Current DD Accumulations

Foliar Feeding Frenzy

Based on what appear to be a copious number of apple flower buds heading into bloom, the cropping potential looks good for 2001. However, considering we've had two consecutive years of moderate to heavy crops in most orchards, one has to wonder if appearances may indeed be deceiving. If so, it might be wise to apply some foliar nutrients during the pre-bloom through petal-fall period to enhance fruiting spur vitality. Pre-bloom applications of zinc and nitrogen have been shown to improve fruit set, particularly where flower buds were weak going into the bloom. Zinc (EDTA chelate, 1 quart per 100 gallons dilute) can be applied during the tight-cluster through pink stage, and then again with the second cover spray. Nitrogen (spray grade urea) at 2-3 pounds per 100 gallons dilute at pink and then again at petal fall gives trees a needed boost during the important flowering and fruit set period. A third foliar nutrient application of boron (Solubor, 1 pound per 100 gallons) during bloom and again at first or second cover is also indicated, particularly where foliar boron content (as indicated by leaf analysis) is low. So give them your best shot and hope for good pollination weather during bloom.

Big Bad Brown Rot

Growers of peaches, plums, and cherries are probably all too familiar with this important disease of stone fruit. Brown rot affects both flowers and fruit, particularly during periods of rainy, warm, and humid weather. The first step towards control is sanitation -- pay particular attention to removing mummified fruit and twig cankers during pruning. Good insect and bird control is essential too, as the disease can easily enter any injury to fruit. Chemical control focuses on the blossom blight and shuck-split/fruit rot stages. Protectant fungicides such as Bravo and Captan are effective during both stages, however, they must be applied before a wetting event. The sterol-inhibiting (SI) fungicides (such as Elite, Indar, and Orbit) provide kickback activity on brown rot during bloom and during shuck-split when applied for control of other diseases such as peach scab. SI's should be rotated with non-SI protectant fungicides to prevent resistance development and for better overall control of brown rot. Other fungicide options exist, including Rovral and Vanguard for blossom blight. Because of the numerous fungicide options and timing/rate considerations for brown rot control, always consult the label before applying! For a more thorough discussion of brown rot in stone fruit, see the April 23 (Vol. 10, No. 6) edition of Scaffolds Fruit Newsletter.

FYI: Say Bye-bye to Benlate®

According to 'Today's Headlines' on the DuPont website, "the DuPont Crop Protection business is informing its customers around the world that it will discontinue the manufacture of the fungicide benomyl and will phase out sales of Benlate® in all its forms from the global market. No sales will occur after December 31, 2001, and it is expected that all product will clear the channels of trade by the end of 2002." See http://www.dupont.com/corp/whats-new/newsfile/010419.html for more information.

Scab Maturity

Squash mounts performed on 23 and 24 April from apple leaves collected in Groton, MA and Amherst, MA showed less maturity than expected. Only about 5% of the spores were mature and no spores were discharged. Keep in mind that this is a small sample and with very warm temperatures, development will speed-up. In the hill-towns, apples went from tight cluster to 1/2 inch green in 48 hours. Some eastern orchards are at tight cluster now. If we get significant rain, we should see disease pressure by early next week.

Too Late for Copper?

We hear that copper was applied to peaches right-on schedule this year, and that some apple growers have been putting it on as their foliage has been approaching 1/2 inch green. Only in the latest developing areas, where foliage is still not quite at 1/2 green, will copper be applied at this point.

Bud Development

Because of recent warm weather, bud development has reached, as of April 23, half-inch-green in southern area of the state and silver tip to early green tip in the western hills.

Tarnished Plant Bugs (TPB)

As the weather warms up, overwintered adult become active and feed on apple fruit buds which may cause flower abscission. TPB populations vary considerably between orchards and white sticky traps placed at silver tip help determine the need for a prebloom treatment. However, few TPB have been caught in traps and numbers are well below spray threshold. For the 7th consecutive year in Massachusetts (1994-2000), TPB injury to fruit in apple orchards were below levels experienced in the early 1990s. However, were heavy activity of TPB are monitored, optimum spraying time should be between late tight cluster and late pink.Apple Blotch (AB) and Spotted Tentiform (ST) Leafminers (LM)

Numbers of adult LM recorded in the field are still negligible. As we reported in the March Message, there's a big change underway in the composition of species of leafminers inhabiting Massachusetts orchards. Sticky red rectangle traps stapled to tree trunks at green tip or half-inch green are reliable for determining abundance of ABLM (roughly 80% accuracy). We have less faith in these traps for assessing the population of STLM. Even so, captures will give a general idea of whether you have a few, moderate or large number of leafminers. Current cumulative ABLM trap capture thresholds from silver tip to tight cluster for Massachusetts growing conditions are 4 adults per trap (on McIntosh cultivar) and 8 (on non-McIntosh).

European Red Mite (ERM)

We are entering this spring with comparatively low numbers of overwintering ERM eggs. Many growers may achieve season long control of ERM with the use of oil alone. Biological control of mites via predators is the best long-term solution to mite management. Hence, we recommend placing a strong emphasis on early-season oil applications that have little effect on mite predators. Oil spray will achieve maximum effect against overwintered red mite eggs if applied just before (but not after) egg hatch, which comes usually around early to mid pink.