Diagnosing Plant Problems

Effective fruit crop production depends on the grower developing a system of crop management that is appropriate for each farm. Decisions need to be made for how to manage all of the normal cultural practices such as planting, fertility, harvesting, and pruning as well as managing the insect, disease, and weed problems that occur either regularly or sporadically. The information in this guide will address management issues related to both common, expected pest problems as well as the occasional appearance of minor pest problems.

Effective pest management depends on:

  • correct diagnosis of the problem and correct identification of the pest causing it.
  • use of techniques to prevent or delay infestations or infections as well as techniques to control them.
  • early detection of pests by frequent inspection of plants.
  • tolerance of pests at population densities that do not cause economic damage.


Correct diagnosis of a problem and correct identification of the pest (insect, disease, biotic factor, nutrition, etc.) causing it are key to successful crop management and profitability. Below is a list of laboratories that offer disease diagnostics on a fee-for-service basis.  In general, virus screening is a procedure that is done outside of this region and is referred out by one of the clinics listed below. Contact your local clinic or lab for more information on virus screening.

In order to submit a sample for diagnosis, some basic preparation instructions should be followed. These include:

  1. Collect specimens that show a range of symptoms (i.e., from healthy to seriously affected), usually collected from the margin of the affected area. Avoid specimens that are completely dead or decayed as they are not diagnostically useful.
  2. Fill out case-history or sample submission form like the one at the end of this guide. This is very important. Without the information included in the form, a correct diagnosis is very difficult.
  3. Pack specimen in dry paper and place in a plastic bag (never pack with wet paper towels).
  4. Mail specimen and case-history form same-day or overnight delivery, or deliver specimen personally the same day. If this is not possible, place in a refrigerator and mail or deliver the following day. Specimens should come to the diagnostic labs early in the week to avoid problems with weekend hold-overs.
  5. Soil samples for nematode analysis.

Plant Diagnostic Clinics of New England

(D=disease ID, I=insect ID, N=nematode analysis, W=weed ID)


The Plant Disease Information Office (D,I,W,N)
The Connecticut Agricultural Experiment Station
123 Huntington Street, P.O. Box 1106
New Haven, CT 06504
(203) 974-8601

UConn’s Home & Garden Education Center (D,I,N)
Radcliffe Hicks Bldg, Rm 4
1380 Storrs Rd., Unit 4115
Storrs, CT 06269


Insect Pest and Disease Diagnostic Lab (D,I)
Pest Management Office
17 Godfrey Drive
Orono, ME 04473-3692
1-800-287-0279 (within Maine)
(207) 581-3880


UMass Extension Plant Diagnostic Laboratory (D,I,N,W)
Room 3, French Hall
230 Stockbridge Road
Amherst, MA 01002
(413) 545-3208


UNH Plant Diagnostic Lab (D,I,W)
Barton Hall, 34 Sage Way


URI Plant Protection Clinic (D,I)
3 East Alumni Avenue
Kingston, RI 02881
(401) 874-2900


University of Vermont Plant Diagnostic Clinic (D,I,W)
Attn: Ann Hazelrigg
201 Jeffords Hall, 63 Carrigan Drive
University of Vermont
Burlington, VT 05405
(802) 656-0493


Agdia Inc. (D)
30380 County Rd. 6
Elkhart, IN 46514
(800) 622-4342