the trees from late pink to early bloom before the fruit is susceptible to damage. Adults are active in the spring when temperatures exceed 60°F, which means that more than likely they've already started arriving. Adult females oviposit in fruit during both day and night but feed mostly at night. Depending on temperature, overwintering adults remain active for two to six weeks after petal fall. Although adults may feed on blossoms, apples are not susceptible to damage until petal fall, at which time adults damage fruit by both feeding and ovipositing. Unlike fruit injured by other pests, many apples damaged by plum curculio will remain on the tree until harvest. Because adults are not highly mobile, orchards near overwintering sites, woodlands, and hedgerows are most susceptible to attack. Fruit damage is usually most common in border rows next to sites where adults overwinter.

Plum curculio adult

Dried sap produced by plum curculio feeding and oviposition wounds on apple

Monitoring for plum curculio is not currently recommended in New York because of the amount of time and labor involved and because plum curculio is generally assumed to be present in every orchard. Although growers realize that initial post-bloom sprays for plum curculio control should begin at petal fall, they are often unsure how many additional sprays will be necessary to maintain protective chemical residues to prevent subsequent damage throughout the PC oviposition cycle, which varies according to temperatures and weather patterns after petal fall.

Following from the fact that PC activity and oviposition are greatly affected by temperature, an oviposition model has been developed to determine when control sprays after petal fall are no longer necessary to protect fruit from PC damage. This model is based on the assumption that residues from control sprays after petal fall only need be maintained on fruit and foliage until about 40% of the oviposition cycle is complete, which is predicted by the model to occur at 340 DD (base 50°F) after petal fall. Probably, this strategy works because, after 40% of PC oviposition is complete, adults usually are not moving into the orchard from outside sources, or moving around within orchards from tree to tree. Therefore, by this time, adults residing in treated trees have already been killed by insecticide residues and are unable to complete the remainder of their normal oviposition cycle.

In order to use this strategy: (1) Treat the entire orchard at petal fall with a broad spectrum insecticide. (2) Start calculating the accumulation of DD after petal fall (base 50°F). (3) No additional sprays are necessary whenever the date of accumulation of 340 DD falls within 10-14 days after a previous spray.

This conventional strategy is probably only necessary for commercial apple orchards in which PC fruit damage has been observed frequently, or for orchards thought to be particularly vulnerable to infestation from codling moth or the European apple sawfly. Usually, orchards that chronically suffer fruit damage from PC are relatively small blocks located next to abandoned orchards or surrounded by woods or woodlots, which are favorable sites for overwintering of PC adults. Some larger orchards bordered by woods on one or more sides may also be at risk for chronic infestations of PC.

In moderate problem orchards, a petal fall application followed by a second spray 10 to 14 days later will provide adequate control. In orchards with more severe chronic problems, or in seasons when adult activity is prolonged by unusually cool and wet weather, two cover sprays applied 10 to 14 days apart after petal fall may be necessary to prevent late damage. Guthion, Imidan, and all pyrethroid insecticides are effective at controlling plum curculio. These materials will also control codling moth later on.

Obliquebanded Leafroller

Rather high numbers of overwintered OBLR are being found in some blocks in the Hudson Valley, particularly in those 'hail' blocks that received minimal management last season. The obvious larvae are in 'shelters' or rolled terminal leaves, and will be difficult to impact with insecticides. A significant number, however, are now exposed in blossom clusters and quite accessible to sprays. Any degree of control now will lessen pressure from the summer brood. Control options are:

1. CONFIRM – N.Y.S. registration is now complete under a SLN 24(c) provision.

2. Bacillus thuringiensis – One could wait until petal fall, but because all formulations are labeled for bloom applications, this timing would be the optimum tactic. Because these larvae are still small, and are exposed, the lower to mid range of rates should suffice (see the Recommends, p.108).

3. ASANA or DANITOL – Although effective, Asana is a tough choice because of a propensity to cause mite flaring. Danitol, however, does not flare mites in a similar fashion and may, in fact, provide early season suppression of mites. Unlike the federal label, the N.Y.S. label (received too late to be included in the Recommends) allows a maximum application rate of 10 2/3 oz/acre per application. Research results from western N.Y. have shown good control of OBLR at this rate.

White Apple Leafhopper

WALH nymphs can be numerous in some blocks, especially in the eastern part of the state. Provado has proven itself effective against this pest, and a petal fall application also gives leafminer control. Furthermore, it will have an added effect on green aphid populations, which might otherwise be more problematic this spring, owing to the advanced tree development and sustained availability of succulent green tissue. Rosy apple aphids can similarly be cleaned up with this strategy, although petal fall is often too late to prevent fruit damage that their feeding may have caused. Growers using Sevin in their thinning sprays will get some WALH control at the 1 lb rate.

White apple leafhopper adult

Alternative choices include Thiodan and Lannate; Agri-Mek or Carzol used for mites now will also do the job, but Carzol will be harmful to predator mites. The damage potential of this first generation should be evaluated carefully before deciding on the need for a specific control of this pest.

Oriental Fruit Moth

OFM has been receiving more attention recently, as we have been made increasingly aware of its tenacious ability to overcome some of the older "safe" OP-based control programs, particularly in peaches. We are in the midst of extensive research to nail down some of its developmental secrets and susceptibility gaps, but for the time being, field efficacy trials conducted last season showed that problematic populations were best controlled starting at petal fall (not shuck split) of peaches, using a pyrethroid such as Asana, and backed up 10-14 days later.

Oriental fruit moth adult

The second brood requires a similar approach, beginning about 6 days after its peak flight, which is expected during the second half of June, but we'll keep you posted on the timing for this one. Pheromone mating disruption seemed to work very well last year, but we're testing it for a second season to better understand its strengths and weaknesses, so we're not recommending it too strongly just yet.

General Info 5.14