SCAFFOLDS Fruit Journal, Geneva, NY Volume 4 Update on Pest Management and Crop Development April 10, 1995
43F 50F Current DD accumulations (Geneva 1/1-4/10): 125 53 Coming Events: Ranges: Green fruitworm peak flight 64-221 19-108 Redbanded leafroller 1st catch 32-480 5-251 Spotted tentiform leafminer 1st catch 73-433 17-251 Rosy apple aphid nymphs present 91-291 45-148 McIntosh at green tip 24-161 4-74 PHENOLOGIES: Geneva, 4/10 Apple (McIntosh): Silver Tip Pear, Cherry, Peach, Plum: Dormant Hudson Valley Lab, Highland Apple (McIntosh): April 10 Quarter-Inch green TRAP CATCHES (Number/trap/day) Geneva: 3/30 4/3 4/6 4/10 Green Fruitworm 0 0 0 0.1 Redbanded Leafroller 0 0 0 0 Highland (Dick Straub, Peter Jentsch) 3/30 4/3 Green Fruitworm 0.75 0.1 Pear Psylla eggs (/terminal bud) - - Redbanded Leafroller 1.75* 0 * = 1st catch
APPLE SCAB ascospore maturity (D. Rosenberger) Highland, NY: Immature Mature Discharged Tower shoot April 7 92% 8% 0% 0 spores
By: Dave Rosenberger
There was no change in maturity over the past week because of cold weather. The lower Hudson Valley had five inches of snow on Saturday with snow cover persisting through mid-day on Sunday. Additional rain showers occurred on Sunday evening. These wetting events posed no threat for scab infections because of the cold temperatures and the lack of mature spores.
Telephone number changes at the Hudson Valley Lab: During the past winter, we added a telephone line and re-arranged assigned telephone numbers at the Hudson Valley Lab. Assigned phone numbers are now as follows:
Rosenberger, Stover, and Straub can also be reached at 914-691-7151 during hours when our secretary/receptionist, Donna Clark, is on duty. Donna works from 8:00 AM to noon and from 1-3:30 PM Monday through Friday. However, she is sometimes away from her desk and unavailable to answer the telephone for short periods during these working hours. When Donna is not available, including sick days and vacation days, the 7151 number will be answered by a research technician if one of them is working at his or her desk. Otherwise, callers will get the answering machine.
We are sorry that we are unable to provide more complete and effective phone answering services, but we believe the current arrangement is the best we can do within current budget limitations.
By: Art Agnello
There's still probably more call for a snowplow than a speed sprayer so far, but the weather is sure to moderate one of these days, so the following is a rerun of our annual message about the effect of spray water pH on pesticide activity. There may be times when you don't get the expected results from a pesticide application, even though you used the correct concentration of the recommended material and applied it in the same way that has given acceptable control at other times. Although you may suspect a bad batch of chemical or a buildup of pesticide resistance, the poor results may in fact be due to alkalinity -- that is, a solution with a pH higher than 7.0. A close inspection of the pesticide label will often reveal a caution against mixing the chemical with alkaline materials such as lime or lime sulfur. The reason is that many pesticides, particularly insecticides, undergo a chemical reaction under alkaline conditions that destroys their effectiveness. This reaction is called alkaline hydrolysis, and can occur when the pesticide is mixed with alkaline water or other materials that cause a rise in the pH.
Hydrolysis is the splitting of a compound by water in the presence of ions. Water that is alkaline has a larger concentration of hydroxide (OH-) ions than water that is neutral; therefore, alkaline hydrolysis increases as the pH increases. Insecticides are generally more susceptible to alkaline hydrolysis than are fungicides and herbicides, and of these, organophosphates and carbamates are more susceptible than pyrethroids. A survey of fruit-growing areas in N.Y. showed that water from as many as half of the sites in western N.Y. had pH values above 8.0. Water at this pH could cause problems for compounds that will break down in only slightly alkaline water, such as ethephon (Ethrel). Compounds that break down at a moderate rate at this pH, such as Carzol and Imidan, should be applied soon after mixing to minimize this process in the spray tank. A smaller number of sites (less than a quarter of them) had pH levels greater than 8.5. Above this level, the rate of hydrolysis is rapid enough to cause breakdown of compounds such as Carzol and Imidan if there is any delay in spraying the tank once it is mixed. In a few sites having a pH above 9.0, compounds such as Guthion and malathion, which would not break down in most situations, may have problems. It is also important to note that in any one site, ground water pH can vary substantially (by nearly 2 pH units) during the season.
In order to prevent alkaline hydrolysis, you should:
Growers may add technical flake calcium chloride to the tank when spraying cultivars such as McIntosh, which is susceptible to storage disorders related to inadequate levels of fruit calcium. However, research done in Massachusetts indicates that, although calcium chloride does not itself affect pH, a contaminant present as a result of the manufacturing process does increase the pH of the solution; this could in turn encourage alkaline hydrolysis. There are a few pesticide materials that should not be acidified under any circumstances, owing to their phytotoxic nature at low pH. Sprays containing fixed copper fungicides (including Bordeaux mixture, copper oxide, basic copper sulfate, copper hydroxide, etc.) and lime or lime sulfur should not be acidified. But if the product label tells you to avoid alkaline materials, chances are that the spray mixture will benefit by adjusting the pH to 6.0 or lower.
For further information on water pH and pesticide effectiveness, refer to N.Y. Food & Life Sci. Bull. No. 118, "Preventing decomposition of agricultural chemicals by alkaline hydrolysis in the spray tank", by A. J. Seaman and H. Riedl, from which much of this information was adapted.
By: Jan Nyrop
If you read last week's Scaffolds article on transferring predatory mites, there probably appeared to be extraneous text that was unrelated to the topic being discussed. This is because there actually was extraneous text -- in this case, the final paragraph. After editing an earlier and more extensive article to produce the write-up for Scaffolds, I neglected to remove some sections from the original file. However, for all you information mavens, Typhlodromus pyri were most common in trees into which T. pyri were transferred at bloom, but least common in trees into which no predators had been transferred. There were no apparent differences in predator species composition in trees into which predators were transferred at half-inch green vs. tight cluster. Also, at both the Minns and Trickler sites, the two 1% summer oil applications resulted in fewer T. pyri (Minns p < 0.01; Tricker p < 0.01). However, the effect of the oil treatments was more pronounced at the Trickler location, where the volume of oil applied was much higher.
Scaffolds is published weekly from March to September by Cornell University -- NYS Agricultural Experiment Station (Geneva), and Ithaca -- with the assistance of Cornell Cooperative Extension. New York field reports welcomed. Send submissions by 3 p.m. Monday to:
Scaffolds Fruit Journal
Editors: A. Agnello, D. Kain
Dept. of Entomology, NYSAES
Geneva, NY 14456-0462
Phone: 315-787-2341 FAX:315-787-2326
Back to the 1995 Scaffolds directory
Scaffolds Home Page