Wet, Cool Weather Spreads Scab

The weather isn't giving trees or growers a chance to really stop scab. Normally by this time of year, warmer and drier temperatures have slowed scab, and the tree itself can do much of rest, perhaps with a little captan. This year, the scab is just chugging along, growing and producing spores.

Under the wet weather, a very few lesions early on have had a chance to grow and produce spores, going through 2, 3 or even 4 cycles since the start of the season. Unsprayed trees are virtually defoliated.

As a result, more and more lesions are appearing on almost a daily basis. It is the worst scab epidemic in Massachusetts and much of the Northeast in the last 25 years. Much of New York is experiencing similar scab pressure, from the Hudson Valley to Lake Champlain and even into western sections of the state.

Even growers who felt in good shape a week or two ago are seeing new scab outbreaks. Growers should not assume nothing new has developed in the last two weeks. Check! Until the weather cooperates, the only option is to maintain tight fungicide application schedules and use full rates of fungicide.

 

Brown Rot Deserves Attention Too

The weather isn't giving trees or growers a chance to really stop scab. Normally by this time of year, warmer and drier temperatures have slowed scab, and the tree itself can do much of rest, perhaps with a little captan. This year, the scab is just chugging along, growing and producing spores.

Under the wet weather, a very few lesions early on have had a chance to grow and produce spores, going through 2, 3 or even 4 cycles since the start of the season. Unsprayed trees are virtually defoliated.

As a result, more and more lesions are appearing on almost a daily basis. It is the worst scab epidemic in Massachusetts and much of the Northeast in the last 25 years. Much of New York is experiencing similar scab pressure, from the Hudson Valley to Lake Champlain and even into western sections of the state.

Even growers who felt in good shape a week or two ago are seeing new scab outbreaks. Growers should not assume nothing new has developed in the last two weeks. Check! Until the weather cooperates, the only option is to maintain tight fungicide application schedules and use full rates of fungicide.

 

Disaster Help Available

The government is beginning to notice that all this rain is amounting to something. Governor Celluci and President Clinton declared the following MA counties "disaster areas": Bristol, Essex, Middlesex, Norfolk and Suffolk. While these are not the major areas of tree fruit production in the state, it is a start. Even if you do not reside in one of the listed counties, there is the possibility that additional MA counties will be declared "disasters."

The declaration is based on the fact that "heavy spring rains, torrential downpours, and otherwise wet weather have resulted in flooding and water damage to homes, businesses, and farms in the counties named above". In an effort to assist those who have suffered damage due to the weather, the governor petitioned the President to declare these counties "federal" disaster areas, thus allowing the availability of low-cost financial relief utilizing federal money. President Clinton made the declaration on June 23, 1998.

Presently there still are details to be ironed out regarding accessing these funds. Both the Massachusetts Emergency Management Agency (MEMA) and the Federal Emergency Management Agency (FEMA) will be involved in this process, but the exact procedure you should use to access this assistance is still being developed. For the time being, if you believe you have suffered damage from the spring weather, and live in one of the above-named counties, please contact your county's Farm Service Agency (FSA). They will document your claim, gather information together and assist with the development of procedures.

EVEN IF YOU LIVE OUTSIDE THE FIVE LISTED COUNTIES, if you believe you should be eligible for disaster relief, please contact FSA also. As soon as we have more information we will pass it along to you.

 

Potential High For Maggot Fly

In keeping with this year's theme, apple maggot fly emergence began about two week's early. AMF have been observed in large numbers in some blocks of trees which border unmanaged trees, with captures approaching 20 per trap.

Unfortunately, many factors have come together this season which increase the potential for heavy AMF populations: 1) high likelihood of survival by overwintering pupae; 2) wet soil conditions which favor AMF emergence; and 3) few fruit on unsprayed hosts, which means that foraging flies will quickly spill over into commercial blocks. Growers should be prepared to treat for AMF fairly soon, as the population has the potential to be both early and heavy. Sticky red spheres remain the best tool for monitoring AMF presence and abundance. For information regarding optimal trap density and placement, refer to the June 24 issue of Healthy Fruit.

From one year to the next, it is nearly impossible to predict the threat posed by potato leafhopper invasion. What is known is that they immigrate from afar, hundreds of miles to the south and west of Massachusetts, and that they primarily damage young, nonbearing trees. Mature, fruiting trees are at very little risk of PLH damage, with the exception of superficial discoloration of the terminal leaves. New plantings, however, are prone to extreme, rapid damage to terminal growth which can stunt the development of the tree.

Generally, when the population of PLH reaches a damaging level, terminal leaves will curl, with discoloration ranging from yellowing along the midrib to browning of the leaf margins. Such damage can appear at an alarming rate, and may be confused with a viral infection. If PLH infestation becomes an issue, a single treatment of Thiodan or Sevin should remedy the problem.

Large populations of white apple and rose leafhopper adults have been observed in several monitored orchards. Treatments aimed at leafhopper adults are largely ineffective; nymphal stages are much more susceptible to treatment with either Thiodan or Sevin. Because of the high number of adults still active, we recommend that treatment be delayed until the next generation's nymphs are evident.

 

Woolys Still Wild

As is the case with leafhoppers, woolly apple aphids appear poised for a banner year, after several consecutive years of light infestation. To reiterate the recommendation of previous issues of Healthy Fruit, a half to full rate of Thiodan should clean up WAA problems.

Leafminer Generation Two

Second-generation sap-feeding mines are appearing in most areas of the state, but few tissue-feeders have been observed. The window of opportunity for an effective treatment with Provado against the second generation is nearly closed. If a treatment is necessary, and has not yet occurred, Vydate and Lannate are still viable options.

Pear Psylla

Summer-generation pear psylla adults are currently present in orchards, but no egglaying has been observed thus far. Early treatments aimed at nymphs were effective in most cases; Pyramite performed particularly well, exhibiting some ovicidal effects as well.

Healthy Fruit is written by Dan Cooley, Ron Prokopy, Starker Wright, Wes Autio, and Karen Hauschild except where other contributors are noted. Edited by Dan Cooley. Publication is funded in part by the UMass Extension Agroecology Program, grower subscriptions, and the University of Massachusetts IPM Program. Healthy Fruit is available on the Web at The Massachusetts Tree Fruit Advisor, (click here). A text version can be e-mailed to you if you contact me, at dcooley@microbio.umass.edu. Please cite this source if reprinting information.