Back to top

Healthy Fruit 1997 Vol. 5:5

May 7, 1997

Growth Stage

Slow and steady blossom development is the rule across the state. Temperatures have not been excessively warm, and depending on whether you're still suffering the effects of the April Fool's Surprise, it hasn't been too cold either. With any sort of warmth, trees will be in bloom next week at this time.

White Traps Losing Effectiveness on Tarnished Plant Bug

So far, the weather has not been favorable for tarnished plant bug activity and trap captures are reflective of low levels of activity in almost all orchards. In one orchard though, trap capture levels are at 8 TPB per trap, which is well over the threshold recommended for consideration of treatment. Unfortunately, the low trap captures to date do not necessarily mean that TPB are finished for the year. Given a few successive warm days during bloom, TPB can cause substantial damage to the fruit. The damage during bloom looks less like the common dimpling of the fruit and has more of a scabby appearance, similar to curculio damage.

Monitoring traps have very little capturing power for TPB as soon as white tissue begins to show in blossom clusters. This is the case because the white tissue of the clusters competes with the visual stimulus of the white rectangle monitoring traps. These monitoring traps are not a good indicator of TPB population densities after mid-pink. Growers who traditionally have problems with dimpling and scabbing of fruit by TPB should visually inspect blossom clusters at late pink and into bloom in order to determine whether or not there is a level of damage which warrants a petal fall insecticide application.

A Ton of Leafminer

This year, there is a considerably greater number of orchards with leafminer trap captures which exceed treatment thresholds than last year. Many of these orchards have reached 50 LM per trunk trap, which is a sure sign that some action needs to occur at petal fall or soon after. Last week's issue of Healthy Fruit contains recommendations for LM management.

Mites Hatching

European red mite eggs have hatched in orchards which are at early pink or later. Although an oil application in the early stages of egg hatch will still be effective against remaining eggs, the benefits of oil applications against mites begin to decrease substantially after egg hatch has begun.

To See Sawfly, Hang Traps

In the earliest orchards, EAS have already been captured. Now (mid- to late pink) is the time to hang white sticky rectangle monitoring traps for sawfly. These traps should be hung as high as you can reach on the south side of the tree canopy, clear of any waving branches.

Pear Psylla Story

In orchard blocks which have not received any oil applications, psylla nymphs are abundant in blossom clusters. Growers observing large numbers of nymphs in clusters should be prepared for a post-bloom insecticide application. Of the post-bloom treatment options, Agrimek has shown good control of psylla when applied 10-15 days after petal fall. Provado is now labeled for use on pears and has shown promise in reducing high populations, but the limited residual control (10 days or so) makes it best suited as a late-season application. With proper timing, Mitac is also effective as a post-bloom treatment for psylla. For growers who are considering a treatment of Mitac, New York recommends back-to-back sprays after petal fall, with one application about two weeks after petal fall and the second application 7-10 days later. For a more complete discussion of recommendations for psylla management, refer to this year's issue of the March Message.

Deep Into the Scab Season

What else is there to say? We are in the middle of apple scab season, and now is not the time to take chances. Wait until a week after petal fall to reevaluate the scab situation, and in the meantime, maintain a tight protective and/or post-infection schedule.

Check Your AgriMycin

As the time to apply copper has long past, the remaining option for those who are concerned with fireblight is streptomycin, sold as AgriMycin. Jim Johnson, of Merck, asked me to pass this on.

A recent audit of our inventory for Agri-mycin (streptomycin sulfate) 17 and Mycoshield (oxytetracycline) revealed that some growers may have product that currently is likely to be out of specification.

We maintain a strictly specified range of percentage of active ingredient for these products and we have found that some of our own retained samples currently contain slightly less than the minimum specified amount of the active ingredient. Although the products fully conformed to specifications at the time they were manufactured and sold, the active ingredients may have naturally degraded over time.

Please contact Dr. Jim Johnson, Merck Technical Services, at (517) 676-0884 (email:, should you have any questions.

Badly Needed IPM Funding Proposed

Bills to provide IPM funding have been proposed in both the national Congress and the Massachusetts legislature.

In Massachusetts, the proposal would move IPM funding from the Dept. of Food & Agric. to the University, a move which would provide nearly $100,000 more available money, thanks to savings in overhead and fringe benefit charges currently made on the DFA based line in the budget. In addition, the a basic funding increase has been proposed. Both actions will either be passed or defeated by May 15.

In Congress, a bill to provide nearly $15 million in extra IPM funds is being considered. This funding, and an increase in the present Massachusetts funding, are badly needed by the UMass IPM program, since approximately $250,000 in special grants available over the past 6 years has been discontinued.