Late season pests of apples

As harvest of early season varieties (Paula reds) begins, things become even busier in the orchard. With harvest in full swing, it can be difficult to find the time to continue monitoring for pests and applying control measures. However, there are some important late season pests of apples that left uncontrolled can be a nightmare at harvest.

Insects

Codling moth

Second generation codling moth flight has begun and insecticides have been applied in most areas of the province. There has been an increase in codling moth damage in apples over the past few years. There are several potential reasons why this may be occurring including pesticide resistance, improper spray timing and coverage. Dr. Ian Scott a toxicologist from Agriculture and Agri-food Canada is hoping to conduct some research to evaluate the development of pesticide resistance in codling moth populations. In the meantime, growers should be sure to keep their crop protected from this pest. Since codling moth flight can continue into the end of August, growers should maintain coverage for this pest. Preferred products for codling moth at this time of year are border sprays of OP insecticides (in orchards that are uniform in shape and size and have not had a history of damage over the past few years.) or cover sprays of neonicotinoids. OP insecticides (Imidan, Guthion) should be re-applied every 18-21 days to ensure an adequate residual. Cover sprays of neonicotinoids such as Calypso and Assail provide control of both codling moth and apple maggot. These products should be applied every 10-14 days to ensure adequate residual. Rimon and Intrepid are also registered for controlling codling moth; however, they do not provide subsequent control of apple maggot.

Apple maggot

Despite the hot dry weather, monitoring by apple consultants suggest that apple maggot pressure is high this year. Apple maggot is a quarantine pest and there is zero tolerance for damage. The application of OP insecticides or neonicotinoids to control codling moth will also control apple maggot.

Oriental fruit moth

In 2001 and 2002 apple growers in Norfolk, Leamington, and Niagara were seeing considerable crop loss from Oriental fruit moth. With no products registered, growers had few options available for managing this pest. Over the past few years growers have done a great job of managing OFM using mating disruption and/or insecticides (Assail, Calyspo, Intrepid, Rimon), and as a result there has been very little incidence of damage from at harvest. However, it is important to remember that OFM has not been eradicated from orchards. There are many wild hosts for OFM and although we are not seeing damage from this pest in orchards, we still need to manage it. This year we have started to see an increase in OFM damage in orchards that have stopped using mating disruption and/or reduced insecticide applications targeting this pest. Late season OFM can cause considerable damage to apples, and damage can go undetected through a packing line resulting in quality issues.

Diseases

Pin Point apple scab

Despite the hot dry year, apple scab is present in many apple orchards across the province. The presence of this inoculum increases the vulnerability of the crop to pin point scab. Pin point scab develops when fruit become infected during the last several weeks before harvest. Fruit with late season infections may not exhibit symptoms at harvest, however lesions can develop on the fruit during the first 30-45 days in cold storage. Optimum conditions for pin point apple scab include: 1) abundant scab inoculum 2) lack of fungicide residue before harvest. 3) wetting periods longer than 30-36 hours occur after the fungicide residue is depleted. Late season Captan cover sprays should be applied leading up to harvest in orchards with optimum conditions for pin point scab.

Black rot

There has been an increase in the incidence of black rot in orchards in recent years. One of the reasons there is more black rot showing up in recent years is due to cold injury in some orchards a few years ago. The black rot fungus colonizes wounded branches, causing cankers, and acts a source of inoculum. Chemical thinners that leave small fruit are very susceptible to colonization of the black rot fungus resulting in mummification which then acts as a source of inoculum for mature fruit near harvest. . These mummified small fruit left on trees from chemical thinning become infected with black rot and late season rains and dews spread the fungus from the fruit mummies onto developing fruit. Although the heaviest infections from black rot occur during the four to six week period following petal fall, secondary infections can occur throughout the summer. Keep fruit protected with Captan, Sovran or Flint.

Flyspeck and Sooty blotch

Flyspeck and sooty blotch are summer diseases that begin to appear on apples from mid summer through harvest. Flyspeck and sooty blotch can be controlled by most fungicides that manage scab except Nova and Nustar. Where flyspeck and sootyblotch are a concern fungicide programs should be initiated in August and September and continued through harvest.