August 9, 2004
|Upcoming Events||Pheromone Trap Counts||Plant Pathology||Horticulture||Small Fruit|
- Tree Fruit Grower Twilight Meeting at Showalter's Orchard and
August 14 - Roadside, CSA and Farmers Markets Workshop,
bud moth second generation egg
hatch is estimated at 35% complete, based on an accumulation of 2470
degree days (DD) since biofix on May 6.
See the July 26th issue of The
Orchard Monitor newsletter for control options and application
Codling moth second generation egg hatch is almost complete, based on DD accumulations (2062) since biofix on April 30. Third generation egg hatch is expected to begin by the end of this week. Insecticides should be applied for third generation control in those orchards where the pheromone trap capture exceeds 5 moths/trap/week. If using Intrepid, Assail or Calypso, initiate control at 2160 DD after biofix (1% egg hatch). If using Avaunt, Azinphos-methyl (Guthion), Imidan or pyrethroids, initiate control at 2270 DD after biofix (6% egg hatch). An initial spray of any material should be followed by a second complete application in about 10-14 days, or three additional alternate-row-middle applications 5-7 days apart.
Oriental fruit moth third generation egg hatch is estimated at 88% complete on peach, based on an accumulation of 2798 DD since biofix on April 16. Egg hatch is lagging behind on apple due to slower development on this fruit crop. Because of overlap between the third and fourth generations, the best policy for the remainder of the season is to base the need for treatment on pheromone trap capture. Initiate insecticide applications about 7 days after exceeding a trap threshold of 10 moths/trap/week, and maintain spray intervals on a 2 week (complete) or 5-7 day (alternate-row-middle) schedule for as long as this condition continues. Control options on peach [days to harvest] include azinphos-methyl (Guthion) , Imidan , Intrepid , Lannate [4 on peach, 1 on nectarine], and carbaryl (Sevin) . Control options on apple include azinphos-methyl (Guthion) , Imidan , Intrepid , Avaunt , Assail , Calypso , Asana , Danitol , and Warrior .
|White apple leafhopper second generation nymphs are beginning to appear on the underside of apple leaves. These may be accom- panied by third generation (second generation on apple) nymphs of rose leafhopper in some orchards. Young nymphs of both leafhopper species appear identical, but older nymphs of rose leafhopper can be differentiated by their spotted appearance (black spots on the back). Nymphs of both species will reach the adult stage during the harvest period and, if abundant, can become a nuisance to pickers. In addition, excretion of honeydew from high populations can result in sooty mold deposits on fruit. Examine the undersides of 10 older leaves per tree on 5-10 trees per block and determine the average number of nymphs per leaf (both species combined). To prevent economic impact from leafhopper feeding, an average of 3 nymphs per leaf is recommended as an action threshold. An average of 1 nymph per leaf is recommended as an action threshold where the nuisance to pickers from adults is a concern during harvest. Recommended materials for control include Lannate, Vydate, Provado, Actara, Assail, Calypso, and Avaunt.|
Lesser peachtree borer and peachtree borer larvae can be controlled on peach and nectarine trees in the postharvest period. For lesser peachtree borer (LPTB), inspect wounded areas on the upper trunk, scaffold limbs and branches to determine the average number of empty pupal cases per tree protruding from the bark. Also inspect wounds for evidence of larvae or fresh (amber colored) gum exudates mixed with wood borings and sawdust-like frass (excrement). Control is recommended if there are more than a total of 2 larvae or empty pupal cases per tree.
For peachtree borer (PTB), inspect the base of trees for an exudation of gum containing frass and sawdust, and examine the soil at or near the base of trees for cocoons and empty pupal cases. Control is recommended for trees up to 3 years old if any evidence of PTB infestation is detected. In older orchards, an average of more than 1 cocoon and/or empty pupal case per tree would warrant treatment. Lorsban 4E is the preferred choice for postharvest control of either borer species. Most effective control is achieved with a handgun application. For LPTB control, thoroughly wet all wounds on the trunk, scaffold limbs and small branches. For PTB control, thoroughly drench the lower trunk, allowing the liquid to pool at the base of the trees.
PHEROMONE TRAP COUNTS
WEST VIRGINIA UNIVERSITY KTFREC
|DATE - 2004||RBLR||STLM||OFM||CM||TABM||DWB||LPTB||PTB||AM|
|DATE - 2004||RBLR||STLM||OFM||CM||TABM||DWB||LPTB||PTB||AM|
RBLR = Redbanded leafroller; STLM = Spotted
tentiform leafminer; OFM = Oriental fruit moth; CM = Codling moth; TABM = Tufted
apple bud moth; DWB = Dogwood borer; LPTB = Lesser peach tree borer; PTB = Peach
tree borer; AM = Apple maggot.
Infection periods. We have recorded 28 infection periods to date (Table 1), two occurring since the last Orchard Monitor was published on July 26, 2004. Proper spray timing is the key to good summer disease control.
Table 1. Dates and conditions for infection periods at the WVU - KTFREC, 2004.
|No.||Date 2004||Hours/ degrees F|
|15.||June 5||4 hr/58 F|
|16.||June 10 - 12||52 hr/58 F|
|17.||June 15 - 16||18 hr/70 F|
|18.||June 25 - 26||12 hr/69 F|
|19.||July 4 - 5||17 hr/72 F|
|20.||July 7 - 8||15 hr/68 F|
|21.||July 12 - 13||12 hr/72 F|
|22.||July 13 - 14||14 hr/ 73 F|
|23.||July 18||14 hr/67 F|
|24.||July 20 - 21||14 hr/65 F|
|25.||July 22 - 24||34 hr/73 F|
|26.||July 25 - 26||14 hr/69 F|
|27.||July 27 - 28||18 hr/72 F|
|28.||July 31 - August 1||16 hr/72 F|
Avoid the "October Surprise!" Pin-point scab. This season has been one of the worst seasons for scab in our area. It may not be over yet, unfortunately. "Pin-Point" or "Storage" scab can develop under certain conditions and ruin a seemingly non-infected crop in storage. Storage scab poses an economic threat only when both of the following conditions are met: 1) scab inoculum is abundant in the orchard prior to harvest; and, 2) fruit in the orchard are exposed to a continuous wetting period of at least 48 hours duration at a time when fungicide residues from the last spray have been depleted.
What constitutes abundant inoculum? Orchards with a few old lesions from infections that occurred in May will not have enough inoculum to initiate storage scab. However, this year some orchards had extensive infections during May and June that resulted in two or more infected leaves per terminal. These infections were frequently arrested by using applications of SI fungicides plus captan. In many cases, the scab epidemic was contained, but enough inoculum has persisted to allow new infections to develop on leaves during late summer.
The best way to determine if orchards have active inoculum is to check the youngest terminal leaves, especially on water sprouts near the upper-center part of the canopy. Where scab has remained active through summer, these youngest terminal leaves are now showing active scab lesions on the upper and/or lower surfaces. Lesions on the lower surface of the leaves vary from pale, diffuse brown spots to very dark-colored brownish-black spots. Scab lesions usually have a fuzzy or velvety appearance with lesion margins that are somewhat indistinct.
Continuous wetting periods of at least 48 hours are required to initiate infections on fruit during the preharvest interval. With extremely high inoculum levels, a few fruit infections might occur with wetting periods as short as 30 hours, but economic damage is not likely unless wetting periods exceed 48 hours. Very severe infections could be expected if we should encounter continuous wetting periods of more than 96 hours. Drying periods as short as two hours in the middle of longer wetting periods will significantly reduce the amount of infection that occurs.
Infections occurring during the last week (and perhaps two weeks) prior to harvest may pose less threat than infections that occur slightly earlier during the preharvest interval. Apparently infections occurring during the last week before harvest are not sufficiently well-established to allow further development during cold storage. However, delays in cooling fruit after harvest could allow even those "last-week" infections to develop symptoms during storage.
The probability of getting weather conditions that favor severe storage scab are relatively low because the probability of having continuous wetting for 4 days during harvest is low. Furthermore, enough rain would be needed prior to the four-day wetting to remove all captan residues from the fruit. Should such conditions develop, however, losses could be very high in orchards with abundant inoculum. Therefore, an additional spray of captan may be necessary in high-inoculum orchards if weather predictions call for extended wetting periods.
If high-inoculum orchards are left unprotected through an extended wetting period, nothing can be done to stop symptom development after the fruit infections are initiated. Postharvest drenches are not effective for controlling storage scab.
If weather conditions favor late-season scab development and high-inoculum blocks are not protected with fungicide, then the best solution will be to sell the potentially-affected fruit as soon as possible after harvest. In experiments conducted in South Africa, the first symptoms of storage scab appeared on Granny Smith after 80 days at 32-34 F as compared to 35-45 days for fruit at 68 F. However, scab lesions might appear in less than 80 days at 32-34 F on fruit that were infected earlier during the preharvest interval. Other studies have shown that new lesions appear more quickly at higher temperatures, but the total number of lesions is ultimately the same if apples are stored long enough to allow symptoms to develop at cold temperatures. Storing apples under reduced relative humidity can minimize lesion size because lesions develop greater size when fruit are held under high-humidity conditions, especially if the latter results in condensation developing on the fruit surface during storage.
The bottom line: Risks of storage scab are relatively small even in a year when inoculum is relatively abundant. However, the consequences of storage scab can be severe since infection rates can reach 100% and the losses become evident only after storage costs have been incurred. Therefore, monitor orchards now to determine if scab is active. Follow weather forecasts carefully. Apply captan in high-risk blocks ahead of predicted extended-wetting periods.
See our "Current Conditions" Web page for details that are updated as needed.
ReTain is Now Labeled for Stone Fruit, Except Cherries
ReTain is now labeled on stone fruit (except cherries) in addition to apples and pears.
ReTain, commonly known as aminoethoxyvinyl-glycine, aviglycine HCL or AVG is a growth regulator produced by fermentation. This product is marketed by Valent USA Corporation. On peaches it can slow the maturation process of the fruit, increase fruit size, maintain fruit firmness, reduce fruit drop, improve fruit quality and lengthen fruit storage potential. It does this by reducing ethylene production, which as you know is a plant hormone that promotes fruit ripening.
On peaches, nectarines, and plums one pouch of ReTain should be applied per acre 7-14 days prior to the anticipated beginning of the normal harvest period. ReTain may be used on stone fruit with or without an adjuvant.
ReTain should be applied under slow drying conditions in the morning or evening to promote absorption. Applications should not be made when the fruit is hot. Spray solution pH should be between 6 and 8 and this product should not be used on trees that are stressed. This material should not be applied if rain is expected within 8 hours of application. The pre-harvest interval for ReTain on stone fruit is 7 days.
Note: PHI for ReTain on apples and pears is 21 days.
(Adapted from article in Kentucky Fruit Facts, July, 2004 by John Strang and Joe Masabni, Extension Fruit and Vegetable Specialists)
New Powdery Mildew Fungicide for Grapes
Quintec (quinoxyfen) is a new protectant fungicide labeled for control of powdery mildew on grapes. Quintec is normally applied on a 14-21 day schedule starting early in the season before powdery mildew infections begin. The fungicide is not to be used within 14 days of harvest and no more than 5 times per season. Quintec would normally be used in combination with a black rot fungicide and is compatible with other commonly used fungicides and insecticides. Based on information from the national Fungicide Resistance Committee, this fungicide has a chemistry and mode of action different from other fungicides such as the strobilurons and sterol biosynthesis inhibitors. Thus, it can be alternated with these fungicides to help prevent fungicide resistance development by the powdery mildew fungus. Quintec is manufactured by Dow AgroSciences. Recommended spray intervals are 14 days for 3-4 fluid ounces; 21 days for 5-6.6 fluid ounces per acre. Minimum spray intervals are 7 days for 3-4 fluid ounces and 14 days for 5.5-6 fluid ounces per acre. Maximum application rate is 6.6 fluid ounces of Quintec per acre per calendar year. Do not make more than 5 applications of Quintec per calendar year.
(Adapted from Kentucky Fruit Facts, July 2004; original article by John Hartman)
READ THE LABEL CAREFULLY AND USE THE CHEMICALS IN ACCORDANCE WITH LABEL CAUTIONS, WARNING AND DIRECTIONS. REQUEST A MATERIAL SAFETY DATA SHEET (MSDS) FROM THE MANUFACTURER FOR EACH PRODUCT YOU USE.
Trade and brand names are used only for the purpose of information, and the West Virginia University Extension Service does not guarantee nor warrant the standard of the product, nor does it imply approval of the product to the exclusion of others which may also be suitable. The West Virginia University Extension service assumes no responsibility in the use of hazardous chemicals.
Individuals requesting an accommodation at a meeting because of a disability should contact one of the Extension Specialists at the WVU Kearneysville Tree Fruit Research and Education Center at 304-876-6353 at least five days prior to the event.
Helping you put knowledge to work
TREE FRUIT RESEARCH AND EDUCATION CENTER
P. O. BOX 609
KEARNEYSVILLE, WV 25430-0609
The West Virginia University Cooperative Extension Service,
U.S. Department of Agriculture, West Virginia County
Boards of Education and County Commissions Cooperating. Equal Opportunity / Affirmative Action Institution