EcoScience Corporation
10 Alvin Court
East Brunswick, New Jersey  08816


     Reference is made to (i) the Stock Purchase Agreement ("Stock Purchase
Agreement") between Cogentrix Delaware Holdings, Inc ("CDHI") and Ecoscience
Corporation ("Ecoscience"), (ii) the promissory note of Ecoscience in favor of
CDHI dated December 30, 1998 in the principal amount of $20,600,000 (the
"Note"), (iii) the promissory note of Ecoscience in favor of CDHI dated March
15, 1999 in the principal amount of $1,000,000 (the "Extension Note") and (iv)
the Stock Pledge Agreement ("Pledge Agreement") dated as of December 30, 1998,
as amended, between Ecoscience and CDHI.

     Ecoscience desires to extend the date on which the principal amounts of the
Note and the Extension Note are due and CDHI is willing to extend such payment
date on the terms and conditions set forth herein.

     By its signature hereto, CDHI agrees that the (i) date for payment in one
installment together with all interest accrued on the Note shall be extended
from July, 31 1999 to August 31, 1999 and (ii) date for payment in one
installment together with all interest accrued on the Extension Note shall be
extended from July 31, 1999 to August 31, 1999. Each such extension shall be
evidenced by the execution and delivery of an Allonge to Promissory Note in the
form attached hereto; provided, that the failure of CDHI to attach an Allonge to
the Note or the Extension Note, as applicable, shall not affect the validity of
the extension of time for payment provided for herein.

     CDHI expressly reserves all rights and remedies it may have with respect to
the Stock Purchase Agreement, the Pledge Agreement, the Note and the Extension
Note and, except for the extension of time provided for payment provided for
herein, no such right or remedy shall be deemed waived by CDHI.


<PAGE>


     THIS LETTER SHALL BE GOVERNED BY THE LAWS OF THE STATE OF NORTH CAROLINA.


                                     Sincerely yours,

                                     COGENTRIX DELAWARE HOLDINGS, INC.

                                     By:
                                         --------------------------------------
                                         Name:  Thomas F. Schwartz
                                         Title: Senior Vice President -
                                                Finance and Treasurer

Acknowledged and agreed

Ecoscience Corporation

By:
--------------------------------
Name:
Title:


<PAGE>


                                     ALLONGE
                                       TO
                                 PROMISSORY NOTE

     ALLONGE to PROMISSORY NOTE ("Note"), dated December 30, 1998, of ECOSCIENCE
CORPORATION, a Delaware corporation, having its principal place of business at
10 Alvin Court, East Brunswick, New Jersey 08816 (the "Maker"), payable to the
order of COGENTRIX DELAWARE HOLDINGS, INC., a Delaware corporation, having its
principal place of business at 1105 North Market Street, Suite 1108, Wilmington,
DE 19801 (together with his successors and assigns, the "Holder).

     The date for payment in one installment of the principal together with all
interest accrued on the Note is extended from July 31, 1999 to August 31, 1999.


                                            COGENTRIX DELAWARE HOLDINGS, INC.

                                            By:
                                                -------------------------------
                                                Name:  Thomas F. Schwartz
                                                Title: Senior Vice President -
                                                       Finance and Treasurer


                                            ECOSCIENCE CORPORATION

                                            By:
                                                -------------------------------
                                                Name:
                                                Title:


<PAGE>


                                     ALLONGE
                                       TO
                                 PROMISSORY NOTE

     ALLONGE to PROMISSORY NOTE ("Note"), dated March 15, 1999, of ECOSCIENCE
CORPORATION, a Delaware corporation, having its principal place of business at
10 Alvin Court, East Brunswick, New Jersey 08816 (the "Maker"), payable to the
order of COGENTRIX DELAWARE HOLDINGS, INC., a Delaware corporation, having its
principal place of business at 1105 North Market Street, Suite 1108, Wilmington,
DE 19801 (together with his successors and assigns, the "Holder).

     The date for payment in one installment of the principal together with all
interest accrued on the Note is extended from July 31, 1999 to August 31, 1999.


                                            COGENTRIX DELAWARE HOLDINGS, INC.

                                            By:
                                                -------------------------------
                                                Name:  Thomas F. Schwartz
                                                Title: Senior Vice President -
                                                       Finance and Treasurer


                                            ECOSCIENCE CORPORATION

                                            By:
                                                -------------------------------
                                                Name:
                                                Title: