Issue 21 - August 28, 2001

Duane Greene ‘Harvest the Potential' Report for August 28

Lack of rain continues to plague the area. If dry conditions persist into September, fruit ripening could be advanced and pre-harvest drop may become severe. (Note: rainfall has been quite variable across the State – some orchards have had adequate rainfall, while others are experiencing drought. JC) Starch iodine testing will become increasingly important as the indicator of stage of maturity. (See 8/21 Healthy Fruit for details.) We urge you to sample individual blocks for starch routinely. Harvest of Ginger Gold is well underway with starch iodine readings generally range between 2 and 4. Paulared season is nearing and end -- starch iodine readings in monitored blocks is between 5 and 6. Application of ReTain on Macoun can be done now and through next week. This week is also the timing for ReTain application on Empire. Those who have applied Ethrel on McIntosh in anticipation of Labor Day should watch maturity and drop carefully. It is important to have NAA well in advance of the anticipated time of harvest.

Post-harvest Peach Tree Borer Sprays Due

A good time to apply trunk/scaffold limb sprays for borers, including both the Peach Tree Borer (attacks trunks) and Lesser Peach Tree Borer (attacks scaffold limbs primarily) would be shortly after the final peach harvest. Lorsban 4E applied with a handgun, and thoroughly wetting the trunk and scaffolds, is the best recommendation. Both borers are common in Massachusetts peach orchards, and if left untreated, will lead to early tree decline and loss of productivity.

Late-season Leafhopper Liability

Significant numbers of white apple leafhopper (WALH) have been observed in several orchards. WALH nymphs and adults are active through harvest, causing white ‘stippling' of leaves. Their excrement results in small black spots (resembling flyspeck) on fruit. WALH adults also fly around during harvest, definitely annoying pickers. Insecticides for control (which is recommended!) include Sevin and Provado (both have short PHI's, check the label) -- Provado likely giving the best results.

Accumulated Rainfall

Weather stations maintained at 5 orchards in MA by the UMASS Fruit Disease Lab show that 14.6 inches of rain have accumulated at the Hawley site from April 30 to July 30. The 4 other sites: Deerfield (northwest corner), Belchertown (HRC), Sterling, and Northboro all show approx. 11.4 inches of rainfall for the same time period.

Summer Disease Update

The UMASS Fruit Team installed 16 air-sampling traps at the UMASS orchard in Belchertown on July 12 and began to collect flyspeck conidia (asexual spores) in most of them by the 16th. There were four sets of four traps, each set arranged so that 1 trap was in the middle of a flyspeck-infected patch of alternate host plants (blackberry, oak, maple, grape, etc.), one trap at the interface of the patch with a block of apple trees, one 20 m into the block and the 4rth trap 20 m further into the block. Trap captures peaked between July 12 and 22 (up to approx. 100 conidia per day per trap), and it appears that there were more conidia in the woods and at the edge of the blocks than at the sites further into the blocks. Since that peak, conidia have been trapped steadily but at lower rates. We expect at least one more peak before Labor Day. Typically, we begin to see flyspeck on apples (that remain unsprayed after June 15) a week or 2 after we start catching conidia in the air, but this year at Belchertown we did not see flyspeck on unsprayed trees until 20 August. The block that was adjacent to the most significant host patch unfortunately has no fruit this year. On the other hand, a block which received some fungicide in Harvard, MA, had flyspeck as early as July 16, and the amount of infection has increased there to 54% in one row and 44% in another row. Interestingly, both these rows are directly adjacent to a dense woods with flyspeck-infected plants. Rows that are more interior have 5% or less. Flyspeck counts are performed at 18 sites around the state, and although some sites are still at 0% infected, half the sites are starting to show infection. In addition to the site mentioned above, the 2 other sites with significant infection are close to infected hedgerows or woods. Heavy rains between now and harvest will dramatically increase the incidence of flyspeck and sootyblotch.