Vegetable Diseases: 2006 - Plant & Pest Diagnostic Laboratory, Purdue University

The Purdue Plant and Pest Diagnostic Laboratory

Asian Soybean Rust

P&PDL Links
Home
About the Lab
Submitting Samples
Frequently Asked Questions
Invasive Species and Other Current Interests
Links and Resources
Archives
Contacts
Search Purdue Links Extension Publications Extension County Offices Agronomy Botany and Plant Pathology Entomology Forestry and Natural Resources Horticulture and Landscape Architecture College of Agriculture Extension

Commodity Summary

2006 Season Review: Vegetable Diseases

Dan Egel, Region Pest Management Specialist, SWPAC, Purdue University

Late April and early May 2006 was very cool and wet (See Table 1). The result was that a significant number of muskmelon and watermelon growers reported transplants dying in the field (Figure 1). Many growers had to replant entire fields since the original plants had died or were severely damaged by the cool, wet weather. Although a few damping-off fungi could be found in isolations of these plants, most transplant loss was due to the abnormal weather. After growers located replants and the weather warmed up, the replants grew well.

Table 1: Weather data is presented to show the cool, wet weather in May 2006 that was responsible for the early season death of many cucurbit transplants in southwest Indiana.
	Precipitation (inches)*	Temperature (Fahrenheit)
May 2006	5.28	59.9
111 year ave	4.24	61.5
111 year rank	87**	40
* Weather information is courtesy National Climate Data Center/National Oceanic Atmospheric Association. ** The wettest month would be ranked 111; the hottest month would be ranked 111.

A few varieties of watermelon transplants were observed with Fusarium wilt while still in the transplant trays. Symptoms of Fusarium wilt of watermelon in the field usually peak around Memorial Day. In 2006, early season observations of Fusarium wilt were less than normal. This might be because once the weather in May warmed up it became very warm. Thus, most watermelon seedlings began growing in very warm late May temperatures. However, there was an increase in observations of mature plants with Fusarium wilt in the mid to late season.

Figure 1: Watermelon seedlings collapsed due to the cool, wet weather in May 2006 forcing growers to replant using new transplants.

Downy mildew of cucurbits was present in Indiana for the fourth year in a row. In 2006, downy mildew was observed in Michigan on 9 June. On 20 July, downy mildew was reported on cucumbers in Kosciusko County, Indiana. On 14 August, downy mildew was reported in Knox County on pumpkins. It is unknown whether the downy mildew infections observed in Indiana came from the Michigan source or a source further south.

Many pumpkin growers complained of either Phytophthora blight or Fusarum fruit rot causing yield losses. Most of the growers with these problems were from the northern part of the state where more rains fell. The fruit rots were part of a regional problem that extended from Indiana to the New England States. The national press picked up on this problem and Purdue expertise was featured prominently.