Healthy Fruit 2001 Vol. 9:13

Hort Chores for Early Summer

Finish hand thinning peaches and apples -- the sooner the better to attain maximum fruit size at harvest. A good rule of thumb is a spacing of 6" to 8" between fruit.

Last chance to apply nitrogen fertilizer -- apples need just a few ounces to two pounds ammonium nitrate (34-0-0) per tree depending on tree age and size -- equivalent to 50 to 60 pounds actual nitrogen per acre. Peach nitrogen requirements are slightly higher at 0.07 to 0.62 actual nitrogen per tree, or from several ounces to two pounds ammonium nitrate per tree, again depending on tree age and size. You want your peach trees looking nice and green now!

Summer prune peaches by stripping-out or cutting vigorous shoots shading the inner canopy. Without sunlight penetration into the canopy, a fruitless tree center will be the result down the road.

Finish stripping and pinching apples to maintain central leader dominance and promote branching. See Issue 9, May 29, 2001 of Healthy Fruit for details. It may not be too late to clothespin developing branches too, or, if already clothes-pinned, move clothespins out onto the developing shoot once the branch angle has set.

Decide which blocks to take leaf samples from -- all apple and peach blocks should have a foliar analysis every 4-5 years. Samples should be collected from late July into early August -- watch for details in an upcoming Healthy Fruit.

Did we forget something important? If so, let us know: clements@umext.umass.edu.

MFGA Summer Meeting

Mark you calendars -- the Massachusetts Fruit Growers Association Summer Meeting will be July 25 at Sunnycrest Orchard in Sterling. Expect a good orchard tour of pest control, herbicide, and nutrition applications of the newest crop protection and enhancement products. Association members will receive a mailing with details soon. Non-members can visit the Association's website for details and updates, but are also encouraged to join Mass Fruit Growers!

Plum Curculio

It's over! It's finally over! The last big wave of immigrating PCs came during the very warm days of June 14-16. Over the past week, there have been only a few stragglers caught on our traps designed to capture immigrants.

Most of the 17 PCs captured over the past week were caught on June 19 and 20. Only 4 were caught during the past 5 days.

Over the past week, injury to apples on perimeter-row trees in 12 commercial orchards rose by 19%(from 3.6 to 4.3% of sampled fruit), whereas injury to fruit on unmanaged trees rose by 49% (from 45 to 67% of sampled fruit).

Overall, most growers did an excellent job of controlling PC this year. PC populations have been high on unmanaged trees, but application of perimeter-row sprays at least once in June has kept late-season PC injury this year well below that of the 10.5% injury experienced this time last year in the same commercial orchards. Last year no perimeter-row sprays were applied in June.

Leafminers

Second-generation LM adults are emerging. But very few orchards are showing enough first-generation miners (13 or more per 100 sampled interior mid-age fruit cluster leaves) to merit an application of pesticide. If you are among the unlucky few, Spintor or Provado applied late this week or in early July should provide good control.

Aphids

Spirea and green aphids have been seen commonly on fresh terminal growth, but plenty of predators seem to be on hand to control them.

Woolly aphids are beginning to show up on some terminals. If these get out of hand, their excrement(honeydew) can lead to building of sooty mold fungus on fruit and create a big mess at harvest. Lorsban was an effective material against woolly aphids but can no longer be applied to apple tree foliage or fruit. Thiodan is the next best choice and is effective even at 1/3-1/2 the recommended rate. Neither Provado nor Spintor is known to be effective against woolly aphids.

Leafhoppers

Adults of white apple and rose LH (which are indistinguishable from one another) are now abundant in some orchards. If uncontrolled, either or both species can build to large populations by September and cause dark spotting of fruit and also become a nuisance to pickers. If you have had trouble with LH in the past at harvest, the best time to control them is in early July, when you see young nymphs on foliage. Nymphs are susceptible to Sevin, Thiodan, Provado and other materials.

A few potato LH adults have been seen this past week on apple trees. The adults migrate hundreds of miles from the southwest and midwest and annually descend on us about this time of year. Adults and nymphs inject a toxin into terminal leaves on which they feed, causing symptoms similar to nutrient deficiency. Leaves turn yellow on the edges, cup upward, and later turn brown. PLH causes no known harmful injury to bearing trees but can be extremely harmful to non-bearing trees. Imidan, Guthion, Sevin and Thiodan remain effective materials against PLH, even at low doses.