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Healthy Fruit 2009 Vol. 17:1

Apr 7, 2009

Current degree day (DD) Accumulations

Location: UMass Cold Spring Orchard (CSO), Belchertown, MA

  • Base 43: 102
  • 50 base: 35

Significant orchard events based on degree days (Base 43):

  • pear psylla 1st oviposition: 40–126
  • spotted tentiform leafminer 1st catch: 110–198
  • McIntosh apple at green tip: 96–148

Current bud stages

apple -- very early green tip
pear -- swollen bud
PF-14 Jersey
peach -- swollen bud
sweet cherry -- dormant


McIntosh Apple Very Early Green Bartlett Pear Swollen Bud Jersey Peach Swollen Bud Cavalier  Sweet Cherry Dormant

The way I see it

Well, the weather is perfoming as usual for early spring, with ups and downs in daily temperatures and extended periods of relative drought followed by extended periods of rainy/showery weather. Some apples are at early green tip. As buds push and more rainy weather must be in the future, you must be prepared to apply fungicide as apple scab ascospore maturity is surely ramping up. Not much has changed in the past week. Insect activity is minimal, with perhaps pear psylla on the agenda for those of you that grow pears. This Healthy Fruit includes an article by Peter Jentsch of Cornell's Hudson Valley Laboratory on pear psylla management.

Guest article

reprinted from Scaffolds Fruit Journal, Vol. 18, No. 3, April 6, 2009


Pear psylla, Cacopsylla pyricola Foerster, is the primary insect damaging pears in the northeast, driving pest management decisions during the pre-bloom period. Adults overwinter along the woodland edge as well as within the orchard. Adults remain well hidden among the scales of trunk bark and branch canopy during cooler temperatures, visibly increasing in number on trees as temperatures rise, and migrating into blocks throughout the early part of the season. Adults will oviposit onto branches along the basal plates of buds throughout the month of April, allowing nymphs easy access to newly developing foliage.

Strategies to manage pear psylla during the pre-bloom period are diversifying as new materials with different modes of action become available in NYS. The traditional pre-bloom oil application can be made as the first egg is observed in a three-minute observation of pear buds. In the Hudson Valley we recently observed oviposition on 23 March. A pre-bloom oil application to delay and reduce adult oviposition subsequently forces the female adults to synchronize egg deposition, delaying nymph hatch and allowing for a more effective application of insecticides to target a more uniform and susceptible developmental stage. To be effective, oil applications should be made well before signifi cant egg laying begins. A dormant application of 3% oil would be made if only one oil application is planned. This rate will also reduce overwintering populations of San Jose scale, European red mite, pear leaf blister mite, and Comstock mealybug. A second approach would be the use of 2% oil at 7 to 14-day applications, allowing for somewhat longer inhibition of egg laying. In laboratory studies, we have found oil to increase mortality of nymphs coming in contact with the spray droplets.

Two relatively new approaches for pre-bloom psylla management can be rotated into our IPM programs. The first is an additional option for ovipositional deterrence through the use of Surround WP, a kaolin clay product, at 50 pounds per acre, made at first egg observation. In the northwest pear-growing region, with their sparse rainfall that allows for long insecticidal residual life, this approach has been used in regional applications quite successfully. In a trial conducted at Cornell's Hudson Valley lab in 2006–2008, Surround WP gave significantly better control of pear psylla adult egg laying than 2% oil at the same timing in a single spring application even under considerable rainfall. Multiple applications of Surround WP used at the 50 lb/A rate, beginning at delayed dormant followed by white bud and petal fall, gave us excellent control of 1st generation psylla, the Lepidoptera complex, European apple sawfly, and plum curculio.

The second approach is the use of an ovicide, Esteem 35WP, used during pre-bloom to kill the egg stage of psylla and reduce the viability of eggs laid by treated adults. It should be applied prior to sustained egg laying, about the time oil or Surround applications would be made, with 0.25% v/v horticultural spray oil. Esteem may be applied once at pre-bloom at 16 fl oz/A, or once pre-bloom and once at petal fall at 13–16 fl oz/A as a tactic for both psylla reductions and as a resistance management strategy. Remember its mode of action is as an ovicide and early instar nymphicide so it will not reduce the adult or nymph population directly. It is most effective if the material is on the wood or foliage prior to the eggs being deposited.

Using oil is a pre-requisite to at least two follow- up strategies. One option after oil is the use of an adulticide, to kill the adults after they have completed migration into pear orchards, and before significant eggs have been laid. In the Hudson Valley, oil is generally applied during the first week of April and migration is completed in late April. Adulticides would be employed in mid-late April to significantly reduce the adult population. The choices to manage adult psylla include Thionex 50WP at 1/2 to 1 lb/A, the neonicotinoids Actara 25WDG at 5.5 oz/A and Assail 30SG at 4.0–8.0 oz/ A, and the pyrethroids (Ambush 25WP at 12.8–25.6 oz/A, or Ambush 2EC 12.8–25.6 fl oz/A; Asana XL 0.66EC at 2.0–5.8 oz/100 gal, Pounce 3.2EC at 8–16 fl oz/A, Pounce 25WP at 12.8–25.6 oz/A, Proaxis 0.5CS at 2.6–5.1 fl oz/A, or Warrior 1CS at 2.6–5.1 fl oz/A). The use of 25% v/v of oil in a tank mix with the neonicotinoids has been found to increase efficacy but is not a pre-requisite for their use. In general, researchers have found the pyrethroids to be less effective at higher temperatures on many different insect species. Their use should be considered during the spring, not during the heat of the summer. They have been found to be more effective with the use of PBO (piperonyl butoxide). Incite, a PBO synergist, when applied 4–6 hours prior to, or in a tank mix with, the pyrethroid application will increase pyrethroid efficacy. The PBO acts to reduce the insect's ability to metabolize or detoxify the pyrethroid, allowing it to reach its intended target site within the insect.

And to add to the discussion of early pest management for psylla, we would be remiss not to say that the use of post-bloom Agri-Mek has been the standard method of psylla management in New York since 1996. Although we have not seen Agri-Mek experience a failure or loss of efficacy in NYS, it's all the more reason to consider a rotational program of Agri-Mek with other effective materials for resistance management purposes.

Agri-Mek can be used from 10 days to about 4 weeks post PF, but its efficacy decreases as foliage hardens off. It requires the use of 0.25% v/v horticultural spray oil to penetrate the foliar waxy cuticle and allow translocation within the leaf for optimum uptake by nymphal feeding. Agri-Mek has been used successfully in multiple applications of 20 oz/A beginning at 10–14 days after petal fall with a follow-up application 21 days post-PF as per label requirements, totaling no more than 40 oz/season. The later application is targeted at new foliage, which is preferred by psylla nymph populations.

A viable alternative to Agri-Mek is the use of Actara 25WDG at 5.5 oz/A. In the neonicotinoid class of insecticides, it's effective against both nymph and adult populations. We have found it has slightly better efficacy when used with a 0.25% v/v horticultural spray oil. It will also control plum curculio and Comstock mealybug when applied at petal fall. This product is not registered for use in Nassau or Suffolk Counties, and the label allows only one application of Actara per season.