Diseases | Credits
SCAFFOLDS Fruit Journal, Geneva, NY Volume 4 Update on Pest Management and Crop Development September 11, 1995
43F 50F Current DD accumulations (Geneva 1/1-9/11): 3394 2459 (Highland 3/1-9/10): 3637 2589 Coming Events: Ranges: Lesser Appleworm 2nd flight subsides 2775-3466 2002-2460 Lesser peachtree borer flight subsides 2782-3328 1796-2359 Codling moth 2nd flight subsides 2782-3624 1796-2582 Obliquebanded leafroller 2nd flight subsides 2809-3433 1930-2359 Oriental fruit moth 3rd flight subsides 2987-3522 2018-2377 American plum borer 2nd flight subsides 3005-3587 2154-2497 Redbanded leafroller 3rd flight subsides 3114-3433 2013-2359 STLM 3rd flight subsides 3235-3471 2228-2472 TRAP CATCHES (Number/trap/day) Geneva: 8/28 8/31 9/5 9/7 9/11 Redbanded Leafroller 0 0.2 0.1 0 0 Spotted Tentiform Leafminer 185 230 89 65 8 Oriental Fruit Moth (apple) 4.8 6.0 10.5 11 7.0 Lesser Appleworm 1.4 2.7 6.2 3.5 5.4 Codling Moth 2.0 1.8 1.1 1.3 0.4 San Jose Scale 0.6 2.5 0.2 0 0 American Plum Borer (cherry) 0.4 0.5 0.1 0 0 Lesser Peachtree Borer (peach) 0.5 2.3 0.9 2.0 0 Lesser Peachtree Borer (cherry) 0.5 0.7 0.6 0.3 0.3 Peachtree Borer 0 0.2 0.1 1.3 0 Obliquebanded Leafroller 0.1 0.3 0.1 0.3 0 Apple Maggot 0.1 0 0 0 0 Highland (Dick Straub, Peter Jentsch) 8/11 8/21 8/28 9/5 9/11 Redbanded Leafroller 0.2 2.3 3.5 0.6 0.2 Spotted Tentiform Leafminer 33.9 57.8 25.9 16.9 12.6 Oriental Fruit Moth 0 0.1 0.9 1.1 0.7 Codling Moth 2.4 0.7 0.5 0.1 <0.1 Lesser Appleworm 1.1 0.4 0.2 0.7 0.5 Sparganothis Fruitworm 1.9 1.3 1.8 1.3 1.2 Tufted Apple Budmoth 0.3 0.8 0.5 0.5 0.4 Variegated Leafroller 0 0.4 0.8 0.4 0.3 Obliquebanded Leafroller 0.1 0.3 0.2 0 0.3 Apple Maggot 0.4 0.7 - 0.8 0.3
By:Art Agnello, Harvey Reissig, & Dave Kain, Entomology, Geneva
Even though insects and mites certainly made their presence known in tree fruits this past season, our view of the 1995 pest situation was that it didn't actually have that desperate, crisis-edged feel that some seasons do, although don't forget that we aren't growers, which is who will have the final say in this matter. Things tended to happen in a big way or not at all, including the weather highlights, which were notable for the amounts of heat (big way) and rainfall (not at all) most areas received, and how this affected pest development and occurrence.
MITES: Far and away the biggest news of the summer was the statewide mite pressure. A great fall for egg-laying, a mild winter for survival, and perfect early summer weather combined to produce record numbers of European red mites by unusually early dates - June, in some cases. Every acaricide available had its work cut out for it, although Omite deserves honorable mention for performing extremely well wherever it was used (given that these were ideal conditions for this product's kind of activity). The hot and dry weather also made it hospitable for two-spotted spider mites in some orchards, not only in apples following (or on top of) ERM, but also in a few pear blocks. Pear rust mite didn't seem to show up as far as we could tell, but the peach silver mite made a worrisome (although probably harmless) showing in some peach orchards. Early season oil worked about average, depending on how favorable the application weather had been, and this year the summer oil programs generally did not do a satisfactory job in the blocks with the highest pressure (read Red Delicious). Most growers needed 2-3 summer acaricide applications in the worst spots to avoid the prospect of severe leaf loss. For what it's worth, most populations seemed to poop out before the middle of August, well before getting the chance to lay many overwintering eggs, so it's likely that our 1996 spring egg population will be much lower than this year, which should help prevent a repeat of the high summer populations. [Note: From what I've heard in other states where Apollo was available as a tight cluster application, populations still broke early enough in the summer to warrant 1-2 additional sprays of a contact material.]
OBLIQUEBANDED LEAFROLLER: This old nemesis provided respectable pressure in western N.Y., with fruit damage reaching 10-15% in some of the localized hot spots. Fortunately, it seems as though most growers were able to adequately address this pest through awareness of block history; that is, by treating preferentially with materials that hadn't been overused in the recent past. It's safe to say that there was a potentially wide range of outcomes (including everything from very acceptable control to abysmal) to strategies using any of the available OBLR materials this year: Penncap-M, Lannate, Lorsban, Asana, and B.t. Conservatism seems to have been the watchword here, with the best results obtained from a first application targeted at egg hatch, and 2Ð3 additional sprays timed to bracket the main period of larval activity. In the future, irrespective of the arrival of any new products, it would probably be a good idea to direct most control efforts at the first summer generation so as to minimize selection pressure on the entire population.
STANDBYS: A number of our normal pests were present more or less as usual. Pear psylla had no trouble getting established under the California-like conditions of this summer. Agri-Mek put up a good effort, but this turned out not to be quite long-lasting enough in some areas of the state, particularly parts of the Hudson Valley, where the sprays went on rather early after petal fall. Comply was also used under an EUP in many orchards, and we're not sure that the 2-spray program being promoted was distinctly different. Mitac ended up being used in most blocks to suppress later-season populations, as it often is. Plum curculio was at least average in severity; several field scouts reported seeing more damage than normal, but it's likely that these cases were probably more a matter of less-than-optimal spray timing. Green aphids occurred at healthy levels in apple orchards, maybe even a little earlier than is typical, but we tended to see populations decline considerably by mid-July, perhaps a result of the scarce shoot growth during our low-rainfall summer. White apple leafhopper was notvery evident during the post-petal fall period, but the second generation in western N.Y. has been about as problematic as usual.
NO-SHOWS: As always, some pests made only nominal appearances or were nearly absent, at least in western N.Y. These included spotted tentiform leafminer and apple maggot, rosy apple aphid, Comstock mealybug, tarnished plant bug, and woolly apple aphid.
By:Dave Rosenberger, Plant Pathology, Highland
Following are some general observations on tree-fruit diseases and disorders encountered in eastern N.Y. during the 1995 season.
Black rot fruit decay on apples has gradually increased in importance over the past three or four years. Most problems occur on cultivars such as Cortland that retain some of the fruitlets that are killed by thinning sprays. These mummified fruitlets become infected with the black rot fungus (Botryosphaeria obtusa) and provide inoculum for infecting other fruit. Mummified fruitlets remaining from the previous year supply inoculum for early-season fruit infections. Infections occurring during the prebloom, bloom, and petal fall period appear as calyx-end infections near harvest time. Infections during summer usually appear as lenticel spots. In most cases, infections on green fruit remain quiescent until fruit begin to ripen and the natural fungal inhibitors in the fruit disappear.
Black rot has emerged as a commercial problem because of changes in fungicide labels and scab control programs. The benzimidazole fungicides, Benlate and Topsin-M, provided excellent control of black rot when they were used for controlling primary scab. Mancozeb is less effective against the black rot fungus, but it appeared to give commercial control when used at the rates of 4.5-6 lb/A. More recently, growers have used mancozeb at the rate of 3 lb/A to comply with label changes, and black rot has emerged as a problem. The SI fungicides, Rubigan and Nova, do not control black rot. To control black rot in future years, I suspect we will need to alter fungicide programs so that either Benlate, Topsin-M, or Captan are included in petal fall, first and second cover sprays.
Fire blight caused sporadic problems despite weather conditions unfavorable for blossom blight. In some orchards (both apples and pears), the first evidence of fire blight reportedly appeared on terminals in late June or early July. In my opinion, the biggest remaining mystery with fire blight is how orchards that appear free of blossom blight can become affected with terminal shoot blight in late June and July. Is inoculum wind-blown during summer storms or vectored by insects? Does inoculum for late-June and July infections originate from unnoticed blossom blight infections within the orchard, or does it come from outside of the orchard? The severity of late-June and July blight infections is probably increasing in N.Y. as we plant more of the highly-susceptible cultivars (Jonamac, Gala, Fuji, Ginger Gold, etc.), push young trees harder to get orchards into production, and supply trickle irrigation to keep trees growing during droughts. We really need a chemical control to slow the spread of blight during summer.
Fruit russetting caused by delayed-dormant copper sprays is again evident in some blocks of apples and pears. Copper sprays have been recommended and were applied to reduce fire blight inoculum. However, this year we had only about 2.5 inches of rain between green-tip on 3 April and kingbloom on 4 May. With so little rainfall, copper residues persisted on the tree and were washed to the developing fruitlets beneath the open blossoms. Copper residues that persist until bloom can cause fruit russetting. When rainfall between green tip and bloom exceeds 3 or 4 inches as it usually does, we do not see damage from early copper applications. However, the possibility that copper can damage fruit in years with sub-normal prebloom rainfall leaves growers in the unfortunate position of having to decide each year whether they prefer to risk copper damage to their fruit or whether they prefer to take their chances with fire blight.
Flyspeck started appearing on unsprayed fruit at the Hudson Valley Lab during the last week in July. Nine wetting periods between 17 May (petal fall) and 2 June provided a total of 144 hours of wetting, and ideal conditions for primary infections by the flyspeck fungus. Dry weather during June and early July slowed symptom development, but disease development was promoted by eight inches of rain and 138 hours of rain-associated wetting between 23 July and 6 August. Commercial orchards were probably well protected from primary infections by mancozeb used in scab control programs. Secondary infections might have occurred in commercial orchards if fungicide cover was compromised by the heavy rains between 23 July and 6 August. However, symptoms from any mid-season infections that may have occurred will probably never appear on fruit before harvest, because we have had only a few hours of wetting since early August. Thus, flyspeck and sooty blotch should not be a major problem in commercial orchards this fall.
A combination of drought and temperatures exceeding 100¡F on July 16 resulted in heat stress damage on scattered apple fruit in some orchards. The heat stress damage first appeared as water soaked areas on the affected fruit 3-4 days after temperatures peaked on July 16. Affected tissues later turned brown and necrotic, and severely affected fruit shriveled. Symptoms appeared more severe where fruit were clustered than where fruit had been thinned to singles or doubles. In some orchards, damage occurred on both shaded and exposed fruit. The amount of damaged fruit was quite small in most orchards. Incidence of sunburned fruit (as distinct from the heat stress damage noted above) was considerable in some orchards that were summer pruned.
Peach leaf curl was extremely severe in Hudson Valley orchards were leaf-curl sprays were omitted. Hudson Valley growers can sometimes get by without leaf-curl sprays. However, leaf-curl infections were more severe than usual this year because orchards were not sprayed in 1994 when they had no fruit, and because we had a very mild 1994-95 winter.
Brown rot on peaches, plums, and cherries was more severe this year than I would have expected. In some orchards where spray coverage was incomplete, infections appeared on green cherry fruit in mid- to late June and on green plums in early August. Some peach and nectarine growers also had difficulty with brown rot during harvest. I suspect that problems developed primarily where growers failed to provide adequate fungicide protection during and shortly after shuck split. As noted above, we had 144 hours of rain-associated wetting between 17 May and 2 June. Mean temperatures for these wetting periods ranged mostly from 50 to 64°F, temperatures that are usually considered too cold to be ideal for brown rot infection. Taken together, however, the extended period of cool and wet weather after bloom apparently provided excellent infection and post-infection weather for brown rot.
Pear fruit with depressed lesions 8-15 mm in diameter have been brought to the Hudson Valley Lab by several growers. Skin over the surface of the lesions has the normal skin color, but the flesh beneath the sunken lesions is corky and dried out. Frequently there are multiple lesions on affected fruit. The lesions are not caused by any recognized fungal or virus disease. In the pear orchard at the Hudson Valley Lab, I have noted stink bugs on fruit that have lesions in various stages of development. I suspect the damage noted on pears is related to late-season stink-bug feeding.
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
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