161 articles tagged "Cucurbits".

In the past two weeks we have heard reports of the Squash vine borer (Figure 1) being spotted in some local gardens. This pest of cucurbit crops tends to be sporadic in our region; you are either battling it every year or it hardly makes an appearance. The squash vine borer is a member of the clear-winged moths, a unique group of moths that are active during the daytime. They are very beautiful with their bright colored orange tufts of hair. At this point in the season, we are encountering with the second generation in Indiana. The larvae feed in the ripening fruits (Figure 2). You can find holes in the fruit and sawdust-looking frass (excrement) indicating larval infestation. If you are planning to treat your crop, you need to target applications before those eggs hatch so that the larvae will ingest the spray upon hatching as they attempt to[Read More…]

Figure 1. Manganese toxicity on cantaloupe.

Manganese (Mn) toxicity was observed in a cantaloupe field at the Southwest Purdue Agricultural Center this year. This is a plant nutritional disorder related to acid soils and it usually occurs in clusters in a field. A plant tissue test confirmed that the Mn level in the leaves of the affected plants was 3766 ppm, which was 23 times higher than the Mn level in healthy leaves. The symptom occurs first on older leaves. The diagnostic feature of manganese toxicity is the tiny pin-hole type lesions with yellow halos clustered between the veins. Leaves are best viewed when held up to the light. In severe cases, it may cause heavy defoliation and exposed fruit to sunburn (Figure 1). More photos and information about the symptom can be found in the article Manganese Toxicity in Cantaloupe published in Issue 631 of 2017.  The remedy for these disorders is to raise soil pH,[Read More…]

About half of the watermelon fields in our area are not equipped with supplemental irrigation. Watermelon production in these fields is therefore dependent exclusively on rainfall. In fields where supplemental irrigation is available, drip irrigation under black plastic mulch is the most commonly used system. Overhead irrigation through central pivot is also used in some fields. Irrigation management is complex in our area because of significant but unpredictable rainfalls during the watermelon production season. Supplemental irrigation is profitable because it avoids water stress during periods of drought, thereby increasing and stabilizing yields. However, there is always a question whether supplemental irrigation is required for watermelon production in our region; if so, how much water should be applied; if not, what would be the consequence if there was an extended drought period. I do not have a straightforward answer to all the questions. But here are a few facts that I[Read More…]

Root knot nematode

On a sandy hillside in a watermelon field, we noted vines that, from a distance, appeared undersized compared to the vines in the flats. Upon closer inspection, some of the vines had either wilted or a portion of the plant had wilted. The wilted vines had discolored vascular tissue. These vines were affected by Fusarium wilt of watermelon. The roots of many of the plants had galls caused by root knot nematodes. That is, many of the vines were infected with both Fusarium wilt and root knot nematode. This article discusses root knot nematode on watermelon. Root-knot nematodes are small, colorless roundworms that dwell in the soil. They penetrate into plant root in the juvenile stage. Once they find a favorable location in plant tissues, they stop moving. Infested root cells start swelling and form galls that are the characteristic symptom of root-knot nematode infestation (Figure 1). Infested roots fail[Read More…]

Contact herbicide

What is causing the spots on the watermelon leaf? A) anthracnose B) early blight C) a contact herbicide   The answer is that the leaf above has been affected by a contact herbicide. The herbicide caused lesions upon contacting the leaf. However, there was no growth of the lesion and no yellowing of the leaf since the herbicide caused no effect after the initial contact. While the distribution of the lesions in the photo above appears like a disease, the lack of ridges and yellowing in the leaf above is why it is not a disease. In the photo below, which is anthracnose of watermelon, the lesions have many ridges caused by growth of the lesion. Plus, there is a bit of yellowing of the lesions.

If they have not already, your early season residual herbicides will soon run out of steam. Depending on the crop and production system, you may soon lose the ability to cultivate row middles. Now what? For many vegetable crops, managing emerged weeds is difficult with few postemergence herbicide options. This article will focus on cucurbit crops, but many of the principles translate to other crops as well. General Guidelines: Do not rely solely on postemergence options: I know hindsight is 20/20, but if you have more escaped weeds than you’d like this year, now is the time to start evaluating changes for next season. With most crops, a weed control program that relies entirely on managing weeds after they’ve emerged is a formula for failure. Consider combining postemergence herbicides with other management tactics including stale seedbed, plastic mulch, mechanical cultivation, cover crops, or residual (AKA soil-applied) herbicides. Always “start clean”.[Read More…]

Downy mildew of cucumber

Downy mildew has been observed on cucumber in Berrien County in extreme southwestern Michigan and in Monroe County in extreme southeast Michigan. The downy mildew spores that cause disease on cucumber will cause disease on cantaloupe and may cause disease on other cucurbits such as pumpkin and watermelon. The forecast is for the spread of the disease to move in a east to southeasterly direction. Therefore, cucurbit growers in northern Indiana should scout and manage for downy mildew. The organism that causes downy mildew of cucurbits doesn’t overwinter in Indiana. It has to be blown in every year. It is common for downy mildew to start the season in the Gulf States and migrate north with the cucurbit crops. Downy mildew apparently overwinters in northern Michigan/southern Ontario in greenhouses where cucumbers are grown year-round. Therefore, downy mildew is often found in Michigan before it is found in Indiana. For infection to occur, free moisture[Read More…]

Squash bugs are a pest of cucurbit crops and can sometimes go unnoticed until late in the season when the local populations have built up and you see them in high numbers (Figure 1) attacking the fruits of your crop. Squash bugs are similar in appearance to stink bugs but smell much more pleasant (in my opinion) when you squish them. They feed on all parts of the plant (leaves, stems, fruits) with piercing-sucking mouthparts and inject toxins in their saliva that can lead to localized wilting and crisping of leaves (Figure 2). Squash bugs are particularly problematic in pumpkin and squash (Figure 3) but can also be quite damaging in cucumber. The adults (Figure 4) are more difficult to control with insecticides, therefore best management practices should target the young nymphs, soon after hatching. The eggs are easy to identify. They are copper-colored and laid on the underside of[Read More…]

Figure 1: Striped cucumber beetle seen feeding on newly transplanted watermelon. The first-generation beetles can occur in high enough numbers to stunt plant growth or kill the seedling outright.

While in your fields in the last week you may have noticed fewer striped cucumber beetles on the leaves and stems of the growing cucurbit plants (Figure 1). This is because there are two generations of this pest in Indiana; the 1st generation adults that overwintered in the field have mated and left behind their eggs in the soil around the crop roots. When these eggs hatch the cucumber beetle larvae will feed on plant roots until they pupate into adults and emerge as the second generation typically in early July. Fields in northern Indiana will likely be 1-2 weeks behind on the second-generation emergence compared to southern regions of the state. This means that while you still may see adult striped cucumber beetles in your vegetable fields, they are likely not going to be found at high enough populations to cause economic damage (1 beetle per plant in cucumbers[Read More…]

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