RI Apple IPM Newsletter

From Heather Faubert and Steven Alm

Weekly phone message can be heard by calling (401) 949-0670 from 5:00pm to 8:00am daily.

Insecticides should not be used now; an insecticide should not be necessary until apple maggot flies emerge and migrate into orchards (see below). Plum curculio are all finished for the season and there are no other pests that require insecticide at this time. Applying insecticides now kills off aphid predators, making the green apple aphid population build up.

Within the week we will have all the red sphere apple maggot traps set up in monitored blocks. We recommend all orchards monitor with the sticky red spheres because it varies greatly when apple maggot flies migrate into certain orchards. In some orchards we find them in early July, in other orchards we do not catch them until August. Traps can be purchased at many garden centers. You need 1 trap per 3-5 acres but not less than 3 per block. Set out traps near the block periphery (one or two rows in from the outermost row) and in early maturing varieties. Traps should be placed about head height in an outer portion of the tree canopy where there is abundant fruit beneath and to the side of the trap. Clear all fruit and foliage within 1-2 feet of the trap. As fruits size up and branches drop, traps may need to be repositioned. Traps should be cleaned of apple maggot flies and other large insects when checked each week and recoated with Tangletrap after 3-4 weeks.

It is time to spray for apple maggots when you catch an average of 2 flies per trap. Once this threshold is reached and an insecticide is applied, ignore trap captures for the next 2 weeks and wait until the threshold is reached again before applying another insecticide. Half rates of Imidan or Guthion control apple maggots well.

Pyramite is now registered in Rhode Island for European red mite, two spotted mite and pear psylla control. It has a restricted re-entry interval of 12 hours, a preharvest interval of 25 days, and is very toxic to bees and fish. As with all miticides, thorough coverage is essential for good control. Use at least 100 gallons of water per acre. The label also states not to apply Pyramite with a handgun sprayer. The rate is 4.4 ounces per acre – it comes in 4.4 ounce, water soluble pouches. Pyramite is suppose to provide knockdown and residual control. A good performance evaluation can be made 4-7 days after treatment. No additives or adjuvants are necessary.

Pyramite can be used twice in a season but it is recommended that it be used only once in a season to reduce the possibility of mites developing resistance. The threshold for red mites from June 15 – July 1 is 55% of middle-age fruit cluster leaves with motile mites. From July 1 – July 15, sample middle-age leaves from anywhere on the tree. The threshold is reached when 65% of the leaves have motile mites. From July 15 – August 15 the threshold is 80% of any middle-age leaves with motile mites. Other available miticides include Kelthane and Carzol.

White apple leafhoppers are present now as adults and large nymphs. It is too late to apply insecticides against them now. We are finding some leafhoppers in orchards where we didn’t see them earlier this season. These could be the adults of the rose leafhopper. Rose leafhoppers overwinter on roses and first generation adults can migrate into apple orchards in June. These adults lay eggs on apple which hatch into nymphs in early July. The white apple leafhoppers also lay eggs on apple but these do not hatch until early August. Rose leafhoppers have required a pesticide treatment in a few orchards in past seasons. Treat with Thiodan or Provado (1 ounce per 100 gallons) if you find 25 nymphs per 100 leaves.

Apple blotch leafminers are present primarily as tissue feeding mines now. Many of the large larvae have pupated and have started emerging as adult moths to start the second generation. To make a decision about treating for the second generation, you need to look at the size of the first generation. If more than 13% of the old, fruit cluster leaves have tissue feeding mines now, you may want to apply Provado against the second generation sap feeding mines. It is more difficult to control the second generation than the first, so two applications of Provado may be necessary to adequately control them. The first application should be applied soon after the second generation sap feeding mines appear, late June to early July. The second application should be made 7-10 days after the first.

Green apple aphids are building up on the new foliage of suckers and terminals. On most of the leaves infested with aphids we also find predators or the eggs of predators. In most instances the predators adequately control the aphids without the use of pesticides. The two most common aphid predators are the syrphid fly larvae and the cecidomyiid larvae. The syrphid fly lays small, long, white eggs among aphid colonies. The eggs hatch into small, motiled green and brown larvae that feed on the aphids. The cecidomyiid eggs and larvae are bright orange. Both species feed by sucking fluids from aphids and leave behind shriveled, blackened aphid cadavers. Spraying Thiodan or Provado against aphids is only warrented if aphid honeydew starts accumulating on the fruit.