1999 UPDATE

NEW ENGLAND APPLE PEST MANAGEMENT GUIDE

Ronald J. Prokopy, University of Massachusetts

D-z-n diazinon AG600 label now reads "Do not apply after petal fall"on apples.

SpinTor 2 SC (spinosad): A microbial derivative labeled for use on apple against leafroller and tentiform leafminer. Highly pest-specific, SpinTor does not have a significant impact on natural predators. Early trials have indicated effective control of leafroller (1.25-2.5 fl. ozs./ 100 gals.), but information regarding efficacy and timing against leafminer (1.0-2.5 fl. ozs./ 100 gal.) is not well established. Must be applied in combination with a penetrating surfactant.

For use against oblique-banded leafroller, the first application should occur at 30% hatch, with a follow-up application 14 days later. For use against spotted tentiform and/or apple blotch leafminer, recommended timing is when most advanced sap-feeding mines begin to reach the tissue-feeding stage (mines visible on top surface of leaf).

A maximum of 3 applications can be used in a season, though to avoid development of resistance, it is not recommended for use against consecutive generations. It is toxic to aquatic invertebrates, and use should be avoided when bees are foraging. Incompatible with tank-mix pH below 5. Restricted entry interval 4 hours. Pre-harvest interval 7 days. 

Vangard WG (Cyprodinil) : A water dispersible granule that can be used alone or in a tank mix for scab management on apples. For pre-bloom treatments use 5 oz./A alone or 3 oz./A in a tank mix with the recommended rate of a protectant or systemic fungicide. Apply at 7-10 day intervals beginning at green tip. Use shorter interval for severe disease pressure situations.

For pink, bloom, and post-bloom treatments use 3 oz./A in a tank mix with a protectant fungicide. Use of an EBDC material will help with cedar apple rust management. Use of sulfur or a SI material will help with management of powdery mildew. For scab management, Vangard has not been rated better than older materials by plant pathologists in the Northeast, but its value may increase if some of them are removed by the re-registration process. Vangard is less effective if the temperature is over 70oF, which limits its post-bloom effectiveness. Although it is not well-suited for repeated applications, it is compatible with oil, and it may prove to have a 48 hour kick-back over a decent temperature range as well as some forward protection. We see it as a "pinch-hitter".

Do not apply more than 22 oz. per acre per crop per season. Restricted entry interval 12 hours. Pre-harvest interval 72 days.

Scab Management and Mowing

In the previous guide, the statement was made that delaying mowing until after primary scab season ended may decrease inoculum, because the grass stops the spores. This remains conjecture, and there are many benefits in earlier mowing. We don't recommend delaying mowing.

Collar rot

Collar rot is most dangerous, and works most quickly, on small, young trees. The primary fungicides for use in managing collar rot are fungistatic. That is, they don't kill the fungus, but stop it from growing for a time. Hopefully, it will stop it from growing long enough for young trees to develop an adequate set of roots to deal with the pathogen. Ridomil and Aliette are not a solution for choosing a poor site and a highly susceptible rootstock. Rather, they are ways to maintain tree health for a year or two while a long-term solution is developed. In addition, trees that are already heavily infected are not likely to be cured with these fungicides.

Powdery mildew

In New England, powdery mildew is not an economically important disease. It can occur on occasion on sensitive cultivars. Ginger Gold is perhaps the most sensitive cultivar, followed by Cortland, and to a lesser extent Gala, Jonathan, Mutsu, Paulared, Idared, and Rome. Fungicide selection can also contribute to mildew outbreaks, as captan and the EBDC fungicides are not effective against the disease. The benzimidazoles, Topsin-M and Benlate, can be very effective against powdery mildew, but resistant strains have limited their use in New York.

The SI fungicides (Rubigan, Procure, Nova, Bayleton) are the most effective materials to use. Generally, the disease will be noticed in mid-June or early July. To halt new infections during the summer, make 2 to 3 SI applications at 10 to 14 day intervals as soon as symptoms are seen. Sulfur can also be effective, but can russett fruit and needs to be reapplied at 7 day intervals. Next season, apply 2 to 4 more SI sprays, starting at pink. Since the SI fungicides are effective against scab in pink, bloom, petal fall and fruit set sprays, simply making sure to use one of the SI fungicides during that period should also eliminate powdery mildew.

Post-harvest rot fungicides.

The post-harvest fungicide options this year are very limited. The only chemicals that remain registered for post-harvest treatment of apples are thiabendazole (Mertect 340F) and captan. These chemicals are used primarily to treat possible Penicillium and Botrytis infections that come about in drench tanks used to treat with the anti-scald chemical, diphenylamine (DPA). Fungal spores build up in the dip tank water, and get into wounds, and eventually cause infections. Only some varieties, notably Cortland and Delicious, are susceptible to scald. If DPA isn’t needed, there is no need to dip, and no need to treat with Mertect or captan.

If apples need to be dipped for scald, then Mertect or captan or both will need to be added to the tank. Mertect, compared to the previously registered fungicides Benlate and Topsin M, tends to settle in the bottom of the tank, where it is ineffective. Constructing or purchasing a recirculating unit for drench tanks will solve this problem. Agitation for 5 minutes every hour will keep Mertect in suspension, but failing to agitate will lead to a failure in control.

Another problem with Mertect is fungal resistance to the chemical. Mertect is a benzimidazole, like Benlate and Topsin, and strains of Penicillium have become resistant to these chemicals. Fortunately, strains that are resistant to benzimidazoles have often been susceptible to DPA, though strains resistant to both chemicals have appeared.

Captan has not proven very effective in postharvest tests on apple rots. However, it was generally tested at relatively low rates. Highest label rates have been effective against Penicillium in overseas tests. It may be particularly useful to combine Mertect and captan to reduce resistance problems.

The biocontrol option, Decco I-182 has not been very effective and may not be available for apples in 1999.

Pre-plant fumigation using a granular formulation

Without getting into the pros and cons of pre-plant soil fumigation, there is a newly registered option for doing it. Basimid Granular (dazomet) is a soil sterilant or fumigant, and has been recently labeled by Micro Flo for non-bearing apple trees (pre-harvest interval of 1 year) for management of diseases, weed seeds, and grasses. The label describes a 7 day program of wetting down twice a day unless tarps are used.

Winter pesticide storage

Vangard: store in a cool, dry place. Basamid: store in a cool, dry place below 95oF (35oC).  (pg. 56)

EBDC rates

Rates of the EBDC fungicides (Dithane, Manzate, Penncozeb and Polyram) present a dilemma. It is tempting to use an inexpensive program of either the EBDCs or captan for the full season. Captan is an excellent scab fungicide, and a bit more effective than the EBDCs. Just how effective is difficult to determine. However, if 1lb/100 gal of captan 50W is giving good scab control, that does not mean that 1 lb/100 gal. of an EBDC will give quite the same control. It appears that using 2 lbs/100 gal. of captan 50W or the equivalent of 2 lbs/100 gal. of a 75 - 80% formulation of an EBDC both give excellent scab control. However, cutting back to the Extended Schedule rates of the EBDCs, something that works out to 3 lbs./acre, may result in application rates of around 3 lbs./100 gal. That is probably stretching EBDC scab efficacy to the limit. If an EBDC is being used for scab control, it is far better to use the 4 application program at higher rates, and switch to another material when the limit is reached. (pg. 57-61) 

Karmex forumulation

In addition to the Karmex formulation of diuron, there is a Direx 80DF formulation. (pg. 98)

Goal time limitation

Oxyfluorfen (Goal) - Time limitation should say "Apply in dormant season before bud swell only." (pg. 98)

Simazine formulation

Replace Simazine formulations with "Princep 4L". Label rate per acre is 2–4 quarts. Soil limitation is "Do not use on gravely, sand, or loamy sand soil." (pg. 99) 

Bar soap for deer

In the statement that warns of possible increased vole damage with use of bar soap, it should be added that this is when soap residues run down or drip onto the trunk. (pg. 45)

Deer repellant

Big Game Repellant or Deer Away is applied to dormant growth. It works as both a taste and odor repellant. Hinder can be used year round, and is an odor repellant. (pg. 45)

Deer fencing

Another disadvantage of electric fencing is susceptibility to lightening strikes. Adequate lightning protection should be employed. (pg. 45-46)

For back cover of guide:

Chemtrec phone number for hazardous chemical spills, leaks, or fires is 800- 424-9300.