Scaffolds 99 index

PREBLOOM PREOCCUPATIONS

(Art Agnello ama4@nysaes.cornell.edu & Harvey Reissig whr1@nysaes.cornell.edu, Entomology, Geneva)

Early season arthropod pests – that is, those present before Bloom – generally fall into two groups: the mites, and everything else. Generally speaking, everyone has to do something about mite populations in their blocks, but not everyone has to do something about the rest of the potential pests, or at least usually not all of them. These include rosy apple aphid, tarnished plant bug, and spotted tentiform leafminer. We've already given our highly subjective assessment of mite management for the early season, so let's leave fuzzy enough alone for the time being and move on to the insects.

Fortunately, all three of these management issues converge at about the time of Pink, together with a ton of other things, but you're probably used to it by now, and anyway this is the crunch you've been impatiently waiting for since that thaw back in January. The whole key behind a Pink strategy boils down to setting priorities, or else call it degrees of sensitivity, and this is something for which most growers seem to have an inherent talent. Everyone has their own version of this process, and all of them result from being familiar with your own orchards - does a given block have a history of or susceptibility to a specific pest? Start with your knowledge of the block, use a sampling procedure where appropriate, and make a management decision.

Rosy Apple Aphid

In our opinion, the most crucial of the pest decisions to be made at Pink has to do with rosy apple aphid (RAA), because this is the last defining period for a truly successful rosy management option. Although RAA feeds mainly on apple foliage, causing leaf chlorosis and curling, its saliva is also translocated to nearby fruits, which become bunched, stunted, and malformed.

Fruit malformation caused by rosy apple aphid feeding

RAA will attack all apple varieties, but varieties such as Cortland, Monroe, R.I. Greening, Idared, and Golden Delicious are particularly susceptible, and those in the McIntosh family are relatively tolerant. As with most aphids, this species has a complex life cycle, starting with black eggs that overwinter on twigs, in bud axils, and in bark crevices.

Wingless rosy apple aphid stem mother produced from overwintered egg

The eggs develop into solitary, wingless "stem mothers", which then give birth to living young, most of which are also wingless. RAA nymphs are visible beginning at about Tight Cluster but are most easily observed at the Pink bud stage.

Our control recommendations for RAA cover the period from Half-Inch Green to the Pink bud stage, using any of a number of materials: Thiodan, Lorsban, Lannate, Vydate, Supracide or Asana, listed roughly in order of increasing harm to beneficial mites. Pink applications of any of these products do a better job than an earlier spray. This is an observation resulting from the fact that, in those cases where aphid populations have built up during early summer on vegetative growth inside the canopy, a Pink spray will have done a more effective job of reducing populations than an earlier treatment at Half-Inch Green. From the standpoint of management practicality, it is therefore easier and more natural to consider the need for aphid control at the time of the Pink spray.

Because RAA populations are highly variable, it is important to assess their densities before making a treatment. In past surveys, approximately 50% of the orchards sampled have ended up requiring treatment. If you are inspecting fruit clusters for STLM eggs at Pink anyway, it is not much more trouble to note the presence of RAA nymphs or damage at the same time. We recommend, however, that a few more clusters be checked for RAA than are required for STLM sampling. Try to select 10 from the interior canopy area of each of 10 trees distributed throughout the block. RAA nymphs are of course present at Pink, and large enough to see without difficulty, but they do occur on the same tree and in the midst of colonies of green apple aphids, which are not usually a problem until the summer.

To distinguish among the species, you can use leaf damage as a cue, as well as the insects' color. RAA nymphs are usually pinkish, sometimes varying to a light brown, slate gray, or greenish black, and the body is covered with a whitish mealy coating. Most importantly, they have pronounced cornicles ("tailpipes"), and long antennae (more than half the body length). Green apple aphid nymphs are clearly green, and without the whitish cast. Their cornicles are little more than buttons, and the antennae are clearly less than half of the body length. Also, aphids found inside curled or distorted leaves at Pink are almost always Rosy Apple Aphids. If you find ONE infested cluster (1%, or stop as soon as you find one), we would advise including an RAA material in your Pink spray; this threshold may be a little conservative for people who are skilled at finding the aphids.

Spotted Tentiform Leafminer

What else is happening at Pink (mites aside)? STLM is laying eggs, but most orchards don't suffer too greatly from 1st brood leafminer, and even if so, a sequential sampling plan can be used to classify STLM egg density at Pink or of sap-feeding mines immediately after Petal Fall (see pages 91, 95 or 97 in the Recommends). Treatment is recommended if eggs average 2 or more per leaf on leaves 2, 3, and 4 of a fruit cluster at Pink, or if sap-feeding mines average 1 or more per leaf on these leaves at Petal Fall.

Eggs of spotted tentiform leafminer

Sampling can be completed in approximately 10 minutes. In recent years, only 1 out of 6 sampled orchards have required insecticide treatments to control first-generation STLM populations. Vydate at Pink or Lannate at Petal Fall have been our standard recommendations for this pest; however, now we also have the Petal Fall option of Provado, which will add to the leafhopper control if you don't use enough Sevin at thinning to do an adequate job.

Miscellaneous

Leafrollers are also out there, but only part of the population is active at this time, so it's better to wait for Bloom or Petal Fall to address this one. Tarnished plant bug is the only player left, and you're going to have to decide for yourself whether it's a major concern to you.

Dimple on apple caused by tarnished plant bug feeding

We have seen few orchards in western N.Y. where TPB control is warranted (slightly more in the Hudson Valley), simply because the most effective treatment to use is a pyrethroid, which a) wipes out predator mites, and b) still rarely lowers TPB damage enough to be economically justified. If you elect an Asana spray at Pink for plant bug, you'll take care of rosy apple aphid (and STLM) at the same time; if rosies are your primary concern, scout for them first, and use Lorsban or Thiodan if you find any.

4.19 General