Apples Diseases Insects Pest Management

Apple Update: May 25, 2016

Crop Stages

Apple buds are at full bloom to petal fall across the province. The warm weather over the long weekend has sped the bud development along.


Growers have been applying Apogee to trees that have 1-1.5” of terminal growth. Some growers have been applying bloom thinners at full bloom; exercise caution with applying bloom thinners at high temperatures.  Growers at a more advance bud stage will be starting to apply fruitlet thinners. There were few nights of frost warnings in Middlesex, Norfolk, Elgin, Northumberland and Grey Counties and Durham Region. The Ottawa Valley experienced temperatures of -1 to -2 one night, last week.


Based on the fire blight prediction maps, a high to extreme/exceptional risk of infection is predicted for most apple growing regions in the province from May 24 to 26 in orchards with open blossoms.  Growers should monitor their orchards closely and take necessary action to protect open blossoms prior to a high risk event. A reminder, the prediction maps will be updated Wednesday and Friday of this week. In earlier regions, Streptomycin and/or Kasumin was applied at the beginning of last week. Those running prediction models noticed some discrepancy between MaryBlyt and Cougar Blight recommendations. While MaryBlyt was predicting a low infection potential based on conditions needed for infection to occur, Cougar Blight was predicting high risk. Many growers that have had fire blight in the past chose to err on the side of caution and put on a cover.

There are still no signs of apple scab lesions yet from earlier infection periods. Some regions experienced another scab infection early last week, though other regions were too cold for the length of wetting required. Based on degree days from bud break, 70-90% of ascospores have matured. With the forecasted rain in the coming week, growers are applying protectant fungicides to prepare for the potentially large ascospore release during the next infection period.


Petal fall insecticide programs are on many growers’ minds right now. Table 3-8. Activity of Petal Fall Insecticides Against Orchard Pests in 2016-2017 Publication 360: Guide to Fruit Production may be of some help to determine the best insecticide for control of pests listed on the product label, while managing resistance  and avoiding unnecessary sprays for non-target pests. Efficacy will be based on rate used.

Oriental fruit moth spray timing is quickly approaching in the earlier regions of the province, but exact timing will depend on product choice. Codling moth biofix has not been set yet. European apple sawfly and San Jose scale have been caught in traps in orchards monitoring for these pests. Petal fall spray timing will be critical for areas with sawfly pressure. Delaying this spray may result in extensive damage. Degree days for San Jose scale have begun to be accumulated and crawler emergence (summer control timing) is predicted mid- to late June.

ALCM adult flight continues to be high. Egg counts are increasing and can be found near leaf folds or margins of young, developing leaves. Leafcurling caused by cream colored larvae can be found in orchards with high midge pressure. This damage is expected to increase in the next week or two.

Spring feeding caterpillars are active in most orchards, with terminal and cluster damage as well as small caterpillars being observed. Some orchards have reached threshold and growers will be applying a petal fall insecticide with activity on these pests.

Mullein bug and tarnished plant bug continue to be tapped out in many regions. A small number of aphids can also be found on tapping trays in some orchards.

Plum curculio adults have been reported in a number of areas, signaling the beginning of movement into orchards.


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