Forecast for the next seven days show a warming trend with prolonged moderating temperatures. That said we are gearing up to flush and calibrate our sprayers this week. Applications for San Jose scale (SJS) control should begin once the insect breaks diapause. Diapause ends as day-length and temperature increases. For SJS the developmental base temperature at which the insect becomes active is 50F. Both day and night temperatures sustained at 50F breaks diapause, increasing the insect metabolism and respiration. Oil is effective against the insect due to its ability to smother respiration while insecticides are metabolized and transferred to a specific target site within the insect to cause mortality. If even a small percentage of your fruit was lost to scale, those blocks need to be managed this spring to avoid losses in 2016. If left unchecked, exponential losses of fruit will occur this season.
San Jose scale Quadraspidiotus perniciosus (Comstock): The SJS is now in the ‘Black Cap’ overwintering stage. The yellow immature females and males are beneath individual ‘scale’ coverings and will complete development, mate and bear live young or ‘crawlers’. They need to breath and metabolize food they obtain from feeding on the sap of the tree beneath their chitinous shell.
One shot may not be enough: The most effective options for SJS management include 1% horticultural oil alone or with insecticides used against SJS. The most effective materials include the insect growth regulators (Centaur & Esteem), Lorsban, 1% horticultural oil alone or in combination with these materials to improve distribution, while penetrating chitin layers. The use of Lorsban to manage scale early (post diapause) provides greatest potential for coverage and reduces the negative impact on beneficial arthropods such as Typhlodromus pyri and Amblyseius fallacies mite predators. If SJS is not a primary concern (ie. No SJS found on fruit in 2015) Lorsban would best be applied at late tight cluster to the pink stage of apple to optimize Obliquebanded Leafroller, Green Fruit Worm, Red Banded Leafroller and early Plum Curculio management, with decreasing efficacy and coverage for SJS management due to increased droplet shading from developing foliage. However if dogwood borer and or black stem borer management is required, then specific trunk sprays using Lorsban should be considered.
Pre-bloom (over the next few weeks) is by far the most opportune time to manage SJS. The overwintering immature stage, protected beneath the waxy covering are least protected from a spray application. However, developing foliage will increase ‘spray shadowing’ as the season progresses, reducing application effectiveness. A most effective timing during this period is delayed dormant, from the time silver tip begins on up to 1/2″ green. We are all familiar with the use of horticultural oil, Lorsban, Supracide directed against overwintered “black caps” during this period, as these are long-time standard control measures.
The use of these tools can suffocate the insect through the use of oil, or outright kill them through interrupting nervous system function (Lorsban & Supracide). The use of Esteem 35WP and Centaur provide control without the need for oil as a penetrant to inhibit SJS development. As we approach tight custer tree phenology the San Jose scale pest control options available to us are numerous, and to succeed, multiple strategies should be considered.
Pre-bloom options included:
* Lorsban foliar application (DD_Pink)
* Supracide foliar application (DD)
* Esteem (DD-Pink)
* Centaur (DD-Pink)
* Oil alone or with insecticides used for SJS (DD-Pink)
Note: Keep oil off the trees before AND after frost and freezing temperatures.
Post bloom 1st and 2nd crawler emergence options are:
* Movento SC (spirotetramat) PF-1C (2-3 weeks prior to crawler emergence)
* Contact insecticides at nymph emergence (pyrethroids, OP’s, Neonicotinoids and pre-mixed formulations)
* Oil alone or with insecticides used for SJS
The Lorsban decision: A single yearly application of Lorsban (chlorpyrifos) can still be made to tree fruit. If chlorpyrifos (Lorsban or similar generics) is used in a pre-bloom foliar application, then it cannot be used in a post bloom trunk application. A pre-bloom chlorpyrifos application made at early pink will have a considerable impact on San Jose scale (SJS), rosy apple aphid (RAA), emerging obliquebanded leafroller larvae (OBLR), mullen and tarnish plant bug (MPB & TPB), European apple sawfly (EAS) and white apple leafhopper (WALH). Most importantly, if bees are brought into a block in a season of cooler temperature and delayed petal fall of later varieties, a pink application provides increased management of migrating plum curculio with less pressure to remove bees from a mixed block while active pollinators continue to work king flowers. It also provides a bit of insurance if beekeepers are delayed in removing hives from mixed variety blocks.
Be aware that the active ingredient in Lorsban and the Lorsban generics is chlorpyrifos, which has a high bee-poisoning hazard. Judicious use of this product, well before bloom, is essential to reduce the risk to active pollinators. Mowing dandelion flowers ahead of a Lorsban application will also prevent looses of native pollinators.
Remember, the earlier the application against the overwintering black cap phase, the greater the likelihood of success. Coverage is critical in scale management, requiring a slow travel speed (<2.5 MPH), low wind speed (<5 MPH) and as close to a dilute application as possible. Increased foliage equates to "shadowing" and reduced coverage, which of course is the essential control component against the overwintering life stage. Infestation levels that exceed just a few fruit at harvest in multiple blocks should be taken seriously. Even after a pre-bloom application is made, further management of populations should be considered as pockets of lingering scale in protected places are likely to remain in the tree canopy. As a follow-up to pre-bloom control of SJS, consider the use of Movento 240SC at 6-9 oz./A plus a non-ionic penetrant such as 0.25% to 1% agricultural oil or LI700 to address the San Jose Scale fruit injury at pack out last year. The active ingredient in Movento, spirotetramat, is taken into the foliage, systemically moving through plant tissue to stems, roots, and leaves to be fed upon by emerging SJS nymphs during emergence and feeding. Our research has found the single application of 9 oz./A at PF or two applications at 6 oz./A at PF and 2C will effectively control the 1st generation of the insect. Be aware that Movento (spirotetramat), a systemic insecticide, cannot be used pre-bloom as per label restrictions, as there is insufficient foliage for effective uptake. Movento has been found to be most effective after PF in one to two applications, requires a penetrating non-ionic surfactant. Incompatibility concerns over Captan use in early pest management programs for apple scab can be a formidable barrier when considering the use of oil. The possibility of phytotoxicity when using Captan near oil applications should be strongly considered when vying for a weather opportunity for SJS management windows. Softer insecticides, such as Esteem 35WP (pyriproxyfen) can be employed with or without oil, acting against the pest as an insect growth regulator (IGR), a unique mode of action for use against the immature scale. As the insect matures, the insecticide acts as a juvenile hormone analog to reduce the insect capacity to molt. Centaur 0.7WDG (buprofezin), also an IGR does require a penetrating non-ionic surfactant such as 0.25% v/v oil to be effective.