RI Apple IPM Newsletter

From Heather Faubert and Steve Alm

Recorded pest message is available between 5:00PM and 8:00AM daily. Call (401) 949-0670.

Here is your 1998 -1998 New England Apple Pest Management Guide!

We are certainly past primary scab season now! Lesions from the intense wet spell of May 4 – May 11 have probably all appeared by now. Check now to see how thoroughly you controlled primary apple scab. Since a scab lesion can continue to produce conidia for 4 weeks once it forms, it is advisable to apply fungicides to try and burn out the lesions. These fungicides reduce the number of conidia produced on lesions and reduce the ability of existing conidia to germinate. Because of the need to cover all scab lesions with fungicide, relatively high volume, low concentrate applications (no more than 4x) will give the best results. Try two full-rate captan applications 5-7 days apart. Read more about eradicating scab on page 15 of the Pest Management Guide.

If you are scab free, or close to it, you can switch to your summer fungicide schedule. We recommend either Captan every two weeks or Captan plus Benlate every three weeks.

If you have applied a full rate of Imidan or Guthion since May 24 or so, you should be finished controlling plum curculio for the season. We did find two plum curculio adults feeding in an orchard this week that had not received an insecticide for 14 days. Continue to monitor trouble spots for late plum curculio activity. Perhaps a border row spray would be warranted if you find fresh plum curculio egg laying scars 10 – 14 days after the last insecticide treatment. Fresh scars are crescent shaped slits that have very little callus tissue associated with them.

This could be a very big year for European red mites! In one orchard this past week we found plenty of red mite eggs where we had found very few, if any, red mite adults the week before. This early hot, dry weather could lead us into a very difficult mite season. The spray threshold until June 30th is 2.5 motile mites (not eggs) per leaf or 62% of leaves with any number of motile mites. Once this threshold is exceeded a miticide should be applied. Pyramite is a very effective miticide but should be used only one time per season so the mites don’t build up resistance too quickly. It is labeled for no more than two applications per season. After Pyramite, what do we have? It is too late in the season for Apollo, Savey, or Agri-Mek. Kelthane and Vendex have not been effective and Carzol is very damaging to predatory mites. There is also the option of using ultra fine oils. Call the recorded pest message to hear updates on results of different strategies attempted for mite control.

Apple blotch leafminer can be found now as sap feeding mines and tissue feeding mines. The larvae have begun to pupate in the mines; adults will begin to emerge in a week or two. Now is notthe time to apply pesticides against leafminer – the mines are too far advanced to be controlled properly. If you are finding more than 7 – 14 mines per 100 fruit cluster leaves, consider treating for the second generation mines with Provado around the third week in June. Since the second generation is more spread out than the first generation, often two applications of Provado are needed to adequately control second generation leafminers.

Green apple aphid colonies are starting to build up on terminals and suckers in some orchards. I expect next week we will begin to find many of the predators that feed on aphids. In nearly all cases the predators will adequately control 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 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 warranted if aphid honeydew starts accumulating on the fruit.

We haven’t seen many white apple leafhoppers this year. Many growers have applied either Agri-Mek, Provado, or Sevin at 1 lb/100 gal. which control white apple leafhopper. Check areas in your orchard that were not treated with any of these chemicals. The small, pale nymphs can be found on the underside of older leaves. White apple leafhopper feeding removes sap from leaves, causing stippling that may coalesce into silvery, white patches. Leafhoppers are easiest to control when they are small, first generation nymphs from petal fall to early June. White apple leafhoppers have developed resistance to several organophosphate insecticides so Guthion or Imidan will not control them. If you do find many leafhoppers control with Thiodan or Provado at 1 oz./100 gal.