Late Bite: Insects To Watch For At The End Of The Season.
With the end of the second generation of codling moth and the decline of the apple maggot flight it’s tempting to consider that the last spray in mid-August would usher in the end of the spray season. The applications of PGR’s for stop drop control and a final fungicide typically put the lid on the spray season. However, there should be some considerations made for a few insect pests that may come back to take the last bite out of a very successful pest management program. Lets look at these late comers that should be kept on the radar.
In past years the second brood of OBLR larva has proven to be a formidable threat in late season insect pest management. Oriental Fruit Moth can cause late season injury to late peach and apple while European corn borer can infest green terminal branches of newly planted trees while late green aphid during fall cool rainy periods that may lead to high populations that feed on fruit, followed closely by the predatory multicolored ladybird beetle damaging fruit while pupating on fruit. Lastly, every block with M-9 rootstock has dogwood borer. Check M-9 trunks for infestation levels at the burr knots, painted or not, before you winterize the sprayer!! Finally, BMSB have been on the increase this weekend and you will need to scout until the last apple is off the tree as late season stink bug management may be required.
Obliquebanded Leafroller (OBLR), Choristoneura rosaceana (Harris) outbreaks in New York, although less prevalent then we experienced in the late 90’s, have resulted in severe damage to apple, peach, and pear fruit in many orchards over the past few years. The biology of this insect is such that in years where foliage is lush due to ample rainfall (or irrigation), larva tend to begin feeding on leaves during the early instar stages, forming a near impenetrable ‘leaf rolled’ barrier to insecticides as it grows, making early management essential to effect control. However, in drought years, foliage provides less ‘appeal’ to the insect and it quickly moves to feeding on fruit. During these situations, it will form a cluster leaf covering directly over the fruit for protection. Once inside this fortress, the larvae are very difficult to eradicate. In either case, research has determined early hatch, prior to the development of these protected sites, to be the optimum timing for insecticide management of the insect. This tends to be more critical with the use of some of the newer insecticides and Bt’s.
Our management strategies have included directed applications during three periods of the growing season, targeting the overwintering generation during late pre-bloom and early post bloom, the summer generation and, if populations warrant (now), the second generation later in August.
Situations that would give rise to damaged fruit from this insect include the successful infestation of abandoned neighboring orchards and or lack of control in nearby orchards from the summer brood during late June and July. If high numbers of OBLR have been observed in pheromone traps over the past few weeks, scouting evaluations should be conducted to determine the presence of larva at the end of August. Fruit clusters should be broken open in the upper canopy during scouting to observe three distinguishing features: webbing between leaves, webbing between leaves and fruit, and small, pin hole larval feeding to the fruit. These overwintering larva will feed on both terminals and fruit, very often infesting varieties such as Spur Delicious and Cortland, well hidden in doubles concealed in tight leaf layers or in dense clusters of Jonamac and tight stemmed varieties such as Macoun.
The first sustained pheromone trap captures of 2nd generation of OBLR were observed at the HVRL on 11 of August (biofix date). It very likely that OBLR were captured early in southern counties with earlier timing of management.
Model predictions used to determine a more precise date for the early hatch of these eggs (360 DD43) forecasts 22nd of August to be first larval emergence in HIGHLAND, NY. Applications should be made shortly after this date. We would then expect 50% hatch to occur after 630 DD (Late August); the 2nd – 3rd instar larva of the early hatch by 720 DD, and 90% hatch of the eggs by 810 DD (1st-2nd week of September).
Weather patterns should be reviewed daily to find the optimum application window. Mid Hudson Valley temperatures are predicted to be moderate (upper 70’s and low 80’s) with 30-50% chance of rain for Wednesday-Thursday. A prolonged period without rain is optimum for control, however, intermittent heavy rains accompanied with wind often help in reducing early instar larvae numbers.
To delay the possibility of resistance you should use different classes of insecticide for each generation. This is especially so with regards to obliquebanded leafroller insecticide resistance management. Each generation should be targeted with a specific mode of action (MOA) or one class of chemistry. For example: if you used an OP (MOA Class 2) such as Lorsban 70WP at petal fall to manage the overwintering generation of OBLR, than Class 2 (Imidan 70WP) should not be used against the summer generation. If you used for example Altacor 35WDG or Belt SC for OBLR 1st generation larvae control, you should not use Belt 4SC or Altacor 35WDG again as they share the same target site where genetic modification can induce population shift leading to insecticide resistance.
In small plot field trials and farm demonstrations in NY, Delegate and Altacor have been shown to provide excellent control of the summer generation of OBLR. It appears to be more effective with the addition of a penetrating surfactant. Delegate, a synthetic spinosad chemistry, has greater efficacy and broader spectrum than its predecessor SpinTor, providing 14-21 days of protection. Dow AgroSciences will soon replace SpinTor with Delegate, maintaining the Entrust formulation for organic management.
Proclaim (Avermectin class), has also shown very good activity against OBLR. It’s mode of action requires the active ingredient be ingested by larvae. Proclaim at the 4.5 oz/acre should be applied using a penetrating spray adjuvant to improve efficacy, such as Damoil at 2 qts./100 gallons. The use of a sticker/binder however should not be used as they may inhibit the movement of product into the plant. DO NOT tank mix Proclaim with Dithane, Rainshield as they act sticker type materials. The addition of Warrior to Proclaim appears to enhance activity / efficacy in studies from Michigan.
Bt’s are most effective when applied during warm weather conditions (daily highs in the 70’s F) and are most effective against smaller larvae. Using 2–4 sprays at the low rate on a 7-day interval, starting 10–12 days after first adult catch, has been shown to be very effective in field studies. Bt products are generally more effective with a lower tank pH.
Intrepid can be employed earlier than (at 260 DD), targeted to cover obliquebanded leafroller egg masses. As leafroller larva emerge, they ingest the insecticide on the egg ‘shell’. Intrepid can also be used later on older larva for fruit protection. Intrepid has a long residual and should be reapplied where necessary on a 14-day schedule to cover new terminal growth. Intrepid is also more effective with the addition of a penetrating surfactant.
For conventional insecticide use, it is generally understood that OBLR aquired resistance in the Hudson Valley and western NY to the OP Azinphos-methyl. If the organophosphate (OP) Imidan, carbamates, pyrethroids, are used, the application should be targeting the first hatch to control larvae before they can form protective coverings or damaging fruit. Some farms still achieve control with Phosmet (Imidan) and pyrethroids. Keep in mind that lepidoptera larva have been known to more easily detoxify the pyrethroids as temperatures increase (above 80F), reducing effectiveness.
Follow-up applications for this second OBLR hatch may not be needed. However, based on past history of leafroller fruit damage on the farm, weather patterns such as rain events and cool temperature, which may prolong the emergence period, as well as insecticide residual efficacy, a second application at a 14d interval may be needed. Delegate and Altacor have long residual activity to 14 days or longer. Bt products such as Dipel can be applied at lower labeled rates but more frequently at 5-7 day intervals as they are susceptible to UV degradation. Pyrethroids are relatively shorter, at best providing 12-14d. Scouting in early September is advised.
Oriental Fruit Moth: A second lepidopteran to keep an eye on is the larva of the 3rd generation of oriental fruit moth, an internal lepidopteran pest capable of causing late season injury to tree fruit. OFM flight in the lower Hudson Valley began on teh 5th of May and we’ve been capturing OFM adults ever since, making the separation of generations very difficult this season. Generally, the OFM larva expected to emerge through August into September. Sprays to control the third generation of OFM may be necessary for high-pressure orchards. For mid-season maturing cultivars this spray timed for early hatch may be the last spray of the season. For late maturing apples, another spray may be needed 10-14 days later. Observations have shown that late sprays (during September or October) may be necessary to protect fruit of late maturing cultivars if damage from OFM is noted during fruit inspections in the summer.” Most applications for OBLR will provide control for the OFM.
European corn borer (ECB): 2nd generation adults are on the wing with relatively high numbers of pheromone trap captures in New Paltz, lower numbers in Warwick and Accord. Extension growth of newly planted young tree terminals are susceptible to ECB infestations, especially if tall weeds and grasses in tree rows are present. Although infestations of ECB are unpredictable, infestations can cause serious damage in blocks with no prior incidence of injury. ECB injury is most often seen in young or newly planted orchards as they often receive low levels of insect pest management. Injury to newly planted trees by larval tunneling occurs in the current season’s growth that results in terminal leaf discoloration. Continued larval feeding will eventually kill the terminal shoot, causing die-back and malformation of the tree. Corn borer attack on young trees can occur from June through August. Two ‘broods’ exist in NY, which include the “Z race” which has one generation per season, and the “E & Z Race”, which have two generations. Over the past few years trap captures of one or both races have been shown to linger into late July throughout the mid-Hudson Valley. Fruit feeding can also occur late in the season through harvest. Delegate 25WG and Dipel 10.3DF are labeled for ECB management, and when used for OBLR management will also control ECB infestations at the onset of hatch and feeding.
Dogwood borer (DWB): was covered very well in Scaffolds last week entitled “IN GALLERIES NOW”.
IF Brown Marmorated Stink Bug (BMSB) makes a late season appearance sprayers will need to be on hand right up until the last apple is harvested. More on BMSB here.