Investigating various tactics of intercropping buckwheat with squash to increase natural enemy populations, reduce pest and disease pressure and increase yield

View the project final report

• 2012 annual report

Commodities

• Vegetables: cucurbits

Practices

• Crop Production: intercropping

A comparison of different buckwheat intercropping tactics with bareground treatments in an organic squash production system determined that yields in bareground treatments were significantly greater than buckwheat treatments, even in the presence of high pest densities and virus incidence. Plant size and yields were reduced in the intercropping arrangements where buckwheat was planted down the middle of a squash bed and where buckwheat was planted on both sides of the squash compared with buckwheat alternating on either side of the squash, and therefore we would not recommend these intercropping arrangements.

Introduction

Zucchini squash, Cucurbita pepo L., is a high value vegetable crop in Florida (Nyoike and Liburd 2010).  Plant physiological disorders and insect-transmitted diseases are serious problems for many growers around the state.  One of the most damaging plant physiological disorders in squash is squash silverleaf (SSL) disorder, which is associated with the feeding of immature silverleaf whiteflies, Bemisia tabaci B biotype (Frank and Liburd 2005).  SSL is characterized by silvering of the upper leaf surface and blanching of fruit, which can reduce the quality of the fruit produced depending on the severity of the disorder (Frank and Liburd 2005, Liburd and Nyoike 2008).  Cucurbit leaf crumple virus is a whitefly-transmitted virus that has the potential to cause significant squash yield losses (Nyoike et al. 2008). 

The implementation of cultural control techniques in agriculture, such as the use of mixed cropping systems and crops interplanted with non-host cover crops (living mulches), when used in conjunction with other pest suppression methods has the potential to reduce whitefly numbers as well as the impact of SSL disorder and other whitefly-transmitted viruses on cucurbits (Frank and Liburd 2005, Liburd and Nyoike 2008, Manandhar et al. 2009).  Several studies evaluating the efficacy of living mulches for the control of whiteflies have demonstrated successful reductions in whitefly population densities, as well as lower incidences of whitefly-transmitted viruses (Hooks et al. 1998, Summers et al. 2004, Liburd and Nyoike 2008).  Buckwheat mulches have been observed to aid in the suppression of adult whiteflies on zucchini squash plants (Hooks et al. 1998, Frank and Liburd 2005).  In addition, flowering buckwheat attracts beneficial insects to the cucurbit crop (Frank and Liburd 2005).  Attraction of natural enemies of whiteflies may be an important advantage of implementing buckwheat mulches, such that natural enemies can play an important role in pest reduction.

A more sustainable approach is needed to address the limitations of the current management strategy, which heavily relies on insecticides to manage aphids and whiteflies and the diseases they transmit in squash.  The use of buckwheat as a living mulch intercropped with squash has shown promise to reduce pest and disease pressure while increasing the abundance of beneficial insects (Hooks et al. 1998, Nyoike et al. 2008, Nyoike and Liburd 2010).  However, yields can be significantly reduced, most likely due to early season competition for shared resources.

The purpose of this study was to evaluate several methods of intercropping buckwheat and squash to find a tactic that reduces pest and disease pressure while increasing marketable yield.  The specific objectives were to 1) to compare several tactics of intercropping buckwheat and squash and their effects on pest and natural enemy densities, disease incidence, and marketable yields in field grown squash, 2) to incorporate a key natural enemy, Delphastus catalinae, into buckwheat and squash crops to determine the effects on pest populations and marketable yields, and 3) to use an on-farm demonstration model to implement the buckwheat-squash intercropping tactic on a grower’s field while incorporating a key natural enemy, Delphastus catalinae, and compare to current organic squash growing practices.