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Early season pests of Apple

As I look out my window at the mounds of snow it is hard to consider that spring is right around the corner. But with the coming spring, will return the early season pests of apple. Most of these early season pests are not major pests, and can easily be controlled in orchards. However monitoring, timing and choice of control measures can play in important role in managing all of these pests.

Rosy apple aphid (RAA)

Rosy apple aphids emerge in apple orchards from pink through early summer. RAA nymphs range in size from 0.4 to 2.0 mm they are purple in colour and have dark cornicles. Adults can be winged or wingless. Adults feed on leaves causing them to curl and turn red in colour. Feeding stunts the growth of shoots and causes malformation on leaves and fruit. RAA exudes a honeydew which favors the growth of mold. Last year we saw high populations of rosy apple aphids in orchards earlier in the season then we usually see them, growers should be aware of this pest and start monitoring for it starting at tight cluster to pink. Cool wet springs are favourable for RAA since the weather is harmful to the parasites and predators that attack them. Elimination of summer hosts of RAA such as narrow leaved plantain and dock can help minimize pest pressure. Lots of great products are available that have efficacy against RAA including Assail, Admire, and the application of Calypso to control other pests will also control RAA. Movento, a new insecticide that is pending registration also has activity on RAA.

Gypsy moth

Last year we saw an increase in gypsy moth populations in orchards early in the season, and reports suggest that this year will be another excellent year for this pest. Gypsy moth larvae are black with a yellow head and long hairs with tubercles on their back. Larvae attack most species of deciduous trees. While Gypsy moths are not considered to be a major pest of apples, they can defoliate young trees. Small larvae are often blown into orchards from adjacent woodlots. Target specific insecticides such as Dipel/Foray (Bt insecticides) can be used to manage this pest. Post-bloom application of broad spectrum insecticides (Imidan) also provide subsequent control of gypsy moth larvae.

Spotted Tentiform Leafminer (TLM)

Although spotted tentiform leafminer was a considerable pest in apple orchards in the past, its prevalence in orchards has decreased greatly over the years. There are several good products available to manage this pest, and often the application of insecticides at petal fall to control other pests such as oriental fruit moth and obliquebanded leafroller also provide subsequent control of tentiform leafminers (Intrepid/Confirm, Altacor) Neonicotinoids such as Calypso and Assail are also effective in managing TLM. As a result the use of a "pyrethroid at pink to manage tentiform leafminer" is no longer necessary.

San Jose Scale (SJS)

In recent years there has been an increase in damage from San Jose Scale on fruit at harvest. Until this year we have only had access to the use of dormant oils to manage scale, but the registration in the near future of Movento will provide growers with an excellent tool for managing scale. There are two generations of SJS each year. Adult male scales usually start emerging in May through mid-June, the second generation of SJS emerges from early August through September. In orchards with a history of SJS problems a dormant oil should be used, and where necessary, Movento should be applied mid-June and/or mid-August targeting crawlers before they mate.

Powdery Mildew (PM)

As our summers become more hot and humid it is likely that we may see an increase in powdery mildew in apple orchards in the upcoming years. Often growers spend a lot of time focusing their disease management on apple scab and may forget about protecting themselves from powdery mildew. In orchards with a history of powdery mildew problems begin a fungicide program as early as half-inch green. In orchards that haven't had problems with scab, PM sprays are not required until tight cluster. Some varieties are much more susceptible than others to powdery mildew. Many of the new varieties such as Ambrosia, Gala and Honeycrisp are considered to be susceptible to powdery mildew.

Black Rot

In recent years OMAFRA staff have seen an increase in damage from black rot in Ontario orchards. As John Gardner puts it "some growers probably have black rot, but aren't even aware of what it is." Black rot causes many different types of symptoms on trees. Symptoms on leaves are called frog eye leafspot, and leaves have small purple spots on the leaves, with a grey centre. Heavy infections of frog eye leaf spot can cause leaves to turn yellow and drop. Black rot symptoms on tree trunks and limbs appear as cankers which are red brown in colour and slightly sunken. Black rot also appears as small black spots on the fruit. These spots gradually enlarge to form concentric brown rings on the fruit. The heaviest infections of black rot occur during the four to six week period following petal fall, however secondary infections can occur throughout the summer. If black rot has been a problem in an orchard growers should apply petal fall applications of fungicides (high rates of Captan, Maestro, Flint and Sovran applied for scab also control black rot). Some varieties such as Gala, Honeycrisp and Sunrise are all susceptible to black rot.